Redrilling a tapped hole ?

[Dougy]

Even. A small tap should not break.

 

Plenty of lube and half turn advance- quarter retard to clear the swarf.

Have tapped many a small diameter in the past when I studied engineering.

What's to loose huh?

Break the tap at the Base, then you need to drill out and start again. You will need a pillar drill and very likely need to tap a larger thread.

So for the sake of £20 it just ain't worth it.

[Jaymo]

Any chance of a photo of the 'item' ( for my collection of pics of course)

What metal is it? Alloy, steel, bronze ? If it's the former or latter then unless you have been buying your tap n die set from the market/ flea bay bargain job then I personally wouldn't think that the tap( when used correctly- most times I saw broken taps was undersized pilot holes, lack of lube or ham fistedness) would shear.

 

Also, from my understanding of your first post, you say the bolt ( hardly a bolt at anything below M4, more screw like) 'bottoms out'? In which case from the amount of lead it would have had then bashing with a hammer as described or other such like would not have given rise to cross threading as its already in a threaded portion so if it was to be 'drifted' in then ALL of the thread would be knackered.

Have you used a torch and a needle along with a magnifying glass to see down inside?

 

Finally, are you sure the screw you have is the correct one?

Edited September 4, 2016 by Jaymo

[NickS]

Most tap breakages occur when you bottom it in the hole. That is why a blind hole is more of a risk than one that goes right through. I was on a tanker, a VLCC when some numpty did that to an M24 tap when clearing the bolt holes for the tank washing machine. The ship had to have all cargo tanks certified gas free and we got a few days in Piraeus, near Athens, whilst a spark eroder was used to get rid of the bits. The whole process took a week and cost a lot more that £20!

Edited September 5, 2016 by NickS