Logan 750 Simplex Plus squaring problem


CGF II, Certified Grumble Framer Level 2
Sep 22, 2003
I've been having trouble cutting square mat blanks with my Logan 750 Simplex Plus mat cutter.
It's not such a big deal on single opening mats but mutli's are making me crazy. I'm currently working on two 20x24's with openings for 8 5x7's, three verticle top and bottom rows, two horizontal in the middle row.

I thought I'd try squaring up the mat board with a carpenters square before putting in the mat cutter. That didn't help.

If the squaring arm stop is set on 20" for example, and I line a ruler up at the the top edge it will measure 20 1/8"

I put the carpenter's square along the mat rail and the squaring arm like the manual said and all looks to be sqaure.

Today I wasted three hours and two sheets of mat board today trying to figure out what I'm doing wrong.

Thank you
This is a goodie. A lot of people don't realize this but some (most?) of those $15 carpenters squares don't come perfectly square. You have to adjust them. The most common way is to use the 3, 4, 5 triangle method. A perfect right angle triangle is formed if one side is a multiple of 3" the other side is a multiple of 4" than the hypotenuse would be a multiple of 5". In use you would measure the short side of the carpenters square to 12" and mark it (if the ruling doesn't match up perfect with your ruler, another common problem) then measure 16" on the longer side then check the hypotenuse for a perfect 20". If it's a little more than 20" set a center punch about a 1/4" in from the outside corner of the square and smack it with a hammer. Keep doing that moving your punch around a little until you have a perfect 20" hypotenuse. If you measurement is a little less than 20" you put your punch in towards the inner angle and punch it there. This is how all the old time carpenters adjusted their squares. Nowadays we tend to assume that they are perfect right off the shelf but there is a reason why people pay $100 or more for a machinist square instead of using a $15 carpenters square.

Another tip is instead of using a carpenters square find the largest draftsman's or architects triangle and use it instead. They have a tendency to be more accurate than a carpenters square.

Check to make sure your squaring bar is perfectly straight, if it has a little curve to it than different sizes of matboard will sit against it differently making one size perfectly square and another will be off. Same with your cutting guide bar. Unfortunately I don't know of any cure for warped bars except replacement.

Of course the final point is that there is a reason why most of us use the more expensive professional cutters….they're more accurate and tend to stay that way.
Thanks for the info Frank.

What does the punch treatment do for the square? I don't get it - so to speak. Am I to make holes in thes square? Call me dumb.

And how do I know a 'professional' mat cutter from a 'non'? I can't buy a CMC.
If you put your square against a straight edge, eg. a table top and draw a line: then turn the square over and draw another line on top of the first.... it will be square if the two lines overlap exactly.
When you use the punch you are expanding the metal either on the outside of the square to bring the angle in or in the inside corner to bring the square out. You don't actually make a hole you are just expanding the metal. Once set the squre will stay that way if it is not abused.
Originally posted by Rosalyn:
What does the punch treatment do for the square?
Punching the outside or inside of the square causes it to bend in or out. Think about a mitered corner of wood...if you were to slip a wedge into the outside of the corner it would cause the two pieces of wood to move inward towards each other and the opposite if you wedge the inside corner. The punch is acting as a wedge on the carpenters square. I should point out that you should set the square on a hard surface like another piece of steel or maybe the concrete floor. Otherwise you'll just bend the square. The punch has to actually penetrate into the metal of the square.

And how do I know a 'professional' mat cutter from a 'non'? I can't buy a CMC.
The smarta$$ answer is "price". How can you tell any professional tool from any hobbyist or homeowner tool? Quality of machining, quality of finish, accuracy, heft, brand name, and recommendations from other professionals of course. Matcutters have been discussed many times on this forum. Most Logan products (not all) are built with the hobbyist or artist framer in mind. They are not built to take the day to day grind (OK...abuse!) of a busy frame shop. Probably the top rated matcutter right now is the new Fletcher Terry 2200. Price? It'll set you back about $1200-1500 depending on accessories. That's a lot more than you spent on your Logan but then again I've had my Fletcher 2000 for 16 years and it's still going strong. You'll never say that about your Logan, I know because 16 years ago I replaced MY Logan 700.