routing holes...

[Bent]

Greetings, another request for knowledge to fill my head with.

I'll be soon cutting the holes in my BP 1503 based AS-15 based SW 12 based subwoofer, and was wondering about the cutting of the holes.
The locations of the 6-1/2" holes to accomodate the port tube are critical, they must be in the same position on each baffle as well as on the braces behind it, so I intended to just stack all the baffles and braces and drill a pilot hole through the hole works of them - this should give me a consistant starting point with the pivot point for the router, but the radius of the cut will be short. How would I set a circle cutting jig in which the pivot will likely wind up "underneath" the router's base? (I haven't purchased a router yet).

Also, the driver cutout - it will be approx 14" diameter, no big deal for a circle jig, but it will be doubled 3/4" mdf. How deep can I expect to cut on each pass?
(I'm sure it will take a few passes, and it might be better if I just use a common pilot hole too, as I intend to do with the port cutout.

And... when it gets to flush trimming the edges of the enclosure, I imagine the whole cut needs to be made at one shot - what type of a bit would work for this and how long of a bit should it be?


And one more question, 1/2" or 1/4" collett on the router? there is a skil brand 1/2" on for about 200 bucks locally (CDN), it comes with a fixed base as well as a plunge base.

Thanks
Ben

[Andrew Pratt]

Ben most circle guides suitable for speaker hole cutting (jasper rig) can do what you need with ease. I keep meaning to buy one of the jasper units but the DIY version I built keeps working so that purchase keeps being delayed Regardless drilling the pilot hole for the port should work fine so long as you keep the hole very small and you use a drill press to make sure its in the same spot on all braces.

As for the doubled driver cut out just keep making 1/4 deep passes and work your way though it....unless your circle guide is very thick you won't have a problem cutting down that deep with a plunge router...and if you do run into problems you can get longer shanked bits.

For the sides a single pass would be ideal...but that never seems to work for me and it isn't usually a problem repeating sections with the router. You'll want to sand it anyway so you can often fix minor bumps or nicks at that point.

1/4 vs 1/2? I'd guess 1/2 would be better but I haven't seen nearly as many 1/2 bits as you do 1/4. My router's a 1/4 and has done all my speaker projects well...but as always you get what you pay for and if you've got the funds to buy up do so.

[Paul H]

Greetings, another request for knowledge to fill my head with.

I'll be soon cutting the holes in my BP 1503 based AS-15 based SW 12 based subwoofer, and was wondering about the cutting of the holes.
The locations of the 6-1/2" holes to accomodate the port tube are critical, they must be in the same position on each baffle as well as on the braces behind it, so I intended to just stack all the baffles and braces and drill a pilot hole through the hole works of them - this should give me a consistant starting point with the pivot point for the router, but the radius of the cut will be short. How would I set a circle cutting jig in which the pivot will likely wind up "underneath" the router's base? (I haven't purchased a router yet).

Also, the driver cutout - it will be approx 14" diameter, no big deal for a circle jig, but it will be doubled 3/4" mdf. How deep can I expect to cut on each pass?
(I'm sure it will take a few passes, and it might be better if I just use a common pilot hole too, as I intend to do with the port cutout.

And... when it gets to flush trimming the edges of the enclosure, I imagine the whole cut needs to be made at one shot - what type of a bit would work for this and how long of a bit should it be?


And one more question, 1/2" or 1/4" collett on the router? there is a skil brand 1/2" on for about 200 bucks locally (CDN), it comes with a fixed base as well as a plunge base.

Thanks
Ben

Ben,

For a circle cutting jig I use an extra base for the router made from 3/8" lexan (or plexi, or plywood, or ..). You can purchase scraps of lexan from your friendly neighbourhood plastics shop.

I simply drill a hole in the lexan at the appropriate distance from the (far) edge of the router bit for the radius circle I want. Put your centre piece in the hole - I use small metal round shelf peg supports, but any cylindrical piece will do.

The number of passes to go through 3/4" mdf depends on bit, router, etc, but as a starting point use at least three passes. Listen to your router while cutting - if it sounds strained back off and cut less with each pass.

Pre-drilling a common hole for multiple layers is the easiest method.

If you cut all the way through with the router you'll cut your centre point loose just as you're finishing your cut. The tendency then is for the router to nick or gouge your (almost) perfect circle. The better plan is to set the depth of bit for the last pass to be just a hair shy of cutting through (around 1/64" or less). Then cut the remainder with a sharp utility knife.

Flush trimming bit:

http://www.leevalley.com/wood/page.aspx?c=1&p=30165&cat=1,46168,46171&ap=1

Get the largest one - you can trim a 1 1/2" thick baffle with it.

