Shear Bolt Keeps Shearing

jb112454 · Sep 8, 2002

I have a Tuffy 5' rottary cutter (brush hog) that the shear bolt keeps shearing on. The bolt I'm talking about is the one that connects the drive to the gear head. It is a 1/2"-13 x 3.0" catagory 2 bolt. Is this the correct bolt? My tractor is 35 HP with 28 at the PTO. Is this brush hog to small for my tractor? Thanks

RobS · Sep 9, 2002

Check out <A target="_blank" HREF=http://www.tractorbynet.com/cgi-bin/compact/showthreaded.pl?Cat=&Board=genoperating&Number=191035&page=0&view=collapsed&sb=5&o=&vc=1>this thread</A>. Similar problem although his solution may be different. Several things to check were mentioned /w3tcompact/icons/smile.gif

MikePA · Sep 9, 2002

<font color=blue>Is this the correct bolt?</font color=blue>
What does your owner's manual indicate?

When does the bolt shear, at startup, while in use, etc.?

jb112454 · Sep 9, 2002

Hi Mike, thanks for repying. the manual recommends a grade 2 bolt. The local NAPA recommends a grade 5. I maybe operating the cutter too low. With 28 hp I can cut real low without bogging down. Thanks for reminding me to read the manual. You know what they say " If all else fails read the manual/instructions"/w3tcompact/icons/smile.gif.

normde2001 · Sep 9, 2002

JB, grade 2 is definitely the correct bolt,(my local NAPA doesn't carry grade 2, that's probably why they recommend grade 5). Sounds like you have the correct size cutter for your tractor. I read that one foot in width for every 5 pto hp is a good rule of thumb. Unless you are dumping the clutch at 2000 rpm or hitting a lot of hidden objects, I would check the driveshaft length to see if is is locking up when you raise the cutter. Those bolts normally take a sharp hit to shear, as opposed to bogging down. If all else fails, you can always get a ($120) slipclutch.

jb112454 · Sep 10, 2002

Norm, I was reading the manual on the brush hog and one of the reasons given for shearing the shear bolt is too high of speed. I've been operating it above 540 rpm so will slow it down. I also have been cutting some heavy like 2" diameter saplings a little too fast. I think my problem is me not the cutter. I'll put another grade 2 bolt in and try to take it easy and see what happens. Thanks for yor input it is welcomed.