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Bolt description

#1

G

ghost1

Rebuilding a Kohler CH26 and upon finding torque specs for piston connecting rod end cap, the bolts are described as either 8mm straight shank, 8mm step-down or 6mm straight shank. Unable to find a definition distinguishing the difference. The original bolts take a 10mm socket and are about 2 1/4 in's long.. Any info would be appreciated.


#2

M

motoman

Ghost, I believe the hole diameter in the cap will dictate the shoulder (step down) or straight shank. The thread will quickly solve itself (6 vs 8mm)when you try it in the hole. I would try to get factory fasteners and observe any locktite and torque callouts.These fasteners will be higher tensile strength. Metric should have 9.8 or 10.9 stamped on the head, IMO.


#3

G

ghost1

motoman said:
Ghost, I believe the hole diameter in the cap will dictate the shoulder (step down) or straight shank. The thread will quickly solve itself (6 vs 8mm)when you try it in the hole. I would try to get factory fasteners and observe any locktite and torque callouts.These fasteners will be higher tensile strength. Metric should have 9.8 or 10.9 stamped on the head, IMO.
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Thanks for response,
I have measured thread pattern of existing bolt and it matches 1.00 on thread gauge. It also matches die (from tap and die set) that is 6mm.. Am I safe to assume I have the 6mm straight shank bolt that is recommended at 100 in. lbs?


#4

M

motoman

ghost. I will look at my metric stuff and tell you what I can. The cap hole should be "filled up" by the shoulder or shaft. Sounds like you have an M6-1.0 . The tensile marking is important . What does it say, top of the bolt head?


#5

G

ghost1

Unable to read any of the markings on the bolt heads (4). I am using the four original bolts that came off the connecting rod caps. I'm leaning at using the 6mm straight shank torque spec which is 100 in. lbs. This is the least amount as both the 8mm straight shank, and step-down specs are 200 and 130 in. lbs.


#6

M

motoman

Yesterday "engineman" posted a nice little spec sheet that looked official. It has disappeared?? I remember he had 3 different torque specs hovering around 100 inch pounds. Can you not obtain new factory replacement bolts?


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