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Best way to cut a perfect circle?
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smalltownguy:
I'm going to be printing my CP overlay soon, and I'm struggling with how to cut the hole for my trackball. The rest of the buttons I'm not too concerned with, b/c the pushbuttons have a skirt on top that will cover the edge of the cutout. The trackball though, will need a carefully cut hole.

I've considered mounting an exacto knife blade to my compass, tracing a circle wood blank with a razor, free-handing it (!!), I just can't seem to come up with any sort of method that I'll feel comfortable with.

So far the only method I've come up with that will get me close to comfort would be to mount the trackball housing without the ball, punch through the overlay with a razor blade, and drag it around the perimeter of the hole.

Does anyone else have any better ideas?  :banghead:

Gamester:
Do you have a lexan top for your CP?  If so, you could use that as your template.  Otherwise your idea of mounting the plate and using the whole CP as a template seems like it would work to me...
Rusty Shackelford:
If you can get a hole cut into a bit of scrap wood with say a hole saw, use that as a template. Or make a template with your cutting method untill you make a perfect circle. Then follow it with a router and pattern bit.
smalltownguy:
No, my CP is metal. The Happs trackball does have a slight lip that comes up flush with the CP, and I'm not sure if I should be cutting the overlay to expose just the opening for the ball, or if I should cut away the opening for the ball and the lip. My CP art is pretty brightly colored, and my trackball is white, so the lip would create a black ring around my trackball. Not a huge deal, but I'm not sure if it's the look I'm going for. Then again, I'm not sure if I cut it right to the edge that I wouldn't get a depression in the shape of the lip ring that will form around the opening after use.
Turnarcades:

--- Quote from: smalltownguy on July 27, 2009, 05:10:05 pm ---No, my CP is metal. The Happs trackball does have a slight lip that comes up flush with the CP, and I'm not sure if I should be cutting the overlay to expose just the opening for the ball, or if I should cut away the opening for the ball and the lip. My CP art is pretty brightly colored, and my trackball is white, so the lip would create a black ring around my trackball. Not a huge deal, but I'm not sure if it's the look I'm going for. Then again, I'm not sure if I cut it right to the edge that I wouldn't get a depression in the shape of the lip ring that will form around the opening after use.


--- End quote ---

Thank heavens for the U-Trak, which eliminates most mounting issues and saves time for cabinet builders like us. When it comes to cutting a perfect circle to size in MDF, we don't go with a standard hole saw, instead we use an adjustable hole cutter like this:



Though of course they are primarily made for cutting wood, they actually 'scribe' their way through rather than cut with teeth, and are better than using many standard hole saws where it is difficult to find the centre of the circle and begin cutting without slipping off - the centre drill bit creates a centre guide, keeping the cutting tips even as you cut down, with low friction.

Have a look and you should find one suitable for cutting metal.
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