DIY bit to cut waveguides

Collapse
This topic is closed.
X
X
 
  • Time
  • Show
Clear All
new posts
  • frascati
    Member
    • Nov 2009
    • 82

    DIY bit to cut waveguides

    I posted this before, but I think the details might have dissuaded anyone from attempting it. Here's a much easier version that works just as well. Turns out that one flute works as well as two since the guide keeps it so stable. That really simplifies the build.

    I was getting something in Home Depot today and got an image in my head of a tool that anyone could build in order to cut a waveguide into a baffle with a drill press. If you have a jig saw and a drill press, this is very easy. No welding necessary.

    Click image for larger version

Name:	SDC10602.webp
Views:	124
Size:	25.9 KB
ID:	946152

    Click image for larger version

Name:	SDC10600.webp
Views:	93
Size:	20.9 KB
ID:	946153

    Click image for larger version

Name:	SDC10599.webp
Views:	88
Size:	33.2 KB
ID:	946154

    Click image for larger version

Name:	SDC10595.webp
Views:	91
Size:	26.7 KB
ID:	946155

    The shaft is 1/2 inch "eye bolt" from Home Depot. It was the only bolt with sufficient length of thread. It's only nominally 1/2 inch (because they go cheap on their "1/2" inch eyebolts and measures 7/16 diam). That's fine.

    The angle iron is just 1 1/2 X 1 1/2 X 1/8 and is available anywhere. They soak you at Home Depot so get it there only if it's your last option.

    I got the eye bolt since the 1/2 inch machine bolts at HD only had about an inch of threaded section. As you'll see, we need more.

    Cut off the eye of the bolt. Cut the profile in the angle iron using Zaph's template posted on his Waveguide TMM page. Again, for simplicity, I only cut profile in one side. The opposite side is cut about 1/8 inch lower so that it does not contact the workpiece. Drill 7/16 hole. Cut out half moon for the bottom nut to fit. All very simple. It took half an hour with a hand jigsaw.

    This was an experiment to see if it would work, and it worked wonderfully in MDF. Only present catch is that the resulting profile is slightly off due to the need to offset the edge from the shaft center. It's likely to be close enough, but a little fine tuning in CAD would correct the original template for the offset.

    This bit takes about an hour to make with common shop tools and did MDF just fine in my smallest drill press (1/2 hp Harbor Freight 39 dollar on sale little wonder). The mild steel needs rehoning with each WG recess completed. Easiest done with the small sanding drum on your dremel. It would take quite a few honings to alter the profile to any degree.

    The 7/16 hole could also be cut as a slot. Interestingly, this would allow the bit to be adjusted to fit different sized tweeter diameters while keeping the same throat angle.

    This waveguide enthusiasm might just die within a month.. who knows? Or someone might establish elliptical guides as so superior that nothing else will do and then we'll be really hard pressed to "roll our own". But for the time being, I'd love to see more experimentation in this stuff by the talented folks who are light years ahead of me in design. This is the most I can contribute.
    Last edited by theSven; 24 July 2023, 21:21 Monday. Reason: Update image location
  • evilskillit
    Senior Member
    • Oct 2008
    • 468

    #2
    Wow, thats pretty slick. Thanks for posting this. I just built my waveguide project using modified MCM waveguides, but I'm pretty intrigued by this. I'll be following the development of this sort of thing to see if its suitable for use if I end up doing more WG based projects.

    Comment

    • penngray
      Senior Member
      • Sep 2007
      • 341

      #3
      Cut off the eye of the bolt. Cut the profile in the angle iron using Zaph's template posted on his Waveguide TMM page. Again, for simplicity, I only cut profile in one side. The opposite side is cut about 1/8 inch lower so that it does not contact the workpiece. Drill 7/16 hole. Cut out half moon for the bottom nut to fit. All very simple. It took half an hour with a hand jigsaw.
      How many would you like to make ?

      Im interested in one if you are making more.

      Comment

      • ---k---
        Ultra Senior Member
        • Nov 2005
        • 5202

        #4
        Impressive. I think you have more guts than I. I don't think I have enough to stick something like that into my router and spin it 6000 rpm.

