How much torque

NickfromWI

NickfromWI

King of Splices
Joined
Mar 30, 2005
Messages
4,992
Location
Snowless California
Before I starting taking bolts off, can you tell what I need to do?

<iframe width="560" height="315" src="//www.youtube.com/embed/i9pXa1ZZ_mw?list=UUVkWHiNsd0qH_4pOal_u0eA" frameborder="0" allowfullscreen></iframe>
 
Bolt-grade-markings-final.jpg
 
They are most likely grade 8 fine thread. Search bolt grade identification chart in google, there are maekings on tops of bolts to determine their grade. Also the same search for thread count. All bolts ive touched on chippers are fine, you will surely notice the difference between the pictures on google.
 
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  • #8
Woah! I never knew the markings at the top of the bolt had an actual meaning!!!

At the museum now. I'll check it out when I get home!!


love
nick
 
+1 on the bookmark

Item 15 that you point to is a 1/2" (nominal diameter) bolt with 13 threads per inch (course) and is 2-1/2" long:

Morbark Item 15.png

It is almost certainly a Grade 8 (six marks) bolt since it is a highly loaded application. It is likely to be plated so the torque spec. listed is 80 ft-lbs. However, if it is not plated the torque spec. listed is 106 ft-lbs.

Morbark Grade 8 Torque.png
 
The spec on the bolt said 1/2-13 - whatever length. That's 1/2" bolt, 13 threads per inch. For 1/2" bolts, 13 tip is coarse, 20 tpi is fine.


Another important thing is that they said to use anti-seize on the threads. This lowers the torque requirement dramatically from the dry torque figure due to less friction between the threads. Using dry torque figures on a lubed thread will likely break the bolt. Using lubed torque figures on a dry thread will result in especially poor clamping pressure which can result in many issues.


Also, they just say use anti-seize, not what type of anti-seize. That really doesn't matter in this application, but different anti-seizes, oils, dry lubes, etc all change the friction differently which results in different "proper" torque values.
 
Morbark is different from some manufacturers in giving a precise torque spec for each bolt grade. Most give you a 10 lb range. Advice USE ANTI-SEIZE and torque to the minimum spec not over. USE ANTI-SEIZE USE ANTI-SEIZE USE ANTI-SEIZE USE ANTI-SEIZE
CARL is giving you good info about dry vs, antiseized specs......but that is most important at very high torque specs and the manufacture is already specifying USE ANTI-SEIZE. The biggest mistake people make in installing knives is failing to use anti-seize. Some mistakenly think that since it makes the bolts easier to remove it increases the risk of them coming loose on their own. Wrong. Properly torqued bolts hold by flexing the threads----which is why they should be replaced after a certain number of tightening and loosening operations.
 
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  • #12
Thanks guys. I'll be honest- the part about the anti seizing compound didn't jump out at me. I might've skipped this step!

Ok- so here's my current plan-

1. After breakfast crack open the chipper and see exactly what bolts I have.
2. Remove knives so I can take pictures to chastise the crew about using the chipper as a rock crusher
3. Head to NAPA or someplace open on Labor Day, buy torque wrench.
4. Re-assemble, using the silver-based anti seize compound I bought for the airspade

u5y7ybyr.jpg


One thing I can't quite tell is how to make sure I put the knives back in the exact spot with the right knife clearance. I think it'll make more sense once I get it all open.

Thanks for the sagely advice. This seems like one of those things that would happen basically instinctually....if I'd ever done it before- but in a decade of doing tree work, I never was in the position to be involved with any chipper maintenance.- so I'm starting from scratch here.


love
nick
 
It's not rocket science....
You need to keep the guys from throwing the rakings through the chipper....
I bought some sand from home depot in those 1000# bags... They are awesome for the final rakings and clean up... Then I just dump the bags where I can. The deposit was like 82.00 for the three bags I got. Cheap and have paid for themselves big time.
We also use them for all the small clippings when pruning. Prunings never hit the ground. Just bag as you snip. Then you can run the smalls through the chipper with out fear of rocks.
But rocks do happen... Sap laden pine cones on gravel drives are a huge culprit.
 
The knives should go back exactly where they were due to the bolt hole alignment and construction of the knife pockets....on most machines. I believe that there are some machines that allow for knife adjustment via a clamping system. Follow your manual. Learn how to do a bed knife/anvil adjustment where applicable also.
 
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  • #16
Yeah. I misunderstood. I thought the knives slid back and forth. Now that I opened it up, I see that they only go in one way in the exact spot.

So apparently my 9" long handled socket wrench is nowhere near long enough to give me the needed leverage to take of these bolts. I got one, but I need more power.

Headed out to buy some tools! (Or at least a pipe to use as a cheater bar)


love
nick
 
Nick, it wouldn't be a bad idea to invest in a nice 3/4'' drive set.

I always clean the threads on the bolts with a steel brush and rag when we do a knife change. There is a lot of crud that builds up.
 
How long have these knives lasted you? On my bandit 250xp I go through knives like crazy and were pretty careful about what gets tossed through. It all depends on what and were we're chipping but my point being don't expect knives to last to long if they've been in there a couple or few weeks your crew is probably doing fine. I have mine sharpened once or twice if possible and then they're to short. I never let them get beat up to badly. Way to hard on the machine.

I've never used anti-seize on my knife bolts and never had a single bolt loose yet. I re-use my knife bolts/nuts five or six times only and replace them.
 
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  • #19
The knives have seen 30 hrs of service.

Really? Can only be sharpened a couple times? Yikes.

Wonder how much a new set is...


love
nick
 
When I got my Morbark I took my old bosses sage advice and bought three sets. Allows you to only do shear bar adjustment every fourth change of knives (this may require letting your sharpening service know you are running them as such so they keep them consistent)
 
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  • #23
I just looked and they aren't that expensive to buy. $130 for a new set at treestuff.

After how many hours are you guys changing your knives?


love
nick
 
That all depends on what is going through the machine. If you have the other Nick working for you, then not very long at all. :-)
 
Too many variables. With low hp machines, sharp is key. Fuel consumption goes way up, and just rattle the machine. I use the knife saver in between, gives them a nice edge.
 
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