Annealed 4140 for project = DIY hardening?

Janderso

Jeff Anderson
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Hi gang,
I plan on making a set of 4 adjustable chuck stops for the t-slots on my 10" Bison 4 jaw.
I got the idea from watching Tom Lipton's video. He got the idea from Robin Renzetti. I won't try to make Mr. Renzetti's version.

I purchased the annealed 4140 from McMaster. It's 1" X 3/4", I'll cut them to just under 3" long. Manageable size IMHO.
My plan is to perform all the machining, cutting, drilling and most of the finishing, then do a backyard hardening job.
I've had good luck so far hardening small parts then bringing them back to a golden straw.
I've always used tool steel, never 4140.
Have you ever done this?
The consistency and the hardness is not critical by any means.
 

RJSakowski

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I would expect some warping of parts hardened after machining. Usually parts would be semi-finished and ground to final dimensions after hardening. If your design is based upon Tom's, you might have some problem with the threads.
 

Illinoyance

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Consider using an oversize tap on parts to be heat treated.
 

Janderso

Jeff Anderson
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Alright, good advice.
I was planning on using my surface grinder for the finish.
I had not considered the threads.
 

Dabbler

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4140 is one of the least warping steels I have tried. Make sure your quench is quick and move it around in the oil so it is quick, and you shouldn't see warping beyond .002 per inch.
 

Dabbler

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A tip: buy a dollar store metal sieve like one used for draining noodles, and nearly fully submerse it in your oil. Drop in the part, and use the sieve to agitate it. Makes the cooling even and very fast, compared to using tongs and swirling it around. If the parts are small, use a large can of oil 1/3 full and just swirl it. note you need a lot of volume of oil or it heats up too much. THERE WILL BE FLAMES.
 

T Bredehoft

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I've been concerned about soaking 4140 at temperature, I understand it should be soaked an hour per inch of thickness, but haven't documented this.

I made an acme threading tool from 4140, did not harden it and have cut several threads with it with no degrading of the cutting surface. I hate to admit this, but I was cutting half hard 4140.
 

Janderso

Jeff Anderson
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Nutfarmer
I may just take you up on your offer.
Thank you,
 

rgray

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Tie a length of stainless lock wire to it for a way to pick it up and dunk it. That way you won't have to worry about the area where it is picked up.
Also less likely to drop it that way.
 
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