Hooked Corners

[scottonnob]

Okay, somebody please help me. I CANNOT cut a mat corner that is not hooked. I just bought a relatively new C&H cutter, thinking that would solve the problem, but I still get hooks. I've used a board underneath the mat, all sorts of blades, you name it -- and I still get hooks. And I just cannot believe that C&H cutters are incapable of perfect, 90 degree corners. I've seen other, apparently mortal, humans get even crumby, old C&H cutters to work beautifully.

Does anyone have any advise for someone in need of remedial education regarding the preparation of window-mats?

Thanks, Scott

 

[Ian Grant]

Welcome to APUG.

It takes practice to use a cutter - there's a knack to doing it well. Usually when I haven't cut mats for a while I practice cutting straight lines, making sure I start & finish cleanly at ruled line. When actually cutting the mats themselves I have some small surgical blades to finish any corners if needs be.

Ian

 

[Akki14]

Try holding the "waste" side of the mat board as well as the bit you want to keep. I find the the hooked corners come from that piece you don't want coming loose and pulling away.

 

[David A. Goldfarb]

Hooked corners are often caused by dull blades, and by not cutting into a clean area in the board underneath the board you are cutting. I just use a Dexter mat cutter and a T-square clamped to the table. Some people change blades for every mat. If I'm doing small ones, I change every few mats. If I'm going to cut a large board, I change the blade first. If the board used to line the table has a lot of cuts in it and the blade gets caught in a groove, that can cause wavy cuts and hooked corners.

 

[Reinhold]

Hooked corners are a sign of blade flex.

The farther the blade projects from it's holder, the more it will flex.
The thinner the blade is, the more it will flex.
If the blade holder cannot clamp the blade firmly ...at it's nose... the blade will flex.
If the blades bevel steers the blade outward away from the holder, it will flex.

Some things to try...

Try making a light shallow cut first; and then a full depth final cut. The shallow cut doesn't flex the blade as much and makes a "channel" for the final cut.

The C&H 1200SE single edge blade steers the cut inward toward the holder rather than outward away from the holder, reducing blade flutter.

Test the blade clamp by trying to deflect the blade. If it wiggles, shim the clamp. I stuck a piece of thin abrasive film into the clamp as a shim years ago. It's still there and eliminated that source of blade flex.

Don't cut too deep. The farther out the blade extends the more it flexes. If you're pushing down too hard on the bar you could be reverse flexing the cutter rail and lifting it off of the matboard, which lifts the blade out of the cut. This makes you think that the blade needs more depth which in turn means more blade flex.

Watch your speed. "Slashing" at start-up can wildly steer the blade. Steady does it...

Make certain the cutter head bearings don't wobble (unlikely, but verify to be sure...)

C&H cutters are good machines. With a bit of tweaking and some practice you'll be glad you have it.

Reinhold

www.classicBWphoto.com

 

[Vaughn]

The way I avoid hooked corners is to start the blade 1/2 inch or more before the corner and get the blade at least halfway into the board before reaching the corner (this is with the Logan mat cutter). I find starting at the corner and pushing the blade all the way in tends to bend the blade slightly -- the blade then straightens out as you start the cut -- thus creating the hook.

Good luck!

vaughn

 

[scottonnob]

Thanks for all the suggestions. I'll try again tonight. But, mostly, I'm encouraged, in that all of you are suggesting that there is no reason that, with a repeatable and practiced system, I shouldn't be able to get great corners. I won't give up just yet. Scott

 

[scottonnob]

Reinhold, Okay, dumb question: which way to place the 1200's in the cutter? Being single beveled blades, I'm assuming only one end is useful. But which way is the bevel supposed to face when clamped? Scott

 

[Reinhold]

Scott,

The C&H single bevel blades are marked. An arrow points to the correct corner.

The basic approach is that the ground bevel faces away from the hold-down rail. This directs the cutting force toward the firmly held matboard and helps prevent the blade from trying to climb up the inclined plane at the cutting tip.

When I said "if it wiggles", I meant to say "if the Blade wiggles, shim the clamp to stop the blade from wiggling".

Yep, only one end is useful... for cutting bevels. But... turn it around and use it on the straight cutting side. It's a tad thin as a cut-off blade, but it's free and plenty sharp.

Years ago I fought the hooked corner hassle, but single edge blades put a stop to a lot of growling.

Vaughn's suggestion is worth trying too, but you'll need to learn exactly when to make the final plunge so your corners don't show overcuts.

Remember... no growling at that nice matcutter...

Reinhold

www.classicBWphoto.com

 

[scottonnob]

Great! Yeah, I saw that the blades were marked, but I thought it unusual that the mark would point away from the side that could be seen. And, as far as the shimming is concerned, are you putting the shim on the any particular side of the cutting clamp? But it seems to me that a shim that made the whole thing real snug would be important. And what sort of materials would you recommend for a shim? I'm not sure what you were referring to by "abrasive film". Again, thanks, Scott

 

[Reinhold]

Scott,

Here's a fuzzy foto of the junk I tacked onto the upper jaw of the clamp. It was done so long ago that I forgot that it's a collection of Scotch tape, a bit of thin aluminum, and a fragmet of microfinishing film I happened to have.

The whole accumulation is enough to firmly clamp the blade between the jaws and eeeeliminate blade flex within the holder. It's been there for years...

Reinhold

www.classicBWphoto.com