Pin drive bolts splitting Help Please

[David Kirkham]

Originally Posted by Ant

David brilliant job, I normally look indepth at components to see if they are engineered correctly, but wouldnt have thought to on the pin drive nuts.

We have machined all our hubs from 4140 front being similar to original with press in pins and retaining nuts so not a problem there, but on the rear we made adapters similar to Trigo, I tested the Trigo adapters before I sold them and they are just normal soft free machining steel from memory so I wasnt happy with them even though that type of steel is probably adequate for the job.

I am using Cap screws and the Trigo Pin drive bolts on the rear, but now have major concerns with the small seating ring area, and I have had two of these trigo pins have approx 3/32" chunks of metal break off the inner sharp taper just with assembly maybe the metal is quite hard or brittle!
I will consider machining the correct taper or making new ones, we used to make them with two flats which isnt as nice to work with as the internal 12pt or if anyone is supplying a better product I would be interested.

Ant,

Hard does not always equate to brittle. Think of a really high quality steel that is properly heat treated. I once saw a F1 1/2 shaft from a crash that was bent at 90 degrees! It didn't break! It didn't even have a crack. But, that junk "free machining steel," "leaded steel," and other such abominations can be quite soft and the lead inclusions will make it brittle. Perhaps that is why we have seen so many of the threads torn and broken. I would have to do a chem and hardness on the pins, but I don't know if I want to spend the 100 bucks on the test.

As for making you pins, that is no problem.

David