Broken Screw??

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Kroll

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DSC02844.JPG Morning guys,well I started on the saddle of my Colchester lathe.Its just about all cleaned up,oil channels flush,all bolt holes have had a tap ran down them except one.Yep it was broken off by the last owner so don't blame me,yetLOL.Anyway its for one of the felt wippers (which I do need to find) and guys I just have never had any good luck trying to remove a broken screw.Its a 10/24 which is just about broken off flush,just a little tip sticking up.I was wondering what your method of removing a small broken screw is?Maybe this will increase my chances of being successful,asking first.Yes I know the pics are big which I have tried to make them smaller and at the bottom of the post but I haven't been successful at that neither.

DSC02845.JPG
 
I always had the best luck with the Snap On Extractors that look like rods with thin ridges on them. I was once a mechanic, so drilling and extracting broken screws was a really common operation.

For you, since you say you have always had bad luck, I would make a drill guide.
You have a nice threaded hole right next to the broken screw. Make a guide from a thick piece of scrap and use the other hole for mounting it to the cross slide - the hole spacing should be easy to figure out. I would drill a few number sizes under the proper tap size and see if it will come out with a standard reverse spiral screw remover. It should just turn right out. If it wont come out, drill the guide to the correct tap size and just drill the screw out. Then tap. It will come out a bit loose, but since it is only for a wiper, it will be more than fine.
 
Being it's iron, weld wont stick to it. If you have a tig welder, weld a large nut to the stud, let it cool to the touch and back it out with a back and forth motion.
The weld will put enough heat in the stud to expand it just enough.
If the weld snaps then the stud is cross threaded, and you will have to do the drill guide as mentioned above.
Ive done this hundreds of times on cast iron.

Sent from somewhere in East Texas Jake Parker
 
I like the drill guide idea, and I would use a left hand bit to drill it. I often find it will come out by itself during the left hand drilling operation.

David
 
Before you screw it up, as mentioned above:

find a small pointed piece of hardened steel, such as a 6-32 tap, Us a brass hammer (it won't slide around on the back end of the tap). Start in the lower portion of the tap, where there is a shoulder (in the break). Using the tap and the hammer, tap gently in a counter clockwise motion, to unscrew the broken screw. I've done this down to 5-40 screws.
 
For small screws, I drill a small diameter pilot hole and then enlarge it to the size required for a screw extractor. If the screw is stubborn (rusted in or cross threaded), I will drill out progressively larger holes until I hit the thread. With each drilling operation, I try to adjust for any visible runout. Many times, this will loosen the screw remnants enough to unscrew. If not, when I hit the tap drill size, I will run a tap in. Ideally, the tap will follow the old thread. I go carefully at this point because it is possible to jam the tap and snap it off. One thing worse than a broken screw is a broken tap.

The last one that I did was in an aluminum caliper mount for a badly corroded M5 screw. The remnants of the screw were pushed out by the tap and the original threads were virtually untouched.
 
I'd go with the drill guide, position it right and use a transfer punch that fits the guide snugly to get the centre exact, then centrepunch and start with a SMALL drill before applying a lefthand bit, usually brings the broken screw out before you've drilled through

For really obstinate problems I've drilled then used a dremelloid and diamond burr to the point where the thread just picks out and unwinds with pliers - e.g. broken disc bolts in alloy motorbike wheels, rounded out SHCS in alloy fork yokes.

Dave H. (the other one)
 
That has been there for a while. You are lucky it is out in the open with nothing obstructing the work area. I would file the broken area as flat as possible without removing material from the piece. You want to flatten the broken piece in order to locate a good center and center punch it. Step drill the hole to remove as much of the broken screw as you can. You will want the easy-out to get down in the hole for a good grip.

Using an extractor check the depth of the screw hole next to it. You do not want to make the hole so big the extractor or easy out ends up bottoming out. And not having any material to grab for the removal of the screw .

Which should not be all that hard, cause it looks like you can clamp the part in a vise to work it. To bad I am not next door, could have that screw out in a heart beat.

If you blow it, HeliCoil will bail you out, but you wont need it cause there is total access to the broken screw. Just take time finding the center, once you have that, you're on your way....
 
I would go with the small pilot drill to drill through the screw hit it with WD and then a left hand bit. Unless it is really bad it should wind itself out.
 
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