I have a John Deere riding mower that I just got. Model X540. It is a fairly good size mower. I know that the previous owner had the electric PTO off a few times as he had replaced it. I acquired the mower knowing that the bolt which holds the PTO clutch on was broken off in the crankshaft. I do not know why the bolt is broken. I do know that the previous owner is not much of a mechanic and many times makes things worse than they were before he attempted to repair it. It is a 7/16 bolt. Probably fine thread. The break is not too far into the crankshaft as I can feel the end with my finger. Just inquiring about some ideas as to how you would extract the bolt. I guess I am thinking that I would center punch the end and try to drill it out with a left hand drill bit. If it doesn't catch and screw out then I would try an easy out in the hold I drilled. I assume the bolt turns right to screw it in. Any other ideas? Thank you.
- Thread starter andy r
- Start date
wore out
Well-known Member
Bolt is RH thread, 3.75" long and comes with locking goo on the threads so it MAY not come out easily.
You say it's broken a ways up inside the crankshaft, are there threads visible or is that area of the bore unthreaded?
Either way, I would make up a guide tool threaded or not as dictated by the bore that fits inside and has a pilot hole/drill bit guide drilled through (luckily I have a lathe).
Inset or screw the guide into the crankshaft, then you can drill a perfectly centered hole in the remains of the bolt, make it as large as possible to allow the use of a larger extractor that won't break as easily, and HOPEFULLY it will screw out.
Steve@Advance
Well-known Member
You are on the right track, using a left hand drill bit.
The trick is to get the hole drilled exactly in the center of the bolt. Using a center punch or better yet a drill guide (but that is only practical if you have access to a lathe to make one).
Everything depends on why the bolt broke. If it was overtightened, and snapped off, it should spin out freely with the left drill.
If it was bottomed in the hole, or the threads galled, it will have to be completely drilled out and the threads chased, something near impossible to do with a hand drill.
You do not want to risk breaking off an easy out! You do not want to risk drilling off to the side of the bolt!
Sounds extreme, but if the bolt doesn't spin out with the drill, best to tear the engine down, put the crank in a lathe and drill the bolt out. You only get one chance at this!
The trick is to get the hole drilled exactly in the center of the bolt. Using a center punch or better yet a drill guide (but that is only practical if you have access to a lathe to make one).
Everything depends on why the bolt broke. If it was overtightened, and snapped off, it should spin out freely with the left drill.
If it was bottomed in the hole, or the threads galled, it will have to be completely drilled out and the threads chased, something near impossible to do with a hand drill.
You do not want to risk breaking off an easy out! You do not want to risk drilling off to the side of the bolt!
Sounds extreme, but if the bolt doesn't spin out with the drill, best to tear the engine down, put the crank in a lathe and drill the bolt out. You only get one chance at this!
Janicholson
Well-known Member
Taking the engine out and working on it on the bench is really the first step. With the oil drained there is freedom to align things and be assured of success. I agree with Steve. Jim
buickanddeere
Well-known Member
Re-using an old bolt and not using a torque wrench are the bulk of the problems .
Determined
Well-known Member
Look up Rigid screw extractor set.
It comes with guide sleeves/bushings that ensure you are drilling a perfectly centered hole.
As others have said this is the most important step, once you drill it off center your odds of success are slim to none at best.
The Rigid spline style extractors work very well, always use the largest one you can for the bolt size you are dealing with.
The nut drive piece that comes in the set can be slid down almost flush with the broken off piece which minimizes any torsional twisting/breaking of the extractor.
Don't cheap out you only have one chance to do it right.
I have a door full of every kind of extractor imaginable that rarely ever get used since I bought the Rigid set.
It comes with guide sleeves/bushings that ensure you are drilling a perfectly centered hole.
As others have said this is the most important step, once you drill it off center your odds of success are slim to none at best.
The Rigid spline style extractors work very well, always use the largest one you can for the bolt size you are dealing with.
The nut drive piece that comes in the set can be slid down almost flush with the broken off piece which minimizes any torsional twisting/breaking of the extractor.
Don't cheap out you only have one chance to do it right.
I have a door full of every kind of extractor imaginable that rarely ever get used since I bought the Rigid set.
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