        So, you just cut the steel with a jig saw?
        - Ryan

        CJD Ochocinco! ND140/BC25SC06 MTM & TM
        CJD Khanspires - A Dayton RS28/RS150/RS225 WMTMW
        CJD Khancenter - A Dayton RS28/RS150/RS180 WTMW Center

        Comment

        • frascati
          Member
          • Nov 2009
          • 82

          #5
          ---k---, sorry 'bout that. I shouldn't presume that anyone's read the earlier post on resizing pdf files. This bit is only for use in a drill press at its lowest speed. That's usually between 600 and 800 rpm. And plan on five to ten minutes to patiently carve out the waveguide. In fact, now that you mention this, the 7/16 diameter version that I just described would be FAR preferable to the 1/2 inch shaft earlier one since it would be almost impossible to make the mistake of mounting it in any common high speed router collet. That would be a bad mistake indeed. But it's a 6.5 diameter bit, so anyone would really have to be trying very hard indeed to kill himself just to get this mounted on a router in any case

          The steel is cut with a standard hand held power jig saw. That get's the profile and cutouts (the half moon is drilled first with a 1/2 bit) to within about a mm and then the profile is brought to the scribed mark in the metal freehand on the bench grinder (or a half round 'bastard' file is just as easy) and then honed with a slight bevel using the sanding drum on a dremel.

          Also, from the other thread, the drill press needs to have a throat depth sufficent to put the bit in the middle of your baffle. Probably will work for most TM baffle sizes on most home shop drill presses.

          (in fact, you can get around this for any size baffle on even a small drill press if you simply cut the midwoofer hole first, remove the head of your drill press, put the press's column through that hole, and replace the drill press head.)
          Last edited by frascati; 06 January 2011, 15:06 Thursday.

          Comment

          • ---k---
            Ultra Senior Member
            • Nov 2005
            • 5202

            #6
            I saw it in the other thread, I just forgot.

            Very interesting.

            You need to build another one, and take step-by-steps photos.
            - Ryan

            CJD Ochocinco! ND140/BC25SC06 MTM & TM
            CJD Khanspires - A Dayton RS28/RS150/RS225 WMTMW
            CJD Khancenter - A Dayton RS28/RS150/RS180 WTMW Center

            Comment

            • Paul W
              Senior Member
              • Oct 2004
              • 549

              #7
              Great idea! This will simplify mounting dome tweeters to the backside of the WG/baffle and "unchain" DIY from the standard profile flares. Super!
              Paul

              Comment

              • looneybomber
                Senior Member
                • May 2007
                • 194

                #8
                Ba da ba ba ba, I'm lovin' it.

                Comment

                • frascati
                  Member
                  • Nov 2009
                  • 82

                  #9
                  Offsetting the blade that little bit in order to use unmodified angle iron changes the original profile very slightly once it is transferred to the work. It would require someone more talented than me to tweak the original profile in CAD to account for this. It's a pretty complex geometry problem that would be cake for any decent CAD program.

                  Comment

                  • Space
                    Senior Member
                    • Aug 2009
                    • 118

                    #10
                    Do you put the end with the threads into the drill press chuck? Somehow it seems like the bolt is installed backwards, unless I'm not seeing this right.

                    Comment

                    • frascati
                      Member
                      • Nov 2009
                      • 82

                      #11
                      The threads mount in the chuck. Plenty of land for the jaws to center on. Here's a quick trial on the little harbor fright :E drill press at about 650 rpm. (actually it's probably the best 40 dollars I ever spent on a tool). 2 scrap pieces of 3/4 inch MDF laminated together. Pilot hole pre drilled with 7/16 bit. Work set up and clamped with the bit guide part way into the hole.

                      Click image for larger version

Name:	SDC10604.webp
Views:	89
Size:	44.7 KB
ID:	946156

                      Click image for larger version

Name:	SDC10605.webp
Views:	94
Size:	39.4 KB
ID:	946157

                      Took a little over five minutes. Important to kind of press, release, press, release, in very small cutting increments to eliminate chatter. Then it works very smoothly. Blade is still quite sharp after this run but should be honed a bit for the next one. (tip for honing is to paint the edge face with a black permanent marker before start. Makes it really easy to get the angle right and to make sure you don't miss spots)

                      Now the back side needs to be brought down in essentially the same fashion as described for the MCM guide to arrive at the exact size hole for the tweeter. I used a trim router and obviously no jig is necessary. Working in a small circle around the opening on the other side you can cut, adjust depth , measure opening, cut, adjust depth, measure opening.... when the hole is perfect then continue around that precise depth with the router bit until you have sufficient area to mount the tweeter.
                      Last edited by theSven; 24 July 2023, 21:22 Monday. Reason: Update image location

                      Comment

                      • dlneubec
                        Super Senior Member
                        • Jan 2006
                        • 1454

                        #12
                        Very cool idea! :T

                        Do you think adding a locking hex nut or lock washer would be a good idea on the topside to ensure that it doesn't work itself loose while in use?
                        Dan N.

