grade 5 bolt hardness

[38racing]

I have my friend's older mtd snowblower. It sheared the auger bolt which appears to have been a regular bolt. There is no head piece still there. One side is flush with the shaft and other side has a recess. Friend may have tried to drill it. Not sure. So I tried to drill the recess side but my drill won't bite, not even a Walter ones. I tried smaller sizes to get started but no go. Then, using a small bit I decided to drill a new hole through auger and shaft in another spot. I'm through the auger front and the shaft I think. Drill battery died at that point. Does that make sense that a regular bolt would be so hard to drill out? Last one I had I couldn't get the drill in place (and didn't think to drill in a spot that was accessible) so I removed complete assembly. IIRC it was still a difficult drill out on the bench.

[bgsengine]

the correct bolts would typically be a grade 3 , or grade 5 with shear points grooved into them, but the simple action of the bolt shearing can make the surface of the bolt very very hard to drill... but what I always did was drive them through with a drift punch and heavy hammer, long as the auger and the shaft holes actually are still lined up.. but if someone put in an ordinary regular hardware bolt, chances are the bolt "bent" into the shaft as it sheared, wedging it into the hole. I never even bothered trying to drill them out if they won't come out with a punch and hammer.. one time we used a oxy-acetylene torch and actually drove the bolt far enough out one way that we were able to cut off the other end (with the "bend" mushroom") with a abrasive cut-off wheel, then drove the bolt back through from the freshly cut side.. but the extensive labor time, once we figured up the cost in labor (if we'd actually billed the time) , would have cost more than just replacing the whole gearbox... although I suppose, if you were to pop out the gearbox, you could then hammer off the augers and mount shaft in a vise or drill press, etc, and get the old bolt shanks out by other means..

[KE4AVB]

This will probably sound crazy. Go get an appropriate size concrete drill bit. They have a carbide tip that will cut through most bolts. I use them to drill out heat harden exhaust bolts.

Also most drill bits you buy at the local hardware are just crappy and dull very quickly. Until I got a set from Fastenal I couldn't even drill a hole through a bed rail (angle iron) without dulling the bits. As with all bit they must be sharp.

[38racing]

I can't find model number on the blower. I was looking to find correct shear bolt. This is likely a mid 90's although has the OHV tecumseh. Friend has some pins from dealer. they have a groove with hole and pin and no greater than 1/4". My 92 uses a 5/16 bolt with nut. I've found newer one from 96 right into 2000's that specify a 1/4 grade 2 which seem to be what he has. My suppliers is saying those are newer used from 2005. Can't really see any reason not to use them in the older calling for 5/16. Just need to have a good supply maybe. Might shear easier.