drilling out broken bolts


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The right day for working on this tractor hasn't been here for a couple of years.  Today was 65 degrees, and Sunny, and being a Holiday, I didn't have any help, so I decided to start in on the John Deere tractor.  

It had four 5/8", and two 3/4" Grade 8 bolts broken off that hold on the front end loader.   I had bought everything I thought I could possibly need over a year ago.

I started drilling the 5/8" bolts with a 3/16" left hand Cobalt drill bit.  The centers of the Grade 8 bolts must not be hardened, because the drill bits went right in.  On the first three bolts, by the time I stepped up to the 3/8" bit, they came right out on the bit when it was about an inch in.  The broken bolt parts unscrewed right off the bit.  I used a 3/8" MIlwaukee right angle drill that I have no idea where it came from, but was the perfect drill for that job.

The 3/8" bit was too dull to cut into the fourth 5/8" bolt, by the time I got to that one, so it will wait until another bit gets here-ordered today.

I had drilled all the way through one of the 3/4" bolts with that 3/8" bit, but the bolt never budged.  In hindsight, I should have drilled all the small bolts before going through that big one.

3/8" was the largest left hand bit I had ordered.  I had ordered a few of them to try, thinking I would have to use EasyOuts, but the left hand bits worked better than any easyout I've ever used.

I had bought a monster 3/4" drill off CL, a while back, just for this job, so decided to try a 1/2" hole with that into the 3/8" hole had already drilled.  That drill doesn't have a reverse.  I was a bit scared of it to start with, but it wasn't hard to handle, and was the easiest 1/2" hole I've ever drilled in metal, not on a drill press.

Then I made a big mistake. I re-shifted to a more comfortable position, and let the drill rest with its weight on the bit that was not quite all the way through.  The weight of that big drill broke the 1/2" cobalt bit off in the hole.

The only die grinder I have is an 1/8" one, and nothing I have to go in that one would reach up in the hole far enough.  The tractor will have to wait a while longer for the 1/4" die grinder, and long tungsten burrs to get here from Amazon to grind that broken bit out.

One of the big bolts had come out before, which is the reason I think that the others broke.  The threads in that hole were FUBAR enough to never be useable again, so I had ordered some 7/8", and 1" taps to tap threads in it up to a larger size, along with drill bits up to the correct tapping size.  I tried the 7/8" starting tap in the hole, and was amazed at how easy it was to cut the threads in the cast iron.  I had bought two large tap wrenches, with one being about 18" long, and the other 32" long, off ebay.  I tried the smaller one first, and it had plenty of leverage. This must be some really good quality cast iron, because the threads are absolutely beautiful.  All the 5/8" holes are fine, and I was glad that I don't have to re tap all the holes.

I was really tickled that it went as easily as it did, but who knows when I'll be able to get back to it.  I have that tractor sitting in the White House (what we call that building) because I need to split it, and replace some parts in the forward clutch pack.  I didn't want to split the tractor by myself, so decided to get into the drilling, and tapping today.

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Oh boy one of the least favorite mechanic tasks on the planet. I haven't used LH bits much, have had good luck with easy outs. Hazet makes a great broken bolt extractor that's cam-operated that I've had for about 40 years. It's for 8mm bolts so more for cars than tractors.

Although I started out on tractors as a kid, I went to cars, airplanes, and plenty of other machinery before I got older and smarter and got a desk job! 

John Deere were always my favorite tractors, but I can only talk to you about the A, B, G, 60 and 70 models as well as the 730 and 820, but anything newer than those and I'm lost :) 

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This is a 1978 2640 w/reverser.  The same tractor Kevin Costner used to build the Field of Dreams.   I built our farm with it, and have put 3,000 hours on it since I bought it used, with a broken hour meter.  I had the forward clutch rebuilt in 2007.  They charged me $1100, and it started leaking at the gasket between the motor, and transmission where they split the tractor soon after.  The tractor had to be split to replace the gasket too, so even though it was their fault, they charged me another $850 to replace the gasket.  They had put a pipe across the hood to hold the front end loader up, and of course, it pushed the hood all the way down to the top of the motor.  They dollied the hood back out.

I asked another JD dealer about rebuilding the forward clutch, and was quoted between 5k and 10 k.   The problem with that particular kind of clutch is a pair of seals that go bad.  I know the disks aren't worn out, because I've been the only one driving it, but if I had to replace every moving part in the clutch pack, it would cost $287.  The two seals that need to be replaced cost $4.70, and $7.70.  I know the day, and instant the seals let go.  It was single digits cold, and happened all of a sudden.  This is a common problem with this particular clutch, which is in a number of tractors, and backhoes from back then.

 I'll probably replace everything in that clutch pack while I have it apart.   I have a service manual, and it breaks down every step of the process, with pictures.  Guys on tractor forums, who have done it before, say it's about a four hour job including the tractor split.  I won't get in a hurry, but it doesn't look that bad.

This is why I work on my own stuff here, and why I want a heated, and cooled shop to do mechanic work in-another thread.

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I'm glad if anyone has gotten anything out of me posting this.  My scientist friends have been following, play by play, by text.

I've learned a lot too.  This is my first time using left hand drill bits, and from now on, it will be the first choice for getting out broken bolts.

For the splitting stand, I've decided to design it around scaffolding casters.  There're plenty strong enough, have a strong height adjustment, and will not need to be modified, so they can still be easily used for their intended purpose later, and I ready own a bunch of them.   All I'll need to buy is a few pieces of steel.

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I ordered them off of ebay, and amazon.  It really surprised me when the first broken bolt backed right out with one.  I think EasyOuts put an expansion force on the bolt that works against you.  I was also surprised today when the big RH drill broke the stuck 3/4 bolt loose.  Both of those, as well as the others, came right out with no extra help.  I guess the threads were distorted enough when the bolts broke that it caused them to bind up.  Once that force was neutralized, it was no problem screwing them out.

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