                        Comment

                        • frascati
                          Member
                          • Nov 2009
                          • 82

                          #13
                          A lock nut might be nice. A serrated lock washer would be best if one is on hand. A little dab of loctite or even superglue in the threads would be as good in this case. A lock nut/washer is best for long term safekeeping over many miles. For occasional use like this, it's fine to just to crank the nut down tight and get on with it.

                          I can almost stop this drill press with my bare hands, so the foot lbs of torque that I'm able to apply to this nut with a wrench far exceeds the demands upon it. In any case, should it come loose during use it poses no danger at all. It would merely stop in the work while the bolt spins.

                          Comment

                          • DavidW
                            Junior Member
                            • Jan 2006
                            • 3

                            #14
                            Is there any easy way to expand the profile drawing automatically to full size? Rather than plotting by hand? thank

                            Comment

                            • ThomasW
                              Moderator Emeritus
                              • Aug 2000
                              • 10934

                              #15
                              I just redrew it using the dimensions there. But for the future. How is it possible to print a pdf to exact scale? I asked at a couple of "computing" forums and was told again and again that you must print, measure, resize, print, measure, resize, etc, to get it right. That seems pretty crude. I can't believe that
                              Last edited by theSven; 24 July 2023, 21:43 Monday. Reason: Update htguide url

                              IB subwoofer FAQ page


                              "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

                              Comment

                              • frascati
                                Member
                                • Nov 2009
                                • 82

                                #16
                                Hold off just a sec until I get a little assist on the matter of adjusting the dxf file for the blade offset. I posted here...
                                Not precisely a resizing question and I hope this is not an inappropriate use of the forum. I only use Google Sketchup for making project plans and for sharing ideas with others online. Rarely, I have a need that is very basic, but beyond the abilities of sketchup. I wonder if someone would be so...

                                ...and will get something soon I'm sure. The angle iron bit sets the cutting edge 11/32 off of it's path so that the resulting waveguide is a little off. It's a very basic CAD fix, but beyond my skills with Sketchup. With the fix, and if care is taken with cutting the edge on your bit, it ought to reproduce that profile of the MCM guide to a very high accuracy.

                                I also want to mention that is just the sort of tricky ground in this hobby where it's easy to step on toes. I hope I'm not guilty in any way. The reputations of the original designers of any project depend somewhat on the faithful application of their measurements and methods, and on people's feedback on the success of the design. It's often been noted that the latter is often compromised by negligence of the former. If I thought this drill press method might lead to any compromise of those designs in the hands of builders, I'd not have offered the ideas. If Jon and Zaph discourage the use of this method for anyone building their designs I'd understand completely and such advice should be heeded. This is proceed at your own risk. But I"m pretty confident that anyone out there with sufficient confidence to cut a woofer rebate with a router can make and use this bit with very accurate results.

                                In any case, this is about as far with this as I'm able to go. My background is in government. I couldn't even call tooling a hobby. I just get an idea and won't take no for an answer sometimes. I hope my enthusiasm has not be misplaced or unwelcomed, but I'll give it a rest anyway. I've followed Zaph's site for years now and recently found htguide and have always been a bit astonished at such generosity of time and expertise, and wished I could contribute something.

                                Comment

                                • evilskillit
                                  Senior Member
                                  • Oct 2008
                                  • 468

                                  #17
                                  Eh, I think its pretty awesome. If it couldn't faithfully produce an accurate profile that would be a problem. But it looks pretty good to me. For someone whose background is in government and not cad or tooling its pretty brilliant. Its not every day that somebody comes up with a new tool. Kudos sir. Hopefully some crafty people take this idea and run with it.

                                  Comment

                                  • thune
                                    Junior Member
                                    • Feb 2010
                                    • 4

                                    #18
                                    frascati,

                                    Blade offset compensation is straightforward trigonometry (after I brushed up on it). For a given waveguide depth, the distance from the center of the waveguide can be translated to a distance from the center of the blade. This is simple in a spreadsheet, but I have no clue for CAD.

