# Fixing my mistake



## shell70634 (Apr 12, 2021)

I bought the wrong size.  Boring head is 3/4.  Bit holder 3/8.  Shank of new tool 1/2.
My choices:
1.  turn shank down to 3/8 and shorten
2.  bore bit holder to 1/2 ( I have another)
3.  Make a new bit holder.

I think #3 is my best choice.  Your opinion?  Would 4140 be an acceptable material?  How about 304 stainless.  I've got both handy.

I hate returning things when it's my fault.


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## NC Rick (Apr 12, 2021)

Seems like a new holder will be the best answer.


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## aliva (Apr 12, 2021)

I'd make a new holder from 4140 and harden.


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## graham-xrf (Apr 12, 2021)

aliva said:


> *I'd make a new holder from 4140 and harden.*


*On the subject of hardening 4140.*
I have a rod of EN24T , and a choice for EN19T. These are European designations for an air hardening steel very like *4140* in makeup.
The intended use is a replacement tailstock quill.

The hardness I have listed for these is the pre-tempered value the have as supplied. 4140 is supplied as 18-22 HRC.
My rods are range 24.2 - 32.1 HRC.

Heat treatment of *4140* is to heat slowly up to 840°C-875°C, and soak (how long). Those would be 1544°F - 1607°F equivalent.
Then cool in air.
Then re-heat slowly to (some temperature??) between 550°C and 700°C depending on how hard you want it to end up, and soak for 2 hours per 25mm of ruling section. Those values are 1022°F - 1292°F.
Then again, cool in air.

I lack the final bit of information. How hard does it get? What is a good final hardness value to have for a tool holder? What temperature do you need to get it there?

I understand that second heating (tempering) value should not use values between 250-375°C because the Izod impact toughness value would be adversely affected. I guess it would still be "too hard", and a bit brittle.


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## T Bredehoft (Apr 12, 2021)

I anneal, (second heat) 4140  at 450ºf in my oven, one hour per inch (or less) of thickness, turn off the oven and let it cool. I  figure this leaves it about 60C, but no documentaiton on this, just feel.  The last I made was a drill jig for .035 inch drills.


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## ericc (Apr 13, 2021)

graham-xrf said:


> *On the subject of hardening 4140.*
> I have a rod of EN24T , and a choice for EN19T. These are European designations for an air hardening steel very like *4140* in makeup.
> The intended use is a replacement tailstock quill.
> 
> ...


4140 is not air hardening.  Cooling in air will probably produce poor results.   A fast oil (warm a bit) would be better. S-7 is air hardening with about the same amount of carbon, but does not get all that hard.  It's great for hot cutting and punching tools.


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## graham-xrf (Apr 13, 2021)

ericc said:


> 4140 is not air hardening.  Cooling in air will probably produce poor results.   A fast oil (warm a bit) would be better. S-7 is air hardening with about the same amount of carbon, but does not get all that hard.  It's great for hot cutting and punching tools.


Eric - if that is the case, then all my info is wrong! I have attached the stuff I have.
4140 is a chromium - manganese - molybdenum - nickel alloy with up to 0.4% carbon. It does not harden and temper like carbon steel.


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## ericc (Apr 13, 2021)

That is correct.  It is not like simple carbon steel, but it does not have enough chromium or molybdenum to air harden.  Also, it shouldn't be used past about 50 RC.  For cutting tools, use another tool steel.


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## NC Rick (Apr 13, 2021)

Why not use pre-hard 4140, i like that stuff.


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## NC Rick (Apr 14, 2021)

shell70634 said:


> I bought the wrong size.  Boring head is 3/4.  Bit holder 3/8.  Shank of new tool 1/2.
> My choices:
> 1.  turn shank down to 3/8 and shorten
> 2.  bore bit holder to 1/2 ( I have another)
> ...


I apologize for not reading your post carefully enough.  Making a new holder would be a fun exercise.  If you have another unused holder indicating the existing hole and boring it out to 5/8 seems like a reasonable option to me.  If a file will cut into the nose of the holder (which I assume it will) i would try a carbide boring bar to get it within a few thou and maybe ream it to size?  I wouldnt have real good confidence in my ability to hold size down the length of that bore with such a small boring bar.  Others will be more experienced than I.


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## MrWhoopee (Apr 15, 2021)

Agree with @ericc, if the material you have is equivalent to 4140, it is an oil-hardening steel with a maximum hardness of about Rc 48-50. Pre-hardened 4140 will be Rc 28-32.

"Heat Treatment
AISI 4140 alloy steel is heated at 845°C (1550°F) followed by quenching in oil. Before hardening, it can be normalized by heating it at 913°C (1675°F) for a long period of time, followed by air cooling."









						AISI 4140 Alloy Steel (UNS G41400)
					

Alloy steels are designated by AISI four-digit numbers. They comprise different kinds of steels having composition exceeding the limitations of B, C, Mn, Mo, Ni, Si, Cr, and Va set for carbon steels.




					www.azom.com


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## shell70634 (Apr 16, 2021)

I made a new one from 4140PH.  Came out great.  I'm not going to harden as the originals didn't appear to be much harder.  If it wears out in whats left of my lifetime I'll be amazed.


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## Manual Mac (Apr 16, 2021)

What exactly is that holder called?
Anybody have a link for it.
I have these that I have made, that work fine, but I like the that you ordered wrong.
Thanks


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## NC Rick (Apr 16, 2021)

shell70634 said:


> I made a new one from 4140PH.  Came out great.  I'm not going to harden as the originals didn't appear to be much harder.  If it wears out in whats left of my lifetime I'll be amazed.


That stuff is so nice to machine as well.  It wont hardly deflect.  Tough one piece chips for me most often though.  I like that i have a ready made part when done with carefully controlled heat treating.  I doubt the originals are made from such good steel. 1045 or 1050 would work but i hate machining it and my “torch and dunk“ heat-treat system isn’t exactly laboratory grade.


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## MrWhoopee (Apr 16, 2021)

For future reference, pre-hardened 4140 is referred to as 4140QT or 4140Q&T (Quenched and tempered). PH is used for precipitation hardening materials like 17-4PH or 15-5PH. Aluminum alloys like 6061 are precipitation hardening (sometimes called age hardening) but do not use the PH designation.






						AISI 4140 AISI 4140 Q+T Round Bar Sales Promotion after coronavirus .
					

In the beginning of this month , we have AISI 4140 Q+T Round Bar Sales Promotion . Thanks all our regular customer to care about our healthy and situation .



					www.otaisteel.com
				









						Stainless Steel - 17-4PH alloy, FeCr17Ni4 -
					

Stainless Steel - 17-4PH alloy, FeCr17Ni4. undefined. Synonyms:  . CAS null. Molecular Weight null. Browse Stainless Steel - 17-4PH alloy, FeCr17Ni4 and related products at MilliporeSigma.




					www.sigmaaldrich.com
				









						Heat Treating Aluminum 6061 - Quenching and Aging Aluminum 6061
					

To highlight our aluminum heat treating processes, we’ll walk through an example of our process with 6061 aluminum as our metal of choice. Contact us now.




					www.jmpforming.com
				




Class dismissed.


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