Diabolus crank integrity after heating

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Diabolus crank integrity after heating
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Posted: Apr 13, 2010 at 14:00 Quote
For all the metal specialists out there:

Well, I finally managed to get my Diabolus cranks out of my 2005 Stab Supreme frame, and by 'I', I mean the wicked guys at Auto Service and Supply in Hamilton Ontario.

After the impact gun wouldn't work, they heated up the socket of the crank bolt with a torch and then used a big ratchet with another tube to get about 4 feet of leverage on it. Man the difference ultra quality tools make......

The main thing I wanted to salvage was my e13 mounting plate, but since the cranks are off now saving them would be nice. The crank bolt is pretty much destroyed as it has a small about of heat burn on the top surface of it and the 10mm socket is now a 12 corner allen bolt so its gone and needs to be replaced, but the cranks look fine.

Question: Is the drive-side Diabolus crank arm still strong enough after that type of heating, or has the strength been seriously sacrificed? There is no obvious heat burn on the crank, and although the crank was hot, it wasn't glowing or anything like that and no paint burned off.

Thanks guys

Posted: Apr 13, 2010 at 18:41 Quote
Anything over 320*F has a detrimental effect on common bike industry alloys. Eventhough time at temperature does need to be there too, I certainly wouldnt trust them with my safety.


As for reasoning behind my thoughts, Im a professional heat treater.

Posted: Apr 13, 2010 at 19:11 Quote
kylemciver wrote:
After the impact gun wouldn't work, they heated up the socket of the crank bolt with a torch and then used a big......

that's totally crazy, sounds like you're trying to take a crank pulley off a 20-year-old car motor. with that much heat I would bin the crank arm and also take a good long hard look at the bottom bracket bearings and any plastic or rubber seals involved. X-type external bearings or traditional bottom-bracket set-up?

pictures would help tons Razz

Posted: Apr 13, 2010 at 20:20 Quote
Thanks for the info.

I'll try and get some pics up tomorrow. I was always planning on getting a new BB because even though they still spin OK I can feel and hear a fair bit of grit when I spin the bearings. Set up is X-type.

Posted: Apr 14, 2010 at 7:30 Quote
I don't have an SLR so the pics are a bit poor.

The crank has no heat burn, or whatever the technical term is, and like I said it was never glowing or anything close to that.
The torch was directed into the socket, not laid onto the whole area and probably for 1min or less total over 5 min of working on it. The interior side of the extractor bolt still has grease on it, which doesn't look worse for wear or charred off except for a very small area directly underneath the burned area, the threads look fine all around. The crank bolt itself looks fine everywhere on the exterior, with lots of wet grease still on the threads and no charred areas.
The extractor bolt on L and crank bolt on R. You can see the heat burn on the extractor bolt, but limited to only part of it.

Posted: Apr 14, 2010 at 11:14 Quote
From the pictures and what you described, it looks ok and there shouldn't be any MAJOR change...

However, like hummeroid said it doesn't take much heat to change properties on bike parts?. Don't trust them. It's hard to tell from all the way over here just how hot it got.


Although I am still fairly new to this metalsmithing game, and heat treating is only a tiny part of my job. So trust his advice over mine tup

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