Annealed 4140

[EdK]

(01-18-2013, 09:06 PM)PixMan Wrote: I'd be happy to run some tests for photos and videos, but all I have is 1" square shank negative rake tooling, so you guys probably wouldn't get much benefit from that.

No 4140 rounds here either, just some 1117 and my 4140 is all square block drops from Burgon Tool Steel Co.

I don't know Ken, I think we would benefit from any videos you would be willing to contribute. Speaking for myself anyway, I'd love to see some videos of machining any shape of 4140.

Ed

[f350ca]

Pictures as promised Ed.
The shaft is 46 inches long 2.357 dia at the ends with an undercut through the middle. As I thought it was too slender to cut in one pass without a follow rest. The middle wasn't critical so I just cut it in sections.



The surface came up good but has a visible pattern, can't feel it but its there. The ends were cut at .004 in/rev feed and the middle at .008 in/rev all at 400 rpm .030 cut. Carbide inserts.



The manufacturers part and mine. They wanted over $600, I charged $200 and the material was $130. There's has a through hole to stop the shaft rotating, it breaks there, stress riser I guess. Bill lost the bolt that goes through, the last one ran its life without it, so we didn't drill this one.

[EdK]

Thanks for posting the pictures Greg. That finish is definitely different from what I was getting.

Ed

[PixMan]

That's a tough job to do with negative rake inserts and no follower rest, nice work! I would have expected some chatter marks as I often get that until I play with insert geometry choices, speed, feed and depth of cut. It can take a few tries to kill the harmonic resonance you get with long turning like that.

BTW, the finish you see is usually a result of short chipping in the turning operation. It's a necessary evil with a long cut, otherwise the long stringy chips can get wrapped around the part, the machine and/or the operator!

[stevec]

Greg, what's the speed of the shaft? Does it run in bronze bushes? how is it lubricated?

[f350ca]

PixMan thats what I was getting long tightly curled cuttings, Much easier to deal with than the stringy ones.
Steve the shaft doesn't turn. Goes across the frame though cast mounts with ball sockets on the end where the blade mounts.

[stevec]

Thanks Greg, I'm having a little trouble picturing the function. If you could take a pic I'd probably understand better. No worry though, I'm just curious.

[f350ca]

No chance of a pick Steve, I never saw the machine just copied the shaft he'd bought. Guessing the idea of a single shaft verses two pins is to reduce torque on the frame rails.

[Mayhem]

(01-20-2013, 12:13 PM)PixMan Wrote: ...the finish you see is usually a result of short chipping in the turning operation. It's a necessary evil with a long cut, otherwise the long stringy chips can get wrapped around the part, the machine and/or the operator!

Ken - can you elaborate on what you mean by "short chipping" - is this the desirable little "9" shaped chips or something different. I get a similar finish in 1040 (feeding by hand). The only difference is I get some full circumference lines from the inevitable pause in hand cranking.

[Highpower]

(01-21-2013, 07:55 AM)Mayhem Wrote: Ken - can you elaborate on what you mean by "short chipping" - is this the desirable little "9" shaped chips or something different.

I'm guessing that is what leaves the somewhat 'mosaic' pattern in the finish as the chip breaks as opposed to the full circumference lines?

Another question: Isn't the goal to get short chips from any material when possible? Or not?

I realize that is probably impossible in some cases, but thinking back - I don't recall anyone ever recommending to TRY and cut long stringy chips in any material. Or have tool geometries progressed enough to eliminate them all together if you have the right insert/chip breaker?