Posted by Paul Cook in Kempner, Texas on Friday, July 14, 2006 at 11:27PM :
In Reply to: For you metalurgists out there posted by Doc Dave on Friday, July 14, 2006 at 2:02PM :
Clearly, the tensile strength of a bolt is a factor of hardness, but it is also a factor of molecular arrangement. I am not a metallurgist but I would believe that the molecular arrangement is engineered specifically for a predetermined shear point. This metallurgical engineering suggests that a shear pin should not have a bolt substituted.
However, there is NO SHEAR PIN on a shredder. They come from the manufacturer with a BOLT. The owner's manual/parts list should tell the Grade of that bolt. A call to the dealer should get you that information. I have been shredding all day and I am too tired to try to find my owner's manual tonight. Sorry.
I use Grade 5 bolts AND NUTS for regular "bolt it together" applications and Grade 8 bolts AND NUTS when the strength is needed. I find that most "blister pack" hardware sold in the hardware sections of "multi-department" stores does not have any Grade markings indicating they are Grades 1 or 2. When shopping in such stores I often have to search to find Grade 5 bolts.
In actual use with various brand shredders and post hole diggers I have found that Grade 5 bolts have sheared without causing any damage to the shredders or my tractor. I also saw a young "assembler" at an implement dealer go to the hardware bin for the right size bolt without any regard for its Grade.
This may not be all that critical. The blades on the shredder are designed to swing away from an obstruction. Normally this is adequate protection for the gear box, the drive shaft, and the PTO. It is only when you wrap heavy wire that you actually stop the blade carrier and put enough load on the drive line to need shear protection. That's when an incompetent operator will try to clear the obstruction with tractor power instead of getting under with wire cutters.
Since 18 miles is a major trip for you, you might use that Grade 5 bolt until you make your next trip into town and just watch where you are mowing.
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