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Punch And Die Help

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Chewy

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Greetings to all!! Need some recommendations for a Hydraulic Punch and Die for punching 1/8” hard black plastic. We are currently using one setup on a 3 ton arbor press with a 3’ handle. Pulling force is (guessing) around 50-60 pounds. The set up punches holes in office chair backs. The original owner (deceased) doesn’t have any records or specifications on what looks like a professionally made Punch and Die. We added a new back that needs a different size opening and that is where the fun begins. I gave the punch to our machine shop who makes some of the parts for us. They can’t handle making and hardening a new one and called some professional companies who want a couple of thousand dollars to make the set and are too busy to bother with it.

Original punch is two 5/8” holes about 1-1/2” overall length. The new set needs one of the holes to be 1-1/8” and same overall length. Think of a cross section of a pill capsule and a pear respectably.

What would be the best steel to use? What kind of clearance tolerances? What hardening procedure would be best? Lastly I’m thinking of dishing the punch to get more of a shearing action. Looked around on the Internet and couldn't find any information that was relevant.

Thanks to all in advance. Charles
 

Wreck™Wreck

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#2
The tool material and heat treat requirements would be dependent on the work material, "hard black plastic" covers a broad range.

The number of parts to be punched with acceptable die life is also a major consideration.
 

JimDawson

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+1 what @Wreck™Wreck said above.

The shape you describe sounds like a ''keyhole'', which is a common standard shape. I'm going to guess that the chair backs are made from Polypropylene or HDPE, so relatively soft and punches well without shattering. My choice of tool steel for this would be A2, hardened to about a R60C. Given the material and thickness, about 0.002 - 0.003 clearance would be about right. You are correct, a hollow ground punch would work well to get some shearing action. ''A couple thousand'' seems a bit on the high side, but maybe not too far out of reason.

If your machine shop had the punch & die, could they mount it in a dieset?

Take a look at this catalog, page 23. http://www.daytonlamina.com/sites/default/files/doc/910_Kommercial.pdf Dayton makes punches & dies in just about any shape you want, at reasonable prices. A quick chat with one of their engineers might be useful.
 

Chewy

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Thank Ya, Thank Ya!!! The catalog answers all the questions. I have (Page 3, Shape o) on the arbor press now. To Wreck™Wreck It has probably done 10-12,000 backs over the years. When the material was made in the USA, we had some idea of what we are buying. Now it all comes from China and I have to buy large quantities because we are the only ones here using it. The suppliers stock only the most popular items for their high volume customers. Who knows what it is made out of. The new punch I'm looking for is page 23, shape C16. I will contact them and see what kind of price and time schedule. I looked up the raw steel and can buy the square stock and flat plate for about $400. That would make about 5-6 sets with material left over. Either the machine shop or myself can mount the sets without problem. The arbor press uses a welded Punch adapter that bolts to the shaft. The Die is a flat plate that is mounted to a box on the arbor base. Simple to alter/adapt a new style of mount. I'm looking to go hydraulic so we can do a whole shipment at one time when it comes in. Pulling on a manual arbor press kills the women so they only do a small number at a time. That keeps the press and boxes out in our way all the time.

Again thanks Jim for the information! Now I have something to go by.
 

DiscoDan

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#6
I have a book on punches and dies listed in another section but it is WW2 era and may not cover plastics
 
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