How to cut masonite?

We need to cut some masonite to be used as templates. The shapes are only large circles, radii and straight lines. In some cases the templates are pretty big, several feet in diameter or larger, so in a lot of cases it is hard or impossible to mount them on machine tool beds.

We tried a scroll saw first. That has the problem that the table does not easily accommodate guide fixtures and it takes a lot of skill to freehand a circle or line using a scroll saw. Also, the line produced is never perfect, but has little tiny jogs in it. Also, the typical scroll saw has a 20" size limit.

The next idea was to use fly cutters. The problem is that the masonite is soft, so the cutter tends to dig it up and form wharfs on the work. I think if the geometry of the fly cutter was correct, I might be able to get a clean circle, but before doing a lot of experimentation with different geometries, I wanted to ask here to see if anybody knows the right shape.

Another idea I had was to use some kind of Dremel setup. Like make a circle cutter and mount the Dremel in it and use a small end mill.

Obviously, I could be sending it out to a waterjet shop or something like that, but it would make my life simpler if I could do these templates in house.

I usually cut it with a jigsaw with a fine tooth metal cutting blade. Small pieces I use the band saw.

If real accuracy is needed, make Al sheet templates in sections, then locate each section as needed on the Masonite board, then use a hand-held router with an appropriate "bearing guide" bit to shape the material.

https://www.amazon.com/Trim-Router-Bits/b?ie=UTF8&node=686959011

It's more work up front, but allows more conventional machine tools to cut the template shapes, the routing guide allows for good fidelity in the final part.

Send it out to a cnc router shop...

Use a roto-zip. You can make simple radius adapters for any size you want.

I hope you're using masonite that is double tempered (smooth and hard on each side). How accurate do your dimensions need to be?

A sharp carbide end mill or router bit will cut it cleanly. Good suggestions above on using a router or laminate trimmer. You can also use or make a router table, with the router mounted upside down under the table. A simple piece of 3/4" mdf will work. Then you can spin circles by using a pin or nail in the center, or make some sort of adjustable gizmo. All sorts of this kind of stuff in the woodworking world out there. You can also cobble up some thing on a B'port or similar. Board fixed to the table, cutter overhead, spin circles on dowel pin. Fine adjustment with the table. Use the highest spindle speed.

I would use a router on a long radius arm, on the floor with something sacrificial under the cutter path. And knee pads!

George B.

I think I may have found a solution. There is a line of flexible shaft grinders made by a company called "Foredom". Wood carvers use them. I can put a roto-zip bit in the handpiece of the Foredom and then I can mount the handpiece, which is cylindrical, in a rotary fixture. In our case, we need to cut both large and small radii, so I can have one fixture for small radii, and a larger radius arm for large circle cutting. To cut the straight lines, I can make carrier sled that holds the Foredom handpiece and rides on a Festool rail. The Festool rail can be clamped to the masonite. Am I missing anything?

jscpm said:

I think I may have found a solution. There is a line of flexible shaft grinders made by a company called "Foredom". Wood carvers use them. I can put a roto-zip bit in the handpiece of the Foredom and then I can mount the handpiece, which is cylindrical, in a rotary fixture. In our case, we need to cut both large and small radii, so I can have one fixture for small radii, and a larger radius arm for large circle cutting. To cut the straight lines, I can make carrier sled that holds the Foredom handpiece and rides on a Festool rail. The Festool rail can be clamped to the masonite. Am I missing anything?

Click to expand...

I have been using Foredom flex shaft tools for decades and have a bunch of them. They are good for the small work I do, both in wood and metal. I would not use one to cut out shapes in Masonite. The motors are not very powerful, the shafts do not like high torque and some of the handpieces do not have robust bearings. The Roto-Zip or laminate trimmer is a much better choice. A big woodworking circular saw is the best machine for straight cuts.

Larry

I agree with Larry. I have Dremels and Foredom tools, they are very light weight and not very rigid. OK for freehand carving and polishing, and maybe inlay. You'll be way ahead with a laminate trimmer (small router). Much bigger bearings, comes with a base, and can be easily modified for all sorts of clever tricks. Can also take 1/4" bits, which are going to be much better in masonite than 1/8"

I make cuts like that with the material on the floor ans a couple inches of insulation board under it. Works with router, jig saw, Rotozip, circular saw.

I agree with Larry & Richard IMO you can do all that with a small router trimmer, which can be got for a lot less than a flexidrive handpiece etc etc, .and are made for the job.

A router is hands down the neatest way to cut Masonite. A trim router will do just fine. I recommend the Bosch PR20EVS or similar. I'm very happy with mine after living with it a while. There are lots of accessories available and the plunge base has a very good dust port as well as a wider, more stable base than the stock base. For best finish, cut a little oversize with a conventional cut and trim to final size with a climb cut.

You can make a compass base out of Masonite, using a screw point for a pivot.

I strongly recommend that you get the ultra-flexible 35mm vacuum hose. It's 16 feet long and more flexible than any other I've used. My only bitch is that the Bosch nozzle and tool adapters don't fit as well as I'd like. I use gaffer's tape to make sure they don't pull loose.

Good point on the vacuum, don't want to take that nasty dust home with you, neither internally nor externally.

jscpm - I'm curious, when you say these will be for patterns, is that for laying out stock, or for some sort of template following device?