Drilling Chrome Steel Help please

[foamcutter]

I need a little help. I have an idea but it involves drilling and tapping threads in Chrome Steel. They tell me it has a hardness rating of Rc60. I don't know much about this but I'm thinking that's going to be really tough to drill and tap. Needing to bottom tap hole about .5 to .75 in deep. Anyone got any ideas? Thanks Ron

[keithorr]

Machine when annealed, and then harden. Rockwell C60 is getting up there. I make shear blades from D2 that gets hardened to C61 after machining, but I back it down with a temper to C55ish, according to the manufacturers instructions.

One blade of each pair is drilled and taped before hardening. The only thing I can do after hardening is chase the threads to remove scale/carbon and the final grind on the cutting edges.

[foamcutter]

Keithorr,
Thanks for the reply. These are already hard. They are 1.5 inch balls. Could I anneal them , drill and thread and then harden again? I have a small electric furnace that I melt and cast aluminum with that will get up around 1200 degrees. Would that be enough to anneal? Then drill and tap. Put back in furnace and heat again and immerse in oil to temper? How much warping or out of roundness do you think I would get doing this?

[keithorr]

Temperature and process depends on the alloy.

http://www.tndie.com/

[HuFlungDung]

Here is another thread on this sort of topic:

http://www.cnczone.com/showthread.ph...hardened+steel

[castguy2003]

Be sure to get oversize taps designed for parts that are going to get hardened or you may be in for a big surprise.

[TAB]

I would suggest having the threads EDMed into the parts. This will cause the least distortion. If you temper and anneal the shape could be altered to such a point where the rods are no longer useable.

This may be expensive so only you will know if these parts are worth the cost.

Good luck.

[foamcutter]

Thanks for all the replies. I have come to the conclusion there must be a cheaper, better way to get where I want to go with this. Trying to drill and tap them is going to be an excersize in waisting time and the price of having someone EDM is too much. It was to be a cheap project, now it is simply waiting til I get a better idea. Thanks guys Ron

[Konrad]

You can try, heat up the balls to a cherry red, then put it in ashes, to cool it down slowly.
Then, see if you can file it!

To re - harden it, heat up again to a cherry red for a few min. then quench in oil.

Konrad

[BT1]

Why not do your operations prior to hardening, then try chrome or nickel plating etc.