What tooling to turn a case hardened Chevy axle

outsider347

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Now that I have a better lathe ...PM 1236, I want to turn a couple Chevy rear axles that I have in stock
I did also move up to index able tooling , CCMT 300 series inserts that I also bought from PM
I am sure that the axle shafts a case hardened...had to cut them with a cut off wheel

Suggestions appreciated.
Tks Gents
ed
 
Case hardening is generally done to mild steel to make a few thousandths of the outside hard by
soaking it in a hot and carbon rich environment and then quenching it in oil. Axel shafts are generally
made of a hardened version of 4140 steel or close to that. You can soften an axle up considerably
by heating it up red hot and allow it to cool slowly in a fire. I have done this several times when I
want to machine on an otherwise very hard truck axle. A wood stove works great for this. IMG_0614.JPG


Note: You can see the end of the axle in the middle between the two logs. They are very machinable
after being in the fire. I use carbide to machine on this but I would think even HSS would work.
 
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Hard turning inserts, find an insert that fits your holders and have at it, I do it several times per month on automotive driveline components, works a charm and gives an excellent finish. Try not to go very far below the case as soft steel will play hell on some insert material.
NO COOLANT and the chip should come off glowing red so do not leave anything in the pan that will catch fire easily such as POM or PE.

https://www.sandvik.coromant.com/en...ning-in-different-materials/hard-part-turning

 
As others have mentioned, axles are are not case hardened. They are typically made of 4142 and hardened way up there in the 58 RC range. The annealing temperature for the chromalloy steels is 1600 to 1650F. You need to hold it at that temperature for 30 minutes for each 1" of cross-section followed by a 12 to 15 hour gradual cool down below 350 F. That will bring it down to about RC 25 which is very workable.

Your machine is a good one (I have the same machine) but, it's not really the best choice for "hard machining". I can and have done it using ceramic inserts but generally, avoid cutting metal that hard. It's tough on the machine. The only time I do that kind of work on my machine is for very small adjustments on simple features. A more suitable machine for "hard machining" is something in the ultra-rigid class with a 7 to 10 HP (or greater) motor.

You could also bring the piece up to about 1000 F, until it's saturated at that temperature then, let it cool down in the oven with the door vented over 12 hours. That will temper it down to about RC 40 which your machine can handle if carbide inserts are used.

Ray
 
I've used a couple of truck axles for shafting. Some cut reasonable with carbide, some eat anything you put up against them. Those ones get tossed as they cost nothing in the first place.

Greg
 
It sort of depends on what you are doing. If the final product can be soft, then anneal as described by others above. If you want it hard, then it is no big deal to hard turn as has also been described above. If you are just doing a few pieces, then most any carbide, speeds, feeds - will be fine. If you are going to do quite a bit, then get some inserts designed for that application.

I have annealed axles and found that they turn out almost "gummy" soft. I've turned axles in the hard condition and you get a beautiful finish, just tough on the inserts.
 
1600-1650 is a bit too high on temperature, that is your Normalizing range. Material will be very gummy to cut and dead soft. 1450-1550 degree F is your annealing temperature range. Just do like Ray said at his last statement, temper at about 1000 degree F. That should get you in the high 30's HRC. IT'll cut nice and sweet with the right insert or even HSS with a ground in chip breaker.
 
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CBN or Diamond tipped (as used in the video)
 
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