Broken bolt removal

[Oldawg]

Not really a tractor question, but there are so many clever people in this forum I thought someone might have an answer to this. Last time I used my John Deere F620 ZTR mower, the electric clutch fell off the Kohler crankshaft when I shut it down. On that mower, it has a horizontal crankshaft engine driving a shaft from the engine to the gearbox which then drives the blades. This shaft has 2 u-joints and a spline, and they all have a little wear causing some vibration. I think that has been the cause of much misery, but the latest is the 3/8 grade 8 bolt holding the clutch on the crankshaft broke off about 1/4" inside the crankshaft. Just far enough in that I can't use a center punch to turn the bolt. I've been trying to drill a hole in the bolt so I can use an easy-out, but none of the drills I have tried, including carbide, hasn't even made a dent in the bolt. Any ideas?

 

[denchen]

I think you`ll have to invest in a set of cobalt drills, they are not too expensive but if they do not work you are in bother. If you get a pilot hole in the broken bolt, you could try a left hand drill...

 

[shovelmike]

When I was tearing down the front end of my 85 Sportster to replace fork seals a bolt in the triple clamp broke off. It wasn't grade 8, so drilling into it wasn't a problem, but easy out didn't extract it. A left hand drill bit spun it out slick as a whistle. As mentioned, a really good carbide bit will be needed for that grade 8 bolt.

 

[HCJtractor]

Maybe a good Mag drill with a good new bit would have enough oomph to precisely drill a small hole and then work your way larger. It would be much better than a handheld drill. Then use your easy out.
Also thought about welding a rod to it but expect it’s too tight quarters or would risk welding the bold to the shaft.
I still thing drilling is the way to go, but with a mag drill going slowly with lube.

 

[RickB]

Left handed cobalt drill bit. Link is for reference, they are available from a variety of sources including Amazon.
Advance Auto Parts - Down for Maintenance

 

[Roadworthy]

Do not scrimp on the left hand bit. Get a GOOD QUALITY bit from a jobber who deals in industrial quality tools, not your local auto parts store or Harbor Freight.

 

[jaxs]

I totally agree about using high quality bits,,,,,,,but you must use them correctly. It is difficult to apply enough down pressure with handheld drill so lay into it and turn bit slow as possible. You need a powerful drill to alow going slow while cutting. If what I'm saying doesn't make sense,here's an easy way of seeing for yourself. Use a drill press at low speed to drill through some metal. Put the same bit in a handheld drill and drill through same metal. The difference is amazing.

 

[ruffdog]

A grade 8 bolt will work harden if the drill is dull or not sharpened correctly and not enough tool pressure is applied to maintain a chip. After someone drills it off center, drilled it crooked, work hardened it, broken a drill/ez-out in it, then they bring it to me. It is much easier for the correct methods to be used early on.

 

[mike48130]

You could try a dent remover stud welder. No that much heat. OR if you have a stick welder, but harder to do. Have someone turn off the welder or pull the clamp just after you hit it.

But first I would probably try a dremel or small grinding bit to grind a flat in it and see if you can use a screwdriver to get it out.

 

[fried1765]

Left handed cobalt drill bit. Link is for reference, they are available from a variety of sources including Amazon.
Advance Auto Parts - Down for Maintenance

I have a complete set of left hand cobalt bits up to 1/2", and several random ones larger.
Don't use the LH cobalt bits often, but certainly would not want to be without them.