Cutting circular corners in beveled mat

Question

I have a silk-screen print on a square sheet of paper. The corners of the printed area are arcs with about a one inch radius.

I would like to cut a beveled mat for this print with the opening about a half inch larger than the print area, but I cannot come up with a way to cut the corners.

If I were making a non-beveled mat, I would use a compass with a blade to make the cut, probably making multiple cuts to make it all the way through the mat. I would cut the arcs first, then join them with straight cuts.

One way to do the beveled arc would be freehand, following a drawn curve, but I know that I don't have the steadiness to pull this off, certainly not so that all four corners would be identical.

Another way would be to use a compass as mentioned above, and arrange the swing leg so that it doubles back to cut at a 45 degree angle, but for it to work it would have to be done in one pass. (If done in multiple passes, each pass would be a slightly different angle, or some magic adjustment would have to be made for each pass.)

For the straight cuts, I have a Logan beveled mat cutter. (in the old days I just made multiple cuts holding the knife a 45 degree angle - of course being freehand after the first pass, each cut was at a slightly different angle from the previous and the results were not always pretty.)

I am hoping there is some way to cut the corner arcs with a device that would produce clean bevels like I get from my straight line bevel cutter.

Does someone know how to do this?

Answer 1

They actually make tools for this. They're called circle cutters. Some of them have the option to do a beveled opening. They're designed to make full circles or ovals but I'm sure you could use them for partial ones, too.

As an example this one has excellent reviews on Amazon and is made by the same company as your straight mat cutter but it looks like it may not be small enough as the minimum circle diameter is 4-3/4 inches and you said you wanted a 2 inch diameter circle.

Here's an example of a mat cut with this cutter:

Hopefully you'd be able to find a similar product with a smaller diameter.

Answer 2

Option 1: CNC A DIE

If you have access to a CNC metal milling machine you could machine a die cutter that is the exact size of your print.

Make it with a CAD program the radii would all be exactly the same and in perfect alignment.

Stamp it out in a single go.

If you yourself don't have a milling machine then a local makerspace might. There is always custom machining shops but it could be expensive.

OPTION 2: VINYL CUTTER

Another option is to feed your prints through a vinyl cutter. These machines are computer guided swivel knives. Let the machine do the cutting for you.

Again, if you don't have a vinyl cutter then checkout a local sign making shop or a local makerspace.

Option 3: CUTTING GUIDE AND SCALPEL

One more option is to use a cutting guide and disposable scalpel (ex. X-ACTO brand scalpels).

The cutting guide would be machined, from metal, with a bevel angle like you require and corners rounded to the desired radius.

On top of a self sealing mat you would lay your board down. On top of the board you would then place your cutting guide and get it into position. Remembering to position the bevel guide in the right orientation. Once everything is in place heavy weights would be placed into the cutting guide. These weight are what are going to hold the cutting guide in place while you make the cut. Do not hold the guide down with your free hand!

Using a disposable scalpel you would run the scalpel following the contour of the guide. This scalpel is the reason for using the weights to hold down the guide instead of your free hand. Scalpels are incredibly sharp. They are also very dangerous!

Here's a sketch of what it would look like.

Note: I think I got the bevel edge backwards. You would probably want to cut the back of the board and not the front. Also by cutting on the back of the board you could spray adhesive to better hold the cutting guide to the board. Still use the weights. The spray adhesive and weights would hold the cutting guide very well with little worry about it slipping during the cutting process. Also by flipping bevel the other way would be easier to see exactly how and at what angle the scalpel is penetrating the board.

Option 4: CNC MAT BOARD CUTTING MACHINE

Find a framing store in your area that has a computer controlled CNC mat board cutting machine and pay them to cut it for you. These machines can cut any shape and have the ability to do bevel cuts as well.

Example: Valiani Maximus CNC Board Cutting Machine http://www.valiani.com/computerised_detail.php?ID=17