Shear pin material

So if I ask for a shear pin a good store will know what I'm talking about? What is a shear pin made of?

Should be nothing more than mild steel, Peter. Check with a magnet to make sure it's magnetic. If it is, anything that could be heat treated would hardly act like a shear pin-----it would likely be too hard to function properly. The whole idea behind shear pins is to let go to save other components. You should be able to make the pin, but if it's a tapered one, please describe it---could be I have one.

Harold

You should take the broken pin with you so you can match it with the new one. If the pin is tapered you have to drive it out with a punch starting from the small end of the pin. Sometimes it is hard to tell the small end, and you have to turn shaft and drive from the other side. Jim

The shear pins on my snow blower are 5/16 grade 5 bolts. my outboard motor takes 3/16 brazing rod. A shear pin is made of whatever material the designer feels will protect the mechanism from serious damage while transmitting sufficient power to accomplish the intended task. Gerry :-)} London, Canada

I agree with Gerry in London(just abit west of me).. my JD140 uses Grade 5 bolts for the shear pin( yes, I found out the hard way....ugh). Number 2 is too soft and may just fold over causing all sorts of grief..number 8 is way too hard and 'other' things will break before the bolt does.

Jay in Ggreensville,Ont

It depends upon the application. My 6' Howse mower (bush hog) uses 1/2" grade-5 steel bolts.

My 6" baby Atlas lathe uses zinc for some, and soft steel for others.

If there is significant "play" in the joint held by the pin, and the actions on the joint are forceful and rapid, definite "work hardening" of a pin could occur. In that case, it might be a good idea to use a non-ferrous pin that is less likely to harden than might some steels.

Check out an outboard marine supply. They have shear pins in a number of sizes. (for outboard engine propellers)

LLoyd

The ones on our lathes are brass. We have had to make a few. :-) They are tapered, I think the same taper as a "taper pin". ...lew...

Would it be wise to spark-test the old one on a grinder to at least get an idea of the pin's composition? Doesn't tell the whole story, but would that be useful?

Dave Hinz

Lots of them are cast iron or soft iron. Some are brass.

Gunner

" We have all heard that a million monkeys banging on a million typewriters will eventually reproduce the entire works of Shakespeare...Thanks to AOL and WebTv, we know this is not possible."

If there is any detectable play in the shear pin joint it is better to ream out to a bigger size so the joint is tight.

On my farm equipment I use grade 8 bolts, they hold well and break clean. Grade 2 and sometimes grade 5 smear at the break and are a real dog to get out.

After a call to Famco who said I needed a #4 taper shear pin of indeterminate material, I yanked the remains of the old pin out. It looked small and straight for a tapered pin... I then perused the 8 1/2 D manual on the Gorton groups website and it suggested a 3/32 pin from unhardened steel be used. I looked at the hole for the pin, looked at the manual, looked at the package of 3/32 welding rod I have and decided that that was close enough.

So far it's working well. Kudos to the poster that suggested wekding rod - you were right!

Peter

I missed the staff meeting but the minutes show "Peter Grey" wrote back on Thu, 03 Feb 2005 01:42:23 GMT in rec.crafts.metalworking :

Sheer pins are made of what ever will bear the load but still sheer off when things go wrong.

Brass, mild steel, aluminum. Whatever you have handy.

(I still have a few brass pins with too much taper, too much chatter, the usual first year student errors when turning small things down.)

tschus pyotr

Chuckle!! And if the grade 8 holds and the gear doesn't, how hard and expensive is it to change the gear(s)?

Shear pins are generally supposed to be the weak link in a circuit-------intended to fail before expensive components do. If you've been shearing grade 8 bolts and they're not undercut, you're one lucky man, unless your equipment is designed around the concept. Does the manufacturer recommend the grade 8 bolts?

Harold

Heehee... a neighbor (NOT very mechanically inclined) insisted on using a "family" tractor (jointly owned by 2 or 3 others) to brushhog a field around his place. As he was constantly going over boulders, fence posts, etc., he kept shearing the pin in the driveshaft going back to the cutter from the tractor PTO. Tired of changing out the shearpin, he went to the hardware store, got grade 8's and went back to work... for a little bit anyway.... BAM.... blew out the castings & gears of the tranny and rear end. Then just left it sit for someone else to fix. I also saw this guy remove the lugnuts from an old pickup truck wheel and give it a jerk - watching the truck fall to the ground because he never put a jack under it. Told my son "Stay the hell away from that guy - he'll get you killed". sigh.... I don't have much to do with him, or the entire family for that matter. I'm just aware of these situations. BTW, a couple of the "other owners" had to fix the tractor - and I haven't seen this jerk use it since.. imagine that ! Ken.

Uh huh!

Exactly my point!

Harold

I'm using it on VERY old equipment, and the grade 8 bolt IS the weak link; I shear one or 2 per year and nothinmg else has broken.

Interesting, considering the tensile strength of the bolts.

Harold