How Do You Make Perfectly Round Corners?

[joobacca]

Hey folks,

I just recently dipped my feet into leather working! So far I've been making very basic card holders and it's been a blast.

As for my question, I was wondering how you get perfectly round corners when cutting leather. So far, I've been using a small bottle to trace and then cutting. It works pretty well, but each corner is not always the same. Is there a better way?

Thank you!

Jason

(Just to be clear, I am not talking about edging!)

[BIGGUNDOCTOR]

One way is to buy, or make a corner 1/4 round punch to cut the entire corner in one shot.

[joobacca]

One way is to buy, or make a corner 1/4 round punch to cut the entire corner in one shot.

Ahhh that makes sense! I guess they make these corner punches in different sizes? I'll check out a local Tandy Leather. Hopefully they'll have a few different kinds!

Thanks!

Jason

[joobacca]

Hmm, looks like the internet is only showing cornering machines and not punches. Tandy Leather has some strap end punches, but it seems like they won't make a perfectly round corner shape.

Jason

[dirtclod]

You can buy a round punch and grind it off till you get the size you want. Or you might take a piece of pipe and grind to the size you and then sharpen it up. The pipe would take longer but it should be alot cheaper. I think that's what biggundoctor was talking about.

[AndyL1]

I use some steel fender washers and trace with my X-Acto blade very carefully to make a curved corner. A little touch up with some sandpaper and they're perfect.

Andy

[Leatherimages]

I think Bob Beard of ProSeries Tools makes them in sizes.

I'm not so sure about shaping a round punch.

A corner cutter would need to straighten out at the edges of the corner.

I've used my swivel knife for this kind of thing before.

Just follow up your cut with you clicker knife and clean it up with a rasp or sand paper.

[Luke Hatley]

I use Metal Washers also .and..........cut very carefully...this works for me..

Edited August 1, 2010 by Luke Hatley

[8thsinner]

Is everyone answering here so young they forget the primary concept when cutting.

Practice

Practice

Practice

Practice

Practice

Practice

It helps to have an extemly sharp blade and to know that blade very well too though.

Of course sanding machines can make up for a lot of our mistakes.

[Kevin]

I don't know how well I can describe this, but, I draw the corner, then use my round knife and rock it forward a little, move the leather into it rock forward again and keep going around until done, like you're just taking off a little chip at a time. It amazes me how a bunch of small straight cuts makes a smooth corner. Leather is soft, so when you stick the knife in and try to just cut around the corner you stretch it out of shape, even if it's 10 oz. firm leather. If you cut a little at a time, you're pushing down and not out. Like the difference between using a rolling blade and a drywall knife on chap leather. Maybe that's almost clear.

Kevin

[Dwight]

Take a piece of 3/4 inch EMT (that's thinwall electical metallic tubing, . . . pipe) about 8 inches long.

Take it to a sander and very carefully roll it around against the sander (keep dipping it in water to keep it cool) until you have a fairly sharp edge made on the inside circumference of the pipe. You should have a long, slow taper to the sharp edge. When you are done it should look like figure 1.

Next, . . . place it in a vise, . . . sharpened end straight up, . . . and cut directly across the full diameter with a hack saw. Make this cut about the depth of the width of the hacksaw blade.

Decide which of the two halves has the better looking edge, . . . cut the other half off at about the depth of the width of the hacksaw blade. Looks like figure 2.

Now comes the fun, . . . you have 180 degrees or a half circle of cutting edge left over. (This makes a wonderful punch for round ends for straps, etc, . . . so you may want to make another one.) I digress, ................... NOW, . . . very gently and very carefully measure and mark off 3/8" on each side where you will cut the pipe twice, once on each side. These cuts will give you a couple of wings on your 90 degree corner cutter. Fold out the wings so they look like figure 3, but also have the basic shape of the little circle (unlabeled figure 4) above figure 3.

Lay those wings against the leather corner on the outside at a slight angle, . . . rock it back, . . . mallet the rascal, . . . perfectly formed corner, . . . every time.

May God bless,

Dwight

cornercutter.bmp

[joobacca]

I think Bob Beard of ProSeries Tools makes them in sizes.

I'm not so sure about shaping a round punch.

A corner cutter would need to straighten out at the edges of the corner.

I've used my swivel knife for this kind of thing before.