                                    Radius translation for a given waveguide depth:

                                    R_blade=sqrt(R_wg^2 - offset^2)

                                    where:
                                    R_blade=distance from center of blade
                                    R_wg = distance from center of waveguide
                                    offset = angle iron blade offset from waveguide center

                                    So using the millimeter scale from Zaph's pdf, and an offset of 8.73mm (11/32 in):

                                    A) R_wg
                                    B) R_blade
                                    C) diff (R_wg-R_blade)
                                    D) waveguide depth
                                    _A____B____C___D
                                    82.5 82.04 0.40 0.0
                                    72.5 71.97 0.53 1.5
                                    62.5 61.89 0.61 4.0
                                    52.5 51.77 0.73 7.5
                                    42.5 41.59 0.91 12
                                    32.5 31.31 1.19 18
                                    22.5 20.74 1.76 25.7
                                    19.5 17.44 2.06 29

                                    (Apologies, I couldn't figure out how to make this table look good)

                                    As you suspected, the change is surprisingly minimal.

                                    Comment

                                    • cjd
                                      Ultra Senior Member
                                      • Dec 2004
                                      • 5568

                                      #19
                                      Can I ask where you DO get your angle iron?

                                      I've been pondering ordering up some tool steel to do something like this with (I have some experience tempering steel, and as I'd not be wanting to touch MDF but use it in plywood...

                                      I'd have done this on the Ansonica if I'd had the parts already.
                                      diVine Sound - my DIY speaker designs at diVine Audio

                                      Comment

                                      • frascati
                                        Member
                                        • Nov 2009
                                        • 82

                                        #20
                                        I live outside of Grand Rapids, Michigan. I stop in G R Central Iron & Steel Inc 1730 Alpine Avenue when I visit GR and get odds/ends. It's one of those little places catering to the artist and hobby type that, very unfortunately, will probably not survive much longer. Like hobby electronics shops and corner hardware stores, nobody frequents these enough anymore. Shame that.

                                        Anyway, I can't imagine that I'm failing to grasp the simplicity of what is needed to adjust the profile of that dxf file. It certainly is a complex trigonomety function. But that is precisely the sort of stuff that CAD enables so elegantly. It is really only a matter of someone who is comfortable behind the mouse to set the image up on the desktop, use it to draw the waveguide in three dimensions, and then pull the intersection forward 11/32 of an inch. Save the resulting new intersection of the profile and that's it. The programmer already put the trigonometry in there.

                                        I was going to try this in hardwood or plywood but I'm not optimistic. With my tig welder I would use tool steel for the blade, slant it 45 degrees and weld it in place, and try the bit in the larger drill press. I'm certain it would work fine. But there's the problem with reconfiguring the blade profile again to account for the slant. Actually that would be an even easier CAD exercise since it involves only a 45 degree adjustment with no other dimensions or numbers to mess with. If you have any old circular saw blades laying around you could cut an edge profile out of one pretty easily using a carbide grit saber saw blade. That would take a heat tempering very well.

                                        Comment

                                        • jkrutke
                                          Senior Member
                                          • Dec 2005
                                          • 590

                                          #21
                                          Nice work on that bit. I have the same $40 harbor freight drill press, I'm still shocked at that value. Still works great after years of hard work too.
                                          Zaph|Audio

                                          Comment

                                          • thune
                                            Junior Member
                                            • Feb 2010
                                            • 4

                                            #22
                                            frascati,
                                            My equation above seems too simple, I know. The first time I worked out the mapping, I got r'=r*cos(arcsin(offset/r)). But this turns out to be equivalent to r'= sqrt(r^2-offset^2).

                                            Click image for larger version

Name:	angleiron.jpg
Views:	4209
Size:	66.1 KB
ID:	854549

                                            I grasped the simplistic equation by considering the waveguide/blade in 2D from above. For a given radius from the waveguide center there is a given waveguide depth (z-axis not shown). That same waveguide radius and waveguide depth maps to a point on the offset blade (in 2D). This point on the blade will now be cut to produce that same depth. For every point on the blade we can form a triangle, a right triangle, and solve for the compensated blade "radius" corresponding to every waveguide radius, using the Pythagorean theorem.

                                            R_blade=sqrt(R_wg^2-offset^2)

                                            I hope this clarifies my previous post. If there is fault in my analysis, please correct me.
                                            Last edited by theSven; 24 July 2023, 21:22 Monday. Reason: Update image location

                                            Comment

                                            • frascati
                                              Member
                                              • Nov 2009
                                              • 82

                                              #23
                                              thune, I'd be near the end of the line of those competent enough to correct your math.. believe me. I have a hunch that it's good just looking at it, but wait, I don't even belong in line. I failed two straight refresher courses in basic algebra when I eventually got to college at 27. They finally, mercifully, found a way to waive the requirement for me.

