Cutting smooth curves in thicker leather?

[Beken]

Ok, so I am very green in working with leather, and I am wondering what the best way to cut curves in thicker leather(8-9oz) is? Right now I am trying to use a box knife, and I am binding in the concave curves. As a result I seem to either get a series of straight lines or undercut the back side instead of a perpendicular cut that's smooth.

I'm positive that this is not a new phenomenon. So any help or advise is greatly appreciated.

Thanks!

edit: grammar

Edited January 22, 2010 by Beken

[King's X]

try to find a large lid, like a coffee can, veg jar, etc. Use it as a template and cut slowly and carefully. I use those folding box cutting knifes from Harbor Frieght and strop the blade before and after use. Also, with a lot of practice, you can also use a 'head' knife to make a clean cut.

good luck

[Beken]

Thanks for the input. I definitely need some "training wheels." I have a head knife on the list, but I haven't picked one up yet. There seems to be a fine art to using a head knife.

The more I look around this place the more I have a feeling that I will be redefining what I consider sharp to be.

[UKRay]

It sounds like you maybe ought to try using a relatively inexpensive hooked blade clicking knife before making the transition to round knife. I purchased a handle and then made my blades from old hacksaw blades. Learn to get that properly sharp first and then you won't risk spoiling a good round knife.I would suggest you invest in, or make a strop board - Mine is a 3" wide x 12" long piece of wood, faced on both sides with 3mm thick leather. A good rub on one side with some red jeweller's rouge will get you started and then finish off the polishing process on the raw leather side.Better people than me will doubtless help you perfect sharpening, but I find a hooked blade great for cutting tight curves in thick leather. When you have a very very sharp blade, learn how to work the leather 'in the air' and not just on a cutting board. It makes the task a lot easier. Ray

[8thsinner]

I have actually had very good success working with the blade from a swiss army card. I used to just dig it into a log, and push the leather around through it.

The blade is small enough that it doesn't bind even doing circles as tight as a cup size, And when properly sharpened it holds a very good edge considering all the price of them.

I have used the replacable blades from tandy lace cutters too but they are too thin and flimsy and curve with the pressure of leather pushing on it.

Mechanically speaking though, you could get an even sharper cut using a concaved curved blade thats thin, maybe like a pruning knife as long as it's thin and shallow.

[Beken]

Wonderful! Yeah the strop has been made.

UKRay, are you talking about something like this? http://www.caribooblades.com/makingahook.html

8thsinner, yeah I was thinking about hawkbill knifes like the pruning knife or maybe even a gut hook or hook utility blade for the box cutter, but I haven't given either a try yet.

Anyone else? Thoughts? Insight on how to cut smooth concave curves?

[JLSleather]

How tight a corner are you talking about? If you're thinking about a round or head knife, thinking you'd like to use those, maybe you just go ahead and get the knife you want and PUNCH out the tight curve and cut the straight lines between, until you gain some proficiency.

[TwinOaks]

Make the investment in a decent head knife or round knife. It is a tool that you'll end up using ALOT, so its just better to get one now and start learning to use it.

[Beken]

JLSleather- Not too tight. I'm was practicing cutting scrap leather with various arcs(CD size to coaster some tighter) and noticed that my concave cuts we not working out so well. Convex worked well because the trim was being pushed away from the piece by the blade. I think my main trouble is that I have too much blade trailing behind the lead edge(a straight blade) to effectively make the inside turns, and I need to adjust the angle when I enter into a concave cut.

That and I need to work on getting the atom splitter edge on the blade.

What would y'all say is the tightest arc that can reasonably be cut by hand with a good round knife? Does it depend on skill or is there a point at which things are too tight?

[TwinOaks]

That would depend on the round knife.....yeah, I know, that's one of those "reach through the screen and choke someone" answers. Really, though, there's a pretty wide variety available. The finer and sharper the 'corner' is, the tighter you can cut. I suppose, though, at some thickness you'd be better off using a scroll saw (sole bends). With that in mind, I've cut 4oz with a round knife to the diameter of a drink straw. Now, I'm not claiming I knew what I was doing or anything, but it can be done. I was just playing around on scrap, and honestly, if I was cutting that small, I'd use a punch, or a trim knife (the one with the curved blade)- much simpler.

Edited January 24, 2010 by TwinOaks