Clean 5Mm Hole Through 12Mm Leather?

[amuckart]

I'm trying to find a way to cut a clean 5mm (~3/16th) hole through 12mm (~1/2") of leather, made up of 3 layers of 4mm veg bridle.

I can't pre-punch the holes in each part beforehand, so I need something that'll go through all of the layers at once.

A drill, even a very sharp one, doesn't leave a clean hole, and I haven't seen any sort of hole punch that isn't tapered on the outside and far too wide 12mm up from the cutting edge to made decent holes.

Has anyone solved this problem already who can give me pointers?

Thanks.

[electrathon]

Find a piece of tubing, like brake line, about 4" long. Sharpen the inside with a countersink. Put it in the drill press and drill through the leather. The finished hole will be the size of the outside of the tube.

Edited April 15, 2015 by electrathon

[TinkerTailor]

You could also punch part way in on both sides and then drill out the middle. That would leave you clean top and bottom edges to the hole. Drill it right after punching because punched holes are a little oversize right after due to stretch and will close up some. Take advantage of this to help prevent the drill bit from touching the top edges of the hole. If it is rough inside the hole, or too small, chuck up a small hardwood dowel and use it to burnish the inside of the hole. A fine chainsaw file would work pretty good for cleaning out the hole or slightly resizing it. I have glued sandpaper around a dowel to clean holes in wood before, you could do this here as well. In woodworking it is common practice to cut the visible part of the joint very accurately with a knife, and hog out the non visible parts with a saw or chisel. Mortises are made this way.

Edited April 15, 2015 by TinkerTailor

[amuckart]

Thank you for the ideas. I don't have a drill press, alas, but I think one of these lipped brad point drill bits with some careful stropping might do the trick. I'll order one and find out. I'll also try and find some tubing if the right diameter.

http://www.leevalley.com/US/Wood/page.aspx?p=42247

[TinkerTailor]

I am pretty sure those bits will grab and chew up the leather no matter how you strop them. The leevalley Carbide-Tipped Dowel, Plug & Tenon Cutters would be a better shape and only go down to a 1/4 inside dimension. Incidently, they probably work best run in reverse on leather. Brad points can be had in offshore cheap variety at any hardwarestores/harbor freight.

I would try the sharpened tubing trick above. You don't need a drill press, you can hammer it through. Use your old mallet, the end of the pipe will chew up the head.

[amuckart]

The Lee Valley brad points are specially lipped so they're a different thing than the cheapo ones you can get. I've tried a normal brad point bit and it doesn't work well because there's nothing to cleanly cut the perimeter of the hole. With the lipped bits there is.

The plug & tenon cutters are no good to me. I'm outside the USA so I work in metric units, not fractional inches.

I'll see if I can find some 5mm OD carbon steel pipe.

[Mark Peters]

Have you considered a hollow paper drill bit? They taper on the inside of the punch.

http://www.amazon.com/Punching-Machine-Straight-Shank-Hollow/dp/B00PZMFA94

Edited April 18, 2015 by Mark Peters

[TinkerTailor]

The Lee Valley brad points are specially lipped so they're a different thing than the cheapo ones you can get. I've tried a normal brad point bit and it doesn't work well because there's nothing to cleanly cut the perimeter of the hole. With the lipped bits there is.

The plug & tenon cutters are no good to me. I'm outside the USA so I work in metric units, not fractional inches.

I'll see if I can find some 5mm OD carbon steel pipe.

Lip or no lip, when the main part of the bit hits the leather it will grab and either twist up the leather or tear it. Leather does not chip like wood, bits dont work the same. You may get it to work going real slow on really stiff leather.

any rigid metal pipe will do. Carbon steel will stay sharp longer You can make a hone basically out of a dowel sharpened like a pencil with 600 or so emery glued onto the cone.Go to the thrift store and look at lamps and light fixtures, the tubing you want might be there.Ikea desks had struts made out of 5mm or so tubing, you get the idea. I have also made punches out of brass plumbing fittings.

Of course you could pay lee valley for good stuff that costs like excellent.

[amuckart]

Have you considered a hollow paper drill bit? They taper on the inside of the punch.

http://www.amazon.com/Punching-Machine-Straight-Shank-Hollow/dp/B00PZMFA94

I hadn't, thanks for that.

[Tree Reaper]

A forstner bit will work but it will have to be cleaned up a few times while drilling because the end will get plugged but both sides top and bottom will be clean.