Sharpening hole punches

[seagull369]

Wanted to do this on at least some larger sized punches I have. Thought about using an emery cloth or wet/dry sandpaper with maybe some oil trying to follow the angle on them.

Good idea or is there a better way?

 

[RoninB4]

Doing that with hand held grit cloth will likely just round the edges and render the punch less effective. Don't know what "angle" is on them but standard procedure for sharpening a punch/perforator is to use a surface grinder and a jig to hold the punch.

Most average people don't have a surface grinder or the tooling so a belt sander can be employed provided you do the following:

1) Do not overheat the punch, if the punch surface burns a drop of oil or starts changing color it's getting way too hot and the temper will be ruined. Use a spray bottle with some water to keep the punch cool.

2) The punch has to be held in a fixed position the entire time so use a "V-block" and a clamp or something that can reliably repeat the position and hold it firmly. Even a block of wood with a notch cut in it can work provided it's firmly clamped.

3) Remove only enough metal to make the edge sharp, do it slowly. Removing more than 1/32 of an inch is a lot on a belt sander and will likely wear out the belt.

4) Duplicate the factory "angle" until you understand why it's that way

5) A coarse grit belt/wheel is better than a fine grit for removing metal if you're new to this

6) Use a 10x magnifying lens/loupe to inspect the edge so you know when it's sharp.

7) If the punch is the beveled type for punching holes in gasket material then it's best to use a small lathe. A more detailed explanation will be required for this. What's the punch look like and what's it for?

There are plenty of ways to do this with a bench grinder or even an abrasive wheel mounted in a Dremel type tool but the rigid holder and dressing the wheel properly make a big difference in your results. If you list what you have in your shop and what the punch is used for a better suggestion could be made.

 

[rlitman]

Before you start sharpening (and messing things up), use a steel to realign the edge. It's usually all you'll need to do.

 

[RTM]

I have a fairly smooth tapered cylindrical stone for repairing any damage to the inside face of my arch punches. For the outside edge, I roll on high grit sandpaper with a block to maintain angle. This is mostly for garage sale finds, my users see so little use, they are safe for the rest of my life, unless I foul up.