Oh, Help - how to cut masonite!??!


SGF, Supreme Grumble Framer
Jun 13, 2002
Fingerlakes Region of NYS
I mismeasured a double moulding for a portrait and need to trim the portrait that is mounted to masonite (by the photographer)...


How can I do this without ruining the portrait.

I have a Fletcher 3000 - but I don't think that'll cut masonite?!?

Rattled Roz

I did the same thing earlier this week. I had a rush order that included a deep scoop linen liner from one frame supplier and a stacked frame from another supplier on 2 large canvasses. I measured the canvasses, measured the foot of the liner to find out how much allowance to give for the stacked frames, and ordered everything UPS red label. Now you have to consider that the liner chops are coming from supplier A and both sets of frames are coming from supplier B and both suppliers are relying on MY accuracy with the measurements!

Everything came in Tuesday and the liners fit the canvasses perfectly! End of the good news!! The frames were 1/4" too short for a proper fit on the liners!! I called the supplier frantically and nobody had any ideas other than to red tag another set of long legs in for each frame and cut the short legs out of the long legs that I already had in the shop.

That would have killed my profit on this job so I decided to try something out of the box. Luckily the inner frame of the stacked frame combination was beefy enough and wide enough that I had an option to try. I set my table saw to the depth of the rabbet of the inner frame and shaved about 1/8" off each leg of the smaller frames from the bottom up. In other words, I added 1/8" to the horizontal size of the rabbet thus making the opening of the joined frame 1/4" larger. After dry checking to ensure that I allowed enough room for proper fitting, I joined the frames and they fit the liners like a glove!! And the outer frames were already chopped to fit the outside of the inner frames so they were a sure fit from the get go.

Bottom line, Roz, if you have a table saw and enough wood on your mouldings to widen the rabbet enough to accept the masonite, you could try the same technique. It may be better than cutting down the artist's mount board and possibly damaging something in the process.

(And ripping almost 4' long moulding in this manner does tend to separate the big dogs from the house pets!!)

(Picture that l'il guy with a stump for a thumb!)

Good luck, gal.

Framerguy -

Sorry about your project.

No table saw here - and not enough wood on the liner to accomodate even if I did!

I have a bud in the area - but my worry is damaging the portrait that is already mounted - eeee...

Masonite is just a bunch of layers of woody/pulpy/yukky stuff - can't be impossible to cut through - can it?
If that's your only recourse, I'd use a very fine toothed blade and run the masonite through a table saw to shave down enough from the edges of the portrait to fit into the frame.

You won't harm the portrait if you keep it face up on the table saw table. And a fine tooth blade will give you a clean cut on the masonite.

Good cutting.



Make sure that your blade is very sharp!! Masonite doesn't respond well at all to dull saw blades.
Originally posted by Rozmataz:
Framerguy -

Sorry about your project.


No sorry involved here!! :cool:

That idea saved my butt and put nearly $1300 in my pocket from an ex-pro football player who was the subject of the canvasses. His girlfriend brought them in and price wasn't an issue at all. She had to have them this week and I did what had to be done to accommodate her wishes. BTW, it was her idea to Red Label the moulding in!! She paid for the shipping and the rush to get the job done.

Roz -
If you are considering cutting the portrait, why not ask the photographer to do it - better that he/she screws it up than you ;)
That said, if it's a case where you needed it yesterday - - - I would first score a line (using a new blade in your 3000) on the portrait side - use a slip sheet between the clamp and the face of the photograph. You could then make several cuts through the masonite, but it will take all day. Or use a circular saw to trim the masonite - be careful again to protect the surface of the print. It's also going to be very dusty - so do it outside.
Actually, I would probably admit to the screw-up w/ the frame and just ask them to wait for the new moulding to come in.
I have cut masonite with the straigth edge cutter on my C&H. You got to take a lot of passes to get it to cut through, but it is a little safer than running the masonite through a table saw.

