Slip Clutch or Shear Bolt Driveline Protection...Which is Best?

I received a couple of letter from viewers, both revolving around driveline protection in their rotary cutters or brush hogs. The topic of today's video is whether slip clutch or shear bolt driveline protection is better.
The two letters came from opposite ends of the spectrum...one viewer is constantly breaking shear pins and they're hard to access on her cutter. The other viewer ran over a 10" stump and the slip clutch or shear bolt protection didn't work.
Shear bolts are designed to break when you encounter an object that doesn't move. Problems arise when they're breaking all the time and/or they're difficult to replace. Some driveline designs have a mechanism built in that is very easy to access which puts the shear bolt out to the side. Others run the shear pin through a shaft and they can be difficult to access because they're buried up under shielding at the end of the shaft.
Sometimes the tractor is the cause of the frequent shear pin failures. My tractor has a very abrupt engagement of the PTO. If you don't move the lever back very slowly, you'll break a shear bolt every time. Also, sometimes the manufacturer's recommendations for the grade of bolt is pretty conservative. If running a grade 2 bolt and constantly having to replace it, you may have to move up to grade 5. The customer who hit the stump may have a grade 8 bolt in his driveline protection, offering virtually no protection.
Slip clutches, therefore, would appear to be the favored version of driveline protection. They are usually about $50-$600 more expensive, but if you hit something, they're going to stop the machine, then you can get back to work without getting off the tractor seat. The problem with a slip clutch is it has to be maintained. Loosening the bolts and "burning in" the clutches every year insures they're functioning properly. Especially in humid climates, a little moisture in the clutches and they weld themselves together and again, they don't offer protection, which could have been the issue when the viewer hit the stump.
In the end, which system is best? If you maintain them, slip clutches are are great way to go. If you're not the most meticulous at maintenance like I am, I'll stay with my shear bolt.
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[@ronniehallmark1278]

The problem is people buy a bushog with a slip clutch and never educate themselves with periodic maintenance. They think it never needs touching unless there is a problem. I'm guessing there is a very high percentage of tractor and bushog owners bushoging with a froze up slip clutch. I prefer shear bolt.

[@jh9855]

Thanks Mike. I have learned a lot from you

[@WilliamsonRidge]

Nice video Mike really appreciate all your videos and advise!

[@jamieshields9521]

Great vid👍shear bolt for me, i usually carry half dozen when using chaser bin/field bins or mixer wagon.

[@jeffstrains4014]

Good tip on checking the slip clutch! We have one with a clutch several years ago hit couple truck tires on rims that had been overgrown a real mess we were clearing. Slip clutch was I guess 10 years old had been even painted over a few times heard a bump and thumping broke the shaft thankfully the gearbox was fine.

[@donniebargo964]

The right advice on the cutteries the best advice is the best advice I have ever heard about bush hogging no one ever talks about how to set the rake on the cutter that is the most important aspect of doing the job for your equipment it is

[@RockhillfarmYT]

Great video

[@a.saintango1311]

The face Mike made when he read that letter about running over a 10" stump ohh lord, I just heard $$$$$. Great explanation for a very simple part of the safety system in our drive lines. I was considering upgrading to a clutch but after watching this, and taking into account the ease and type of use I put my Kioti through, I think just keeping a few extra bolts around is the way to go.

[@larryezell5106]

Thank you, thank you for all the information on shear pins. We just bought a Kubota L4701 and a 6 foot County Line brush hog. The brush hog is running through cheap Tactor Supply Number Two shear pins like a hot knife through butter. The last one I put in lasted ten minutes cutting some small locust trees.

[@michael.w.salter]

I have the bush hog with the bolt thru the shaft. Removing the cover is a pain, but I use a punch to remove the broken bolt. I’ve learned to pickup rocks, know where the stumps are, and don’t try to cut to low. I rarely break one anymore.