                                              But whether it's correct of not may not matter at all. I could never apply it with brute mental force. The fact that I can render fairly complex objects in Sketchup is no less than astonishing given my almost complete lack of math skills. You mathematicians, God bless you, have programmed all of that into the GUI for me.

                                              And I'm going to be really embarassed after all if this is not the easy fix in CAD that I"m imagining it is.

                                              John, that press gets most of the use in my basement shop. I've got a larger craftsman but so much of what I do is very small work that most of my bits and tools end up scattered around this one. I did replace the motor last year with a 1/3hp Dayton blower motor that was sitting under my bench. Despite the similar rating it seems to give it more grunt.
                                              Last edited by frascati; 16 March 2010, 10:28 Tuesday.

                                              Comment

                                              • moose404
                                                Junior Member
                                                • Mar 2010
                                                • 5

                                                #24
                                                Heres the offset profile in DXF and 1:1 PDF.

                                                Hope this helps.
                                                -Moose
                                                Attached Files

                                                Comment

                                                • frascati
                                                  Member
                                                  • Nov 2009
                                                  • 82

                                                  #25
                                                  Wow, thanks moose404. I did it in sketchup this morning and once I figured out how to use the right tools it was came out as I imagined. For the life of me I can't understand why I was so incapable of communicating this right because it really does turn out to be a very simple fix in CAD.

                                                  Click image for larger version

Name:	newprofileblade.webp
Views:	95
Size:	7.0 KB
ID:	946158

                                                  Click image for larger version

Name:	firstversionofcuttingbitjpeg.webp
Views:	92
Size:	6.9 KB
ID:	946159

                                                  The red is the corrected blade profile. It should correspond to yours. It would take me a while yet to learn how to save that slice in two dimensions with the profile included in it. I realize it's nitpicking, but might as well do it right if at all. I'm going to draw that bit with the new profile in sketchup and then post a PDF file that can be printed out as a template. It would be easier if you could tell me precisely what the bottom line that originally measured 39mm ended up being. I can scale it really easily in sketchup with that figure.
                                                  Last edited by theSven; 24 July 2023, 21:24 Monday. Reason: Update image location

                                                  Comment

                                                  • moose404
                                                    Junior Member
                                                    • Mar 2010
                                                    • 5

                                                    #26
                                                    Here is a dimensioned drawing of the cross-section. That should allow you to check your dimensions in Sketchup.

                                                    I'm an engineer who designs in Solidworks for a living, so this sort of thing just took me a couple of minutes to do. I'm not that familiar with Sketchup, so I can't help you there.

                                                    Moose
                                                    Attached Files

                                                    Comment

                                                    • Bill Schneider
                                                      Senior Member
                                                      • Sep 2007
                                                      • 158

                                                      #27
                                                      Well, doing it mathematically took me a little longer than using CAD (long, long ago I practiced engineering with a slide rule and a Mutoh drafting machine. Never learned CAD :cry: ), but I found a solution that confirms that moose404's CAD illustration is accurate.

                                                      Here's a plot of the original waveguide contour (top plot shown in red), and the tool contour plot overlayed with moose404's drawing. You can see that the tool's contour deviates from the waveguide shape mainly at the throat when you compare the red plot with the CAD drawing - and I expected that.

                                                      The CAD overlay is so exact that it's a little hard to see the underlying points and plot under the CAD drawing. The CAD drawing is a very close match to the calculated values found in the mathematical approach.

                                                      Click image for larger version

Name:	waveguide-comparison.gif
Views:	3846
Size:	74.4 KB
ID:	854662

                                                      I reorganized John's waveguide dimensions so that I could use regression analysis to find a good fitting polynomial curve through the points. I then used that formula to calculate new tool radius values using the method described in thune's post.

                                                      Like I said, I was a little late to the party, but it was fun using some math that's been dormant for 40 years. Looks like you are good to go.

                                                      Edit: Just in case you want to create more points for the tool profile (for an offset of 0.3438"), use the following formula:

                                                      "blade radius" = 5.1857683*height^5 - 11.6256475*height^4 + 9.0841616*height^3 - 2.0232016*height^2 + 1.1756056*height + 0.684609

                                                      Enter arbitrary heights from 0 (at the throat) to 1.142" (at the outside surface of the waveguide) in the formula above to calculate the "blade radius" as defined in thune's post/illustration. In my calculations, a small radius number is closer to the center of the waveguide throat, not a distance from the waveguide's outer edge as shown in John's original illustration. Also, a waveguide height of zero in the calculations above is at the throat, also different than John's usage.

                                                      The R^2 fit for this polynomial formula was 0.99977 (where 1 is a perfect fit).

