Rotary Cutter Bush Hog Troubleshooting - Woods? Slip Clutch Issues with Kubota M60

[Brian62]

Afternoon,

I recently acquired a bush hog (potentially a Woods model, unsure) and am experiencing issues with repeated sheer pin failures when using it with my Kubota M6040 tractor.

Initially, the sheer pin would break quickly upon engagement. I then loosened and cleaned the slip clutch, and recalibrated the springs. This improved things slightly, but the sheer pin still breaks when encountering rougher patches.

I have two main questions:

1. Identification: Is there a way to positively identify if this is a Woods bush hog?
2. Compatibility: Could the PTO shaft and/or slip clutch be undersized for this bush hog and my M6040 tractor?

Any advice or insights would be greatly appreciated, as I'd like to get this bush hog working this season as an alternative to my flail mower in certain areas.

Thanks in advance for your help.

 

[nybirdman]

Don't know why it would have both a shear pin and a slip clutch.If the clutch is working go with a grade 8 shear bolt.
Looks like a lite duty model.

 

[Brian62]

Yeah, I don't really don't know much about this. My neighbor gave it to me when he was moving out of his house after his divorce and it's pretty much set in my yard for about a year or so. I saw somebody on Facebook market page that has one almost exactly like it and they label it a Woods so that's what I'm thinking it is.

I thought about using a grade 8 sheer bolt, but I was afraid that it could do some damage to the gearbox if I hit something too hard. But I think I might give this a try as I'm getting ready to do some briar cleanup in the coming week.

 

[Lineman North Florida]

As long as you have backed the nuts off of the slip clutch a little ways and then engaged the PTO several times to make sure the plates are broke free and slipping and then re-tightened them to spec then there should be no reason to not upgrade to a grade 8 bolt on the drive line and put it to work.

 

[ssgp2]

Sounds like the clutch is frozen or it has the wrong bolts in it. The bolts should have extra threads showing past the nuts, and looking at the picture, doesn't seem to have any or they are loosened all the way already and it is indeed frozen (rusted). Proper adjustment can be found online and most slip clutches are real close on adjustment specs and slip procedure that should be done at the beginning of mowing season .
Some units use a regular bolt while others use tapered bolts without a head to secure the clutch assembly to the input shaft. Also, a sheer bolt would be in the grade 0 to 3 range. Grade 8 isn't considered a sheer bolt.

 

[geneP]

There is a brush cutter on my local Craigslist that is built exactly like yours and the seller says it is a Woods.

https://jackson.craigslist.org/grd/d/bolton-bush-hog/7835491401.html

 

[Brian62]

As long as you have backed the nuts off of the slip clutch a little ways and then engaged the PTO several times to make sure the plates are broke free and slipping and then re-tightened them to spec then there should be no reason to not upgrade to a grade 8 bolt on the drive line and put it to work.

Thanks.

 

[Brian62]

There is a brush cutter on my local Craigslist that is built exactly like yours and the seller says it is a Woods.

https://jackson.craigslist.org/grd/d/bolton-bush-hog/7835491401.html

Mine is a 6 foot, but looks exactly like the one you linked to.

 

[Brian62]

Sounds like the clutch is frozen or it has the wrong bolts in it. The bolts should have extra threads showing past the nuts, and looking at the picture, doesn't seem to have any or they are loosened all the way already and it is indeed frozen (rusted). Proper adjustment can be found online and most slip clutches are real close on adjustment specs and slip procedure that should be done at the beginning of mowing season .
Some units use a regular bolt while others use tapered bolts without a head to secure the clutch assembly to the input shaft. Also, a sheer bolt would be in the grade 0 to 3 range. Grade 8 isn't considered a sheer bolt.

thanks

 

[gstrom99]

Like others said, it shouldn't have BOTH safety devices. There's lots of info "out there" on slip-clutch adjustment. I just bought a new rototiller with one, and I feel I need to check it's function/adjustment before I use it. The separate PTO shaft manual it came with doesn't really address that.

Here's one link:

How to Properly Adjust & Maintain Your PTO Slip Clutch | IronCraft | Tractor & Skid Steer Attachments

INTRO: A slip clutch is a mechanical device used in PTO machines to protect components from damage caused by excessive torque or overload. The slip clutch m ...

www.ironcraftusa.com

 

[5030]

Looks like a Weasler slip clutch to me and Weasler sells new plates for it. Needs to be slipped (to remove the rust buildup) every year prior to first use.

 

[RayIN]

Use the correct size shear bolt, slop increases the shear effect. The gearbox shaft is hardened. Tighten the nut to its maximum torque value, no lock washers. If the nut works loose, a drop of LocTite is needed after removing all oil N grease, or 2nd nut.

 

[sandman2234]

Make sure there are no sharp edges on the sides of the hole where pin goes thru. I had a pin shear, and got smeared around the inside of the outer piece, which caused an edge. I kept shearing pins till I took a dremil tool to it.
David from jax

 

[BackRoad]

Good stuff above, the only thing I might add is your tractor could easily turn an 8' rotary cutter, so it's possible you are over powering the 6' mower...but by all means, go with what you have!

As others have mentioned, break your slip clutch free. *IF* that is set correctly and working as designed, the grade 2 sheer bolt is redundant and the weakest link. Sounds like it is breaking before the slip clutch gets a chance to...slip.

As Mr. Lineman mentioned, you can safely increase the bolt grade (hardness) and rely on the slip clutch...if you have it dialed in.

You might need to go easy with the mower, meaning low RPMs when you engage the PTO, then increase to 540 RPMs, and limit the size of saplings and brush you attack until you've confirmed the slip clutch operation.

Cutting brier canes should not be a problem...

 

[gstrom99]

You might need to go easy with the mower, meaning low RPMs when you engage the PTO, then increase to 540 RPMs, and limit the size of saplings and brush you attack until you've confirmed the slip clutch operation.

Cutting brier canes should not be a problem...

I NEVER engage the PTO on anything, at more than 1/3 throttle.

 

[BackRoad]

I NEVER engage the PTO on anything, at more than 1/3 throttle.

For my implements, engaging the PTO at idle seems to be the least stressful method.

I have an old 5' brush hog of unknown manufacture which functions well behind my 60 yr old MF TO35 which bragged of 32hp at the PTO when new. Cutting fields is easy, and brush or saplings upto about 2 inches are no problem...never broke a shear bolt.

That same 5' rotary mower behind my 60hp Kubota MX6000 goes through shear bolts pretty regular on PTO startup if I don't baby the PTO. The torque hit at anything above idle twists them in two. Once up to RPMs, it cuts field grass without issue.

And behind the MX, powering through brush of 1 to 2 inches can result in broken shear bolts. That's why I bought a much beefier 7' Woods!