Achieving Square Cuts

[PhotonPhotographer]

I'm going mad. I can not for the life of me achieve 90 degree angles with straight lines. I've been using a metal square with both a rotary cutter and a sharp knife with no success. They always come out somewhat cockeyed.

[RockyAussie]

Maybe chuck that square away. Do you wear glasses when cutting? that can distort things a fair bit unless your looking straight down. If you pull knife toward you curl in at the end a bit and if you push away curl in a bit. The knife will veer away as the thinner piece gets close to coming off. Have fun

[TheCyberwolfe]

The only way to achieve a truly straight 90 degree corner in an organic product (wood, leather, etc.) is to use clamps and machinery. You're never going to be 100% doing it by hand, so shrug it off and reach for the sandpaper

[MADMAX22]

What kind of knife are you using? 

Straight cuts are achievable or atleast pretty darn close. Sand paper wont give you a straight edge unless you have a good sanding block and you still run into the same issue of keeping it straight to the edge. 

With my round knife I can get a good straight edge, with one of those box cutters I personally cant control it worth nothing unless its very thin leather.

[Dwight]

Personally I own a whole slew of knives of different sizes, shapes, . . . round knife, . . . butcher knife, . . . pocket knife, . . . little plastic box cutter, . . . standard "Stanley" box cutter (4 of em), . . . and a couple other "specialty" blades.

Sometimes I use a square, . . . sometimes a rule, . . . sometimes a line on the leather, . . . sometimes a plastic triangle, . . . they don't help the 90 degree part, . . . just the line being cut where I want it.

The Stanley box cutter is for me THE BEST.  

First thing I do when I put in a new blade, . . . it gets stropped 25 times in each direction.  Periodically, . . . it continues to get stropped as needed, . . . 

There comes a time, however, . . . when for some reason I have yet to discover, . . . it no longer wants to sharpen.  I turn the blade around and start again on the other point.  When it won't strop up nice and sharp, . . . I toss it.

The KEY thing, . . . MOST IMPORTANT thing to making good cuts, . . . is a SHARP, SHARP, SHARP cutting instrument, . . . AND, . . . practice with it.  I used to grip mine with my index finger holding down the tip, . . . arthritis does not let me do that any more.  I hold it like I would hold a claw hammer, . . . and I make "next to" perfect 90 degree cuts.

But then again, . . . been doing this stuff for a bunch of years, . . . the experience is quickly attained, . . . it's the practice that keeps the experience sharp.

May God bless,

Dwight

[Colt W Knight]

1. What kind of leather are you cutting? 

2. Metal framing squares are notoriously out of square. If you Google how to fix a framing square, it will show you how to check which way it's out of square, and where to strike it with a ball pain hammer to fix it. I usdually use drafting squares and a straight edge to get nice 90° cuts. 

On soft temper leather, like deerskin, I use a template to mark the leather, then cut with scissors. It stretches a lot. 

[johnv474]

If you use a head/round knife or rotary cutter, start with the blade directly above the corner and push straight down, then push/pull toward the next corner, but not all the way. Do the same thing at the next corner and come back to meet your cut line. Do the same thing perpendicular to the first cut for your 90 degree corner (assuming you have good square here).

 

That is not how I cut my corners, but it should work. The idea is that the leather can't stretch out of square if it's not being pulled/pushed by your blade.

[zuludog]

Have a look at this video on YouTube

'How to Use Japanese Leather Knife' by leathertoolz

It's worth watching the whole video, but at about 4' 40'' he shows how to cut a right angle in leather, and that as you reach the end of a cut you tend to distort the leather slightly, even with a very sharp knife.; so you need to cut downwards. It's easier to see on the video

At the moment I'm making a Japanese style leather knife from an old plane blade - must get a move on!