Sheared Frame Bolts - B8200HST

[warriorjoe]

I have a REAL problem. I have acquired an old B8200HST. The loader was wobbly. Observed several missing bolts that attach the frame to the engine. The bolts that attach the loader to the frame are OK.

ALL the 16 bolts (eight on each side of the frame) which were originally 10mm have been drilled out and replaced with 1/2" SAE bolts. Only two bolts on each side were present, and these are stripped! The others are either missing or sheared off in the hole. I have gotten all but one bolt out via easy-outs.

My approach to a fix is to drill out the bolt holes for a 9/16" bolt (9/16" is about same dia as a 14mm bolt). I am worried about enough meat being present in the engine casting to handle the larger 9/16 bolt. However, I really don't have any choice, because the 1/2" holes have stripped out threads!

So if someone that has an old 19hp block like this tractor could look at the sides of the casting where the frame mounts (there are eight holes on each side) and advise me if a 9/16" bolt could be made to fit in drilled out holes I would appreciate it.

Also, a question regards fine vs course thread. The original 10mm bolt is fine to medium thread (like 1.25). Should I use a 9/16 SAE fine thread or a course thread bolt? What advantages does one have over the other?

Thanks very much!

Joe

 

[hodge]

I can't help you with the questions you have asked, other than fine vs. coarse. Fine threads have more surface area, so they will hold more torque.

 

[Bluegill]

Fine thread will be stronger. I also don't think a 1/16" larger hole will weaken the casting. I have a buddy who let the same bolts get lose on his tractor, he drilled and taped to the next size and has no problems. He does check them regularly now.

 

[Ach]

I just replaced a sheared bolt for the loader subframe on my yanmar

I helicoiled the hole and put in a new bolt. Worked great. Can't imagine that the larger holes will prove to be a problem on your tractor.

Be careful when drilling so as to avoid drilling into your crankcase.... Been there done that....

 

[Apogee]

warriorjoe,

You might consider going back to metric threads. The metric sizes often land in between the SAE sizes and you might find a metric size that will work without requiring drilling such a big hole. You might find you can simply tap the existing stripped holes to metric and move on.

The other option would be to have the holes welded then re-drill them. The work would need to be done by someone who really knows what they're doing because it's on cast iron, but should be doable without replacing the block.

Good luck,

Steve