Is this shear bolt to big

[RobJ]

Just noticed on my TSC brand 4' bush hog. Looks like a 1/2" bolt. There is nothing else in the link that will shear. It must be a perfect because there is no slop. If I put in a 1/4" or 5/16 there will probably be some slop.

What do yall think?

Thanks,
Rob

 

[1948berg]

That is not a shear bolt! Just for fastening the shaft.

 

[1948berg]

And a dangerous one! Clothes can get caught in it! You should probably have one of the type that you smack in with a hammer (dont know the name for it!)

 

[SimS]

Rob;
Don't worry a 1/2" Grade 2 bolt will shear just fine when you hit something solid. I have changed a bunch before I went to a slip clutch. Good Luck;

SimS

 

[HomeBrew2]

Yep, my Bush Hog brand calls for/uses a 1/2" gr. 2 bolt as well, exactly as yours is shown.

 

[greg_g]

</font><font color="blue" class="small">( Just noticed on my TSC brand 4' bush hog. Looks like a 1/2" bolt. There is nothing else in the link that will shear. It must be a perfect because there is no slop. )</font>

If the implement end of the PTO shaft slips over a round transmission shaft with a hole through it, then you use a shear bolt the same size as the hole. If the transmission shaft is splined, then it's simply a fastening bolt. The shear bolt principle only works on smooth shafts.

Assuming it is in fact a shear bolt, Grade 2 hardness is usually specified. You must get the right diameter, or the hole will become egg-shapped. The length need be no longer than necessary to thread a self-locking nut until it's flush.

//greg//

 

[BB_TX]

As the others said, 1/2" is the correct size for the shear bolt. And even though it looks quite large, a grade 2 definitely will shear if you hit something. I use a slightly shorter bolt and a lock nut with plastic insert. Bolt ends just barely past the nut to keep from having the long end sticking out. That is just waiting to grab something.
And you really should put a safety shield on that shaft.

 

[Newblue]

That bolt looks exactly like the shear bolt on my King Kutter finish mower. The bolt extends beyond the nut just like yours does. It came in a blister pack of five and had the King Kutter label on it. I think it was 1/2" x 4".


Mike

 

[Soundguy]

Rob.. despite what 1948 said.. that bolt, if it is coupling a smoothID yoke to a smooth OD gearbox input shaft, is indeed the shear bolt.. and a soft gr2 bolt is what you use.. and is what KK sells in 4 packs on the wall at TSC.

As Greg points out.. if those are keyed shafts, or splined shafts.. it's just there to couple.. though i would assume it would ahve been a roll pin.. in any case.. my bet is on a shear pin, as if it was a splined shaft and roll pin coupled.. I'd expect to see a torque limiter on there.. and i don't.

Soundguy

 

[RobJ]

Thanks for the replies men. Since the tractor is up at the weekend place I can't tell if it's a smooth shaft or not. Probably so based on the other owners posts. I guess I'm not use to seeing one that big. On most of my BIL's stuff he uses whatever is handy, 1/4", 5/16" nail. /forums/images/graemlins/grin.gif Funny his 15' batwing will usually go a while with a 5/16" bolt. But that's just mowing grass.

Thanks Again,
Rob