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Un-plugging a Pritchel hole


Aaron J. Cergol

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Ive got a 360# north German pattern double horn that I'm currently using. It's all torch gouged up, but has a flat face and tremendous rebound. The Pritchel hole is plugged with...metal? And is rustd solid. I've soaked the Pritchel in penetrating oil for weeks, moved it under the drill press and tried drilling it out. Three drill bits later, still nothing. I took some heat to it, but don't want to get it hot enough to ruin the temper. As a last resort, put a round punch in it, and struck it repeatedly with a sledge...didn't budge. Being that its a German pattern, I cannot access the hole easily from the bottom as the foot of the anvil would be in the way.

Any ideas?

Aaron

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If you couldn't drill it out that could mean that there is a piece of hardened tool steel broken off and jammed in there from some sort of tool like a punch or it's hardened weld material.  I don't know why anyone would put weld in a pritchel hole but I guess it's possible.  When you tried to drill it out what did you see in the hole afterwards?

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It seemed as if there were two pieces of metal wedged/rusted in. The first one was on the surface of the face and drilled out easily. The other seemed to be hardened and was deeper in. Looking in with a flashlight after drilling I barely see any shiney spot. Looking up from the bottom, its well rusted in. Being a German pattern, the pritchel hole goes through a solid 4.5" of material making this even more fun. :P

 

Thanks for the acetone mix-I will try this.

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Aaron - you burning the bits up or breaking them?  You should be able to drill it out, you just need the right bits.  And start small.  Possibly try a screw extractor?  If you can get it to bite you should be able to stick a wrench on it and get it to vibrating with a hammer.

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I have seen people drill hardened tool steel with carbide tipped bits. Slow drill speed, and I would think coolant would help. Some people have used the coal drill with a carbide bit to drill through leaf springs and I am sure they are very hard.

 

Maybe look into using a magnetic base drill with a carbide cutter in it. 

 

Can you heat some from the bottom so there is less chance of over heating the top?

 

Good luck, and some pictures could help us suggest more tips of removal.

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Tried cobalt, tried black oxide, tried carbide bits under the press going at a very slow RPM. nothing, no chips. Center punched it first and used copious amounts of oil. Cant get an EZ out or extractor in there with no pilot first though. I have often thought a mag drill might be the ticket. I have a freind who has one, that might be next.

A cole drill isn't a terrible idea! I think that might just work, and certainly in conjunction with some heat. Will have to figure a way to clamp it though...nothing to really get a firm grip on as everything that is available to grab is angled.

Macbruce-I don't have a compressor or air chisel, but I do have access to a jackhammer...hopefully it won't come to that. :P

Aaron

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I'd sure try to get a punch in there from the bottom. You could bend the punch to pass the foot or hammer on a second bar laid across the punch. If it's wedged in from the top, so some impact from the bottom might be just what it needs.

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Aaron:  Their is a diesel engine repair shop in Irwin, Il.(west of Kankakee, Il.) that has a machine that can vibrate/heat its way thru a broken headbolt or whatever without putting too much heat on what you want to save.  I can't remember the name of the machine however.  The point is their should be a repair/machine shop in your area that would have thise same machine that you could  take your vise to.  Maybe somebody on this site can put a proper name to this machine.  Meantime I will try to get more information tomorrow.   Armand

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Sounds like you have tried and been given alot of good suggestions. Last resort would be to heat the mass with a cutting torch and blow a hole through the center and then try to hammer and chisel out the remainder. It might loosen it up with the heat and by blowing out the center it will give it room to move. I know you are worried about ruining the temper but as long as your below 500 degrees you should be ok. You are heating up just the obstruction not the anvil. Good luck how ever you go.

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The absolute LAST THING TO USE is an Eazy-out, like never!!!!!! Drill slow with water as cuttting fluid, oil is a lubricant, lubricates the cutting edge, WRONG thing to use!!!! If you can't punch it from the back-side, either drill VERY SLOW with a diamond bit (or ceramic) or cut it out with a torch and an oxygen lance. EDM would work well.

 

Maybe it is a candidate for shooting!!! gun powder might shake it free!!! :)

 

Neil

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A few small drips of nitric acid a few times a day for a few months.

or

solid Bronze rod a bit smaller than the hole wanted with course grit diamond dust (lapidary store or ebay) and water slurry on low setting under your drill press. Hang a weight or spring off the feed handle on the drill press and walk away. Clean out the hole every five minutes and add new dust/water. Be done in an afternoon.

 

Ric

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  • 3 weeks later...

Hi    I dont know what a cole drill is but a cobolt Drill bit should bore through just about anything as long as its done slowly and cutting lubricant is used one of the water based emulsions are best,you say there is a lot of tourch guogeing evident so may be you are worrying about the temper a bit to much as its already been knocked about. good luck and let us know how you get on

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  • 3 weeks later...

I was thinking the same thing about it being tapered and wedged in from the top. I believe your best bet would be to try to drive it out from the bottom. Though the gunpowder solution might be fun :P Tap the bottom of the pritchel and make a breech plug, with some black powder... (I'm not serious, depending on the weight of the plug, even a relatively slow speed like 500fps would send it through anything it wanted to, just about)

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