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The Stuff from hell :-)

Got a job in our shop right now that I wish would go away. Putting a

2-3/4" hole 8" deep through a block of 718 Inconel. Shoving a spade drill through it takes a couple of hours(2-1/4") with a 1/2" starter hole first. The spade drill inserts will be toast when done :-) The turning and boring is slow but not to bad, 40-50 fpm. Also have to put 4 3/4-10 tapped holes in one end. The set-up time is the real killer on this stuff, took a couple of days to figure out the procedures. Hopefully no more glitches and we can finish up the rest of the pieces.
Reply to
machineman
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Sounds like a job for EDM

Gunner

"I mean, when's the last time you heard of a college where the Young Republicans staged a "Sit In" to close down the Humanities building? On the flip side, how many sit in's were staged to close the ROTC building back in the '60's? Liberals stage protests, do civil disobedience, etc. Conservatives talk politely and try to work out a solution to problems through discourse until they believe that talking won't work... they they go home and open the gun cabinets. Pray things never get to the point where the conservatives decide that "civil disobedience" is the next step, because that's a very short route to "voting from the rooftops" Jeffrey Swartz, Misc.Survivalism

Reply to
Gunner

I've been told that HSS works well in Inconel, as opposed to carbide (though that could be incorrect).

You should ask for recomendations on alt.machines.cnc. There are a bunch of competent machinists there who should know how to deal with super alloys. Have you talked to your carbide salesman?

Regards,

Robin

Reply to
Robin S.

Unfortunatly thats not an option :-( Burn time on nickel alloys would be pretty long, even if using thin tubing for an electrode. Plus the recast layer would be pretty hard as well, probably really screw up the inserts on the finish bore :-) Slow and steady on a good solid machine does the trick, and hss tools seem to work well, just have to keep an eye on them and resharpen as needed.

Reply to
machineman

we made breaker plates from an inconel alloy, a honeycomb of 3/16" holes thru 1/2" thick

hss worked better than cobalt

the drills had to run rediculously slow, the mill head in back gear, maybe

80 - 160 rpm? I just remember the squeak squeak squeak

had to re-point the drill every other hole

Reply to
Jon Grimm

Yup. I tried a carbide tipped drill for the tap drill, worked for about

4 holes before shattering, probably due to chip packing that wouldn't allow the coolant down. I switched to a good quality hss drill with a really thick web and TIN coating. I ground it on our drill grinder and split the point by hand. ran it at 94rpm and feed at .33ipm. I check it after every 8 holes and resharpen as needed. I have 10 more to do, I am just hoping the 3 taps I have will last :-)
Reply to
machineman

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