[@johnthorpe1071]

Thank you Mike as always great video! Went to my dealer to get some shear bolts for my R C and it came in a "kit" (parts guy said he "assumed" the kit included the nut... oh wow what a deal!) for $22.70...........Went to Tractor Supply and got 6 grade 2 bolts and locking nuts for $9.00. Haven't broken 1 yet but sure I will.

[@earlyriser8998]

excellent explanation

[@robertheinkel6225]

When I was repairing hay balers, my most frequent call was shear bolts. Many customers tried to save money and not buy the correct shear bolt, and would put in anything that would fit. Their complaint, was it was breaking frequently. Some I could break turning the flywheel by hand. Putting in the proper bolt, solved their problems.

[@lilredcummins]

Good video Mike!! Have had both and prefer the slip clutch. The problem with the shear pin is that I forget to take a spare with me when away from home and don't have it when I need it. Since the safety mechanism is built into the PTO drive shaft, you can change the shaft to the preferred design for ~$200.00 on Cat1.

[@jacklopez552]

Good to know.

[@shesh17]

Great video as usual Mike. From Shesh in Canada.

[@TractorMike]

Hi there Shesh!

[@dyannevans9179]

Yes I use to have a bush hog with those bolt . Broke them all the time. Sold that one and got a new One and never had that problem again. Ron

[@manwar999]

thanks

[@drgnner6028]

I like shear pins. I did learn not to over torque them which stretched the bolt and made it weak.

[@stubbshomestead1316]

I personally like the slip clutch but I like the set it and forget it of the shear bolt. So i guess im fine with either one. I have a slip on mine and I use your video on how to do it 1 time a year.

[@MyClutteredGarage]

Great info. Maybe I'd better do that slip-clutch maintenance. You know what I don't like? The PTO connections with the ring around them. You have to use two hands, which is a pain - especially with the plastic drive shaft sleeve protectors in the way. I prefer the push button on the side of the PTO connection - unless I'm doing it wrong!? Thanks! -Ed @ MCG

[@tomoaktree4951]

Hi Mike, Good Video. Regarding hitting the stump. It's possible to hit the stump grazing the top of it, and or it hits the stump jumper disk, it will shove the cutter over and still not cause the shear bolt, if it has one, to break. If it has a slip clutch, it may or may not have broke loose. I'm like you in that adjusting slip clutches is not something I like to do, but it must be done, especially on a piece of equipment that sits outside and doesn't get used very often. For brush cutters that are continually being used, then a slip clutch is the way to go! For shear bolts that are breaking too often, the first thing to determine is whether it is the correct hardness and diameter.

[@timhood6970]

Doing bushhogging for the public, making the move to a slip clutch unit was the best move I ever made, in my opinion!

[@extraacct478]

Have slip clutch - very simple and reliable. Once a year just back off all the way and engage pto at full rpm. Done. Adjustment doesn’t really matter just tighten enough so it doesn’t lose the nuts and it will cut rated thickness no issue. No need to measure bolt lengths etc. The absolute worst that then happens is it MAY slip a couple of times per hour but so what - not enough to even get hot and gives great protection.

[@bteamshorts]

I bought a budget Land Pride rotary cutter and it would break a shear bolt in tall grass 😂 I added a slip clutch and it was the best thing I ever did!

[@SynKronos]

Hi Mike, Good advice. For most farmers here in Scotland clutch's appear to be prefered to minimise break downs in the field. Typically plenty time for winter maintenance. That said. In Alice's case the issue will be the bolt bending in the shaft prior to breaking suggesting that you are correct, it's too soft as equally it then needs thumped out. (Low tensile strength) This way the manufacturer can get away with using lower grades of steel on the PTO and possibly the gearbox. So careful here as using a higher tensile bolt/ pin may result in damage to the affixed components. Personally I am with you. Run an 8 in this instance. But then one can install a clutch adapter dependent on the maximum and minimum length of the existing PTO with respect to the attchment.

