How do I cut a perfect 3" trackball hole?

[javeryh]

I don't want to use a holesaw or a large foerstner bit because I don't have a way to make the bit exactly perpendicular to the wood.  I want to use the mounting plate to make a jig for my router.  Will this work?

1.  trace circle from mounting plate on 2 pieces of MDF.
2.  Cut once circle out LARGER than the circle I just drew (this panel will be a "spacer")
3.  Cut the other circle out on the inside getting close to the line (this panel will eventually be the jig)
4.  Drill holes in both panels so the mounting plate can lay flat
5.  Stack the pieces with the jig panel on the bottom, the spacer next and finally the mounting plate
6.  Use my pattern bit to cut out a perfect circle on the jig panel - the ball bearing will ride on the edge of the mounting plate hole
7.  Use the jig to cut the hole in my CP

This should work, right?  Am I nuts?  Is there something obvious I'm missing?

[nuka1195]

check out mountains arcade thread, not the jukebox one. he used the mounting plate with spacers.

[Neverending Project]

Maybe someone else with more woodworking experience can shed some more light, but in my experience using a pattern bit (or flush-trim bit) to cut through 3/4" MDF is going to cause it to get very hot. Hot enough to burn the MDF, possibly. They are designed to trim an edge to a pattern - but using it as a saw (in other words making a cut with it) is a lot of work for your little bit.

You could drill a small hole (1/4") in your CP (inside where you want your trackball hole to be) and rough-cut the 3" hole with your jigsaw first. This will greatly reduce the amount of material that your router needs to remove when you use your jig. If you don't rought cut out the hole, just take your time with the router, and you may want to take a couple of breaks to let your bit cool off.

[javeryh]

check out mountains arcade thread, not the jukebox one. he used the mounting plate with spacers.

Ahhh the spacer!!!  mountain is a freaking genius. 

Maybe someone else with more woodworking experience can shed some more light, but in my experience using a pattern bit (or flush-trim bit) to cut through 3/4" MDF is going to cause it to get very hot. Hot enough to burn the MDF, possibly. They are designed to trim an edge to a pattern - but using it as a saw (in other words making a cut with it) is a lot of work for your little bit.

You could drill a small hole (1/4") in your CP (inside where you want your trackball hole to be) and rough-cut the 3" hole with your jigsaw first. This will greatly reduce the amount of material that your router needs to remove when you use your jig. If you don't rought cut out the hole, just take your time with the router, and you may want to take a couple of breaks to let your bit cool off.

I definitely plan to cut out the middle as close to the line as possible!   

[Encryptor]

I just got got a 3" hole saw.


Encryptor

[scotthh]

By Mountain's thread, I assume you mean this post. Mountain uses Happ's spacer as a template/jig. The "spacer" javeryh refers to it the first post doesn't need to be a circle at all, it just needs to not jut out into the cutting area and support the router. This will enable the bearing on the bit to run along the trackball plate/spacer and the cutting edge to only cut the CP (not the trackball plate).

If you're only going to be routing one trackball hole, I would use the plate or spacer as your jig as Mountain did.  If you're going to be making lots of trackball holes, I think this is a fine idea and you'll have a great jig. Just to clarify, to make an MDF jig, for step 3, you're going to need to use the pattern or flush-trim bit with the mounting plate or trackball spacer as the guide.

[javeryh]

By Mountain's thread, I assume you mean this post. Mountain uses Happ's spacer as a template/jig. The "spacer" javeryh refers to it the first post doesn't need to be a circle at all, it just needs to not jut out into the cutting area and support the router. This will enable the bearing on the bit to run along the trackball plate/spacer and the cutting edge to only cut the CP (not the trackball plate).

If you're only going to be routing one trackball hole, I would use the plate or spacer as your jig as Mountain did.  If you're going to be making lots of trackball holes, I think this is a fine idea and you'll have a great jig. Just to clarify, to make an MDF jig, for step 3, you're going to need to use the pattern or flush-trim bit with the mounting plate or trackball spacer as the guide.

That is exactly right.  I am going to be routing at least 1 trackball hole but I can't imagine this will be the last CP I ever build so I'm going to make the template.  Plus, the one I'm working on is going to be a wood stained top with no mounting plate (trackball will be mounted from underneath).  Since there will be no artwork, I can't drill the 4 through holes for the mounting plate - I'm going to be cutting the 3" circle and then removing material from underneath until I get the 3/16" thickness needed for the trackball to poke out of the top.