Punching holes in rubber sheet
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  1. #1
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    Default Punching holes in rubber sheet

    I want to punch some 2" diameter holes in 1/2" thick rubber (neoprene) sheet with a durometer of 70A. I need about 20 discs. In other words, I need the drop out, not the hole.

    Is a punch like this going to give me good results, i.e. a clean edge and easy cut?

    McMaster-Carr

    I'm thinking of not hitting it with a hammer but rather using my Dake arbor Press. Good idea?

    Or am I better saving $77 and making my own punch on the lathe out of steel pipe?

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    How long will it take to make one on the lathe? I would spend a few minutes making one with a nice, sharp cutting edge and trying it before buying something with edge geometry meant for sheet metal.
    And before pulling it from the chuck I would get something flat that's bigger than the part you want to punch and put it against the tail stock with the rubber between that and the punch, then lock the tail stock in place and crank the handle around to push the nose of the tailstock toward the chuck. You'll find out pretty quick if your punch will do the job. If it gives you trouble you might be able to lubricate the punch to help it slide as it cuts.

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    I find that arch punches work better in rubber if you rotate them instead of applying a straight axial force. I have made my own leather/rubber/gasket punches up to 1" diameter out of drill rod and heat treated them. They need to have a long taper and they need to be sharp.

    For your purpose, I would use pipe and turn it in the lathe with a 2" bore and a long taper on the OD. Leave the punch in the lathe and fit a wood pad to the tailstock ram. Then cut your discs by running the lathe slowly and using the tailstock ram to feed the rubber into the punch. Some lubricant will cut down on friction and make it easier to hold the rubber so it does not spin. Neoprene is oil proof. Waterless hand cleaner is a good rubber lube.

    Larry

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    Never tried 1/2" thick rubber, but in 1/4" felt, and in heavy collapsible discharge hose (3/16" thick? with fabric core) as well as cork or paper gaskets, I can get between 1 - 3 hits with the shop made pipe cutter against a plastic backer sheet before it needs the edge doctored. It works fine, but the really honed sharp edge ideal for felt and rubber does not stand up well in the soft metal. If you don't mind running a burr stone around the edge between hits, it should work for you.

    Like someone else alludes, you can try it with about 5 minutes work. Maybe 10 if you have to find the pipe and cut the end off first...

    If you decide to make one and shop harden it out of tool steel (I'd suggest S7 for this) I'd grind a steep hollow on the OD for clearance and hone it. A soft pipe cutter won't take a steep (seriously acute) cutting edge, though you can thin the OD down before putting on the edge.

    smt

    Edited: (I was writing while Larry was posting) Larry is right, I rotate the punches by hand, a back anf forth sawing motion even when using in the thin stuff I generally cut. Lathe idea sounds interesting if really low rpm is available, or merely turn the spindle by hand while advancing the TS.

    smt

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    I made a quickie cookie cutter on the lathe out of some scrap sch 40 pipe for just the same use.

    Cut the edge of the pipe to a sharp tapered edge, leave the part in the machine, take a block of wood with your rubber sheet wrapped around the face, turn the lathe on low speed and use your cross feed to push the rubber into the pipe, turn off the machine and your rubber disc will be inside the pipe, perfectly cut!

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    You can make a punch on the end of a piece of stainless or tool steel with a small center hole for knockout. it will work for 20 parts without hardening. Bore to the size of your disk 5/8 deep with a 20 degree taper on the outside to razor edge. Make it thin wall say 1/16. The dake works well for this along with a piece of butcher block maple on end. Depending on how sharp you make the punch will determine how much hourglass on the sides of the part. Using lubricant helps a little, and you can also spin the punch in a drill press at a slow speed and feed.

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    When punching holes through rubber stoppers, "universal solvent" works well as a lube. Also
    alcohol.

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    Thanks guys, I'll try those ideas.

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    Stop by your local muffler shop and ask to go through their scrap drops and you should be able to find a lot of sizes. Offer them a couple bucks for a few pieces.
    Cut square and sharpen the edge.
    I cut 3" plugs in 1/4" neoprene using homemade cutter and my 20 ton press. I don't need much pressure but the press makes it easy to control. I cut against some soft PVC (old piece of vinyl siding).

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    If you ever need to do it in qty don't punch into wood, control your punch depth to only just kiss the anvil and use something hard but totaly flat, like a ground block of mild steel or ideally hardened tool steel. You can get 10's of thousands of clean punches this way. At the bare minimum use something plastic as hard as nylon. End grain of wood might be good for the punch but it does nothing to help - soon gets chewed up!

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    Make a cheap "Steel Rule or Cookie" die as suggested by "Shadon" .

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    Quote Originally Posted by adama View Post
    If you ever need to do it in qty don't punch into wood, control your punch depth to only just kiss the anvil and use something hard but totaly flat, like a ground block of mild steel or ideally hardened tool steel. You can get 10's of thousands of clean punches this way. At the bare minimum use something plastic as hard as nylon. End grain of wood might be good for the punch but it does nothing to help - soon gets chewed up!
    It doesn't sound like you ever made or used rule dies or punches.

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    I've punched many 2" holes in 1/4" neoprene and used an arbor press and a punch turned up on the lathe with a piece of delrin backing up the rubber. I've also made 6-9" holes in same material by making a steel rule die out of an old bandsaw blade and a piece of plywood. I like the idea of using the lathe as the press because I had trouble getting a clean cut all the way through and would sometimes have to rotate the punch of move the work to the edge of the ram where I wanted it to pierce. Having the punch rotate while applying pressure with tailstock would be great.

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    a steel rule die would cost 50 bucks and last a long time and can be used in an arbor press. Paragon Steel Rule die in Rochester NY is one of a hundred makers.

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    I was always told that high heels would punch holes in rubber sheets, but.................

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    Hi

    Send them out to a water jet cutter. You will get a clean square edge at low cost, probably less $$$ than a punch tool.

    Dazz

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    Quote Originally Posted by Mike72 View Post
    It doesn't sound like you ever made or used rule dies or punches.
    I don't know if Adama has the same sort of rule die experience as you, but he's a lot of experience in the printing trade and the info he gave me was 100% - he helped me a few years back when I had to make 100 washers out of PEEK film.

    The same punch and anvil have done over a thousand parts without so much as a hone of the cutting edge.

    To repeat, the setting of the punch against the anvil is critical.

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    If you have the time, and want to fool with it, that's fine. If you don't, contact FLNMAR, in Holyoke Ma.,Fln-Mar - Industrial Distributors and Fabricators Since 1969. I use them all the time. They are reasonalby priced and do quality work.

    Stevet

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    Half inch rubber is pretty thick, and sounds pretty stiff (based on your durometer number). Is there any reinforcing in the core of the material (like fabric belts)?

    How about a bandsaw?

    Thanks,
    Jim.

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    2nd the water jet idea.... We have 1/2" rubber isolation dampeners cut all the time. Stinking cheap to do with a dual head.


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