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Old 12-21-2019, 07:54 AM   #1
AgentX
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Default Clutch pushrod re-hardening?

Hi, all-

Bottom line up front: If I grind my Norton clutch pushrod end to reshape it, does it need to be heat-treated again?

If so, how? I made an initial attempt with a plumber's torch, heating to just above a dull red glow, quenched in vegetable oil, and tempered till it just turned a light blue.

Context:
I installed a Newby clutch on my Matchless G15-CS. (I can cross-post a thread I have on Access Norton if anyone's interested...) Was a little more than an easy drop-in, but not too complicated.

The arrangement requires a rounded pushrod end. I had been using a ball bearing in the position originally, but after shortening the transmission mainshaft for some wear clearance, that arrangement looked sketchy as the ball wasn't really captive in the pushrod tunnel anymore.

So lacking machinists' tools and skills, I put the pushrod segment into my cordless drill chuck, clamped it to a bench, and spun it against a counter-rotating Dremel flap wheel until I got the right shape.

Figured I'd re-heat treat it, and gave that a try, but now I need to remake the whole arrangement due to the length changes in the mainshaft anyhow.

Appreciate any insight you can give someone new to anything metallurgy-related.

-Mike

Edit: Link to the Newby installation thread on Accessnorton:

Last edited by AgentX; 12-21-2019 at 08:01 AM.
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Old 12-21-2019, 09:30 AM   #2
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Default Re: Clutch pushrod re-hardening?

You can get a piece of drill rod and make a new one...it takes a heat treatment well. In the past I have also brazed a ball bearing onto the end of the rod, ground it down to the right shape and then heat treated it afterward.
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Old 12-21-2019, 10:16 AM   #3
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Default Re: Clutch pushrod re-hardening?

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Originally Posted by Goldy View Post
You can get a piece of drill rod and make a new one...it takes a heat treatment well. In the past I have also brazed a ball bearing onto the end of the rod, ground it down to the right shape and then heat treated it afterward.
Thanks, Goldy...great ideas. I had considered getting drill rod from McMaster instead, but Norton clutch rods aren't very expensive, and the cost of shipping might even out any savings. But I might need other stuff from McMaster, too.

Just for my info, does any grinding I do affect existing hardening? Especially/essentially...is the hardening effect surface-only, or does it extend through the depth of the piece?

If I do need to re-harden it, is there a better method than what I've done?
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Old 12-21-2019, 11:17 AM   #4
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Default Re: Clutch pushrod re-hardening?

I do hillbilly heatment a lot.... if it's good steel that will harden, heat the end bright red and plunge in oil... it will make smoke....Once cool, heat to about 400F, a straw color, let it cool slowly to temper it so it's not brittle..
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Old 12-21-2019, 11:57 AM   #5
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Default Re: Clutch pushrod re-hardening?

If your reshape is a couple thou, and you are careful to not get it hot grinding it will be fine. If you do get to needing to reheat treat there are plenty of how to's on line. I'd have a close look to see what the color is at before you start so you have reference to return it to.
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Old 12-21-2019, 04:51 PM   #6
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Default Re: Clutch pushrod re-hardening?

Trucked/Joe, thanks a ton.

I have to do some significant reshaping, so I'll reharden and temper as described. I followed the Wikihow the other day, but think I over-tempered it, taking it to blue rather than straw.
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Old 12-21-2019, 06:59 PM   #7
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Default Re: Clutch pushrod re-hardening?

I think straw would do, that would be like a screw driver. Even to purple would still likely be good.
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Old 12-22-2019, 03:27 AM   #8
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Default Re: Clutch pushrod re-hardening?

is that a ball and ramp, helical gear or actuating arm acting on the push rod, can't remember from my Matchless days. Whatever, if it's an arm don't lose the mechanical advantage buy having the rod too short. To keep the length I've put the BB at the clutch end next to the adjuster and a;so had two piece rods with the BB in the middle.
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Old 12-24-2019, 06:55 AM   #9
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Default Re: Clutch pushrod re-hardening?

Thunderbird, the actuator is an arm which cams a large, captive ball bearing against the pushrod in the tunnel.



I forgot exactly how it worked, and ended up trying to put a ball bearing next to this assembly...and promptly jammed it up when the small ball rolled into the actuator mechanism. Had to take the outer cover off and clear it from the outside. Multi-rod assemblies have likewise been difficult to take out of the pushrod tunnel.

I think I'll ultimately go with a two-piece rod with a long inner section, ball bearing, and shorter outer section with rounded nose. But might just go with a one-piece rod for simplicity till I have everything else working perfectly, too.
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Old 12-25-2019, 02:48 AM   #10
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Default Re: Clutch pushrod re-hardening?

not sure if you're saying you put an additional smaller BB next to the one illustrated? whatever, personally I'd stick with the original actuating end set up . just make sure you use the correct size BB and there isn't constant pressure on the rod between the arm and BB otherwise you're back in the hole with case hardening failing.
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Old 12-25-2019, 07:09 PM   #11
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Default Re: Clutch pushrod re-hardening?

Quote:
Originally Posted by Thunderbird View Post
not sure if you're saying you put an additional smaller BB next to the one illustrated?
I did, briefly. It was not a good idea.

I tend to run the pushrod adjuster on the looser side of things. Figure just a little looser is better than too tight, as you note, especially as things heat up.
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