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Posted by: aggiezig Feb 6 2019, 02:15 AM

Anyone know of a good source to buy class 12.9 M7 hex bolts? I'm looking to replace the bolts that hold the caliper halves together, if possible.

I had my bolts re-plated in zinc not realizing they were 12.9 grade bolts. Apparently, this is a no-no as harder bolts are more susceptible to hydrogen embrittlement during the plating process.

Any tips appreciated. I've done a lot of online searching but this is just a really odd sized bolt and hard to find, especially in 12.9.

Posted by: ConeDodger Feb 6 2019, 02:42 AM

Call PMB and buy from them.

Posted by: Mark Henry Feb 6 2019, 06:33 AM

New? good luck.
Off of a core or PMB

Posted by: mepstein Feb 6 2019, 06:53 AM

I'm pretty sure PMB replates their bolts. New ones are NLA. I think they need to be baked during the plating process.

Posted by: bbrock Feb 6 2019, 09:23 AM

I've read and watched the PMB brake rebuilt How-to and video many times as I'm doing it myself. He clearly states the fasteners are replated in black zinc. Everything I've read about hydrogen embrittlement says the parts need to be baked at 375F-400F for 4 hours within 4 hours of plating to drive the hydrogen out. Maybe ask the plater if they baked them?

Posted by: aggiezig Feb 6 2019, 08:19 PM

Great tips everyone, thanks. I believe the plater baked everything but not 100% certain.

I have a couple of cores laying around so may try to salvage those bolts, if not PMB is a good option, too.