Is it safe to re-use the old bolts that attach the lower ball joint to the spindle?
These have been torqued to 100 ft/lbs and loosened with over 100 ft/lbs, and have aged 42 years - are they still equal to a new grade 8 part?

What do the experienced people here do?

One of the lower holes in a 10" drum spindle is threaded.
Both of the bolts removed from these threaded holes on the 1966 donor car were damaged.
It is possible that these bolts currently in my 9" spindles will also be damaged (or a different size). Or they may be weakened from stress.

So far, drilling out the threads and using new grade 8 bolts may be my only option.

Should I worry about drilling out the threads (with a hand-held drill)?

Should I worry about the actual strength of very old bolts?

Where are the scientists like Lou when people need them?

9" and 10" brakes use different size bolts. IIRC, 9" are 1/2" and 10" are 5/8".

_________________
Official Cookie and Mater Tormentor.

No.
The butt of a 1/2" drill bit barely squeezes into the hole in the 1966 10" spindle I'm holding. 9/16 is a no-go.
I only wish that it was 5/8" because I would have ordered the sbp disc kit from espo to get the supposedly more robust disc lower ball joint.


Even if the holes were 5/8, the same questions apply.

What's an IIRC, some radio-controlled or infrared thing?

The only reason I went with new bolts was that I was doing a disc brake conversion and had to use a larger bolt size than stock. The other reason to replace the bolts is if they have any visible damage - stripped threads, rust pitting, or cracking. If the bolts fit and are in good condition, I wouldn't hesitate to reuse them. Connecting rod bolts are subject to considerably more cycles, and they still hold together fine for 40+ years.

Drilling out the threads is a viable option if there is a good seating surface at the back of the hole. That is, a flat area perpendicular to the bolt and wide enough to accomodate a nut. If the surface there is off-perpendicular, don't do this unless you want to machine it flat. If that's the case, or you feel nervous about making such changes, you can use a Helicoil.

_________________
"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

I would use new bolts anytime the old ones are in question. You already know to use grade eight. They should be fine thread. Not made in China. I would use partially threaded bolts so if it ever did loosen, the ball joint and spindle would be trying to shear the full bolt diameter and not the reduced diameter of the threaded section. This is what the factory used. I have not seen the spindle type you want to drill. If it has enough meat around it I would go for having it drilled. I would only have it done on a drill press so it is straight and square. If you end up doing this make sure the face under the bolt head or nut is spot faced or already machined square to the hole. The head hight of the bolt is probably not an issue but worth checking to make sure it does not hit anything. good luck.

No drill press available.
The best I can do is slam a few dozen espressos to get the wavelength and amplitude of my shaking hand down to a minimum.

I will do my best to rescue the ones on my 9" spindles.

I guess I can take the spindles to a machine $hop if one breaks.

IIRC=If I Remember Correctly

_________________
Official Cookie and Mater Tormentor.

YD

=You Didn't


(but thanks anyway)