Just follow up your cut with you clicker knife and clean it up with a rasp or sand paper.

Thanks! Just sent him an e-mail!

Take a piece of 3/4 inch EMT (that's thinwall electical metallic tubing, . . . pipe) about 8 inches long.

Take it to a sander and very carefully roll it around against the sander (keep dipping it in water to keep it cool) until you have a fairly sharp edge made on the inside circumference of the pipe. You should have a long, slow taper to the sharp edge. When you are done it should look like figure 1.

Next, . . . place it in a vise, . . . sharpened end straight up, . . . and cut directly across the full diameter with a hack saw. Make this cut about the depth of the width of the hacksaw blade.

Decide which of the two halves has the better looking edge, . . . cut the other half off at about the depth of the width of the hacksaw blade. Looks like figure 2.

Now comes the fun, . . . you have 180 degrees or a half circle of cutting edge left over. (This makes a wonderful punch for round ends for straps, etc, . . . so you may want to make another one.) I digress, ................... NOW, . . . very gently and very carefully measure and mark off 3/8" on each side where you will cut the pipe twice, once on each side. These cuts will give you a couple of wings on your 90 degree corner cutter. Fold out the wings so they look like figure 3, but also have the basic shape of the little circle (unlabeled figure 4) above figure 3.

Lay those wings against the leather corner on the outside at a slight angle, . . . rock it back, . . . mallet the rascal, . . . perfectly formed corner, . . . every time.

May God bless,

Dwight

Thanks for the detailed explanation Dwight! I wish I were more of a handy man. If I were, I'd definitely try my hand at this, but alas, I am not!

Jason

[joobacca]

Thanks for all your help folks! I will definitely give the metal washer a try. I haven't had any trouble cutting the leather, it's just that when I fold the piece of leather together, the corners don't always match up evenly. I thought if I used a punch, it would keep things a bit more consistent!

Thanks again,

Jason

[DaveT]

Here's a couple ideas. Mark your corners like you've been doing, anything round will work as a template. You can use a knife (Any kind) to cut the corner at a 45 degree angle to nip off the extra material. Now repeat a couple times until you are really close to the curved line. Once you have all the corners nipped off, fold your card case so the opposite corners match up. (Do all this BEFORE laying out your stitching lines!) If you don't want to tap the fold lines flat with a hammer (I use a polished smooth faced ball peen hammer) clamp the edges in line with clothes pins, binder clips, or small plastic spring clamps. Cover the clamp jaws with some masking tape if you're worried about leaving marks. Now use a rotary tool (Dremel) with a sanding drum or a small belt sander to sand the corners to the marked line. This way all the layers of the leather match up and are sanded to the same shape.

Finally, to make your own half round and quarter round punches, I buy a cheap set of hardware store hole punches. (http://www.harborfreight.com/9-piece-hollow-punch-set-3838.html) Using a grinder or dremel with cut off wheels, remove half or three quarters of the punch. For larger sizes, use a hole saw that you grind the teeth off of, then grind the edge to sharpen it. Remember to keep the steel cool by frequently dipping in water. Keep your fingers near the area you're grinding, if it's not too hot for your fingers, it's not hot enough to ruin the steel.

Hope this helps

Dave T.

[leatherkind]

. . . rock it back, . . . mallet the rascal, . . . perfectly formed corner, . . . every time.

Thank you Dwight for your suggestion.

I was looking for something that would allow me to make repeatable and high quality cut.

Followed your instructions I was able to make a 75 mm diameter (3 inch) corner rounding punch.

http://leatherworker.net/forum/index.php?showtopic=7801&view=findpost&p=216263

It works very good.

[FlHobbyist]

I've done a fairly through google search and it looks like the answer is still two options:

1) Buy metal working equipment, learn how to use it and make your own quarter round punch.

2) Put in an order with Bob Beard and with a little luck you should have it in a year or so.

There is another pair of observations for doing quarter rounded things that weren't mentioned here:

External corners: Draw corner on leather and use good scissors to make the cut. Scissors are a lot easier to control than a razor knife. Admittedly this method won't work with thick leather. What is thick leather? For me the answer is 8 or 9 oz is going to be about it with my pair of scissors. This trick was in one of the Hurst videos.

Internal Corners: Draw lines of where the corner will ideally be, then carefully align circular punch on top of lines and punch out the corner. This trick was in one of the Stohlman books.

