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Making splined shafts/axles, heat treat before machining?

Great conversation!

I am only making 1 or 2 of each shaft. These are CV axle shafts for custom AWD car build.

I am leaning very strongly towards the the heat treat and then machine. I am going to reach out to my local heat treater today and see how long of a bar they can do and if they can hang them vertically. But, my thought would be to by a 6 or 12ft piece and have the whole bar heat treated to 45 Rc. That way I would have plenty of stock on hand to make axles. After machining, they are ready to go.

Thoughts?
Tim

Depends how much you have to remove. If you HT the whole bar before machining and then remove a bunch of material you're going to have a softer part. A quenched bar cools slower in the center, so the outside is the hardest and it will be softer toward the core. I don't think that they'll be able to vertical quench a 12' bar either. Maybe your best option if you want to go that route is to have a small sample bar hardened and then machine it afterwards and have the hardness checked. You may find you want the raw bar hardened to 50 HRc so that your core is closer to where you'd like it.

Keep in mind, this will raise your tooling costs; as Bob noted, it's usually a much better idea to rough out first and leave finishing stock for after heat treat so there's not a lot of machining of very hard material. It will be especially brutal on any HSS tooling, and even carbide will take a beating cutting splines from solid at 45- 50ish HRc.
 
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I would guess the method is more even heating of the parts and a vertical quench. If you get it right there's usually very little warpage that way. The part being the same temperature throughout is also important to keep the parts as straight as possible. If it's hotter on one side than the other, even a vertical quench can result in warped parts. Many modern heat treating lines in mass production rotate the parts as they go through the oven for this reason.
Thanks, that makes sense in the context of what He wrote.
Beyond belief what was endured and tried, at great cost to find what's common knowledge today

"Men Perished in winter winds till one smote fire
From flint stones coldly hiding what they held,
The red spark treasured from the kindling sun;
They gorged on flesh like wolves, till one sowed corn,
Which grew a weed, yet makes the life of man;
They mowed and babbled till some tongue struck speech,
And patient fingers framed the lettered sound.
What good gift have my brothers, but it came
From search and strife and loving sacrifice?"

- Edwin Arnold
 
What are you doing with cut splines, anyway ? Roll, baby, roll !
You are correct.
In high volumes it is Kinefac or Anderson Cook style around here. Both are expensive tooling and and somewhat challenging to setup/adjust when new tooling put in.
It took me years and seemed like art but it is not.
Interesting in a big shop there not one ME in the office knew how this works. Oh the stuff team leaders would do chasing the specs trying as best to hit all the gauges.
They also do not want to hear anything at all from some old guy working as floor supervisor.
Splines on a axle shaft seem simple.... but....................

So a finished part here goes out the door for $3.00 max price of making.
What to make one or four and first part good ? Everything changes so no rolling.
Now you have to cut, worry about heat treat worse cases and dial it in.
Call it 2nd 3rd 4th op fussy work but worse is the extra cost.
 
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Thanks, that makes sense in the context of what He wrote.
Beyond belief what was endured and tried, at great cost to find what's common knowledge today

"Men Perished in winter winds till one smote fire
From flint stones coldly hiding what they held,
The red spark treasured from the kindling sun;
They gorged on flesh like wolves, till one sowed corn,
Which grew a weed, yet makes the life of man;
They mowed and babbled till some tongue struck speech,
And patient fingers framed the lettered sound.
What good gift have my brothers, but it came
From search and strife and loving sacrifice?"

- Edwin Arnold

Yes, it's pretty amazing how far we've come. It has taken a while though. The greatest ideas don't come along all that often, and some take a whole hell of a lot of toil to implement.
 
I am concerned about the shafts warping after heat treat and having to be straightened.

also depends on the heat treater, I don't do especially long shafts, but for instance around here (SoCal) Certified Heat treat can quench vertically, and depending on length some can't. I've had 30" long 4140 shafts that most local heat treaters couldn't do, but Certified could do vertically. Even so Certified had to do some straightening on the last shaft they did.
 
