Snow DK40 OEM Snowblower

[spindlewood]

I have a DK40 OEM Front Mount Snowblower and broke the fan shear pin - a rock got wedged in. The manual lists it as an M8 x 1.25 x 35 gr. 6.6.

There is only one place on the whole web which references a grade 6.6 bolt - this post on tractorbynet where the user Chilly807 says that

I believe 6.6 is equivalent to grade 2 in the SAE system, and grade 5 is very close to 8.8 in metric.

Amazing that a reference to this grade is otherwise nowhere to be found. Anyone else ever hear of a grade 6.6 (metric) and does a Grade 2 (SAE) sound right for this? It's weaker than the Grade 5 - and am ok with that as I don't want to risk breaking the PTO shaft. But also don't want to put something needlessly weak into it.

 

[PEJ5]

Check this out. It seems reputable.

Metric Bolt Conversion | Elgin Fasteners

or more specifically:

http://elginfasteners.com/wp-content/uploads/2014/01/strengths.gif

Peter

 

[Kioti Paul]

Check this out. It seems reputable.

Metric Bolt Conversion | Elgin Fasteners

or more specifically:

http://elginfasteners.com/wp-content/uploads/2014/01/strengths.gif

Peter

I believe you are making spindlewood's point. While your links provide valuable information, there is no mention of grade 6.6. I too searched for 6.6 grade bolts (& shear pins); and came up blank. One contributor made a very convincing argument that using to soft a bolt is not a good idea in that it will likely "smear" as it breaks, making it very hard to get the pieces out - I have had that happen, & it is no fun.

Several people recommend to go to the next harder grade, (grade 5, ot 8.8, in this case) and machine a shear line on the bolt where you want it to break. Makes a lot of sense to me...I personally do not think it is terribly critical, just get as close as you can.

 

[PEJ5]

Ooops, I guess I read too quickly. I have Grade 8.8 on the brain because the PTO shaft on my new-to-me blower requires a metric bolt Gr 8.8 and I still have yet to pick one up. Definitely have a punch at hand when trying to remove a broken shear pin. As for the grade, I am not a mechanical engineer, but the materials in manufacturing are normally way over engineered to ensure long product life so a presumably a gr 8.8 vs 6.6 bolt would break long before the blower shaft. Some of us are old enough to remember selecting the fuse value for the old fuse panel - dead shorts still blew the fuse!

 

[Kioti Paul]

I really suspect it is a misprint by Kioti...there are many typos in my manuals...but I don't know for sure about this.

 

[spindlewood]

Thanks everyone for your perspective. I called the dealer and the parts person advised grade 5 - suspecting a misprint as well. So that's what I put in. Hope to never scoop another big rock into the fan again.

 

[jrskblx125]

Yeah i dont have a kioti blower, i have woodmaxx rear blower. The shear bolts for the pto shaft, and chain drive shaft are grade 2 bolts. I have sheared them multiple times with rocks and such but in my experience i would rather have a grade 2 than grade 5. The grade 2 doesnt smear it shears well. I typically install with a slight snug on the lock nut. If theres no play itll shear fine.

I’d rather replace a bolt than busted internals any day of the week thats for sure lol.