Hardened driveshaft?

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JMotuzick
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Hardened driveshaft?

Post by JMotuzick »

I’ve got a 106 that was dropped off today for a creeper install. The clutch is warn and the owner wants that replaced as part of the work. He made a drive shaft from “tool steel”. I’m not sure of the hardness. He is concerned that it might be to strong and that it should have a little give. Does anyone have any thoughts on the subject? Ken? Thanks for any input.
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Klapatta
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Re: Hardened driveshaft?

Post by Klapatta »

Hi Joe, if it's fairly easy enough to file its tough enough to take the torsion. I have used ground, unhardened A2 several times over the years with very good results. It's possible that's what you have there, if finish is ever a likely indication.
55,000 psi yield strength. Excellent wear resistance around throw out bearing. This one is a refurbished 15 year old former pulling clutch returned to near stock using the original A2 shaft. Free machining using HSS tooling with 8% cobalt bits. With standard HSS bits you may be for some tough drilling. My go to choice because it's easy for me to obtain.
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So I'd say it stood the test of time. Oh by the way the disc came from Dave's ground pickings. Always knew that would come in handy one day :D
McMaster - Carr# 8888K19.

Another more common choice is 4140 alloy rod. Somewhat more free machining compared to A2. 60,000 psi yield strength. Usually will have a more rough, cold rolled finish- still it's very accurate on the size.
McMaster- Carr# 5252T515.
Both list at around the same price so no real gains there either way.
Give it the old file test and go from there. ;)

JMotuzick
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Re: Hardened driveshaft?

Post by JMotuzick »

Ken
He said the finish was not polished. He also said something about the hardening was 1/32. Something else about the holes shink a bit so the spiral pins might be hard to install. I’ll try the file test tomorrow.

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Jeff in Pa
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Re: Hardened driveshaft?

Post by Jeff in Pa »

JMotuzick wrote:Ken
He said the finish was not polished. He also said something about the hardening was 1/32. Something else about the holes shink a bit so the spiral pins might be hard to install. I’ll try the file test tomorrow.
Do the file test. If it cuts, you'll be fine. If it "zings" and knocks the edge off the file, it's too hard. Just don't have your surface footage ( rpm ) too fast if drilling.

As a machinist, I'm having a difficult time with "hole shrink". It's not a plastic composite so hole size is hole size. Depending on what the drill composition is, it may cut tight but it's not going to shrink.

Jeff
125 & 125 with hydraulic lift

JMotuzick
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Re: Hardened driveshaft?

Post by JMotuzick »

Jeff
Thanks for the input, headed to the shop and I’ll try the file test first thing. If it passes I’ll assemble it and start the task of getting it in the tractor. I’ll post back tonight with how things work out.

JMotuzick
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Re: Hardened driveshaft?

Post by JMotuzick »

Jeff ken
Thanks for the help it filed just fine, so I assembled it! Mostly back together, still to install hood/grill and readjust the pto. I think he will be happy to get it back, I had told him it might a few weeks due to the holidays.

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Jeff in Pa
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Re: Hardened driveshaft?

Post by Jeff in Pa »

Glad I could help. They make fancy file kits that will only cut in specific hardness ranges but they are a few $$$

Although everybody wants "super tough" and high strength material, sometimes it's better to use something on the "softer" side as that material absorbs shock better and will slightly deform instead of breaking.

It's not a big deal in our regular use but material selection is more important in higher HP applications like the non stock pulling tractors. I don't know exactly what HP those folks get ( they tend to keep it a secret) but it is multiples of what our Cubs were originally designed for.

Jeff
125 & 125 with hydraulic lift

DaveKamp
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Re: Hardened driveshaft?

Post by DaveKamp »

I'll echo the others' sentiments about material hardness in drivelines. Having case hardening on wearing surfaces is desireable, but you don't want to harden a shaft for increased torsional strength. Any hardenable steel left soft, is fine, as you know you'll be getting good quality material, but having it hardened makes it subject to fracture.

The drivelines on these tractors, particularly the single cylinder powered ones are under a rather high Service Factor.... meaning, the torque they're transmitting, is not particularly smooth. Think of it this way... that single-cylinder K341 fires once... and from TDC to 180ATDC, the driveshaft goes from no load, to max torque, and back to zero... and after that, there's an exhast stroke, an intake stroke, and another compression stroke to go through.

The shaft is amidst torsional oscillation during the entire time... and those oscillations are REALLY FORCEFUL at times... much much more than say, a twin cylinder, or a four cylinder, or even a two stroke, will have a lower service factor, because they spend more time on power strokes,than the single.
Yes, I'm a Mad Scientist... but I'm usually happy, even when things ain't goin right.

Klapatta
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Re: Hardened driveshaft?

Post by Klapatta »

I did make one out of titanium however I must confess the time to give it a proper try out has never really come along.
So it's still sitting in the milk crate.
Yield strength 63,000 psi.
That said, I have made the collars out of A2 or 718 Inconel, both with very good results.
Yield strength of non heat treated 718 is 199,000 psi so maybe one of these days I ought to give that a try.
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While here I'd like to wish everyone all the best for a Happy New Year!
Ken

DaveKamp
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Re: Hardened driveshaft?

Post by DaveKamp »

Kinda slow on the take here...

but my opinion is that the driveshaft really isn't the component subject to greatest failure issue, and when it IS, it'd be most likely occuring in the spot where a hole was drilled through it, rather than in the main portion... the next most likely issue, is wear on the machined surface where it fits into the coupling (the pilot pin).

SO...

I'd keep the shaft soft, and if better wear resistance was necessary at the end, put a hardened sleeve, or a bronze bushing on it instead. Then, the only thing left in the 'weak link', is the hole, and the pin that goes through... and the jaws that the pin fits into.

But if I was REALLY wanting something more robust, I'd just nix the whole thing in lieu of a pair of sturdy U-joints and a slip-yoke type of PTO shaft material...

But that'd be silly, wouldn't it... :roll: :D
Yes, I'm a Mad Scientist... but I'm usually happy, even when things ain't goin right.

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