shear pin vs. slip clutch

[John Weaver]

I am planning on buying a Bush Hog (brand) SQ600, 5 ft. rotary cutter. I heve read the old threads and think a shear bolt arrangement would be best for me. Where is the shear bolt? In the drive shaft? Can I change to b slip clutch by buying the slip clutch drive shaft? Also considering the RDTH 60 Bush Hog grooming mower. Are the drive shafts interchangable? Are drive shafts usually interchangable between manufacturers / equipment? You probally have guessed by now that I don't have any PTO equipment. Thanks for comments.

[wen]

The squeeler Bush Hog rotary cutter is a little expensive, but an excellent choice. Unless you have over 40 PTO HP, I wouldn't be concerned about a slip clutch. The "shear pin" is normally a 1/2 in bolt that bolts the PTO drive shaft to the mower gearbox. It is not likely that you will shear one in a year of mowing unless you hit one of those immovable objects. An old tire seems to be a prescription for disaster. I have hit pieces of steel pipe and the cutter will actually cut through the 1/4 in walls. Actually, if a blade comes loose it can go through the side of the mower. Be sure to get the mower with at least the rubberized fabric guards on the front AND rear of the mower.

Yes, you can normally change to the slip clutch, but the expense is not normally worth it unless you start out with it. It is normally only standard on gearboxes greater than 60 HP for protection of the drive line. Unfortunately, if not kept properly maintanined, it provides far less protection than the shear bolt.

Read the instructions carefully when you get the mower. Some installations require you to shorten the drive shaft. Not likely, but it is all covered in the manual.

Each piece of equipment normally comes with it's own PTO drive shaft and they are not normally interchangable since the length is usually different. They are kinda expensive, so taking good care of them saves a lot of grief and money.

The PTO is inherently very dangerous as a shoelace caught in a revolving shaft can break an ankle or worse in less time than you can react. The shields are all there for a purpose and should NEVER be defeated. Turning the PTO OFF before getting off the tractor is the only safe thing to do.

A rotary mower can hurl objects at high speeds and break windows or hurt people. Keep people far away and put cars in garage when mowing. The guards are a good start to minimizing this hazzard.

Probably the Rotary Cutter like you are getting and the box blade are the two most common implements used on tractors.

[Hawgee]

Wen says it all pretty good.
I would only add never use any bolt stronger than a grade 5 for the shear bolt protection. Stronger bolt may cause damage to equipment, drive shaft or gearbox or people. [img]/w3tcompact/icons/frown.gif[/img]

"What is a weed? A plant whose virtues have not yet been discovered."
Ralph Waldo Emerson (1803-1882)

[Phazer]

I broke the shear pin on my BushHog yesterday. Do I need to get a special pin to replace it, or is it safe to just put a regular 1/2" x 3 1/2" bolt in the shaft?

Thanks

[MChalkley]

Phazer - The manual will usually tell you the correct bolt to use if the original factory part is unavailable, but you should be safe using a grade 3 bolt, or maybe even a grade 5, but definitely nothing stronger than that. If you don't know for sure that a grade 5 is acceptable, I'd start with a grade 3. You didn't say how big the cutter is (maybe you did in a previous post) but unless it's a really big one, a grade 5 1/2" bolt will probably be too heavy.

Mark

[wen]

Mark,

I used so many shear pins on an auger, that I finally started just using all thread and re-using the nuts. Would go through 20 or 30 in a day trying to drill post holes in rock. Seldom lost one with a rotary cutter, but always just used the low strength bolts (grade 3).

[MChalkley]

Wen - I know exactly what you mean. I buy plain old grade 3 bolts at Northern by the pound to use as shear bolts. I buy 1 Nylock nut for every three bolts and I'm all set...

I've been tempted to use grade 5's, but bolts are a lot cheaper than gearboxes.

Mark

[wen]

Yeah, my son put a grade 5 in a post hole auger after he had sheared several grade 3 bolts. It held just fine but it twisted the ear off of the auger head which he had to take to a welding shop to weld it back on. [img]/w3tcompact/icons/frown.gif[/img]

Here it is Tractor Supply that sells bolts by the pound. They sell both Grade 3 and Grade 5 but not metric. [img]/w3tcompact/icons/smile.gif[/img]

[Wingnut]

I'll say "ditto" to the comments about shear pins being preferable on the smaller stuff. Certainly easier to maintain - lubricate!
I'd make one comment, though, re Hawgee's suggestion. I'd think that most manufacturers specify grade 2 bolts rather than grade 5. The purpose is to secure the PTO to the 3PT implement ... but allow for a "quick disconnect" if you tie into a too large tree like I did (or tire as some others have mentioned). Hawse, KingKutter and several others specify grade 2.
A grade 5 bolt will take lots of force to break and could easily allow damage to the implement or the tractor PTO before letting go. Grade 2's are much softer ... which means they'll break much easier. Far cheaper to replace more bolts than fix the implement or the tractor! ... just make sure you throw some extra in the toolbox.

too bad that common sense ain't

[JerryG]

If it is a Bush Hog brand, e-mail them. They take their mail serious. I had a question and e-mailed it. I wanted a e-mail answer, so I didn't fill in the phone number. Two days later the area rep. called me. They had went through directory assistance to get my number so, that they could better answer my question and any more that I might have. WOW I did't think any company would do that any more. Talked to the rep. for 30-45 min. JerryG