Set up on a lathe for drilling out broken bolts

[Paul Alciatore]

I have four words for you and your friend:

Left hand drill bit

They are my first "go to" tool for broken screws and bolts. The great thing is you almost never have to actually drill through the stub. They usually just back out from the torque and vibration before the drilling proceeds even one thread pitch into it.

When I said the first tool, that does not mean that I do not give it a good soak with penetrating oil. My favorite is Kroil and I like to give it hours or even over night to soak in. On really stubborn ones, striking it with the center punch while soaking can also help. You need to make a dimple in the stub anyway so using it to help the penetrating oil to wick in is a bonus.

[Frank S]

I have four words for you and your friend:

Left hand drill bit

They are my first "go to" tool for broken screws and bolts. The great thing is you almost never have to actually drill through the stub. They usually just back out from the torque and vibration before the drilling proceeds even one thread pitch into it.

When I said the first tool, that does not mean that I do not give it a good soak with penetrating oil. My favorite is Kroil and I like to give it hours or even over night to soak in. On really stubborn ones, striking it with the center punch while soaking can also help. You need to make a dimple in the stub anyway so using it to help the penetrating oil to wick in is a bonus.

My problem there is I never get the offended part before someone else has had a hand in trying to remove them on their own. Left hand drill bits do work I'll give you that. Most of the stuff that comes to me has suffered every malady a piece of earth moving equipment can endure and more. Far too many maintenance men will impact a bolt into a thread ed hole that has rust dirt and everything else in it, galling the threads on the bolt and the hole the whole time, on top of that they will pour in half a bottle of red loctite before even screwing in the bolt then wonder why they can't tighten the bolt properly or the next time they have to change out something they snap the bolt off with a 1" drive impact. I have drilled completely through bolts with left hand drill bits and stepped all the way up until nothing would be left but the Dutchman of a thread and still not had them come free, but other times when I look at a broken bolt and just dread what it is going to take to remove it the thing will back out on its own accord nearly as soon as the bit touches it.

[Improvised DIY]

Sometimes the threads are so gulled that you can't pull the bolt's threads out even after drilling a thou into the casing's threads. Fine threads are the worst. They almost cold fuse together. I had this issue with a lawnmower. The bolt was broken of at an angle and my mill was too small to fit it in so I had to hand drill it out. I tried easy-outs with no luck. I managed to get just enough threads out to get a tap to bite and break out the bolt's threads with the tap. I wish I had left hand drills but in RSA it's like chicken teeth and very expensive.