Thread: Punching circles in Cork

In the good old days (when things were often not as good as we remember) we made gaskets for all sorts of things from cork or leather. 'Wad punches' were used to make neat holes up to 40-50mm diameter. I have never seen any larger than 2 inches in diameter, but they may have existed. My dad's set was similar to this, (but in a wooden box). You can also buy punches individually if you only need a couple of sizes.

Much depends on the grade of cork, but the stuff used for gaskets was good to cut & punched cleanly - not all cork is created equal & some, like the stuff used for corkboards, may crumble rather than cut cleanly. For best results get yourself a solid block of a suitable firm but not-too-hard wood (radiata is fine) with a clean-cut end and sit whatever it is you want to punch on the end-grain.

Cheers,

I've punched quite a few holes in cork, rubber, plastic etc. I usuallyuse a hollow punch set I purchased form Hare and Forbes about 15 years ago and is similar to the set Ian points to. I see that set is no longer showing up on the H&F website. MCjing has a cheap set of dedicated punch sizes that might suit.

I agree with Ian about using a solid block underneath.
If you really want a good clean cut put the block on top of something even more solid. I put mine on my Anvil but even a concrete floor would suffice.

The other thing I have done many times when none of my punches are the right size is make my own punches.
If I can find a piece of steel pipe that is about the right size I just cut a short (50 mm) length of the pipe and square up the ends on a grinder. Then I ground an edge on the outside of the one end.

I have used them up to 50mm diameter on thin rubber and cork - for large sizes to make sure the whole end of the pipe is struck as evenly as possible I place a piece of steel across the end to be struck and strike the centre of the steel plate.

For a very specific size I have even turned up punches on my MW lathe. For soft materials the steel does not need to be a specific steel but I have made a couple out of tool steel to cut sheet metal and rough hardened and tempered the punches. These have worked rell

Hanks everyone, I will order a set fom McJing.
Much appreciated.

Are you using cork or a combination of cork and rubber ?

Originally Posted by BobL

The other thing I have done many times when none of my punches are the right size is make my own punches. If I can find a piece of steel pipe that is about the right size I just cut a short (50 mm) length of the pipe and square up the ends on a grinder. Then I ground an edge on the outside of the one end.

For a very specific size I have even turned up punches on my MW lathe.

Regarding Ian’s earlier post, I’ll never understand why people ever used wad punches to make holes. Wad punches make wads with perfect edges and holes with tapered sides that will split if you punch them too close to an edge. The tapered sides of a wad punch deform the material so you end up with a gasket or whatever where the material directly around the holes is slightly thicker than the rest. It’s not that great a technological leap to reverse the profile...

The only manufacturer of proper hole punches that I know of is a Swedish company called Maby; they do them in a set for making ring gaskets but you can use either the outer wad punch heads or the inner hole punch heads on their own. The handle has an internal L/H thread to screw in a hole punch head and an external R/H thread to take the outer wad punch. Spring ejectors are fitted to both so that the gasket and waste are cleared from the punch.

Hand hole punches have straight outer sides and have the taper ground on the inside. I too have had to make my own on a metal lathe. Haven’t needed the pipe idea but it would work fine if the taper is ground on the inside with a die grinder or Dremmel. Here are some I made years ago; two from scratch and a couple I repurposed from Sidchrome “hollow” punches.

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That’s a 3/4” hole just less than 4mm away from the edge of a 1/4” thick piece of cork tile; a wad or “hollow” punch would have split the material. But the wad would have been excellent, not like the poor deformed thing my punch made.

Industrial-made gaskets are cut using concentric punches and dies that produce both a perfect hole and a perfect wad!

Originally Posted by Chief Tiff

Haven’t needed the pipe idea but it would work fine if the taper is ground on the inside with a die grinder or Dremmel.

It's quite easy to turn a very fine taper on the inside of a tube with a boring bar.

Chief, while you are absolutely correct, as usual, in 99.5% of cases I was involved with, any slight edge deformation & taper caused by an outside-beveled punch wasn't remotely a problem - getting the holes in the right places was often more vexing when you destroyed the original gasket getting the pieces apart to fit the new one (usually because someone used an inappropriate glue in an attempt to stop itl from leaking (unsuccesfully!).

The main reasons for using wad punches was a) they were easily obtained, b) the outside bevel was far easier to sharpen when necessary, and c) quite often it was the wad that was needed, not the 'ole....

Cheers,

(Responding to Bobl’s post regarding boring bars) True, but I was assuming most people wouldn’t have access to a lathe so grinding the taper by hand would be needed.

I miss not having access to a lathe anymore . It’s remarkable what you can do with one and a little bit of lateral thinking...
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This is a dowelling jig I made at sea 20 years ago from a piece of round bar. At the time I had a Harrison M300 but only standard turning tools. The rebate was made using a boring bar held in a 4-jaw chuck with the workpiece held in the toolpost!

Originally Posted by IanW

in 99.5% of cases I was involved with, any slight edge deformation & taper caused by an outside-beveled punch wasn't remotely a problem - getting the holes in the right places was often more vexing when you destroyed the original gasket getting the pieces apart

Yep, been there a few times! A great deal also depends on the material thickness too; on gaskets only a mil thick the deformation is minor and often negligible unless you’re making precision gaskets like on Japanese motorcycle carbys (DAMHIK). I usually worked with 1/16” to 1/8” thick CAF (compressed asbestos fibre), 1/8” to 3/8” cotton impregnated rubber sheeting or 1/8” to 1/4” rubberised cork. You were better off nibbling around the hole with an in-cannel gouge than trying to belt a wad punch through it and expecting the hole to be serviceable. I had a bad habit of “float testing” tools that irritated me, wad punches fell into that category quite regularly.

Originally Posted by royflatmate

Are you using cork or a combination of cork and rubber ?

I believe it is just cork