Drilling out broken screws

I know from experience how a simple job can become a major disaster. The first thing is to get the centre mark in the right place, and to have the means to correct it, if the drill wanders. One possible way worth considering, is to glue a washer accurately over the screw. the smaller the washer hole the better, but it is not critical. Run a drill that is an exact fit in the washer just long enough to form a small central mark in the broken screw. Then drill out the screw. If the washer does have a hole no bigger than the screw, then you may be able to correct it if the drill wanders.
 
Just to reiterate several important points. In drilling SS you must have slow speed and high pressure to get a proper cut swarf or at least plenty of chips. Use oil for lubrication it will also start to smoke if the job gets too hot. Heat will harden the SS (work harden) and damage the drill bit. Use a drill press if at all possible.
As said beware of tapered extractors. They can be good but SS corroded into aluminium almost certainly means you must drill out all the screw and tap a new thread. Probably larger. Frotunately often the heat of drilling out will dislodge the remaining bits of old screw. good luck olewill
 
One way is to file the screw flush & put a new hole in a different place. Thus bypassing the problem altogether


Alternatively drill a hole about the size of the screw in a piece of alluminium or ply. Clamp it firmly over the screw so the centre of the screw is centre of the hole. Use a drill bit slightly bigger than the screw so if you do go off line you still get all the screw out
The hole in the piece of aluminium is to stop the drill bit wandering off line
 
huldah said:
I know from experience how a simple job can become a major disaster. The first thing is to get the centre mark in the right place, and to have the means to correct it, if the drill wanders. One possible way worth considering, is to glue a washer accurately over the screw. the smaller the washer hole the better, but it is not critical. Run a drill that is an exact fit in the washer just long enough to form a small central mark in the broken screw. Then drill out the screw. If the washer does have a hole no bigger than the screw, then you may be able to correct it if the drill wanders.
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Good one thanks
 
Working on the car last week and I snapped a steel bolt in an alloy head. Screw extractors wouldn't budge it, so as there was about one thread still showing, I tried welding a nut on. That didn't work either and the nut came adrift, but the heat from the weld must have freed it, as when I went back with the extractor it came out very easily...........
 
It has struck me that that although there are some responses suggesting "good quality drills", that might not be of much help to the OP. Can anyone recommend brands that they're happy with? I'll start the ball rolling and say I've been happy with anything with "Dormer" or "Presto" written on it. Also DeWalt's own drills seem OK.
 
Avocet said:
It has struck me that that although there are some responses suggesting "good quality drills", that might not be of much help to the OP. Can anyone recommend brands that they're happy with? I'll start the ball rolling and say I've been happy with anything with "Dormer" or "Presto" written on it. Also DeWalt's own drills seem OK.
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Bosch Cobalt have also worked for me but as mentioned many times above, getting some heat into the area is key. I would be reluctant to place too much hope on an extractor unless you could use heat at the same time. Often the drilling will generate enough heat but a small blow torch / gas soldering iron can be very helpful. I've never heard of the "jump leads" method but that has gone into the memory bank for future reference!

Richard
 
Centring the drill bit on the broken screw/bolt is the tricky bit, in my experience. How do you tell if the punch is centred? I've also blunted the point of a centre punch on a SS bolt. I bought a set of quikcenter tools (http://www.quikcenter.com) when they were on special offer following a disastrous attempt to drill out a SS bolt from an aluminium casing. Only used them once, and not really in anger, but if you have a bolt to remove, this is the way to do it.
 
Neil said:
Centring the drill bit on the broken screw/bolt is the tricky bit, in my experience. How do you tell if the punch is centred? I've also blunted the point of a centre punch on a SS bolt. I bought a set of quikcenter tools (http://www.quikcenter.com) when they were on special offer following a disastrous attempt to drill out a SS bolt from an aluminium casing. Only used them once, and not really in anger, but if you have a bolt to remove, this is the way to do it.
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I was thinking of them but couldn't remember what they were called - they look like decent tools and are sensibly priced, shipping is a bit pricey though.

Did you buy direct from the states or from someone a bit closer?
 
You can buy "spotting" drill bits online from machine shop and engineers supplies they are more pointed than jobbing drill bits and will make it easy to be accurate when starting also get some decent drill bits at the same supplier.
 
Neil said:
Centring the drill bit on the broken screw/bolt is the tricky bit, in my experience. How do you tell if the punch is centred? I've also blunted the point of a centre punch on a SS bolt. I bought a set of quikcenter tools (http://www.quikcenter.com) when they were on special offer following a disastrous attempt to drill out a SS bolt from an aluminium casing. Only used them once, and not really in anger, but if you have a bolt to remove, this is the way to do it.
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I've not seen the quikcenter gizmo before but from the video it looks as if you have to have a few threads intact and proud of the substrate?

