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Broken tap


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Nothing to do with plumbing!  For some weird reason all of the screws on my external fittings are rusty!  I reckon whoever painted it last removed the originals (all 5mm metric machine screws) and replaced them with plain steel or at best zinc plated Posidrive countersunk (NOT galvanised).  So, I've been working my way through removing them and replacing them with decent stainless countersunk Allen head screws.  So far so good - and I'm managing to remove most of them without the heads rounding off.  However, under one off the door hooks they obviously broke off the tap when threading the hole - re-drilled another hole adjacent to the first and broke the tap in that as well!  There's not room to drill and tap another new hole under the hook plate.....! So I have two broken taps stuck in the bulkhead and only one screw holding the door hook.  Any good ideas on how to remove the broken taps so that I can put new fixings in?  Can't realistically apply heat because of burning off the paint etc. and because of how the tap is broken can't get a drill to start on it properly to drill it out.

 

Thanks!

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You have a big problem.

Even if you could drill it out you most likely couldn't as it will be really hard steel.

I suspect its not really viable to get to the back of it and use mole grips?

Careful impacts with a hammer and centre punch can sometimes work them loose, then use the hammer and punch to rotate them out, but chance of success is not too high.

Leave them in place and start again with some lateral thinking is probably the way to go, maybe make some decorative plates to bolt over the bad holes, (fixed on with new holes) and drill and tap this plate to take the hook plate?

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6 minutes ago, dmr said:

You have a big problem.

Even if you could drill it out you most likely couldn't as it will be really hard steel.

I suspect its not really viable to get to the back of it and use mole grips?

Careful impacts with a hammer and centre punch can sometimes work them loose, then use the hammer and punch to rotate them out, but chance of success is not too high.

Leave them in place and start again with some lateral thinking is probably the way to go, maybe make some decorative plates to bolt over the bad holes, (fixed on with new holes) and drill and tap this plate to take the hook plate?

 

You could cut a circular hole out around the taps using a hole saw in a drill, then plug the hole with a glued-in circular offcut the right size -- I've done this before when a hole was drilled in the wrong place...

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18 minutes ago, dmr said:

 

Careful impacts with a hammer and centre punch can sometimes work them loose, then use the hammer and punch to rotate them out, but chance of success is not too high.

 

That is what I have done in the past. Tap it anticlockwise to screw out towards you.

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You can buy 3 pronged widgets for unscrewing broken taps. The prongs go into the flutes.    Try MSC.

The tap may be jammed by its swarf, which will make life difficult, or it may have broken because of side pressure  which is easier.  

 

Or buy a short series solid carbide drill of tapping size and at slow speed with plenty of cooling stuff drill the tap out.  MSC sell them if you don't  have a handy engineers merchant. If you can get a left hand one that will tend to unscrew the tap as well. Grind the end flat and a Carbide drill will usually start without needing a centre.

 

Always try to buy HSS taps for work where the boat can move relative to you. They are much less brittle than carbon steel, but dearer too.

 

N

 

 

 

 

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57 minutes ago, Bob Chamberlain said:

Nothing to do with plumbing!  For some weird reason all of the screws on my external fittings are rusty!  I reckon whoever painted it last removed the originals (all 5mm metric machine screws) and replaced them with plain steel or at best zinc plated Posidrive countersunk (NOT galvanised).  So, I've been working my way through removing them and replacing them with decent stainless countersunk Allen head screws.  So far so good - and I'm managing to remove most of them without the heads rounding off.  However, under one off the door hooks they obviously broke off the tap when threading the hole - re-drilled another hole adjacent to the first and broke the tap in that as well!  There's not room to drill and tap another new hole under the hook plate.....! So I have two broken taps stuck in the bulkhead and only one screw holding the door hook.  Any good ideas on how to remove the broken taps so that I can put new fixings in?  Can't realistically apply heat because of burning off the paint etc. and because of how the tap is broken can't get a drill to start on it properly to drill it out.

 

Thanks!

I've managed to remove broken taps in the past by sliding a couple of nails down the flutes and twisting them back and forth with a pair of pliers so as to unscrew the tap. Take your time over it and you'll get there. Good luck.

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Screwfix do threaded metal inserts (next day order)  with a M5 internal thread which might be useful if you can remove the taps. Code 1166X, £2.39 for a pack of four. While intended for screwing into timber, they could be secured in metal using an epoxy adhesive such as Araldite. 

Edited by Ronaldo47
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Ive had a lot of luck removing broken taps with oxy ......the flutes provide plenty of space for the flame ,and the hard steel burns in a few seconds,leaving a bit of crumbly metal and oxide to pick out or blow out with an air jet...............there is no risk of cutting the solid metal,which conducts heat away.

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A 5mm tap doesn't give you a lot of scope, the flukes are tiny no room to get anything down.

I've always managed to break them out with a punch, and believe me I've done a few over the years! you will probably destroy the punch in the process but small price to pay....good luck 

  • Greenie 1
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1 hour ago, john.k said:

Ive had a lot of luck removing broken taps with oxy ......the flutes provide plenty of space for the flame ,and the hard steel burns in a few seconds,leaving a bit of crumbly metal and oxide to pick out or blow out with an air jet...............there is no risk of cutting the solid metal,which conducts heat away.

Surely this will damage surrounding paintwork?

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