Shear Bolts

[treefarmerguy]

I can't find shear bolts for a Puma 74 inch rear mount snow blower. Owner's manual calls for a Grade #2 for the auger. Can I use a regular grad#2 bolt of the same size? The drive shaft calls for a M6 x 40mm bolt with no grade# indicated. Any suggestions appreciated.

 

[George2615]

Yes, you can use any grade 2 bolt of the same size. Check your local Tractor Supply Store or whatever hardware store near you that carries M6 x 40mm bolts. A standard bolt is a different diameter and if substituted will cause it to shear prematurely. Buy extras when you get them.

 

[jaydee325]

Metric equivalent to an SAE Grade 2 is a 4.8.

Metric fastener strengths are named property Class and not grade. Even so, the Property Classes are roughly equivalent to the SAE Grade system. The following provides some examples.

Metric Grades
Property Class*****************SAE Grade
4.6****************************Grade 1
4.8****************************Grade 1
4.8****************************Grade 2
8.8****************************Grade 5
9.8**************************9% Stronger
10.9***************************Grade 8
11.9***************************NONE
12.9***************************ASTM A574


The easiest way to tell a metric fastener Property Classis by looking at the fastener for a numeric designation. These decimal numbers will be marked on the hex head or on the top or side of a socket head fastener.

 

[RickB]

I can't find shear bolts for a Puma 74 inch rear mount snow blower. Owner's manual calls for a Grade #2 for the auger. Can I use a regular grad#2 bolt of the same size? The drive shaft calls for a M6 x 40mm bolt with no grade# indicated. Any suggestions appreciated.

The auger drive uses a common grade 2 bolt as the shear bolt. No relief cuts or fracture points, just a regular hardware store bolt with no marks on the head. The PTO drive shearbolt s a 6x40MM 8.8 hardness. That is a typical good quality metric bolt and will be marked 8.8 on the head. Just about any source of metric hardware will have that size in 8.8 hardness.