Quote:
Originally Posted by JSchmitz
Hardening is a touchy thing. More isn't necessarily better. A lot of people assume that Grade-8 bolts are always better. They are better in tension but nut in shear. Learned that at a very young age. Put Grade-8 bolts in a Brush Hog drive shaft. They broke immediately. I played around with Cherry Red powder hardening compound in the machine shop. I made a T-bolt for the lathe compound rest (just playing around). I hardened it with the Cherry Red. It snapped as soon as I started tightening it. It was made from good quality high carbon steel. If you start with crappy material, no amount of metal conditioning is gonna produce a good product. I suspect this to be the case with the oil pump drive shaft in question here.
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I deal with that on gear motors. Sometimes on motors with a lot of side loading the grade 8 bolts would shear so we went back to grade 5.
I play around with steel, heating, putting some carbon in it and quenching. Making punches, chisels out of old grade 8 bolts. If you heat them up too much and quench, talking beyond slight cherry red, bright orange that home made chisel will bust a corner off. Dangerous.
The less heat you use the less chance of being brittle while still inducing hardness,
A little light cherry red, then turn off the oxygen and add some carbon to the hot steel surface and quench is good enough. I do it twice.
We have some hex steel of good quality in different diameters I make pry bars out of and heat treat.
Now a broken grade 8 bolt removal vs a grade 5 is a different deal. A old trick is to heat up the broken bolt stub expanding it and then quenching it shrinking it. Many times that is enough to make just enough clearance to remove the bolt with a sharp chisel or other means.
But once you do that on a grade 8 bolt you are not getting a drill through it to use a Easy Out, not happening.
A grade 5 bolt does not get very hard heating and quenching and you can still drill it.
It pays to know what kind of steel you are dealing with first.
And this issue is one of the reasons I have gotten so good at just cutting the bolt out with a torch leaving the base metal. You can weld a nut on the bolt and taking it out with a impact gun.... maybe. If that does not work, cut it out.