If that's the case their application might be a bit limited as the broken bolts or studs I've had over the years have not usually been that obliging.

Richard
 
RichardS said:
I've not seen the quikcenter gizmo before but from the video it looks as if you have to have a few threads intact and proud of the substrate?

If that's the case their application might be a bit limited as the broken bolts or studs I've had over the years have not usually been that obliging.

Richard
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If you dig around their terrible website you eventually find the application notes: http://www.quikcenter.com/application.htm which show how it works with various types of broken studs, I reckon their "flush with surface" instructions are a bit hopeful to say the least, the rest looks interesting.
 
DinghyMan said:
If you dig around their terrible website you eventually find the application notes: http://www.quikcenter.com/application.htm which show how it works with various types of broken studs, I reckon their "flush with surface" instructions are a bit hopeful to say the least, the rest looks interesting.
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I hadn't seen that but I am in full agreement with you. "Broken above surface" and "broken below surface" look plausible but "broken flush with surface" or close to that ..... no chance. I would rather clearly see the entire broken stud face and take my chances with a punch.

Richard
 
DinghyMan said:
I was thinking of them but couldn't remember what they were called - they look like decent tools and are sensibly priced, shipping is a bit pricey though.

Did you buy direct from the states or from someone a bit closer?
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I bought them online from the US. Don't remember the postage being too pricey at that time - maybe it's gone up - too many dodgy customers saying it didn't arrive....
 
I'm intrigued by this topic, which seems to surface so regularly, with so many responses. For the past 50 or more years I've owned old boats, old cars and made model steam engines etc.
I can't really remember having to drill out a broken screw, maybe a couple which I've now forgotten about.
A broken tap or three, but that's a different PITA.
 
I didn't see you mention what the broken screw was into. When I bought my boat there were three rusty stubs of screws in the GRP were something had been removed in the cockpit. After a frustrating couple of hours trying some of the above I found it much easier to open up a small hole around the screw, fasten a small mole grip and unscrew it. Meant a slightly larger hole to fill but 100 times easier than drilling out the old screws. May not be appropriate for your situation.
 
earlybird said:
I'm intrigued by this topic, which seems to surface so regularly, with so many responses. For the past 50 or more years I've owned old boats, old cars and made model steam engines etc.
I can't really remember having to drill out a broken screw, maybe a couple which I've now forgotten about.
A broken tap or three, but that's a different PITA.
Click to expand...

I think its a case of it only has to happen once in a while for it to be a real pain to fix, at least with taps you can usually disolve them

corbu said:
I didn't see you mention what the broken screw was into. When I bought my boat there were three rusty stubs of screws in the GRP were something had been removed in the cockpit. After a frustrating couple of hours trying some of the above I found it much easier to open up a small hole around the screw, fasten a small mole grip and unscrew it. Meant a slightly larger hole to fill but 100 times easier than drilling out the old screws. May not be appropriate for your situation.
Click to expand...

Something like http://www.rockler.com/screw-extractor might be better for screws in wood or grp?
 
earlybird said:
I'm intrigued by this topic, which seems to surface so regularly, with so many responses. For the past 50 or more years I've owned old boats, old cars and made model steam engines etc.
I can't really remember having to drill out a broken screw, maybe a couple which I've now forgotten about.
A broken tap or three, but that's a different PITA.
Click to expand...

(Stainless) Steel bolts in aluminium castings submerged in seawater. I've had a ss bolt sheer off in a lower outboard leg and my attempts to drill it out were a complete disaster. I bought the Quikcenter afterwards so it would never happen again. Good insurance against a repeat performance, bolting the stable door and all that!

Did use it to drill out a stub of an engine anode without damaging the thread, but that wasn't really a test

Better to avoid the sheering bit. A MAPP gas torch on the casing will often get it out without snapping it's head off
 
Sorry all: I hoped to have an update by now. I ordered 5% cobalt drill bits from amazon which were expensive but had good reviews. I investigated the brands recommended on this thread but some seemed to only be available from the US. Premier charge me £25 a month for renting a mailbox made out of tinfoil to which mail regularly goes missing (they blame royal mail and I have no reason to disbelieve that). The drill bits seem to be the latest victim of this. Whether it's the post office or someone has half-inched it from the the post room (they've apparently had "some vandalism" recently and the tinfoil door to my mailbox fell off in my hand today) I don't know and they don't keep records of non-signed-for mail delivered. Apparently it's my responsibility to contact the post office who I would lay good money aren't likely to much care...
 
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