I just picked up a stump grinder that uses a conical bolt to secure the PTO shaft to the implement side. The shaft has a clutch so I don’t think it has a protective function like a shear pin. The nut backed out and it came apart. By some miracle, nothing broke and I found the bolt. I bought a nyloc nut hoping for a better result but I don’t get a lot of thread engagement and when I check it every 30 minutes of operation, I get about a quarter turn. I’m worried I’ll forget to check that often and the next failure will be catastrophic. Can I replace it with a regular bolt that’s longer so I can put a split ring washer on there to hold the tension? Thanks for any advice!
Conical PTO Bolt Replacement???
- Thread starter Matlax
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Thanks! You’re talking about drilling the coupling so it’s a straight hole?
Yessir. I'd say the original conical bolt was intended to keep the joint tight. And, for all we know, the bolt may be conical because of its loose fitting after starting out in life as cylindrical. These couplings are usually just cast steel so not a lot of trouble. But keep the holes you wind up with as small as possible to avoid fracturing the coupling later on. Drill it as 1 assembled unit so all the holes are beholden to the holders honors..
Thanks ZZ!
Use a nordlock washer and red loctite. Easier to find would be an internal toothed lock washer and red loctite. Other option, order a new longer conical bolt from Agrisupply, etc
SPYDERLK
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Yes. Do not do away with the conical bolt fastening if it immobilizes the joint. Its meant to immobilize the joint. An immobile joint does not wear. It is permanent and unchanging. If the bolt is worn so much as to prevent this get another bolt. If that doesnt result in a stable situation then you can feel justified in thwarting the design by straight bolting it.
Thanks Spyder. Great point. Do you know if they’re standard diameter? I’ll have to remember to bring my micrometer out there next time to get a measurement.
SPYDERLK
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Probably there are different sizes. The taper angle may be standard. Ive only encountered them a few times and never needed a replacement. - - Cant you get the part from the stump grinder maker?
5030
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Use 272 high strength thread locker on the threads. Make sure it real thread locker and not the imported junk Amazon sells.
mrmikey
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Lockwashers are only good once the connection comes loose and then it's too late. Nordlocks ( Nord-Lock Washers ) are a different beast.altogether and are supposed to be good but I've never used them so I can't comment.
Use a gr. 8 locknut and a gr. 8 bolt along with red Loctite for good measure if you want.
5030
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Many grades of genuine threadlocker, not just one or two. Has to be the domestically made threadlocker as well which is Heinkle. There is wicking, non wicking, remove with heat and no heat as well as specialized threadlocker for stainless fasteners. I'd use 272 non wicking myself but you need to clean the mating threads with a dry solvent like non-chloronated brake cleaner before hand.
Curious as to what make your grinder is... I have a Land Pride which is the same as a number of articulating grinders and mine uses the indexable carbide inserts produced by a domestic company. Mine also has the slip clutch arrangement though mine has never come loose.
Curious as to what make your grinder is... I have a Land Pride which is the same as a number of articulating grinders and mine uses the indexable carbide inserts produced by a domestic company. Mine also has the slip clutch arrangement though mine has never come loose.
dadohead
Platinum Member
When I started in engineering 30 years ago, an older engineer told me then "nothing will ring your phone in your career more than hardware and springs". He was right!
In a properly designed joint, the energy spent tightening a bolt is stored by stretching it. So, the joint must be ridged and the bolt stretches like rubber. The joint is held from slipping by the clamp of the bolt. When clamp alone won't hold, you add bolts (more clamp) or a mechanical means such as a pin. Your joint appears to be doing this. I wouldn't drill it out.
Know that most lock washers, lock nuts, etc are bandaids that actually soften the joint and make it harder to put energy into the bolt where you want it. Avoid them! Instead, use high grade hardware and torque the joint to proof. Remember: torque is what we do. Tension is what we want.
In a properly designed joint, the energy spent tightening a bolt is stored by stretching it. So, the joint must be ridged and the bolt stretches like rubber. The joint is held from slipping by the clamp of the bolt. When clamp alone won't hold, you add bolts (more clamp) or a mechanical means such as a pin. Your joint appears to be doing this. I wouldn't drill it out.
Know that most lock washers, lock nuts, etc are bandaids that actually soften the joint and make it harder to put energy into the bolt where you want it. Avoid them! Instead, use high grade hardware and torque the joint to proof. Remember: torque is what we do. Tension is what we want.
SPYDERLK
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I use Loctite retaining compound #638 usually. It is very strong at below 100F but weakens a lot up around boiling and above. You can get a nut or whatever off without heat damaging a nearby seal. As far as using a threadlocker on a torque locked joint, its really just insurance. A real advantage in any case though is that the joint is seal from corrosive elements.
I worry about using a threadlocker in OP case. We really dont know whether the bolt is fully seated in the taper. It may be shy of its locking point and slowly moving in to a true taper lock. OP mentions few threads engaged using his replacement nut, so he may be tightening gingerly - 1/4 turn achieved each time. You wouldnt want to prematurely lock that thread.
If I were the least unsure I would buy a new taper bolt and correct nut, clean the socket and tighten to spec.
dadohead
Platinum Member
Absolutely.
The only issue I have with thread lock material is that it disturbs the friction factor in the bolted joint. You have to assume this bolted joint is engineered (not a generic erector set joint) and the published torque was developed with the hardware as delivered. Adding an agent could easily take the bolt beyond it's proof load and yield it.... or add friction and not let the bolt achieve full tension.
Nylock nuts are almost always low grade and soft (allowing them to head the nylon retainer in place after plating). You need to use hardened nuts and washers (if required) with high grade bolts to achieve the designed tension in a joint. Hope this helps!
I actually found it after it came out. It’s so short that I can’t get a split ring lock washer on there. I got a nyloc nut and the end of the bolt sits flush with that when tightened. I’m nervous I’ll forget to check it routinely.
Thanks for all the help guys! They didn’t publish a torque spec with it. I noticed today I didn’t get as much nut movement, which makes me think the tapered bolt wasn’t fully seated and I’ve been slowly pulling it in. In hindsight, I probably should have given it a few taps with a hammer to seat it better. I’ll give that a shot next time I’m out with it.
It’s the Woodland Mills WG28. It has a slip clutch too. The taper bolt is on the end that connects to the grinder. I’m absolutely loving the grinder though!
oldballs
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Seems like I have one or two of those tapered bolts on some of my attachments. It is sometimes tricky to get the bolt fully in place, such that it is seated properly. Having a clean joint and an eye for the proper fit is necessary...... has been my experience.
Cheers,
Mike
Cheers,
Mike
