Rotary Cutter PTO shaft came off of Howse Brush Hog. What now?

[AllenArmory]

Newbie here. I have a TYM554C tractor and a Howse CRB72C brush hog, both with less than 12 hours on them. After running the brush hog for a few hours cutting pasture grass and some light wooded areas last weekend, the PTO shaft came off the gearbox of the mower, probably when I hit a ditch. The cutter has a slip clutch, but the PTO shaft is held on to the cutter gearbox using two bolts. The dealership mechanic told me that they are standard shear bolts and that I can probably get them at Tractor Supply.

After visiting TSC, they only have one type of shear bolt (1/2" diameter) and they didn't fit my PTO shaft. After measuring the holes, I found out that 7/16x3" bolts fit the holes. After looking in vain for shear bolts in this size, I bought two grade 5 bolts at TSC. Before I use them while mowing, I need some help from the forum. Are these bolts safe to use?

The CRB72C is a round back, medium duty cutter. I have the owners manual, and the only mention of the bolts are that they are "anchor bolts." No mention of size or grade. I will try to contact Howse, but I'm not getting my hopes up since they recently declared bankruptcy and their website is MIA.

A picture of the PTO shaft is attached, if it helps.

Thanks!
AllenArmory

 

[RickB]

Go back to the idiot dealer who didn't tighten the special metric tapered pinch bolts that attach your clutch to the gearbox and tell him to get you two new ones. And let him supply them at no charge.

 

[kthompson]

Grade 5 bolts will take a lot more to shear than proper shear bolts. At least use common grade bolts which had no marks on the head. Those are grade 2 or 3.

 

[204saskman]

I would just install a grade 2 bolt but make sure that the shoulder of the bolt is what contacts both sides and no threads are in the hole. Most sheer pins/bolts are fully shouldered.

 

[Oldoak]

I think RickB offered the best advice. Those are not "shear bolts" in that location.

Shear bolts are located on the shafts so that if they shear all it does is stop driven half of the shaft from rotating without separating form either end.

Also, a PTO drive shaft has a slip clutch (which yours has) or a shear bolt, not both.

 

[IslandTractor]

Agree with RickB and Oldoak. No need for shear bolts if there is a slip clutch.

BTW, you do a adjust and maintain your slip clutch right??? Don't let it freeze up.

 

[jenkinsph]

Agree with RickB and Oldoak. No need for shear bolts if there is a slip clutch.

BTW, you do a adjust and maintain your slip clutch right??? Don't let it freeze up.

Sounds like no one set up the assembly correctly to start with and did not check to see if the mounting bolts were tightened after a short run time.

 

[aczlan]

I think RickB offered the best advice. Those are not "shear bolts" in that location.

Correct. There is no way for shear bolts to work on a splined shaft like that goes over.

Aaron Z

 

[JRobyn]

I concur with everyone else - those are CLAMPING bolts, not shear bolts. They may or may not be the special tapered-type locking bolts that some cutter/shaft manufacturers use (like my BushHog/B&P). Howse is your best bet for the details and for correct OEM replacements (unless they confirm that they are just standard grade __ bolts).

A concern now is if the splines on either side of the joint got too chewed up to reuse.

 

[RickB]

It's pretty easy to tell if they are tapered pinch bolts; The holes in the clutch will be different diameters on one side than the other. The side where the nuts go will be machined flat; the other side may not be.