I had the benefit of not having the photo mounted to the masonite, I was cutting it for support inside a shadowbox (don't ask!)

I had a customer who had a 4' by 4' sheet of masonite that he had painted on. Of course it wasn't square, so I did trim it down by clamping my 48" rule to it and cutting with my box cutter. Again slowly and with many passes.

If you try cutting it why not get a scrap from the lumber yard and practice cutting it. The mat cutter gives a consistent straight edge.
Oh, boy... I am a patient person.. so I'm trying the all day long project of many passes... the cost of the mouldings is way more than my time at this point! And I don't think the photographer does this himself - he probably orders it "in" this way...

This goes down as a really dumb mistake and/or mismeasure of all time.

Wish me more luck (and patience!)


Roz, I had a customer while I was posting, so I didn't see the other responses. You can cut Masonite with a utility knife and a straight edge. Don't use a table saw, too dusty, too much clean up after the fact!

Be brave use your utility knife! You can do it.

Oh BTW if you "mess up" I never wrote this!! ;)
I used to trim masonite all day long years ago when we used it for flooring underlayment under vinyl flooring. There are two types of masonite. Tempered (hard) and untempered (somewhat softer). However they both can be hand trimmed. Use a good straight edge (must be non-slip bottom) and a good Stanley (utility) knife. Just take lightly firm score after score till you get through. Don't spare the blades. Keep it sharp. Doesn't take that long and I could trim as little as an 1/8th of an inch off with no problem. 1/4" is what I worked with....yours may only be 1/8" thick.
Hope this helps...and I understand your problem.

Use the mat cutting blade on the 3000 and cut in from the face. It will take multiple passes - but not that many with a sharp blade. Make the first passes holding off some of the spring pressure. Then let the spring do the work. You will be surprised how fast it goes.

Pat :D
I'm so grateful to all of you. And Bob, thanks for the extra "attagirl" - I'm working thru it... it's not that bad.... slow but sure - careful!! Don't want a more costly mistake than I already have!!
Another tool you can use is a plexi cutter. I have one with a hefty black handle that holds the cutter blade The blade is a sort of hook and will scrape a groove in the masonite the same way it scrapes the plexi. You do need to cut thru the portrait mounted to the masonite with an exacto blade first and remove the piece before going to work on the masonite. The masonite will score thru just like the plexi and when you are almost all the way thru, you can shave the rest off with a utility knife. That and a wood rasp file to finish up. I do this when ever a customers piece isn't square.
It's done.

It only took 4 full length breakaway blades (totalling about 40 blades!!) and my rotary cutter!!! The rotary cutter was the kicker!! Like cutting thru a thick crust of pizza. And side with the grain went alot faster! I now have carpal tunnel in both hands!! (Sort of, or just using muscles I don't normally use)

Thanks for all your support!!
One thing that would have been interesting to know with this is how far off you were in your measurements...it must have been quite a bit?
I know it's a bit late for you at this point (no pun intended), but I've got one word for you:
Roz, you are actually very lucky. Really!

Normally, when these kinds of things happen, the photo is too small for the stacked, perfectly joined frame.

"Hey, look. I threw in a fillet. No extra charge!"

Originally posted by Rick Granick:
I've got one word for you:
Pssst! Rick, that's two words.
Hey, look, a new Wisconsin Grumbler!

Welcome, Julie.

That makes, what, about 6-8 of us? We're catching up with North Dakota.

Kit, how 'bout a survey?

[ 03-11-2005, 08:43 AM: Message edited by: Ron Eggers ]

Actually I didn't mismeasure. I was originally designing the piece for mats when the customer decided to change to moulding with linen liner... and Duh-umb me - forgot to change the image size.

The difference was enough to give me something to trim not just shave off the edge!!

Relieved Roz
I've used a hand held belt sander to trim masonite down. Clamp the masonite over the edge of a table and hold the belt sander vertically. A third hand with a shop vac will help keep the dust down. It's messy but safe.