Having to remove the ends of some sheared off bolts in cast iron, I wonder what's the best way (preserving the threads in the hole as much as possible) to do this.
I ran some 2mm drills down the threads, one on each side, then a larger hole down the middle to join, as near as possible, the two smaller ones:
,-. ' ' o O o
I usually drill a 3mm hole hown the middle, then enlarge it to say
5-6mm, then tap in a screwdriver. Works most of the time.
first off I try welding onto the broken bit and try molegrips on the resulting lump, works about half the time.
Accurate drilling down the middle with progressively larger drills till the threads can just be seen then remove the 'spring' that is left behind. If you mess up the threads in there then get a stud and set it in place with loctite and put a nut on it, that way you can screw right to the bottom of the threads in the casting, often the end ones are still good. Or just put a helicoil in.
mrcheerful
drilling a decent side hole of good depth then using a tap&die set with a anticlock wise thread, put in a bolt off the correct tap die and bingo! it unscrews the old bolt/screw.
-- Sir Benjamin Middlethwaite
In message , Chris Bacon writes
[..] 1 - Easy Out 2 - Left handed drill bitHth Someone
Go to Halfords and buy some of Facom's parallel pin bolt extractors. You'll also need a good engineering toolshop and a good quality drill bit of _exactly_ the right obscure diameter. Keep the drill(s) with the extractors for this purpose alone.
These aren't the old "tapered screw wedge" extractors, they actually work.
And the usual stuff about applying heat or real Plus-gas beforehand. Even a dose of electrolytic de-rusting can be useful on cast iron.
The message from somebody contains these words:
They're the dog's danglers if you can get 'em.
There used to be things of purpose called Easyouts. Don't know if they are still available?
-- Holly, in France Holiday Home in Dordogne
So that's using
a) an expensive left handed tap b) an expensive left handed bolt
Never heard of second hand shops? Erm! the dies that you bought from the secondhand shop create a lefthand thread.
-- Sir Benjamin Middlethwaite
Got an URL for this? I can't find them.
Use this instead.
Snap on sell them, not too dear either.
mrcheerful
Those taper things are a waste of time unless the bolt is already loose, if the bolt is tight then they spread out the remainder and ensure it never comes out.
mrcheerful
Um. They're worse than useless on anything that's really seized, unfortunately.
Again, look in snap on catalogue, they are a pin with tiny ridges along the sides, you drive them into a predrilled hole and using a special nut thing you turn the broken bit out, the advantage is that they don't spread the stud out (making it tighter in the thread)
mrcheerful
Stud extractors, which come in various forms. Simplest is the Draper four piece set. To use those, drill a hole down the centre of the bolt, insert extractor and unscrew the stub of the bolt. It works about half the time. You can also get heavy duty ones that use a 1/2" square drive to extract the bolt, which tend to be more reliable, but you will probably only find those at an automotive trade supplier.
Colin Bignell
The message from "Holly, in France" contains these words:
They almost always snap off in the hole, leaving you worse off than you were before 'cos there's now an over-hardened lump of metal in the middle of the offending stump. Perhaps really good quality ones are properly heat treated to make 'em tough instead of brittle.
The message from "The3rd Earl Of Derby" contains these words:
Unless the're really good ones, they just snap off 'cos the Chinese don't understand proper case-hardening.
Those things (Lord Stanley just posted a link) are great if you have a loose bush in a hole and you need to lock it permanently in place. They're tapered and so they act to jam the thing you're trying to remove even more firmly into the hole!
The good ones (Facom or Snap-on) are a parallel splined pin with a "driver" nut that fits accurately over them. They're a bit fragile, but they work very well without the wedging problem.
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