Knuckle repairable?

[Godwin]

I've just stripped down a front axle and the caliper bolt holes on one of the knuckles have been resized. Stock caliper bolt diameter is 12 mm, the upsized bolts that I pulled out have a diameter of 13.8, or ca. 14 mm. Can these holes be repaired with a helicoil or have they been excessively enlarged?

 

[esh]

I wouldn't feel comfortable with helicoil on a safety component. I would probably take it to a machine shop to be filled and retapped (and get their opinion).

 

[2mbb]

Mine stripped out and I did replace it with a helicoil (12mm)--no problems yet. However, if your's was resized, I don't know that I would go back to the 12mm helicoil, not really knowing what they did to resize it. Another fix that people do is to drill and re-tap the stripped hole for the next size up SAE thead (1/2" I think)--do a search to make sure. Maybe that's what's been done to yours. Maybe the best solution for you is what Esh recommends, to weld up the hole then redrill & retap. And, you made also be looking at new calipers if your PO oversized that hole too.

 

[Godwin]

Yeah it was drilled and retapped to the larger size and the caliper which was on it had to have the bolt holes for mounting enlarged. Head size on the bolts used was 22 mm.

If the cost is reasonable I'd like to have it repaired so that stock bolts could be used, or at least a more stockish size. Any future caliper change would require a redrilling of the caliper mount and I want to avoid that. I'll check into the welding, drilling, and retapping option.

This was a parts rig and the PO had been driving it this way for who knows how long.

 

[3_puppies]

you should be able to pick up a used knuckle fairly cheap any one from '79 up including mini truck would work.

try in the wanted section

 

[Wile E Coyote]

you should be able to pick up a used knuckle fairly cheap any one from '79 up including mini truck would work.

try in the wanted section

With local pickup to avoid $shipping, I'll guess that this would be a cheaper and likely simpler solution. Assuming you don't just helicoil at the current bolt hole size.

 

[3_puppies]

With local pickup to avoid $shipping, I'll guess that this would be a cheaper and likely simpler solution.

Flat rate thru US mail even the big box is only $12 or $15 any where in the US.

the clerks look at you kinda funny, but you get your money's worth.

 

[Godwin]

I have two sets of 60 series knuckles on hand so no need to buy another. What I wanted to do was use one set on my 40 for a knuckle and brake upgrade and sell the other set. If I can properly repair this one knuckle so that there are no safety issues I'll keep and use it, otherwise I'll use the other set on the 40.

 

[ntsqd]

Look into using a Time-Sert or a Keensert instead of a Helicoil. For a given bolt size both of those thread repair options use a bigger pilot hole than does the Helicoil.

I don't have any worries about a properly done thread repair of this sort in a safety related part. Knowing that they are castings, no doubt good (steel?) castings, but still castings I'd have more concern over a welded repair. Far easier to screw that up.

 

[Godwin]

Look into using a Time-Sert or a Keensert instead of a Helicoil. For a given bolt size both of those thread repair options use a bigger pilot hole than does the Helicoil.

If this knuckle were some irreplaceable and unobtainable part the Time-Sert or Keensert approach might be the way to go. But for the price of some of these kits I could buy a couple of good parts rigs.

 

[ntsqd]

Hum, I just go down to my former employer's shop and use their kit. Had no idea that they were significantly more than a Helicoil.

 

[Godwin]

I had another repair option pop into my head this morning. Is this feasible?

Clean out the holes well and using the oversize bolts torque them in good with some high-strength loctite. Cut off the bolt heads and grind the shafts smooth with the knuckle face. Then drill and tap the bolts to the stock threading of the caliper bolts.

 

[ntsqd]

The minor diameter of the oversize thread needs to be something larger than the major diameter of the bolt that you intend to use. The closer those two diameters are together, the stronger the thread insert material has to be. This is a place where a G8 is not going to work unless the insert is huge, it needs to be something stronger.

Even the 620 or 680 Lock-tite would be on the low end of retaining choices for me. I would be looking more towards an epoxy like Miller-Stephenson 907 or consider brazing or silver soldering the 'bolt' into the hole. Staking it might work too. If it were a frequently disassembled joint I'd say that staking would be a short term solution as it would eventually work loose. Might be OK in this case.
Helicoils don't need any such methods because they are designed to be mechanically locking in the hole.

Also, suggest that pilot holes be drilled on center in the 'bolts' before they are installed or you may have a hole wander and then nothing fits.

For me, given the time that I have available to work on things I'm better off spending the money on a Time-sert, but that isn't true for everyone. Didn't used to be true for me either. I need to find that again......