Noobie with question on cutting

[StickHer]

i bought some scrap leather on amazon and am finally cutting for the first time. ive probably attempted 50 straight line cuts with a ruler/exacto knife today on an self healing mat  (which stinks really bad). For some reason no mater what i try the cut is straight except for the bottom corner . im cutting vertically from top to bottom and and the bottom comer simply isnt stright. The corner stick out further away from the line. if i was to guess the leather is being stretched when cut. any ideas or tips to help with this. Also the leather moves a lot when i attempt to bevel. 

Edited May 17, 2021 by StickHer

[Hardrada]

That happens because you're pulling the leather with the knife when reaching the end. It's kinda "normal" to happen when performing the cutting motion, but it's definitely vexing and leaves you with a crooked line at the end.

A number things you can do:

1. Leave some leeway, so that your project doesn't end at the crooked end, and you can just trim the crooked tail.
2. After cutting, leave the ruler in place and trim the protruding tail with a skiving knife.
3. Start the whole operation by making an incision along the ruler ~1/4" to 1/2" from the end, and then cut from the top as normal: the knife will run into and join the pre-cut portion without pulling the leather.

 

[LatigoAmigo]

51 minutes ago, StickHer said:

attempted 50 straight line cuts with a ruler/exacto knife

We all have different approaches, and offer a myriad of advice. What I would add is that over the years I've upgraded from Exacto knives to a "break-point" utility knife. The blade is always sharp and is heavier that the Exacto blade. That helps, especially on heavier leathers. Then I use a straightedge made from a piece of 1/8" aluminum stock from Home Depot, cut down to 48". Then, when I can't make any mistakes, I will use C-clamps to press the straightedge against the leather hide on my bench. With both hands free, I can do a better job of keeping the blade from wandering.

Edited May 17, 2021 by LatigoAmigo

[chuck123wapati]

xacto blades are to thin and bend with the force it takes to cut the leather also. get a box knife at the least.

[zuludog]

Yes, the leather is being stretched as you come to the end of the cut at the edge of the leather. Various options to prevent this are -

Press down hard on the ruler in the area at the end of the cut to hold the leather more firmly

Make a short cut, say 2" in from the end first; then make the main cut all the way from the other end, so it runs into and joins up with your first short cut

Use a round knife, or a head knife, or a Japanese leather knife. As you get to the end of the cut, say the last inch or two, instead of continuing right off the edge of the leather change from a horizontal cut to a sort of rolling or chopping action so you press down on the leather instead of pulling it along

Use a rotary blade knife, which uses more downward pressure than horizontal

In any case, an Exacto knife is OK for thin leather, say up to about 1,5mm thick, bit for anything thicker use something heavier, like a Stanley/Utility/Box cutter knife; and strop it frequently, even if the blade is new

Have a look at this video. He shows how continuing off the end of the leather stretches it, but a chopping action to finish does not. 

If you watch other videos of people using a round/head/Japanese knife to make various finished items you'll see them using a similar chopping action.  JH Leather's videos show this technique in many of her videos

Edited May 17, 2021 by zuludog

[Rahere]

You've learned a lesson! Excellent. There is another lesson, cut on the waste side. You can always turn it around and cut back from the far end. 

Another approach would be to be a little less gung-ho, cutting straight through in one swoop, instead cutting a groove and then through. This can be an important skill in tooling, just cutting the surface: that cut will then guide the knife for a clean final cut.

[TonyV]

whichever knife you choose it must be sharp sharp sharp.  I suspect the pulling you're experiencing comes from a blade that could be sharper.

If you use a utility knife use a new blade each project.  If a fixed blade knife, learn to sharpen and hone it. 

Keep the knife at a low angle to the leather to keep the blade in close contact with the leather..

You don't have to cut through the leather on the first pass.  Cutting carefully,  2 or 3 lighter passes with the blade will often give a better result than one heavy-handed cut.  This ain't a demonstration of strength.

Moving around while you're edging also indicates a dull edge.

Edited May 18, 2021 by TonyV

[StickHer]

i appreciate all the responses , was not expecting this many people to help out. will buy a box cutter soon. i think the leather i got from a scrap bag is extremely thin and the leather is stretchy. i will try those techniques and see if it helps. thanks again

[fredk]

6 hours ago, StickHer said:

i appreciate all the responses , was not expecting this many people to help out. will buy a box cutter soon. i think the leather i got from a scrap bag is extremely thin and the leather is stretchy. i will try those techniques and see if it helps. thanks again

add to your shopping list a rotary blade knife of 45mm or 60mm diameter. You'll not be sorry. 

I use one on any leather thinner than 1.6mm, or 4 oz. It really reduces that pull-out

 

[tsunkasapa]

I use a utility knife upon occasion, I've used the same blade for months. I always sharpen the new blades before I ever use them, and keep stropping/sharpening as I use them. They come sharp, but not REALLY sharp. Using a new blade each time is just wasting money. The same goes for Exacto blades too.