                                                      BTW, do NOT extrapolate the blade radius equation above for smaller throats. It is a good match for the existing points, but begins to deviate quickly from a waveguide shape at the throat if extrapolated.
                                                      Last edited by theSven; 24 July 2023, 21:15 Monday. Reason: Update image location
                                                      My audio projects:
                                                      http://www.afterness.com/audio

                                                      Comment

                                                      • jkrutke
                                                        Senior Member
                                                        • Dec 2005
                                                        • 590

                                                        #28
                                                        Doh. Even though this only took me 15 seconds, I'm still too slow. But I see that everyone has the right idea right down to the math.

                                                        With all these tools at my disposal, I worry I am going to forget all the stuff I used to know 15-20 years ago. I did my share of manual work with a pencil but I sometimes feel like CAD is dumbing me down.

                                                        Click image for larger version

Name:	Image1.jpg
Views:	1748
Size:	24.7 KB
ID:	854554
                                                        Last edited by theSven; 24 July 2023, 21:15 Monday. Reason: Update image location
                                                        Zaph|Audio

                                                        Comment

                                                        • cjd
                                                          Ultra Senior Member
                                                          • Dec 2004
                                                          • 5568

                                                          #29
                                                          The question now is, should we use this profile at any given final *center* radius? Is it optimal? Because it would be little effort at this point to be able to adapt the adjusted profile to remain static for various tweeter diameters, rather than current which will alter the shape at the throat as you change tweeter diameter... not to mention the WG depth.
                                                          diVine Sound - my DIY speaker designs at diVine Audio

                                                          Comment

                                                          • frascati
                                                            Member
                                                            • Nov 2009
                                                            • 82

                                                            #30
                                                            John discovered a serindipitous match between this MCM guide and a SEAS tweeter. Whether it matters or not that the same profile and depth be applied to other domes, with different apertures, once the template is a printable file it can be easily modified.

                                                            If you do want to maintain the same depth and profile as long as the same 11/32 offset is accounted for, the shape at the throat as well as the depth will be unaffected by adjusting the blade sideways for a different aperture (bottom hole). That would be a better way to change the aperture size than by going deeper. The bit temlplate could just be drilled for its 7/16 hole anywhere within about 5mm on either side of center. The half moon cutout and the leading edge of the blade where it touches the center line of the bolt would just be moved the same amount. Profile stays the same. This would provide an opening diameter in the bottom up to one centimeter larger or smaller than that specified for the current SEAS tweeters being used. But the profile of the walls and the depth would be unchanged.
                                                            Last edited by frascati; 19 March 2010, 13:45 Friday.

                                                            Comment

                                                            • Bear
                                                              Super Senior Member
                                                              • Dec 2008
                                                              • 1038

                                                              #31
                                                              I'd love to have something like this that can handle BB or LBL... But DIY tooling is Not My Thing.
                                                              Welcome to Rivendell, Mr. Anderson.

                                                              Comment

                                                              • cjd
                                                                Ultra Senior Member
                                                                • Dec 2004
                                                                • 5568

                                                                #32
                                                                Birch may be possible - LBL I think you'd need tempered tool steel absolutely for sure.
                                                                diVine Sound - my DIY speaker designs at diVine Audio

                                                                Comment

                                                                • Bear
                                                                  Super Senior Member
                                                                  • Dec 2008
                                                                  • 1038

                                                                  #33
                                                                  Originally posted by cjd
                                                                  Birch may be possible - LBL I think you'd need tempered tool steel absolutely for sure.
                                                                  Agreed. I'm just trying to encourage a small side business be created...
                                                                  Welcome to Rivendell, Mr. Anderson.

                                                                  Comment

                                                                  • cjd
                                                                    Ultra Senior Member
                                                                    • Dec 2004
                                                                    • 5568

                                                                    #34
                                                                    Originally posted by Bear
                                                                    Agreed. I'm just trying to encourage a small side business be created...
                                                                    How much would you pay?

                                                                    These would probably end up being at least a couple hundred bucks in tempered tool steel unless we farm it out to a production house and someone does a bulk buy-in, in which case we'd be looking at someone that doesn't mind losing money for the rest of us, OR a significant group-buy effort.

                                                                    If I were building for bulk use I'd build the guide and core assembly with a bolted-on cutting blade. We might be able to get a decent price from the folks that do custom blades for shapers - should look into what that would cost. You send them a profile, they one-off blades (and that may even be available in carbide!)

