BillFitzmaurice.info

Started building on a slim Tuba HT a couple weeks ago. I'm still a little nervous when cutting but I have gotten better. So far I have the sides cut, the access cover cut, pretty much
cut all the panels in one day. Today I tried to cut the baffle and ended up cutting an inch too big. I don't know how I did that. I never cut speaker holes before so I am really trying to
get this right. Also, I think I made another error. I cut the hole diameter exactly 12" inches. I am sure I was supposed to cut to the inner diameter of the speaker gasket is this correct?
I was using the Rockler Circle Jig and I could have sworn the instructions say to measure from the outer edge of the bit to the center of the pivot screw. How an earth did I mess that up?
Also can anyone confirm that I can assemble the panels with right angles and not really have to make those small angle cuts. I am working on getting pictures up soon. I can't seem to
remember how to get the high definition pics to the right size required without losing a lot of details.

When using a circle cutting jig, you also have to take into account the diameter of the bit you're using. I'm assuming that Rockler jig is a router jig? I have the acrylic Jasper circle jig, and it is sized for using a 1/4" straight bit. If using a 1/2" bit, you must add another 1/2" to the pivot hole you use. I.E. if using a 1/2" bit, if I want a 12.0" circle, I have to place the pivot pin in the 12.5" hole. I hope you bought a sheet or two of spare ply. Building speaker boxes is unlike building anything else...so many different types of cuts to deal with. Angled panels, hole cut-outs, handle holes, etc. Keep posting; we'll help you.

*edit*
Reverse the math on what I said. For a 12.0 circle, you set the pivot at 11.5" IF using a 1/2" bit. Thanks, Tom.

miked wrote: I have the acrylic Jasper circle jig, and it is sized for using a 1/4" straight bit. If using a 1/2" bit, you must add another 1/2" to the pivot hole you use. I.E. if using a 1/2" bit, if I want a 12.0" circle, I have to place the pivot pin in the 12.5" hole..

I don't have that jig, but, shouldn't you put the pin at 11.5"?

Tom Smit wrote:

miked wrote: I have the acrylic Jasper circle jig, and it is sized for using a 1/4" straight bit. If using a 1/2" bit, you must add another 1/2" to the pivot hole you use. I.E. if using a 1/2" bit, if I want a 12.0" circle, I have to place the pivot pin in the 12.5" hole..

I don't have that jig, but, shouldn't you put the pin at 11.5"?

/faceplam

You're correct. I "put the numbers the wrong way"...I went up instead of down. I had a few last night...I don't do the maths very well when I've got a little buzzy-buzz going.

Thanks miked for that tutorial. I see now where I went wrong. I originally measured from the front cutting edge of the bit
to the center of the pivot. I am using all 1/2" bits. I didn't take into account that the back edge of the bit was going to be
within the circle. Oh and yes the Rockler Cutting Jig is for routers. I do have a spare sheet of plywood. So I'll be able to cut the
panel over.

Edit. I meant to say that my router bits are 1/2" blades for cutting on a 1/4" shank.

I keep tons of scrap wood around for this very reason. When in doubt, make a test cut on scrap to see if your circle is the correct size.

Tip: The wood cutting area at Lowes and HD typically has a dumpster of some kind nearby; they throw off-cuts and "waste" in there. I have found 2x4' sheets of plywood with one busted edge in there. I simply ask if I can have it, and they write something on the wood and I make sure to show it to the cashier/security guy. You can't beat free.

I made a circle jig that is infinitely adjustable, from a trammel head point and a beam attached to the router base, but you can use a commercial type circle jig as well. What I do is draw my circle first with a compass, and then make an smaller diameter, shallow (1/16") trial cut, and then fine adjust the trammel head until I get the outside of the cut on the pencil line. Once it's set to the desired size, I repeat the cut a little deeper, 1/8" to 3/16" or so, and then hog out the center with a sabre saw, close to, but still inside of the finished line.

After the center is removed, I just use a flush cutting bit with a top bearing riding on the 1/8 deep cut as a guide to clean up the small amount of wood left after sawing. This sounds like a lot's of steps, but it's fast, repeatable, cuts a perfect finished circle and lends itself well towards making multiples at the same time if you are building a number of boxes at the same time.

Small diameter disks like for a phase plug, I make like this:http://www.youtube.com/watch?v=Wxbzrf4z_cg

Hi kenkenni

Sorry, but yes you really have to make all those little angle cuts, and no you can't just cut them square.

There's a bunch of reasons.
The first is ensuring your cab is airtight. PL will fill little gaps, but can only do so much because it's an adhesive. A cab not being airtight is one of the most common reasons for Bill's designs to not perform as well as it should.

Structural intergrity. The two edges where the PL adheres need to be able to mate together to ensure maximum bond for cab strength. Otherwise we'd be using what everyone else does, 3/4" ply to get that structural integrity.

So just take your time with it all. It does get easier

This sunday I couldn't get much done because of the rain, but I did manage to re-cut the baffle to correct size
and I also cut and completed the spacer. I figured out what was going on with my cordless circular saw. I had to
change to the correct blade that actually spun in the correct direction. Still working on getting up pics.

Have pics but I can't figure out how to get the images to post from Photobucket.

Can't figure out this pic thing. Using Photobucket, everytime I copy
the image url and post no picture shows up.

After you copy the image in photobucket, you have to click on IMG on the reply page and copy the image in there. Then it will show up. It's just like posting a link, but you use IMG instead of URL.

I just tried it but all I get is the actual text or a link to the image. I still can't get a picture to show in the reply

I give on the pics tonight. I'll try again tomorrow.