Need some advice / help on broken off bolt.

[Ace12GA]

Well, if you noticed my other thread, you noticed I recently got a nice little lathe. I have been having a lot of fun with it too.

Problem, I went to tighten the tailstock lock down handle for the first time a couple of days ago, and it twisted right off. No not the bolt that holds the tail stock to the lathe bed, the bolt that locks the tail stock extension in place when using say, a live center. I wasn't really upset by this, it looks like cheap alloy steel. I figured no big deal, I'll turn a new one, and it will make a great project. Well, I picked up an easy-out bit from the local hardware store, drilled the appropriate sized hole in the broken off bolt, and then proceded to break off the easy out. Bugger. I take the tail stock off the lathe, drop it on my drill press and attempt to drill the bolt and broken easy out, right out. 3 drill bits later, and one really ugly mess, the broken off bolt and easy out are still mostly there. I have damaged the threading for this bolt as well in this misguided attempt to fix it myself. Any advice gentlemen? How can I drill this out, or remove it without causing further damage. As it stands I will have to drill and tap the tail stock out larger than it was just to make a new lock, which is ok, if I could drill the damn thing out!.

Help.

[HuFlungDung]

My advice is this: take it easy on the easy-out, they are not unbreakable!

Grind the broken easy-out flat on top to help keep the bit from wandering.

Get a short carbide die drill to drill with. You likely do not have one of those. A masonary drill can be made to work, but you will have to cut it off so it is very short and stiff (ie., rigid) for chucking close to the end. Masonary drills do not cut steel very well unless they are resharpened (on a green SiC wheel or diamond) to have some proper geometry, but mainly to create a style of split point to reduce the enormous pressure required to force the thing to make some dust.

I have also used worn out carbide burrs and ground them into a steel cutting spade drill type point (a basic thin wedge) and had a certain degree of success that way. The tool has to be retracted and cleaned very often because it has no flute to speak of.

You might also rig up some kind of a guide bushing to keep the drill from wandering off even more than has happened already. You cannot successfully start a carbide drill on a sloped surface in hardened material.

Wear safety goggles!

[jkeyser14]

Do you have a welder? If so, weld another bolt to it so that you have a head to put a wrench on.

[vulcom1]

There are several ways for doing it as mentioned. What size is the bolt to start with and is it flush with the surface? I have removed some with a small chisel but it takes time. This may be the way to get the extractor out if it is the spiral type. You have to tap in the opposite direction but I find if you can get it loose, just work it back and forth till you get it out.
Sometimes you can centre drill with a cobalt bit as some of the easy outs are softer in the centre. A reverse drill bit is also better and NAPA sells a small kit that you reverse drill then tighten up for removal. Another way is find some business with a sinker EDM (hole popper) and they can do the job. Very easy with that and I have removed a 4/40 tap with one.
What part of Canada are you in?
John

[tobyaxis]

Here is another option. Start with a flat surface, drill a small hole 1/8 the diameter of the bolt fairly deep. Then use a 4 flute left handed End Mill HSS (not carbide) in a drill press at the slowest rpm. If that doesn't work you have the option to mill out the bolt without hitting the threads. Be sure not to go too deep, just enough to get it to come out the other side. I have a few left handed drills, special ground taps, and end mill for this type of thing. Sometime they work, sometimes they don't. Do a lot of begging in most cases like this one.

[Geof]

Is it possible for you to set it up accurately and firmly on your drill press to drill through from the opposite side? If it is anything like some small tailstocks I have seen the hole is blind but it could go right through. When drilling from the opposite side it is possible that the drill will screw the broken piece out.

Your description of what happened and the problems you are having suggests it might not be simply that the bolt broke off but that the cause of the breakage was the bolt seizing up in the thread. Many times these small machines do not have tapped holes nicely cleaned out before assembly and rarely do they have decent lubricant smeared on the threads during assembly. The combination of soft material for the bolt, maybe chips from the tapping and inadequate lubrication is a perfect recipe for galling and seizing between the bolt and casting. It is a good idea bfore using these machines to take out all these bolts and clamp and sliding things, give them a good deburring and cleaning and then reassemble with Never-Seize or a good grease to guard against galling. Bit late in your case but best of luck.

[Runner4404spd]

if all else fails take it to a local place that does edm work. i ahd to do this with a cylinder head once. they guy charged me $80 but it fixed the problem. then you can use a helicoil or tap the hole the next size up.

[ZipSnipe]

And remember, when tightening, if ya go a couple a hairs past snug, that will usually do the job especially for live center. As for getting the easy out out, I,d probably go with Hung Flungs suggestion.

[gotis]

Try these the next time you break off a bolt.

http://www.ridgid.com/Tools/10-Screw...-Set/index.htm

[ajl6549]

If you have access to a mill i.e. bridgport type you can drill it out with a carbide end mill.

[vulcom1]

The rigid set is sold by a few other company's. I have a Snap On set for years but on the box it is 1/4" and up. They are good as they have the centre sleeves and if you get one in they grip. I have bent a couple.
I would like to know what the size is as that makes it different the way you go about it. I agree the EDM is the best as that is why I made mine but not everybody has one. I have also used a dremel with a small grinder to get started. If the break is on an angle which they usually are it is easier to get centred. A little cutting oil when grinding helps along with some spare stones.
Helicoils on the small size go down to 4/40 which I still have some. Not sure how small they go in metric which you will need.
John

[StealthDumpKits]

...my quick & dirty broken tap extractor is a 40 amp plasma cutter. Works great on thru holes in steel, just make sure it's centered. One to five second burst and the tap is blown out the bottom. If it gets too hot and slag sticks to the threads, I just enlarge the hole with it, then weld it back up.