pnut

problems punching holes in flat bar

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Yesterday I decided to make another pair of easy tongs and instead of drilling the holes I decided to punch them. This was my first time punching stock and it didn't go so well. The stock was only 1/8 inch thick and instead of shearing through the metal it was stretching it. I was using a bolster block underneath the bar and drove the punch nearly through and flipped it over and drove it though the other side but instead of a biscuit falling out it stretched into the bolster. I was wondering if this was due to the stock being too hot or something else I'm not seeing. I managed to get one hole punched but it wasn't a clean hole by any means. Maybe I should have slit and drifted to final size? Any help would be apprecated. Here's a pic of my punch.  

Pnut

 

IMG_20190714_092308.thumb.jpg.9778c9499b4adc9c7ad893564e68f1b2.jpg

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Are you starting over the bolster? Try on a flat surface first. I got a flat piece 1/4 thick i put on the face of my anvil. Punch one side, flip it over do the other side. You can feel it when you get through. Then i move over my pritchel hole and push out the biscuit.  That works for me at least. I do not think the plate on my anvil in necessary becuase you are not hitting the face with the punch, the biscuit is in between, but better safe than sorry. It also helped when i was trying to show someone how to punch a hole who could not hit the same spot twice to save his life. 

Hmmm...biscuits, time for biscuits and gravy.  

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Start punching at a high heat, you will "feel" the punch "bottom out". When you flip the piece and as it's losing heat (dull red to almost black, dependant on thickness of course but for thinner material black heat is fine to pop the slug) you should see the area where the punch bottomed out. Center the punch in that circle and punch back through. The last I move it to the pritchel hole and pop it through if it didn't just pop out on the face of the anvil. 

Reheat the piece to drift the hole. 

It takes practice to get the feel for it. Get a piece of stock and practice punching holes. Once you get the hang of it, it can be quicker and easier on some pieces than getting out the drill. 

 

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If I have the energy left when I get off work today I'm going to give it another go. Thanks gentleman.

I did start over the bolster. That's the problem I'm sure. Looking at it now it makes sense that it would stretch into the bolster. I think with the advice you fellows gave me I should have a better outcome this time around.

Pnut

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It sometimes helps to put a slight radius on the working end of the punch. The radius is just enough to knock off the sharp edge and get things started.

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Brian Brazeals punches have a slight point to them which helps in a number of ways, If  you want to know them check out his how to videos, he or Lyle do a much better job of explaining the hows and whys. I just attest to how well they work.

Das explains the hows of punching holes nicely, I concur. I center punch the spot cold so I can position the punch if I need a precise location. You can see center punch or chisel marks on HOT steel better than scratched marks and forget about soap stone.

Just takes practice use scrap or a test strip till you get the hang of it.

Frosty The Lucky.

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What does Mrs. Nut think of you bringing your punch in the house?

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Posted (edited)

Bachelorhood has it's plusses

Pnut

I should rephrase that. Living alone hasit's plusses.

Edited by pnut
minimizing danger to life and limb

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God willing, I will never have to experience that again. :D

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I agree with Das, with one addition: when you flip the workpiece over after punching from one side, give a quick hit to the shiny spot that forms between the punch and the anvil. Then put your punch in place and proceed as described.

When you punch from the top, the bottom bulges out, even if you're not over the pritchell hole. That quick hit takes the surface from convex to flat, which makes it much easier to center and hold your punch steady before you hit. 

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Forget the prichel hole, punch from one side 3/4's the way thu, then on the other side in the same heat, - take your time a bit - cool your punch in the slack tub - even let a few drops of water hit the sweet spot your punching, locate your sweet spot, then with one quick firm hit shear the slug. The problem ppl have is trying to shear the slug out when its to hot - hence the roll-over of the slug edges and the chasing it back and forth thru the cross section, let it cool a bit so it shears. Practice is key.

I use flat ended punches.

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And if you punch the slug out through the pritchel hole put some sort of catcher underneath it. You don't want that little sucker down your boot.

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Punching over a bolster on the anvil face will both provide clearance for punching and keep the slug out of your boot.

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Wear your LONG pants outside your boots / shoes to keep HOT stuff out. Of course watching someone dance around trying to get a boot off is GOOD entertainment at a club meeting or demo.

Think of the audience.

Frosty The Lucky.

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I'm not a shorts wearing type of guy unless I'm at the pool. I do cuff my jeans though and I make sure to roll them down before I light the forge. A cuff is a perfect scale catcher.

Pnut

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Not yet. It's been too hot all day at work. By the time I get home I'm too tired to do anything but eat and fall asleep.  Don't feel too bad today but it can't decide if it wants to storm or not. I started to light up the forge and it started pouring again. It stopped but it's been raining off and on all day. Leftovers from the hurricane I guess. I'm off Friday so I'm going to try again if I don't get to it before then. I think it's gonna go better this time.

Pnut

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Going to be a scorcher Friday. I think here it is supposed to be 93 and of course humid. 

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Heat index here is often lower than the ambient temperature example: "Temp 95 feels like 94'

I remember 107 degF in Fort Smith with no AC...

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I was stationed at Ft. Hood for a couple years and it was hot. But the humidity was not near as bad. Then we had to go out to Ft. Irwin in the Mojave for a month out of the year for desert training. I remember one evening standing around before formation, nice summer evening, when the Capt. had us fall in he asked if any of us knew the temp. It blew my mind when he said 114*. I would have guessed upper 80's. 

I think it has peaked today at 95*, no idea what the heat index is but i would guess 105*

 

 

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I was stationed for three years at Ft. Irwin. I never thought temps in the 70s would feel cold, but those 40-degree swings between day & night sure did it!

Of course, I was quite a bit younger back then... *harrumph*

Anyway, heat indices here are over 100 all week. Not a deal-breaker for forging, but it requires some extra precautions and planning.

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