                                                                    hmmm...
                                                                    diVine Sound - my DIY speaker designs at diVine Audio

                                                                    Comment

                                                                    • cjd
                                                                      Ultra Senior Member
                                                                      • Dec 2004
                                                                      • 5568

                                                                      #35
                                                                      In-industry parlance we're really looking for a really wide diameter rosette cutter.

                                                                      Non-custom profiles in carbide with a 2.125" diameter are just shy of $100... a 2.5" diameter is $240...

                                                                      Going this route in a custom setup would exclude the ability to adjust for tweeter diameter. And would be insanely costly.

                                                                      I will see if I can give a call out to one place for just the blade, we'll see.

                                                                      On the other hand, 5.5" diameter Raised Panel shaper cutters are $150 - to use this cutter style we'd have to through-drill a center hole, but a custom profile would probably be a LOT less costly.

                                                                      These prices are NOT for custom profiles.
                                                                      diVine Sound - my DIY speaker designs at diVine Audio

                                                                      Comment

                                                                      • cjd
                                                                        Ultra Senior Member
                                                                        • Dec 2004
                                                                        • 5568

                                                                        #36
                                                                        Whoop. Found a place that sells JUST custom knife profiles in high-speed-steel or carbide tipped. Need to contact them now. And verify they're safe/legit...
                                                                        diVine Sound - my DIY speaker designs at diVine Audio

                                                                        Comment

                                                                        • Space
                                                                          Senior Member
                                                                          • Aug 2009
                                                                          • 118

                                                                          #37
                                                                          Originally posted by cjd
                                                                          Going this route in a custom setup would exclude the ability to adjust for tweeter diameter. And would be insanely costly.
                                                                          What if you got a custom bit with a bearing, and you could first drill a center hole the best size for the tweeter. The overall profile would be slightly different depending on the center hole, but that might not be a problem?

                                                                          This would require a router table rather than a drill press. Probably would have to inch down in several passes.

                                                                          Comment

                                                                          • penngray
                                                                            Senior Member
                                                                            • Sep 2007
                                                                            • 341

                                                                            #38
                                                                            Originally posted by cjd
                                                                            How much would you pay?

                                                                            These would probably end up being at least a couple hundred bucks in tempered tool steel unless we farm it out to a production house and someone does a bulk buy-in, in which case we'd be looking at someone that doesn't mind losing money for the rest of us, OR a significant group-buy effort.

                                                                            If I were building for bulk use I'd build the guide and core assembly with a bolted-on cutting blade. We might be able to get a decent price from the folks that do custom blades for shapers - should look into what that would cost. You send them a profile, they one-off blades (and that may even be available in carbide!)

                                                                            hmmm...

                                                                            I paid about $80 For a 1 1/4" round over bit so.....

                                                                            Comment

                                                                            • ---k---
                                                                              Ultra Senior Member
                                                                              • Nov 2005
                                                                              • 5202

                                                                              #39
                                                                              Sounds like CJD is going to be the one going into waveguide drill bit business!
                                                                              - Ryan

                                                                              CJD Ochocinco! ND140/BC25SC06 MTM & TM
                                                                              CJD Khanspires - A Dayton RS28/RS150/RS225 WMTMW
                                                                              CJD Khancenter - A Dayton RS28/RS150/RS180 WTMW Center

                                                                              Comment

                                                                              • frascati
                                                                                Member
                                                                                • Nov 2009
                                                                                • 82

                                                                                #40
                                                                                I tried a piece of scrap oak today. This took about ten minutes of slow going. I would have kept going just to say I did it, but I was flogging my hapless 1/3 hp drill press like a knobby kneed little mule. I'm pretty confident that on a >1hp press with a beefier table, and a pause to rehone the bit, this would have been a success.

                                                                                A bit like this is not suited to anything beyond DIY. Where time equals money, or where thousands of parts need cutting, it would be a flop.
                                                                                It's fine for DIY projects because we have the 'luxury' of taking five to ten minutes to cut each recess, and then hone the bit for the next cut, or even toss it in a drawer and build another one for a different profile.

                                                                                Click image for larger version

Name:	SDC10607.webp
Views:	91
Size:	69.0 KB
ID:	946160
                                                                                Last edited by theSven; 24 July 2023, 21:25 Monday. Reason: Update image location

                                                                                Comment

                                                                                • frascati
                                                                                  Member
                                                                                  • Nov 2009
                                                                                  • 82

                                                                                  #41
                                                                                  I posted the jpeg above yesterday but the image disappeared from imageshack for some strange reason. Did they killl it because it was too large?