[@CountryCraziness]

Awesome thumbnail. 🙈

[@alexlail7481]

Even though very few people understand/ consider a properly designed v- belt drive is also a system with built drive line protection (the same function atleast from an engineering perspective). Though very few belts are as cheap to replace as a shear bolt. And they alert with a nice squeal and rubber smell 😉

[@rodneytaylor6261]

Thanks mike.......Massey Ferguson 35 with 5 foot slasher / bush hog ... Felidquip brand.... Just got them I don't have a manual for the slasher. So if the slip clutch slips I do it up half a turn till it stops slipping. I have a clean paddock no junk in it ... I use to now it with my draftsman yt4000 ride on but takes to long in summer. Hence the Ferguson..... Just bought a 6 foot box blade for it $1300 Australian $$$$$ ... Love it it will out last me.. I'm 38 yo...thinning about buying a flail mower ?$?$?$ maby ...love the vids mike your the best tractor educational bloke on KZbin... I've used tracto when I was YOUNG BUT THE FERGUSON IS THE FIRST I own .... Plan to do a paint job and pretty it up a bit as I use it for my bisniss/work .,............stay safe take care ......Queensland Australia.....

[@jphickory522]

I have both and prefer the shear pin also due to its fail proof simplicity. In reality, hard to find the time to adjust the clutches annually. Even after they have been adjusted I find myself wondering if they are still in adjustment after a few months.

[@bobdavis6103]

After reviewing your slip clutch video I had the confidence to service mine on my Bush Hog. It had been about a year an a half since the purchase so it was time and the procedure was simple.

[@boardride]

I have a PTO wood chipper, and recently I was breaking shear bolts far too often, and far under the chippers diameter capacity. I went through about 10 bolts before checking the manual to ensure I was using the right grade (5). While in the manual, I noticed the recommended RPM was 'up to' 1000, not 540 like all my other implements (doh!). What a world of difference. I now run closer to 1000 rpm and can chip anything I put in it, as long as it's wood :)

[@S200059]

I am having same problem with a chipper I just bought. Mine seems to engage ok but after 10 15 revolutions the shear pin breaks. I tried multiple times (even with a grad 8 bolt) and it always breaks. This chipper is old and discontinued so I didn’t get a manual, I am at a loss as to what to try next.

[@regsparkes6507]

Time;y video,..I am thinking about buying a mower like this,.and wondered about this topic. I now know which way I'm going. Thank you Mike!

[@philipchamberlain9563]

One thing I like about the very old IH 300U is that the pto is wet clutch driven/engaged. The cutter I have had a slip clutch on it bit it never went off (tractor PTO clutch always did first). The issue is I lent my cutter to my dad and the slip clutch on it was rusted together, ended up breaking the pto drive train in his Kubota (someplace in the transmission). Sometimes old stuff is just designed better (the pto clutch on the IH 300U is just a better design than the newer tractors).

[@danacross3427]

Agree on the shear bolt, I have rough ground. I don't like changing the shear bolt so I am cautious where I cut (walk through, start cutting high, drive slow). Slip clutch gives a false security, more expensive, and as you say more maintenance. I start my mower (6 ft) just over 1000 rpm and then ease it up and have no shearing problems.

[@ryanfowler6900]

I like my shear bolt, I keep them in the box with a set of wrenches and a hammer. 90 seconds and I'm back in business. No Shields on my old brush hog.

[@mongomay1]

My home l use shear bolts, I keep kitted together with tools on tractor. The fields tend to grow rocks where I am at. It is an old 5 foot field mower I got for "free" with the new tractor out of their boneyard had to weld on it for a week and straighten the blade bar, no stump plate..

[@chevyon37s]

Never “burned” in a slip clutch, and have never had a problem and I mow a few hundred acres a year with a JD HX-15. Mow over small trees, bushes, etc and have gotten barbed wire hung in it and have yet to knowingly slip the clutch from use, and have never broken any drive line parts, or frankly anything on the mower.