I strongly prefer and recommend 1/2" bits when at all possible - they're just much safer by way of being much stronger. It is best to have both collet sizes though as some smaller bits are only made with 1/4" collets.

If you're going to be using a router a lot, and can afford to, spend more than you've mentioned. Get a variable speed, with both size collets.

Paul

[ThomasW]

For the original AS-15, a pattern was fabricated for the braces, multiple copies were individually made. Nothing was stacked.

The holes cut in the bracing for the port aren't critical and were cut oversized. That makes sure that there's no problem installing the port

All the circles in the braces were cut with a Jasper jig. The asymetrical shapes were cut by hand with a jigsaw.

For routing circles in material thick and thin, I use the 1/4" solid carbide spiral cut up twist bits.

If the material is too thick to plunge through in one direction, I cut as deep as possible from one side then flip it over and finish the cut from the back side.

One should always use multiple shallow cuts instead of one deep cut.

[cjd]

FWIW, Freud also sells a 2" (half-inch shank) flush-trim bit - available through Amazon.

I have a 1/4" shaft flush trim that sheared (where the shaft flares out to the cutter) after only about 80 linear feet of use. :evil:

C

[David R.]

Bent, Buy the 1/2" collet router..

The piece of wood or plexi screwed to the bottom of the router works well.. Just requires extra care in measuring the pivot locations.

My new jasper jig should be arriving today. woohoo

[Bent]

thanks everybody - I have almost a full 4' X 8' sheet of plexi (1/4"), in wich I intend to build a circle jig out of.

I was under the impressino that the port support holes in the AS-15 were just that - port support... It will make it much easier if they are a bit larger.

This is lookin very promissing

[Brian Bunge]

As David said, DEFINITELY get the 1/2" collet. If you ever want to use a roundover bit with more than a 1/2" radius you'll have to have the 1/2" collet. Also, all routers I've ever seen that come with a 1/2" collet also have an adaptor for 1/4" shank bits as well. Oh, and make sure your flush trim bit has a 1/2" shank. If you try to trim off more than about 1/8" of material you'll be putting a lot of stress on the bit.

[Jack Gilvey]

In case anyone's interested, Parts Express is selling a combo pack consisting of the Jasper 200 and 400 model jigs for under $50. Click on the banner at the top and search for "Jasper".

[Bent]

Well, I think that for starters I'll pick up the Skil 1/2 inch combi-base router - If I really get hooked on this speaker building thing I can get the heavy DeWalt stuff at a really good discount through my office's corp. rate arangements with the local retailers and sell the little skil unit.

One more dumb question, how thick is veneer for this purpose (typically?). I ask beascause I can't get my head around how I would trim the edges of this box and not see the cross-grain on the butted edges of the veneer.

[David R.]

The veneer i use is 10mil paper backed.. Its very thin, i would guess 1mm total.. Just use the flush trim bit, and some sanding afterwards and you will get a near perfect seam.

[Bent]

I understand that a veneer with a paper backing - the paper acts like wallpaper "sizing" to allow a bit of "squirming" and not show through on the veneer, right?

[JonMarsh]

That's basically correct. Good paper backed veneer is fairly easy to work with, compared with solids; it's generally quite flat, and won't need any treatment prior to veneering. You can even cut it close to size with a set of Fiskar shop scissors, such as you can get at a big box store or woodworking specialty shop. Trimming after you've laminated it up is easy; for right angles, a laminate bit works well, in special cases, such as bevel angles, even a sharp utility knife does a good just with just a little care.




Many folks use contact cement for attaching paper backed veneer, but I've had the best results using PVA type glue (Titebond, for example), two light coats to both MDF and back of veneer, then layup veneer just after the second coat has dried, and bond with a hot iron (Black and Decker, of course!) and moderate pressure. I apply the glue with a squeegee. Whether you use contact cement or PVA glue, you need to have thin even layers without any build up, or the veneer surface won't be as flat as it should be.

Which brings up the drawback to paper backed veneer- the wood is VERY thin, and won't tolerate much sanding- I've found it best to use an absolute minimum of sanding after filling the grain, with 220 grit, then 400 grit, before the final finish.

~Jon

[David R.]

I use the iron/wood glue method as well to. I find it works better then contact cement, and has no fumes/smell.

[Andrew Pratt]

Ben if you want to borrow my router and DIY circle guide for a while you're more then welcome to it.

[Bent]

Thanks much Andrew - but I bought the 1/2" skil router today.
a fixed base and a plunge base, 1/4" collet adapter, variable speed, 2.25 HP, and a case to boot. All for less than 200 bucks on sale.

Now just to pick up some bits...

