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broken bolt removal?

D

Dave H (MI)

Well-known Member
On a IH Cub Loboy. This is in regards to a belly mount sickle mower mounting. There are two 3/8 bolts that attach a plate with a pulley below the PTO shaft. The bolts thread into the cast tractor body. Not sure why, but one of these bolts broke off inside the hole. At least a quarter inch in from the surface. I cannot see this happening if the hole had threads all the way to the surface so maybe it was stripped out at some past date by the PO. Tractor has a new paint job so I do not really want to take a torch to it. Can't even see it so I cannot really work on it to get it out. I was thinking of drilling it thru and re-tapping the hole. Not really seeing an option here but willing to listen to suggestions. What would be the best drill size if I wanted to try to keep it at 3/8"?
 
5/16 is the tap drill size for the bolt. were it mine, I would take a 5/16 rod of mild steel and put it in a lathe. I would drill it on center to 3/16". I would cut off an inch of it and use it as a drill guide/bushing to assure a 3/16 centered hole in the bolt, drilled to the far end of the broken piece. I would then use a 5/16 drill to remove the remainder, and a tap to clean the remaining thread "spring" Jim
 
I would buy a few left hand drill bits in say 1/8 or 1/4 inch and try them and see if you luck out and have them catch and screw the broken bolt out. If you had my set of ez-outs I would say try that but few people have the good ez-outs
 
Check to make sure that its not just dirt filling the hole that has been painted over. A bolt hole filled with dust can compact as hard as rock from vibration over the years, IMHO. jal-SD
 
I'm not really sure where exactly you are talking about as I don't have an IH Cub Loboy. However you could just drill out the remains of the old bolt and re-tap the threads to clean them up. If the threads are messed up and a 3/8 bolt will no longer thread in then you could install a helicoil. Whatever you do just don't break off a tap in the hole.
 
soak it with penetrating oil (for days). then use a small left hand twist drill bit. try to go slow. maybe the bit will catch and the bolt,
will back out
 
Your drill bit size is deterined by what easy out are you using important thing is getting drill centered that is the most important part with your removal. I use the spring loaded center punch from Snap-On after careful cleaning of the broken part.
 
Helper can hold a 3/8 nut over the hole while
you use a 3/32 welding rod to weld on the
broken stud--bringing it up to surface level.

Then weld inside the new nut until it is full
of new weld. Let everything cool for a couple
of minutes. Rock back & forth while applying
penetrating oil.

Weld at around 80 amps--maybe a little less.

May have to go 2 or 3 times on the welding thing
to get it out. It's the heat that breaks the
rust in the threads.
 
Jim...I only wish I had the resources and skill to do that. If it weren't for that big pond in between us I would sign up for a couple of your classes in a quick minute!
 
For that matter Rich, I think the threads probably go all the way thru the casting, I right hand drill might just push it thru easier than it would come out. Probably not much rust on those threads on the inside. Might have to look into that.
 
I was fortunate in the early days of my education to see someone break a tap in a hole. Since then I have been really careful to not have that happen. Guess I will look into this today since the rain has me indoors.
 
That would be ok if you can get to the end of it to throw it away. I know I would not want ti to just lay around inside something
 
(quoted from post at 10:44:02 06/27/15) I was fortunate in the early days of my education to see someone break a tap in a hole. Since then I have been really careful to not have that happen. Guess I will look into this today since the rain has me indoors.
Click to expand...

Taps are hard but they can be shattered with a punch then dig the pieces out with a pick or magnet, too much experience talking!
 
The bolt may not be stuck in the hole, it may just be fractured and loose. If you have no access to a lathe, drilling out a 3/8 course bolt so it has a 3/16 hole through the center will also work. Just screw it in the hole and drill through it into the broken bolt. Getting a centered hole on the bench would be pretty easy, and if not successful easily repeated until a centered one is made. After drilling the broken bolt, putting a straight fluted (not spiral) remover. This is tapped into the 3/16 hole and used to remove it. Many IH bolts are drilled and tapped into a location with a closed "bump" or boss on the reverse side to reinforce it and keep it from leaking. Jim
 
If it's 1/4" below the surface you should have 4 good threads above the broken part(3/8-16 thread). I would find a friend with a lathe & drill a 3/16" hole into a 1" long piece of threaded rod. Screw it into the hole and use it as a guide to start drilling a 3/16" hole thru your broken bolt. If you can find a left hand drill bit you stand a good chance of having the broken piece back out when you drill it. In any case go up to a 5/16 drill, then carefully pick out any remaining pieces and re-tap. I have zero use for easy-outs on rusted broken bolts, based on 45 years of tool & die experience. If the bolt is broken but not stuck they will work, but not on rusted ones.
 
I forgot to tell you this but I often will drill out the hole to where it is close to the threads. Then I use a die grinder with a carbide burr bit and carefully grind until I get the bolt razor thin. If you are careful it will eventually spit out the pieces that are left without messing up any threads. I also use the same trick for when I don't quite get the bolt drilled in the center. Then I can get it centered.
 
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