When you guys say "straighten" do you mean just bending it back straight? Like with a press or even with a hammer?
 
When you guys say "straighten" do you mean just bending it back straight? Like with a press or even with a hammer?
Yes.
If you make car axles or even 1/8 inch HSS end mills your raw stock comes in on coils so they run through a "straightener" before the cutoff and turn/grind operation but that is different.
I am talking here about press or peen after heat treat. Tricky and art. Done right and you can get to tenths but I do not like it.

In this things twist and move as they enter the quench oil so the way the "dunk" done becomes very important.
A sideways or batch drop not same as a length drop even though this is seconds.
On induction hardened the quench coils following are fussy guys in alignment, flow and timing. Change to a new quench ring and all is so wrong.

One gets used to the worst case distortion you see and how to deal with it.
Your nicely made to tents or microns tool holder for a CNNG-432 may come out spot on or way outside the .001/.002/.003 F/H/L
Bob
 
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Bob, I wonder if rotation during quench would be helpful. Lots of interesting ideas that I'm sure have been tried, but nobody wants to give away the trade secrets!
 
When you guys say "straighten" do you mean just bending it back straight? Like with a press or even with a hammer?


With a press

--------------------------------

Last place I worked we made parts out of 17-4/15-5/13-8 quite often off the machine they needed starightening, the owner was a genius with an oxy/acetylene torch and wet rags to straighten parts. The customers wouldn't have approved (NASA/JPL etc) what they didn't see didn't hurt them
 
The customers wouldn't have approved (NASA/JPL etc) what they didn't see didn't hurt them
Need to be careful with this. In some cases, what the customer would not have approved did hurt them. Especially in aerospace, where stuff is not engineered with a 5X safety margin due to weight constraints.
 
Need to be careful with this. In some cases, what the customer would not have approved did hurt them. Especially in aerospace, where stuff is not engineered with a 5X safety margin due to weight constraints.

These weren't flight hardware, test hardware, so no lives at stake, the FS on these parts was typically 4 or greater
 
Bob, I wonder if rotation during quench would be helpful. Lots of interesting ideas that I'm sure have been tried, but nobody wants to give away the trade secrets!
Parts need agitated during quench. If not steam/vapor bubbles clinging to surface make uneven cooling.
 
Parts need agitated during quench. If not steam/vapor bubbles clinging to surface make uneven cooling.

Yup. I wonder that rotation on axis and also in a sort of planetary manner might help with keeping things a little straighter. My luck I'd probably end up with a corkscrew.

Some places agitate the quenching baths too (pumped fluid currents).
 
300M with vacuum heat treat and high pressure quench. Mid to upper 50s on the C scale. May need some straightening but splines will be good to go. If this is a custom AWD car and it’s going to do anything exciting, just do it right.
 
Rockwell used 1045 for axles up to 4 ton ,and 4140 over 4 ton......if you go back to prewar days ,truck axles were made of 3% Nickle steel.,high load gears made of nickle chrome steel,.......this material was phased out early in WW2 ,as nickle was needed for battleship armour.
 
I am getting close to making the shafts I asked the question about. I spoke to a heat treat house, getting material. If anybody is interested in the project I first had to respline the CV axles these shafts will be used with. I made a video about it I can share. Is that allowed?'


Here is a slightly older video where a resplined the output of my transmission.


Thanks for the help and setting me in a good direction.

Tim
 
Checking splines is a bitch. Seems easy just rolls and measurement.
But then they do not fit.
Big high five to making a fit.
The adjustable thing is sort of not normal. I do wonder about balance and torque/shock load capability.
But if it works.(y)
Did work making and shipped these parts in large volumes.
Little Chevys to Doge Demons.
When mixing housing and attachment these things are graded and matched to each other.
Big fun when you have 2000 "green" spiders, 2000 "blue" housings and 10 hours away from ship time.

Just to give an idea of mass production vs one off. We would put these splines on in less than 20 seconds. Part load/unload the bigger part of cycle time.
The above video and making is so cool with me. Like it in so many ways.
Bob
 
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