[Andrew Pratt]

Good deal :T

[Bent]

I had one more question - I picked up some green sewer pipe today, it was used but I cleaned it out . :rofl: :rofl: :rofl: :rofl: :rofl: :rofl:

actually it was just an off-cut from some town piping they were laying, so it wasn't really "used".

I was wondering what a quick and accurate way is to right-angle cut the end of this pipe? I tried a guilotine type band saw, the kind used for cutting ,metal pipe... and can't easilly get a square cut, the blade of the band saw will travell fairly well in the vertical direction but the pipe is never really squar with the saw in the fore-aft direction. Any hints from anyone on dealing with this 6 inch material?

[ThomasW]

I had one more question

Somehow I doubt that ...:wink:

Take a wide piece of heavy paper that's longer than the circumference of the pipe. Use this as a guide to mark a line around the tube. Then hand cut the tube with a jigsaw.

I rotate it with the 12" blade of my radial arm saw locked in place. This just a bit dangerous....

[Bent]

Thanks Thomas, I thought of that and was hoping to do it something a little more "automated".

Oh well, I'll get the jig saw charged up and see what happens - there's always sandpaper...

[Andrew Pratt]

I just did the paper and jig saw method on the ones I've used...it doesn't have to be perfect either

[Bent]

Well, paper and a jig-saw worked as close to perfect as I would have expected to get.

(although I've only done one cut.)

[gimpy]

Bent, lots of good advice. One place to get a fairly nice set of bits (go 1/2 inch shank if possible) is at www.bladesnbits.com. They are in Canada and the bits are real reasonable price wise and of reasonable quality.

When cutting the circles you can either use a glue gun with a dab or two of the glue under the "circle" part of the cut or two-sided tape. This will/should keep the round piece of wood where you have your jig connected to, from moving when you cut completely through the wood.

thx, Frank

[Hank]

Bent, you're on your way to an addiction. You have been warned :twisted:
Let's see...you can stack your baffles and drill your circle jig pivot holes at one time IF your drill bit is perpindicular. And you can route a through-hole through a very thick baffle sandwich from both sides of the baffle, and again, your jig pivot hole must be exactly perpindicular or the through-hole will not have even, smooth edges. I recommend you purchase the Jasper jigs. I have the original model and will buy the small one when I get around to it. I do all my hole routing with a smallish clone of the little-known 1/4" collet Freud router that has a dust collection port. That router is easier to handle than a big 1/2" collet unit and I haven't broken a bit yet - BUT you have to plunge in small increments - no more than the 1/4" the guys have recommended. BTW, my monster 1/2: collet Freud router is mounted in my router table/cabinet for the big jobs. Here comes my lecture on dust ports: buy routers with dust collection ports if you work with MDF. If you've never routed MDF with a router that has no dust collection port, you'll see/smell/feel what I mean after your first experience. Without a dust collection port hooked up to a shop vac, the mess will be terrible and you'll want to take the work outside, but then there'll be MDF dust all over your drivewas, grass and bushes. End of lecture.
My favorite place for router bits is MLCS:
http://www.mlcswoodworking.com/ I turned Jon on to them a year or so ago. That's also the source of those neat Merle clamps.
Now that your hooked, go make some MDF dust and enjoy the music :T

[Bent]

Thanks to both Gimpy and Hank - the 1/2" skil router I bought has a dust collection port, but I would need to buy (or rig up) the adapter - maybe I can utilize some PVC electrical conduit fittings and a inside junction box flange to make my own.

I don't know about routing the pilot hole in spite of my router having plunge capabilities - but I do have a couple of drill presses at my disposal. I also have cut some of the plexi to at least call it a "start" on costructing my circle jig.

[Hank]

Gimpy: good note on the tape. I use a couple of pieces of carpet tape that are long enough to stick not only what will be the cut-out disc to the scrap backing board, but also the baffle and backing board will not move in relation to the disc. When the router but cuts through, nothing moves.
Bent: I didn't mean to imply that I plunge the jig pivot holes with my router. I use my drill press for that, and in the case of a large subwoofer baffle that won't fit the drill press, I use a drill, carefully held perpendicular. I just bought a new DeWalt drill with a nifty feature; a built-in bubble level that will help me hold the drill perpendicular to the wood.

[taz13]

Ben
You want the ciic numbers for what you need for good dust collection?
Just happen to know as the skill router is the one I have here at work for the projects I do in here. And for bits Crap Tire has a reasonable set of 1/2" Mastercraft maximum on sale for $79 cdn 14 piece with multiple bearings for the kit. For normal home use they make a very good starting set and cost less then 1 of my roundover bits. :T

[Bent]

Taz, yup... that would be great.