                                                                                  Comment

                                                                                  • penngray
                                                                                    Senior Member
                                                                                    • Sep 2007
                                                                                    • 341

                                                                                    #42
                                                                                    What is the difference between this and using something like the 1 1/4" round over?

                                                                                    Comment

                                                                                    • Bear
                                                                                      Super Senior Member
                                                                                      • Dec 2008
                                                                                      • 1038

                                                                                      #43
                                                                                      Originally posted by penngray
                                                                                      What is the difference between this and using something like the 1 1/4" round over?
                                                                                      Concave vs. convex curves, for a start.
                                                                                      Welcome to Rivendell, Mr. Anderson.

                                                                                      Comment

                                                                                      • cjd
                                                                                        Ultra Senior Member
                                                                                        • Dec 2004
                                                                                        • 5568

                                                                                        #44
                                                                                        Frascati, if you're having problems hosting files toss 'em in an email to me, I'll put 'em up on my website.
                                                                                        diVine Sound - my DIY speaker designs at diVine Audio

                                                                                        Comment

                                                                                        • frascati
                                                                                          Member
                                                                                          • Nov 2009
                                                                                          • 82

                                                                                          #45
                                                                                          What is the difference between this and using something like the 1 1/4" round over?
                                                                                          It's 6.5 inches wide. As has been mentioned, it's possible to come up with a high speed router bit that might reproduce that waveguide recess, but it would be only slightly smaller and actually be insanely impractical for any sort of hand held use (as well as insanely expensive). You'd need a cnc rig just to run the thing. This diy bit is for slow speed shaping of the waveguide in a common drill press.



                                                                                          Just a small improvement to the bit design. The cutting edge is now on the left. Rotatating clockwise the sharp edge faces away from you viewing the template. Because the blade is offset from the axis plane this allows the following edge (the left one) to 'cut' a little more than 'scrape' because it's angle has changed in relation to the wood surface. This difference is negligible at the outer edge and most evident at the throat. The cutting edge is now also only 1/32 in the OTHER direction of the modeled ideal that was mentioned in my last post so no need to worry with that. A little of the cutting edge has been kept on the leading edge (to the right) next to the shaft simply because the following edge would not do a very good job of cutting there where it creates a vee recess against the shaft. Where the previous version needed only a couple of degrees of bevel on the main profile edge (edge 'C') this one needs more like thirty, particularly nearer the throat. If you can picture what is happening you understand why.

                                                                                          Image not available

                                                                                          Drawn to scale, this is the bit guide shaft and blade at the very bottom of the throat looking downward while cutting. Using the left side for cutting, as in the first template design, rather 'scrapes' away the profile. It's surprising actually that it works so well. It works very well in MDF and even makes it through oak as I showed above. Slow speed is the reason mild steel works here. Heat is as tough on an edge as friction alone.

                                                                                          For woodworking, this whole exercise has been a good lesson for me in slowing down and taking my time on some things. At much higher speeds typical of most modern wood working tools, unless you've got super sharp carbide edge profiles heat buildup would destroy this project or the tool before you could get anything done at all. At 650 RPM, some good music, maybe a can of beer, you can do more than you thought possible.

                                                                                          Using the right side of the blade in the image above (the left side on the template printout) provides more cutting action, although the advantage is greatest at the very bottom of the throat and progresses toward negligible near the outer perimeter of the cut. In fact the right side bevel is almost 35 degrees at the 39mm throat in the image above and would only need a couple of degrees at the top of the curve (outer perimeter of the waveguide).

                                                                                          Altogeter the first design works really well enough. But if any of my tortured description makes sense to you, you might want to give the second version a go.
                                                                                          Last edited by theSven; 24 July 2023, 21:25 Monday. Reason: Remove broken image link

                                                                                          Comment

                                                                                          Working...
                                                                                          😀
                                                                                          😂
                                                                                          🥰
                                                                                          😘
                                                                                          🤢
                                                                                          😎
                                                                                          😞
                                                                                          😡
                                                                                          👍
                                                                                          👎
                                                                                          Searching...Please wait.
                                                                                          An unexpected error was returned: 'Your submission could not be processed because you have logged in since the previous page was loaded.

                                                                                          Please push the back button and reload the previous window.'
                                                                                          An unexpected error was returned: 'Your submission could not be processed because the token has expired.

                                                                                          Please push the back button and reload the previous window.'
                                                                                          An internal error has occurred and the module cannot be displayed.
                                                                                          There are no results that meet this criteria.
                                                                                          Search Result for "|||"