[@SouthernPioneer1965]

Go for a slip clutch, I have run them for years never any problems at all and never had to adjust a single one

[@oldretireddude]

Shear pins need to be long enough that the threads do not fall at the shear region. Threads in the shear region will lower the shear bolt strength. Or if the bolt & length is correct make sure that the direction of install doesn't leave the threads in the shear region.

[@svtirefire]

My boss was complaining that the auger drive gears in his snowblower stripped out when he hit something, and the parts were expensive. I said "that's odd, I wonder why the shear pins didn't break?" Then he told me that he previously had replaced the shear bolts with regular bolts because they kept breaking. 🤦‍♂️

[@andrewg9379]

Added an aftermarket slip clutch to my shear pin pto shaft for under $100, had to cut the shaft length down a few inches

[@markmonse5285]

Glad to see you're OK. From the thumbnail photo I thought for a sec that you had taken a leak a little too close to the live PTO shaft.. ;)

[@johnthorpe1071]

Or the E fence lOL

[@dantadysak5485]

I bought an 1997 Kubota L3600 and I was surprised to find the tool box full of “stuff”. There were screwdrivers doubled ended wrenches and pins. What I could not figure out until I watched this video was that there was a box of 50 bolts approximately 5/16 diameter and 3” long with a box of 50 nylocks. I was assuming it was something like a fence or gate they were maintaining. Now I get it, they were grade 3 or 5 bolts used for shear bolts on a 3 point implement. My first reaction is oh crap is my PTO damaged or at a minimum had a rough life. I hope I have not found the reason it was sold but I will cross that bridge when I get to it. I guess after watching it will depend on the engagement on the tractor and the attached implement.

[@spudgamer6049]

Rsndom thought occured to me. Seems to me that it is almost impossible to find some types of implements with a shear bolt. Tillers, for instance. Similarly, I don't think I've ever seen a PTO driven auger with a slip clutch. Oh, and a bit of advice for anyone unfamiliar with slip clutches when buying a new implement. Ask that the dealer's service department adjust the slip clutch before you take delivery. If it has been sitting in storage a long time, especially if part of that time was outside exposed to the elements, it may well be in need of adjustment even if it had previously been correctly adjusted. And it doesn't hurt to ask if they'll show you how to do it at the same time.

[@tsimmons1974ts]

I grew up with shear pins HATE THEM !!!!! Clutch all the way.

[@lesgobrandon]

Damn a shear bolt.

[@crazyuncleduke8012]

We use grade 2 shear bolts in both our Rhino and Land Pride brush hogs. We've broken hundreds of them over the years but they're cheap enough at TSC to justify the additional cost and labor involved with a slip clutch. That's my two cents on the subject Mike. :-)

[@wegotthis2734]

Have the same cutters as you but having problems with my shear bolts breaking all the time even snapped a grade eight. The 5/16 bolt doesn't seem near big enough in diameter

[@crunch_amp9282]

My 6-ft brush hog will shear a grade 2 manufacturer rated bolt just by starting it at an idle damn near every time.

[@bibleandbibs6407]

I have gone to all shear bolts, I like to hook and go.

[@danstevens2204]

You can purchase pto shafts with clutches attached or clutches individually as well as parts and they are inexpensive. Very basic to adjust, you should be back there checking gearbox oil levels at least each year anyway.

[@upandadam9080]

Mike on a Tc33 you can push the foot clutch, engage the pto and then let the clutch out, can u not do that on a 40? I'm not a fan of new holland but that was always one thing I liked about the tc33...

[@toddholmer9700]

Another issue Alice may have is that the pto shaft is too long causing stress on the shear bolt. I had this problem once. If she is on rough ground this could very well be the problem.

[@MIRUSTICS]

i Have to say I agree with the shear bolt over the slip clutch for how cheap it is to replace. the clutches do keep you mowing the same day after you hit something whereas a bolt shearing means you're taking a break to replace that sucker. but for me i'll keep a few bolts in the ole IH toolbox.

