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Discussion Starter #1
Torquing the pto v pulley retaining bolt, threads into the crankshaft, 35 ft lbs. Is it possible to strip strip the threaded hole in the steel crankshaft?? The never seemed to offer any resistance to turning? I have another bolt that I'm going to try
 

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Have a close look at the bolt you're using, if it won't tighten, you should see some of the thread stripped off. A standard grade 5 bolt shouldn't strip the threaded crank pto end, so my guess would be that you're using a smaller diameter bolt, possibly a metric where you need an SAE. I think the correct bolt size is a 3/8 NC but you should confirm that.
 

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cliffh - It is a 3/8" - 24, not a hard bolt. just came home with a 3/8"- 24 helicoil insert kit as additional insurance, as I was already out doing other errands. No auto parts places stock these on the shelf. I haven't had a chance to check the bolt that is in there.
 

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Some tractor supply stores stock SOME NF bolts. both Gr 5 & Gr 8.

From the parts diagram FOR A 317, it lists the material as A17D which is the SAME as a shear bolt and Gr 5. I would think that a 3/8-24 Gr 5 bolt will work just fine.

You say it's not a "hard bolt." How many lines are on the head of the bolt? No lines = Gr 2, 3 lines = Gr 5, and 6 lines = Gr 8. If no lines, you probably just have a stripped bolt. If a Gr 5 or Gr 8, I wouldn't attempt to guess! Inspecting bolt should tell you this.

If you decide you need to re-tap for helicoil, PROCEED WITH CAUTION !! You're only removing a small amount of material and the drill is going to want to grab...even a 1/4" drill can grab and REALLY hurt your wrist! Also, don't run drill fast. Crankshaft is alloy steel and on the hard side. Too fast and you'll burn your drill bit out. I'll also recommend tapping compound when retapping, usually available at auto parts stores.

I've said this in other threads, but, to make ME feel better, I'll say it again! Reading threads here and other sites, you really don't know what other people know or don't know. Please don't feel insulted!!! If you already know what I've posted, consider it as a reminder. If you've no clue what I'm talking about, just ask! Bob
 

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cliffh - It is a 3/8" - 24, not a hard bolt. just came home with a 3/8"- 24 helicoil insert kit as additional insurance, as I was already out doing other errands. No auto parts places stock these on the shelf. I haven't had a chance to check the bolt that is in there.
I'd be very cautious about drilling out the crank for a helicoil, I would make sure the crank threads were shot before I stuck any drill bit into that hole. It should be very easy to check out the tap into the crank by running a tap through to clean out the threads and then screw in a NEW 3/8 bolt to see how well it will tighten. This is a lot easier and cheaper if it's the bolt and not the crank than to destroy your crankshaft and your hands at the same time.

If you do decide to drill out the tap, make sure you have the crank secured so it can't fly around when the bit grabs (you can do this by bolting a solid strap to the flywheel or something similar) and use a good bit - maybe carbide, if you can get one to match the helicoil required size. The next hurdle would be to tap the hard crank straight and not to break the tap while doing that (I've made some of these types of mistakes in the past) Personally, if I was doing this now, I'd pull the crank and get a machinist to repair it for me or get a replacement crank depending on which was cheaper.
 

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If the bolt won't take torque, it's the bolt threads or the crank nose threads.... And probably both.

I would very strongly recommend a very careful investigation as to what failed and how, BEFORE you do much of anything else. Spend three minutes to look at it like a scientist. Is the bolt in there the right one? Is the bolt the right length? Is the bolt actually broken? Are the bolt threads the correct size and pitch. Are the bolt threads severely damaged, or just "rounded a little at the peak of the thread"? Are the inside threads shiny or corroded? (In the deep parts, the "top" of the inside threads got polished just now, no matter what...) Are the inside threads one continuous, smooth, consistent coil shaped ridge, or are there periodic interruptions? (That indicate cross threading from a previous forcible installation of an incorrect bolt).

You might well end up needing new threads and a new bolt. A Heli-coil will make an excellent repair for the crankshaft, stronger than the original. It's gotta be close to accurate, but it's a place where if you're not doing machine shop quality work with your hand drill, as long as you're not out in left field, it'll be fine. It's a risk though. The drill bit called out (or included) in the kit is A, not negotiable. If you need to get your own, don't substitute. The next size is really close, but not close enough. But the problem here is the drilling. You're drilling just a whisker of material on the outside of the hole. That means that the drill bit is gonna want to thread it's self into the hole. That means sudden stops, jolts, completely uneven engagement as there is always one "hard spot" in the hole where the high spot of the thread is that you're drilling out. Just not a nice drilling experience. (relatively speaking of course). If you break a drill bit inside of there, I'll guarantee you're gonna wish you wouldn't have... That's my biggest advice for the short term, is that there's a risk in this repair. Make SURE it needs this repair before you do this repair. Then do the repair carefully if it's needed.
 

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If you break a drill bit inside of there, I'll guarantee you're gonna wish you wouldn't have...
I still wishing that.
 

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Grrr, I knew I saw this thread before!!! Just responded in MTF (??)

OK, We've determined it's a 3/8-24 bolt. Ogura only knows what they recommend for a bolt size, so I would totally disregard their information. This thread could go on for a while, based on yield strength values, types of lubricant, bolt finish, etc!

So! If a grade 5 bolt, I would torque to 26 ft-lbs lubricated. If a grade 8 bolt, I would torque to 35 ft-lbs lubricated. Bob
 
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