Chipper shear pin replacement

   / shear pin replacement #1  

Bruster

New member
Joined
May 19, 2016
Messages
6
Location
Eureka,CA
Tractor
Kioti (Coyote) LK3504
We just put a new BX42 chipper on our Kioti 35 hp and it chipped great for the first hour in the 540 PTO and 2800 rpm engaging at low rpms to start. Then the shear bolt in the PTO went with nothing unusual going through the chipper and the PTO shaft level. Two questions if anyone can help me. Is a standard 50 mm 8.8 bolt the same as the 50 mm 8.8 shear pin bolt that fell out? They look and feel very different and I can't find anything on the web about this. The shear pin bolt is marked SC 8.8 and the standard bolt is marked 8.8 with a small triangle under it. Also, since the chipper is designed for 18 to 45 hp tractors and mine is 35 could I safely move up to a 9.8 or 10.9 shear pin bolt? Thanks
 
   / shear pin replacement #2  
NO.... The higher the tensile strength of 9.8 or 10.9 will increase resistance to shear, it may become safety hazard... Low value of 8.8 is for a reason it's to keep you from injury and forces that can damage or destroy your equipment...

A 8.8 bolt is a 120,000 psi medium carbon steel
A 9.8 bolt is a 131,000 psi medium carbon steel
A 10.9 bolt is a 151,000 psi medium carbon alloy steel...

The psi rating is sear strength when torquing (tightening) and hardness of bolt will also increases the "rotary" shear point when used as safety "pin"...

Non metric bolts (SAE) shear bolt are almost always grade 2 which is 74,000 psi low carbon steel...

s-l300.jpg


Dale
 
   / shear pin replacement #3  
Do not put a grade 8.8 bolt in there. It will not sheer. Best thing to do buy more from manufacturer, or call Titan and they could recommend a replacement.
 
   / shear pin replacement
  • Thread Starter
#4  
Do not put a grade 8.8 bolt in there. It will not sheer. Best thing to do buy more from manufacturer, or call Titan and they could recommend a replacement.

Thanks for both these posts. It is what I suspected, but not what I hoped for, as I don't want to replace sheer bolts every hour. I know there are a lot of these BX42's out there if anyone has a suggestion on how to avoid the sheering problem.
 
   / shear pin replacement #5  
Thanks for both these posts. It is what I suspected, but not what I hoped for, as I don't want to replace sheer bolts every hour. I know there are a lot of these BX42's out there if anyone has a suggestion on how to avoid the sheering problem.
Wallenstein manual has shear bolt M8 x 45 mm Gr. 8.8. If this is the first bolt sheared on a new chipper, I wouldn't worry about it. 3rd or 4th time, then maybe. The bolt may have been weakened by high RPM startup, or engaging while raised (the angle of the shaft can put extra stress on the shear bolt). Was the chipper delivered in the crate, or bought assembled?
 
   / shear pin replacement #6  
We just put a new BX42 chipper on our Kioti 35 hp and it chipped great for the first hour in the 540 PTO and 2800 rpm engaging at low rpms to start. Then the shear bolt in the PTO went with nothing unusual going through the chipper and the PTO shaft level. Two questions if anyone can help me. Is a standard 50 mm 8.8 bolt the same as the 50 mm 8.8 shear pin bolt that fell out? They look and feel very different and I can't find anything on the web about this. The shear pin bolt is marked SC 8.8 and the standard bolt is marked 8.8 with a small triangle under it. Also, since the chipper is designed for 18 to 45 hp tractors and mine is 35 could I safely move up to a 9.8 or 10.9 shear pin bolt? Thanks

Go to the hardware store and buy a grade 2 bolt that will fit the hole and a lock nut....get several sets. Metrics are usually slightly larger than the comparable SAE size. Most rotary cutters run one-half-inch diameter (don't know about other machinery, but the function is the same) which will fit the next size up, Metric.

The bolt needs to be longer than what's required because you want to have a little slop in it, especially with the nut. Install the locking nut but don't bring it down against the yoke. Let it rattle a little. In 40 years of trying to learn how to farm this has worked best for me and regardless of what's in the owner's manuals....like Grade 8 recommended for my JD round baler, Grade 2 gives the best service and is the easiest to find to knock out the pieces when you need to install a new one.
 
   / shear pin replacement #7  
The 50 mm bolt is just shy of 2 inches long. The 8.8 marking is hardness and is equivalent to grade 5. If it was me, I would forget the metric bolts because they are hard to find. I would buy a handful of grade 5 (3 hash tags on the head) 2 inch long bolts and all-metal locknuts. Draw it down snug but not overly tight and use a drop of blue Locktight.

[h=2]Approximate Equivalency Chart Metric/US Roughly Equivalent US Bolt Materials[/h]
Metric Nut ClassSAE J429Normally UsedGradesASTM Grades
4.64or 51A307,Grade A
4.84or 52.
5.852.
8.885A325,A449
9.895+A193,B7 and B16
10.910or 128A490,A354, Grade 8D
12.910or 12.A540;B21 through B24
 
   / shear pin replacement #9  
I also have a Wallenstein on a Kioti and get my shear bolts at Tractor Supply. They have both metric or sae bolts in the grade you need or you can get shear bolts if you prefer. They do recommend a grade 10.9 or 8, but I use a 5 which tends to break more. I may get the next grade higher once these bolts have all broken. Shear bolts, Pack of 5, for Wallenstein Woodchippers


Shear Bolt Replacement
PTO models are protected by a shear
bolt on main rotor shaft. If shear
bolt shears remove broken shear bolt and install replacement shear
bolt.
For operator safety, never use a harder grade of shear
bolt than recommended
.
BX40 SHEARBOLT– M8 X 45MM (GRADE 8.8)
BX60 SHEARBOLT— M10 X 55MM
(GRADE 8.8)(MOST SHAFTS)
— M10 X 65MM (GRADE 8.8)
 
Last edited:
   / shear pin replacement #10  
Try a standard bolt from Tractor supply. Cost way way less than the pe-packaged shear bolts.
 
 

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