I believe if someone with a little metal working skill wanted to make some money, this would be a good place to start.

[Northmount]

Can also use wood carving tools ... sweep, gouge, etc. available in various curves.

Tom

[FlHobbyist]

Can also use wood carving tools ... sweep, gouge, etc. available in various curves.

Tom

Thank you for the clue. Just eyeballing it, it looks like a #8 sweep gouge is what one needs. I'll be ordering a #7 and a #8 this afternoon, and I'll post back my luck either good or bad.

[FlHobbyist]

Doing some more searching on ebay, it looks like at least 1 shop in China might be making these punches. They're calling them "English Semi Point" though one has to be careful as it looks like "English Semi Point" may mean other things to other Chinese entrepreneurs. In any event here is a link to a current auction offering them. Late next month I'll add to this thread with what they sent.

http://www.ebay.com/...984.m1497.l2649

Edited August 30, 2013 by FlHobbyist

[Trevor]

My two cents worth. Get yourself an electric drill and a vice to secure it in. Next get a round disk sanding abor from your local hardware store. Also get some fine sandpaper disks and some rougher ones and put the paper into the abor. With the whole thing mounted in the vice securely turn on the drill and lock the switch, then with the curve drawn on the leather and a basic cut done first to remove the bulk of the edge, sand the edge until the leather is perfectly round and smooth. You will find that its easier with heavier leather. Also heaps of dust. but you will end up with a very nice corner after some practice. Hint: Get an old vacuum cleaner from the op shop and mount the hose next to the disk to collect the dust. Use the heavy grit for big jobs and the fine for anything delicate. Cheers TK

[silverwingit]

I don't know how well I can describe this, but, I draw the corner, then use my round knife and rock it forward a little, move the leather into it rock forward again and keep going around until done, like you're just taking off a little chip at a time. It amazes me how a bunch of small straight cuts makes a smooth corner. Leather is soft, so when you stick the knife in and try to just cut around the corner you stretch it out of shape, even if it's 10 oz. firm leather. If you cut a little at a time, you're pushing down and not out. Like the difference between using a rolling blade and a drywall knife on chap leather. Maybe that's almost clear.

Kevin

IMHO, Kevin has it right. Unless you are cutting the exact same radii all the time (and how boring would that be?), use what a mathematician would call a piecewise linear approach like Kevin describes. It works with all curves, not just circular ones, and not just ones that cut a 90 degree corner.

Scribe your curve (a 90 degree circular arc in this instance) however you do it. Then start where the curve first breaks from the adjacent straight line and angle your knife (any good, sharp knife, not just a round knife, though that works best for me, too) to make a very fine cut at a very oblique (slight) angle from the straight line, shaving off just a sliver of leather. Then repeat, advancing the cut's position to be just slightly ahead of the previous one and at just a slightly less oblique angle so as to shave off a similar sliver as the last cut delivered. As you repeat this process a smooth curve will gradually appear just along the curve you've scribed, ideally removing the scribe mark itself. With experience you realize that you needn't completely remove each sliver and can use the rocking motion that Kevin described.

It's easy and takes only a moment or two and again, it works with ~all~ outside curves. Inside curves are another story.

Michelle

Edited August 31, 2013 by silverwingit

[Northmount]

Here is another option I just found http://www.allimageprinting.com/corner_cutter.html corner cutting press and pliers type with dies.

Tom

[silverwingit]

Sheesh, Tom, I just realized I have one of those somewhere. I'll have to give it a try sometime.

[Crimson Hides]

I recently order a set of corner cutter from Elfita

Very happy with their service.

http://beavertools.co.kr/xe/index.php?mid=knife&document_srl=527

[FlHobbyist]

My strap end cutters came in from China and they look like they are indeed around 90 degrees. In the next day or two, I'm going to cut out a couple of small pieces with one of them, and I'll post the results good or bad.

The one I bought (though the listing will disappear in 90 days or so. ): http://www.ebay.com/...984.m1497.l2649

The term most of the ebay sellers are using to describe them is "English Semi Point". Though it is very important to check the picture and make sure the cutters are 90 degrees and not 180 degrees. Many of the sellers are not particularly good at English since it is apparently a second language for them.

Edited September 12, 2013 by FlHobbyist