[@geremychubbuck3730]

Shear Bolt. Tough to beat.

[@ericduck8273]

I bought a new cutter, the second time I used it, the shear bolt broke. I replaced it with the recommended bolt which has worked for several years. I don't think the nut was on tight and it fell off. The bolt slipped out enough so that the bolt sheared on one plane in lieu of on two planes as designed.

[@4x4Moses]

My rotary cutter came with a Grade 2 shear bolt, which broke almost every time I engaged my "electric-over-hydraulic" PTO. I contacted the manufacturer, and asked if moving to a Grade 5 bolt would void the warranty. They said "no," so I replaced the old bolt. Haven't had any trouble since.

[@terryk3118]

Is there a way to replace the through-the-shaft shear bolt with the style that you have on your bush cutter?

[@mrchildgrownold3852]

I keep expecting to break a shear bolt, I cut stuff beyond my brushogs capability. No trouble yet 🤞

[@crazycoyote1738]

Why you advise Alice to trade her cutter and not buy a pto shaft with a slip clutch for the existing cutter? You can add a slip clutch to any implement.

[@edwintaber6465]

The primary driveline protection is the pivoting of the blades. The engineering of the driveline components on the cutter are calculated by the anticipated force at the blade tip. That anticipated force is dependent upon the weight and speed of the blade. Using additional blade speed to cut stuff larger than the machine was designed for shortens the life of the components of the machine. Stop trying to beat things to death with poorly maintained blades - try keeping a designed cutting edge on them. The greater the speed of the blade the greater the force necessary for it to pivot backwards. Also - shear pins are engineered to superior specifications and proven by superior quality control than hardware store bolts. Shear pins fitting too lose are subject to "hammering" which is additional beyond rotational forces.

[@dlunday2]

Grade 5 shear maybe for brush cutter ? Dunno, don't have one. I do have a PTO Chipper and use a grade 3 there. Only breaks if I start it too fast, too often or the blades stop on a piece of wood.

[@jonathanfrecking1210]

Slip clutch is the only way to go. I've got 3 on my 15 foot batwing bush hog. Came standard on it . Ive also got an 8 foot bush hog with a slip clutch too.

[@hugostiglitz8465]

I have a kubota with 18pto and slipped the clutch in but the tiller stalls the engine if I hit a branch or root. I guess if you have low enough pto it doesnt matter.

[@davewarrender2056]

I watched a video of a guy using a cheap brush cutter with shaft drive attached to a skid steer, he hit some unseen rocks and bust the drive plate in the cutter as well as the drive shaft, repaired by putting in a slip chain between the gearbox and drive shaft, way he explained it was the chain could slip a little if the cutters caught something, or the chain would break preventing damage to the gearbox, seems like a no brained to me

[@billyw3781]

PTO slip clutch cover? 5 gallon bucket cut in half vertically mount horizontally with it covering the slip clutch with a hinge and put a bungie cord over it to hold it down over the clip clutch. Simply release the cord and tilt back.

[@TractorMike]

I like it!

[@banjopicker1215]

Mike would a cutter have a slip clutch and a shear bolt?

[@Pete.Ty1]

👍

[@marknerren402]

The only thing I don't like about my slip clutch is its inaccessibility due to the safety guard. I wish the guard were removable for maintenance (replacing the guards afterward, of course).

[@doylemarkham1010]

How is the slip clutch attached to the rotary tiller? My pro has the slip clutch attached to it & I don't know how to attach it to my rotary tiller. Help please, Thanks Doyle

[@crunch_amp9282]

Seems to me like they under rate all of the PTO gear boxes I can take a lot more than what they're rated for obviously if it'll share a grade two bolt just by turning your PTO on on your rotary cutter

[@HamiltonvilleFarm]

Yet again another solid video👍 surprised to hear you say shear bolt. I bet you would change your mind if you didn't have the shear bolt set up that you have on your cutter😂

[@rodneytaylor6261]

PS box blades are a bit rare in Australia ???? Straight are more common ..... I'll take box blade any day....only problem ive done all I need to do...... Oh well.......... Anyone in Australia.. south east Queensland.... Sunshine coast need any work done????

