High Tensile Bolts

[ALAN COCHRANE]

Hi Everyone

Can anyone clarify whether hot oil dipping high tensile bolts alters their tensile strength.
The reason I ask is that I’ve just rebuilt a spare set of Girling 16P calipers for the GT6. As part of the rebuild I split the caliper bodies and replaced the internal O rings. The four bolts holding the two half’s together had some surface rust around the heads but were otherwise in good nick. I heated each one with a blowtorch until red hot and then dunked them in oil. They now look nice and black, but I’m now wondering if this was the right thing to do.

Cheers

Alan

Alan

[JagWaugh]

You've hardened them. Hardening also makes them more brittle.

Buy new bolts.

Get a bottle of gun blacking. Or Google "DIY Parkerizing".

The formula I use is pretty much this: https://www.milsurps.com/showthread.php?t=43247

Parkerising is dead easy.

[ALAN COCHRANE]

Thanks for the info. I suspected this was the case.
I now have the option of nickel plating as well since buying a kit online. I’ll swap the bolts out of the existing callipers and use them if they’re in gods nick.

Cheers

Alan