Best way to cut a perfect circle?

[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? 

[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]

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.

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.

[smalltownguy]

Thanks for the cool looking tool, but I'm just looking to cut my control panel overlay -- the adhesive backed vinyl itself.

I've already got all my holes cut perfectly to size in my panel, I'm just looking to get a nice circular hole cut in the overlay for my trackball opening. I'd stick it on my control panel and trace cut the opening from underneath, but I'd get a bit of overhang, which is unacceptable.

[bkenobi]

Have you considered installing the overlay first, then cutting across the opening a bunch of times (basically a bunch of x and + cuts).  If you cut enough, you can fold the art down and fix it on the bottom of the CP.  It won't give you a 100% perfect circle, but it will give you a nice looking edge that should do what you want.  The more cuts you make, the better the edge will look within reason.

[Bender]

your first idea is the the way to go, there are compasses or compass attachments that hold a #11 exacto knife
as long as you can find the exact center(which is easy with a regular compass) it should come out perfect
use a brand new blade
do it after the CPO is already stuck down to the CP

[smalltownguy]

In the end, I was able to take a 'low tech' approach with acceptable results:

The dirty deed:





And the results:



B/C my hole was nice and smooth, I was able to drag the razor blade right around the circle.
Thanks for the help, folks! 

[bungy]

Great job, looks real clean.

I have tried the same technique when trimming the vinyl on the sides of my cabinet and it doesn't always work so well.

[javeryh]

Wow that took some cajones.  I would have been shaking with the razor.  Nice job!

[severdhed]

good job, looks like that turned out perfect

[telengard]

In the end, I was able to take a 'low tech' approach with acceptable results:

The dirty deed:


And the results:


B/C my hole was nice and smooth, I was able to drag the razor blade right around the circle.
Thanks for the help, folks! 

As I was reading the thread I was going to suggest a razor or exacto, which is what I do.  Seems you figured it out, looks good!

~telengard

[bkenobi]

If there's any chance that the adhesive will peel while cutting, make sure to cut towards the CP.  If you cut in both directions and the overlay pulls up, you will get ugly mars.  Looks like your's turned out great though!

[rEd86]

I know your post was more regarding cutting out the CP overlay, but I wanted to share a jig that I used for cutting the hole in the wood top for the Electric Ice-T track ball I just mounted in my build.  It replaces the base of a router and does a great job of cutting a perfect circle from 1" to 7.5" in 1/16" increments. (for those here in the US)

It's the Jasper 400J Model 400 Router Circle Cutting Jig and sells on Amazon for less than $22.  Your local Rockler store might also carry them.




It is easy to use and a versatile tool to have if you need to cut various size circles in wood.  A must have for anyone with a router.

--Ed

[Percipio]

Looks nice!  I was recently doing the same thing.  Thought I'd post in case anyone else comes across this thread. 

I used a tool that I originally bought to cut a hole in the resonant head of my bass drum.  It's made specifically for cutting holes in bass drums.  I found it at my local drum shop, but it's available online at Musician's Friend and other places.

http://tinyurl.com/nnxs45

You set the pivot point in the middle to the size, and the cutting wheel on the edge cuts the whole.  I set the size to 3" and it worked great for cutting the trackball hole in my CPO. 

Hope this is useful for someone else!!

[smalltownguy]

For those of us who are lazy 

This thing looks GREAT! I'll have to get one.