[How do I?] Machine This

mf294-4

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IMG_0006.JPG Bought a old military air hammer at a garage sale for $5. It had riveter heads which fit and some chisel heads that will work but the retainer will not go over them to hold them in. Need to machine them down to the profie of the riveter head. Very hard. Metal comes off in very thin strings red hot. Do I have the wrong equipment or is this something I can't do. It goes through carbide like crazy. Any other ideas?
 
Ditch the carbide and go with HSS. Try a slower speed till you get past the work hard surface. Carbide does not like interrupted cuts.
**********Just Saying***********G***************
 
Based on their purpose I would'a guessed them to be not very hard......hard usually means brittle, not so good for a hammer function.

As Gator said try HSS, if that doesn't work then tool-post grinder perhaps, but cover your ways to protect from abrasive dust.

I have had luck cutting and grinding "regular" air hammer/chisel tools. Maybe the military uses some high-price alloy.

Please let us know if you find something that does work.

-brino
 
I don't think you stand a chance with HSS and I wouldn't try to anneal either.

Now, not all carbide is created equal. Are you using brazed carbide bits or inserts?

i got a box of brazed on carbide tool bits at an auction years ago. They are 10X better than what you get from Enco. I'll give you one if you need.

If using inserts look for the grade just for cutting hardened tool steel. If you happen to be using a size Sandvick carries, look for grade 4040. don't know what other companies call this special grade.


EDIT:

I just looked up the Sandvick guide. Got CRS, its NOT 4040 that's for milling (that's Can't Remember S***)
http://www.sandvik.coromant.com/en-us/knowledge/milling/grade_information/pages/default.aspx

hardened steel is a ways down the page
 
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Those Heads are probably made from H-13 tool steel. Or D-2 tool steel. What color is the stringy chip when it cools? If the carbide is holding an edge, keep cutting. Small stringy chips maybe all you can do on cutting without doing an annealing process to the material. If made from tool steel, it will be through harden, not case harden.
 
Possibly just the outer skin has been work hardened, and will be soft inside, just need to get through the tough exterior to the chewy centre


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If nothing else works; cover up your lathe like a mummy, turn it on, and break out the angle grinder.
 
Guys, you are missing the point here.

These pieces are not CASE HARDEN!!! They are through harden. These are made from a grade of tool steel. My first guess is H-13. If not H-13, S-5 according to the Jorgensen blue book.

The hardness is probably around 50-55 HRC. That's why you are getting the red hot stringy chip off of the part.

These are tought parts, they take a beating in use. Normal 1018-1045, 41xx, 8620 steels will not hold up for this application.

And as I have said, they are not case harden. You cannot remove the hardness by cutting the surface down like you can on something that is case harden.

Ken
 
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