How I milled my waveguides

[evilskillit]

With me working on a Zaph Waveguide TMM and the Modula Mk2 waveguide project coming up, plus some other WG stuff in the horizon I figured I would post some pictures and explanations of how I milled my waveguides (WG from here on out).

This is going to be a big post with some big, hopefully pretty pictures.

First I made a sort of U shaped guy and screwed the waveguide to it.



Then I put that on my chop saw.

For the Zaph WG make sure not to cut into the first rib, if you cut that you've taken off too much. Also be mindful of the copper/brass threads inside the thing. My saw blade didn't seem to mind them too much, but the again it was only $20 so if it did hurt it I wouldn't be out a lot of money either.



Pic of some of the cutoffs. I kept thinking they were rolls of electrical tape laying around. (There are 4 because I botched two waveguides.)


Then take it off of that and mount it to an other U shaped sled for milling with your router.


Make sure the rails are nice and flat or your milling will be all wonky. Then put a nice wide flat board on the bottom of your router, put the router assembly on top with an apropriate blade and mill away. I think a 1/2 spiral upcut bit would be ideal. My router doesn't accept 1/2 bits, so it took a while to get it really smooth with that little 1/4 guy.
I got this idea from Collo over at www.subwoofer-builder.com so I can't take credit for having come up with it. I don't know if he can either, its probably a pretty obvious trick, but without it I couldn't have made these.


Thats about it. Now I'll show off some finished product. Zaph calls for these things to have an opening of EXACTLY 1.5". Well lets see how close I got?



He says the depth will be "a bit less than 1.25" when done. Well lets see where 1.502 inches gets you depth wise.



Here is one dirty, but happy Matt, holding some WGs.


Comical note: my finger got smashed bad and we were out of band-aids, so I had to make a man-daid. I'll tell the smashing story later. I think that might be another post.


Edit: No that is not really dark dense black chest hair in my pic. Its ABS plastic shavings. I found some in my belly button too. Might be some in my boxers for all I know. Note, don't wear an open collared shirt when working with that junk. It goes everywhere.

[Paul Ebert]

Thanks, Matt! So, do you end up having to cut through the copper ring? I had thought that I would use my bandsaw where you used the chop saw, but if it's got to cut the copper that will probably not work too well (the bandsaw is a wimpy little thing).

[cjd]

It's probably a brass fitting, and a carbide tipped blade and patience will cut it without trouble, but take it slow.

A band-saw fit with a metal cutting blade is probably ideal, they tend to do OK on plastic as well.

[xyrium]

Nice work Matt! Your meticulous work will certainly pay off with those towers. Please keep us apprised of your progress. I eagerly await listening impressions!

BTW, locating shavings in your belly button might have been a little more info than necessary. :lol:

[Bear]

Thanks for the detailed write-up! I may have to substitute a hacksaw for the chopsaw, but this looks to be a better process than taking a grinder and hoping I let up at the right depth with a level cut.

[evilskillit]

Yeah the metal seems pretty soft. I tried to cut to the inside of it with my chop saw but given the thickness of the blade and not knowing exactly where the metal stopped trying to cut inside the metal threads without cutting too far into the waveguide was a pretty tricky proposition. I clipped the edge of the brass on every cut I think. A band saw blade is thinner so you would probably have an easier time not hitting the metal, but you still might without realizing it, but as previously stated a metal cutting blade would probably make short work of it.

One of my two ruined wave guides was because the WG was not 100% flat to the jig on the chop saw and just being off a couple of degrees made it cut way too far into the plastic on the bottom of the cut, so it doesn't take much. Unless you have a few spares and don't mind using them better to err on the side of caution when removing the brass threaded part.

Thanks for the kind words Xyrium. I'll post progress as its made, but I'm not rushing these things as I don't want to make any more mistakes than absolutely necessary so they'll be done when they're done. When that time comes tho I'll get on here and gush about em for sure.

[JonMarsh]

Thanks for the detailed write-up! I may have to substitute a hacksaw for the chopsaw, but this looks to be a better process than taking a grinder and hoping I let up at the right depth with a level cut.

I'll be posting a detailed write up, too, especially in the PDF in preparation. It's really not any big deal... once you've thought it through. I just ordered some more MCM waveguides so I'd have parts to "demo" on.

[BobEllis]

I just cut the brass end off with a hacksaw and started at the mill with your router phase using a similar setup and it worked fine. The stuff cuts so easily it wasn't a big deal (other than the pile of ABS chips)

[evilskillit]

Yeah John, I wanted to wait for your instructional but I had some free time and got impatient so I figured I'd show how I did it. Besides I think you're going to use a router table and that is something I don't have. Granted I could probably build one in the time it took me to make that milling jig, but I figured I would go ahead and figure it out and show my way. The more information there is on how to do this the better seeing as how up to this point there didn't seem to be much of anything.