PTO Driveshaft Shear Bolt

[Trails End]

The manual for the pto drive shaft (T40) for my Pronovost Puma-74 snowblower
calls for a M8 x 50mm safety shearbolt, but doesn't specify a grade. Does anyone
have information on what grade shearbolt this should be?

 

[gengine]

I think my auger says the same thing, but I've been using grade 3 sae bolts for the last few years

 

[Trails End]

My auger drive shaft shear bolt is specified to be a 1/4" NC x 1" Grade 2 with nylon lock nut.

 

[kco]

The Comer shaft for my Meteor specifies a metric grade 8.8 bolt. That is roughly equivalent to SAE grade 5.

The auger shear bolt is an SAE grade 2.

I suspect your PTO bolt is 8.8 but you should contact Pronovost.

 

[Trails End]

I already sent one email to Pronovost asking about an assembly/setup manual for the Puma-74
snowblower, but haven't received a response from them yet. My blower only had a operator/parts
manual but nothing on assembly/setup. I'll send another email, asking about the shear bolt.

 

[RickB]

The spec is for metric bolts 8.8 hardness.

 

[Trails End]

Thanks, all! I received a response from Pronovost, and they confirmed that the
M8 x 50mm shear bolt is grade 8.8!

Thanks again, and wishing everyone a very happy and safe new year.

 

[jimainiac]

Just curious, but I wonder how the metric hardness grading numbers compare to U.S., SAE grades. I always thought shear bolts were supposed to be soft so they'd break away before anything else broke.

 

[Trails End]

According to the chart shown at this web page Bolt Grade Markings and Strength Chart
metric class 8.8 is similar to SAE Grade 5.

 

[Trails End]

Ooops, Sorry Jim! I hit "Post Quick Reply" before I'd finished.
It looks like more snow coming before the end of the week. I just might
get a chance to try out the new snow blower yet. Should be interesting, with
the driveway covered with a thin layer of ice now after the inch of rain we
received here in Candia, and no chains on the tractor.

Happy New Year

 

[jimainiac]

Thanks for posting the SAE/metric bolt strength chart. I'll have to put into the memory bank that 8.8 metric equals grade 5 SAE.
Hope your drive isn't too hilly, pushing the snowblower on ice without chains. Any chains are better than no chains on an icey slope, but I can't say enough good about the Trygg chains I got last year - problem solved!
Good Luck!

 

[Trails End]

Jim - Is there a local dealer for Trygg chains?

 

[jimainiac]

Last year at about this time, I got my chains from Nash Equipment on Rt. 26 in Colebrook, N.H. Their telephone number is 603-237-8857. They had a good selection in stock. Other places I checked would have had to order the chains special. Some sold Aquiline Chains, which are similar, and similar price. There's a store in Gorham, N.H., called Labonvilles, that sells heavy-duty logging equipment, and they sold Trygg chains also, but were quite a lot more expensive. I think they sell a heavier duty version, but that would be overkill for me. The model I got were the "Flexi", which have three adjustable links in the side chains so you can get a perfect fit without using spring tensioners. They are very rugged chains with fantastic bite.
Trygg has a good website, with installation videos. Maybe someone closer to you sells Trygg chains, or at least can order them for you.

 

[jimainiac]

Just one caveat about this type of chains with such aggressive studs. If your driveway is paved, they may be pretty hard on it. Our drive is gravel, so no problem, but the concrete floor in the garage was getting chewed up, so I laid some sheathing down to drive in on.
If you have a paved driveway you might want to use more standard "ladder" type chains, better than no chains, but less damage.