[@wildbill23c]

Can you install a slip clutch on any PTO implement, or are you stuck with shear pins if that's how its setup?

[@SynKronos]

Typiclly yes. I do believe they can be bought as adapters but one must allow for the maxium and minimum reach of the PTO. Here is one for example: www.amazon.co.uk/DETACH-OVERRUNNING-CLUTCH-COUPLER-FERGUSON/dp/B00DMEBSES

[@rkwill100]

so, the choice is adjust the slip clutch one a year or replace the shear bolt several times a day. To me, maintenance once a year is a much better choice.

[@LedgemereHeritageFarm]

I prefer shear bolts on a brush hog because they take such a beating and keeping the slip clutch adjusted is a nightmare.

[@williambradley948]

Mike, where can you buy a higher grade shear bolt? Tractor supply only sells one grade. My Kubota 4710 must be too much tractor for my Tractor supply 5ft mower. I broke 3 in the last 2 days.

[@TractorMike]

William, if it's a regular bolt, you can just go to Lowe's or Home Depot with the old one and get one the same size in a higher grade.

[@hugoburton5222]

The thumbnail though.

[@kevinb7540]

Could you explain or show and brush hog going through a dip in the land... I can't find anywhere showing or explaining how much you can flex or dip when moving with the brushhog. Thank you

[@MJADoingStuff]

Is it ok to have both?

[@TractorMike]

Yeah, but the weakest one will be the one to give. Won't hurt anything but won't really give extra protection.

[@BillTheTractorMan]

After years of running equipment on the farm, I swear the slip clutch is best! Too much inconsistency in bolts, the shafts rust together and might not give. However if you maintain a slip clutch, it wont rust together and will always give at the right amount to torque to protect the equipment. We had converted our square baler to slip clutch because the bolt hole was worn and the slop would shear the bolts.

[@donniebargo964]

Mike for $200 he can go buy the whole shaft assembly like you've got there at just about any tractor dealership if it's not worth $200 to fix the problem then it's not worth anything

[@breakheartorchard4761]

I cant understand why anyone would sell or buy a rotary cutter without a slip clutch. If you ever try cut down two or three year old regenerative growth after clear cut, you would need a pocket fill of shear bolts and would literally spend half your time fixing the darn thing.

[@garypuls5263]

She could just buy can you drive shaft with a slip clutch rural king or Tractor Supply not that expensive

[@alanfisch6912]

Quit messing with the clutch. Check it by making it slip. If you put the right torque on the pro shaft and it slips you’re done

[@murky2502]

How do you put the right torque on the PTO shaft?

[@fhuber7507]

Both can fail to protect if not given proper maintenance.

[@fhuber7507]

The woman constantly breaking shear bolts needs to raise her mowing height or do something to remove the things she's hitting.

[@DLTJR1959]

I'm 60 and have done my share of brush hogging. Much prefer slip clutch. Just my experience. Shear pins work great but really slow down progress.

[@bearkatljl]

We used grade 5, the manufacturer recommended grade 2 but those were so soft you couldn't even get the blades spinning. With that being said, slip clutch is so much better.

[@rodneytaylor6261]

10 inch stump f%#@ ... I've seen what hapens to a car rim and tyre when the main roads mob now over them very impressive the damage they do..... Glad it ai nt m y tractor....... KEEP AWAY FROM TRACTORS WHEN BUSH HOGGING / Slashing .....mike will agre to that...... Hay mike....

[@danstevens2204]

Shear bolt design is far from ideal in this application. It’s normally used after a slip/over running clutch in the driveline. Eg baler flywheel or stuffer. There is no disadvantage to a slip clutch. Far more shock load with a bolt

[@vtdrive129]

Always buy slip clutch. After you replace 10 shear bolts, you'll understand why..