What tool or technique is best for cutting circles in matte board?

Question

I am laying out a frame where I will have to cut approximately 200 aligned 35mm circles in a matte board or foam core board. I will be putting plastic coins into the holes and backing with another board (exposed foam board or something with a little give to mould to the piece) to secure the coins from sliding or rotating.

I purchased a Fiskars Circle Cutter but have discovered through testing that while the device can make the circles, it lacks the depth to cut through the whole board. I checked to see if they sell a replacement blade with more exposed length but they do not appear to.

This then resulted in me fiddling about with an Exacto knife trying to make a clean completion cut.

If I had to do a few holes I would accept this method, but I am somewhat nervous at the thought of repeating the process 200 times without scoring or marring the matte.

Is anyone aware of a simpler technique?
I believe a punch is probably the correct tool, however I am reluctant to invest too much for a one-off project. I also considered using a bore saw and my hand drill but am concerned that it would just make a horrid mess of things.

Answer 1

Several years ago I had my own "mount these coins" project. My solution was to use a forstner drill bit mounted in a drill press. In my case I was mounting dimes in matte board and they squeezed into the holes very nicely. It sounds like you are mounting US fifty cent pieces which are slightly larger than the 30mm that you mentioned, but should be able to nicely squeeze-mounted in 30 mm holes.

If you Google "50 mm forstner bit" you will find several choices ranging in price from $9 to $25. If you are going to drill only 200 holes in matte board, a less expensive bit will certainly be adequate.

You will need to carefully mark the locations of the centers of the holes and I would push an awl through the matte board to help make certain that the tip of bit goes to the exact center of the hole. As with any first time project, it would be wise to make several practice holes so that you certain that you can get each hole started exactly where you want it to be.

You will want to set the speed on the drill press to approximately the middle speed on the drill press.

Of course if you do not have access to drill press (any woodworking pals?) all bets are off. I would not try this method with a hand held power drill because the quality and consistency of the holes is quite likely to suffer.

Answer 2

A hole saw should work fine if you can find a fine tooth model. They are not as easy to find as the common coarse teeth models meant for wood. One with a thin kerf would be best.

I have also used the sharpened steel tubing trick mentioned by @fred_dot_u. An alternative to punching is pressing the sharpened tube against the board and spinning it. The spinning action makes it work like a circular knife, cutting the fibers cleanly. If you can't find a 35 mm steel tube, you can get almost as good a result by wrapping thin aluminum from a soda can around a 35 mm thick piece of plastic or wood.

To align the holes perfectly, it will help to make a template. Cut three holes in a smaller piece of board, align two of them to existing holes on your workpiece and then put your cutting / drilling tool in the third hole to keep it in correct position.

Answer 3

You may be able to create your own punch by finding a piece of steel tubing of the correct inside diameter for your holes. Using a file or grinding wheel, work away at the outside edge of the tubing to create a sharp edge. Further refine the edge with sandpaper of gradually increasing grits.

You can stop periodically and test your work by placing a piece of the board atop the pipe, sandwich it between the pipe and a piece of solid lumber. Hardwood end grain is best, also more difficult to source, but for a 35 mm hole, not as bad as a 200 mm hole.

Rap the wood with a mallet until the hole is created. This process will eventually dull the edge, but you can touch it up with a file (or grinding wheel) as needed to keep a clean cut.

You can also place the lumber under the foam board and wallop the pipe.

Laser cutting is an option if there is a suitably equipped maker space, but that will leave burned edges unless the power is quite high. My 60w laser will create discolored edges and also under-cut (melt) the foam in foam core.

Hobby cutters may work but require more than one pass. CNC routers will definitely work (maker space possibly) and if one equips a CNC router with a drag knife, you're good to go.

Answer 4

Have you tried using the circle cutter from the front and back? On mine the centre pin is long enough to mark the back of the foam board I've used, but you may need to push a stiff pin through in your case.

You do need to be very careful to hold it exactly vertical if you're doing this, or the holes won't align, but that's always true in thick material.

Answer 5

You're gonna need a bigger boat! .. I mean knife ..

The simplest would be to have a blade manufactured (or 3d printed if that gets sharp enough edges?) that meets your criteria, e.g length. if you order a bigger batch, they might get cheaper.

Also you could try finding a blade from another manufacturer and then build an adapter to fit it to yours. If you post some photos, people could come up with solutions.

Answer 6

A "circle clicker die" in a "clicker press" will do the job cleanly and efficiently at just a few seconds per hole. Circle clicker dies are available online in many sizes, and a clicker press can be found in any shop that makes leather goods. The shop might even have the exact size clicker die that you need. If you lay out the matte board with appropriate pencil marks where the holes need to be, it should all go smoothly.