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.
 

Janderso

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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

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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.
 

Janderso

Jeff Anderson
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Got started on the project yesterday. Cut 4 to size,laid out scribe lines etc.
I am drilling through holes (#3) for the 1/4 28, that went fine, I center drilled and ran a #28 pilot hole for the 7/16" -20 threads for the adjusters.
The book says to use a 25/64 drill. I broke 2 drill bits.
I'm thinking I need to gain on the size, too big of a bite or the bits are too hard.
This is annealed 4140, I am trying to avoid work hardening the material so I'm going in pretty heavy.
Ace had Milwaukee black oxide "Thunderbolt" 135 degree tip, Maybe the lightning made the bit too hard?
I wonder if they will take it back-exchange? I'm gonna try.
Your thoughts?
 

Bob Korves

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It might be annealed as purchased, but it sounds like you have work hardening. If you dwell with the drill rubbing, it will get harder than Kryptonite. But you probably already know that, Jeff. If that is the issue, it will need to be annealed or maybe use a carbide drill, though that can just ruin the carbide tool. What machine and speed are you using to drill the holes? I do not trust ANY hardware store drills any more, regardless of brand.
 
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RobertB

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Ace had Milwaukee black oxide "Thunderbolt" 135 degree tip, Maybe the lightning made the bit too hard?
I wonder if they will take it back-exchange? I'm gonna try.
Your thoughts?
Review of these from Milwaukee's site:

Bit snapped in half drilling second hole
Used a 27/64 bit to drill a hole in an acrylic pen blank. On the first blank it drilled a nice clean hole. On the second blank the bit seized and snapped in two. Generally I have had good success with Milwaukee products. Right now I am considering this product failure a fluke. Too early to provide any type of recommendation, will wait to see how the remaining bits perform but I would say I am disappointed.



  1. Response from Milwaukee Tool:
    Anonymous
    · 2 years ago

    Thank you for your feedback. We would like to learn more about your experience and work with you to rectify this issue. If you could please contact us at socialmedia@milwaukeetool.com we would appreciate it.


 

rgray

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I center drilled and ran a #28 pilot hole for the 7/16" -20 threads for the adjusters.
The book says to use a 25/64 drill. I broke 2 drill bits.
Are you doing this on a mill? If so don't drill a pilot hole. Spot it and drill with the 25/64 drill. Start at 500 rpm and if easy increase to 685 at most.
Don't get crazy about work hardening. Don't know if you have down feed but if so feed at 5-7 thousandths per revolution.
It's not stainless never had the work hardening with it as bad as with stainless.
 

MrWhoopee

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Jeff, it sounds like you might be pushing the feed too hard out of fear of work hardening. #28 is a fairly small pilot, so I doubt the drill is self-feeding. Use cutting oil and drill like it's cold-rolled. As long as the drill is cutting you won't get work-hardening.
 

Janderso

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I'm running at 500 rpm, it just seems right.
I hadn't thought of no pilot. I ran an H (.266) cut like butter.
I'm thinking I'll just get a quality bit next week. I buy all my drill bits from McMaster Carr.
I've had good luck with their products and you can't beat the service.
I don't know, drill bits have to be tough enough but not too brittle.
The Norseman Magnum, ( Super Premium, Made in USA) letter set, is the best quality drill bits I've ever owned.
I'm still going to try to exchange the bit from Ace.
It's pouring rain right now. I may melt.
 

rgray

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HSS drill at minimum. Cobalt even better. Harbor freight actually has a set of cobalt drills that are decent.
Tried looking them up and mine are standard point and if I remember $40.00 range.
All I find on their site now is split point and they are $65.00 item # 61885
May be decent.
 

Janderso

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I was able to exchange the Milwaukee bit.
Let's try this again.
 

Janderso

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Idecided to add the 10/32 allen set screw with a brass tip on the end of the t slot chuck stops I’ve been working on.
I ended up heat treating my prototype this afternoon. 753EE0DE-A9D2-428F-8E35-1F54F6405413.jpeg 04912771-0AED-4A98-80B4-3BD7D3A9AEAF.jpeg 6D4E6A79-E8B3-4A91-BE18-7C0232D8C045.jpeg 02254093-DE7D-4B3C-82BB-B29A088DD52E.jpeg
It went well, it is pretty tough now.
The next three will be done in series at the same time.
 
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