making threads

[VicS]

....... if I may add something also, most taps come in 3's a starter which is tapered, a second for obvious reasons, and a bottom tap which is to get maximum depth if the hole is 'blind'

Thats more like repeating than adding!

 

[TiggerToo]

3.5mm hole, 4mm tap?

yes, you got it in one.... thanks everyone for the advice

 

[Thistle]

Workshop bible

Lots of suggestions about drill sizes etc. Perhaps a little surprising that no-one has yet suggested http://www.amazon.co.uk/Precision-Reference-Drawing-Toolroom-Workshop/dp/B0000CLZUO. No workshop should be without one.

 

[TQA]

Lots of suggestions about drill sizes etc. Perhaps a little surprising that no-one has yet suggested http://www.amazon.co.uk/Precision-Reference-Drawing-Toolroom-Workshop/dp/B0000CLZUO. No workshop should be without one.

Linkie no workie

 

[VicS]

Workshop Bible?

Lots of suggestions about drill sizes etc. Perhaps a little surprising that no-one has yet suggested this. No workshop should be without one.

Or a copy of The Quran in some parts of the country perhaps

 

[VicS]

Linkie no workie

Actually its to Zeus ....... thread that small not in my copy ..... but is a pretty old one, 1965 !

 

[lustyd]

I always use a guide block with a starter, that is a piece of hard material, (mine is bakelite) about 1/2 to 3/4" thick in which a hole is drilled through at 90deg. the same size as the tap dia. place and hole in the block over hole to be tapped and the tap will stay at 90 to the work being tapped.

That's a very good idea! I've taken to using the power drill when tapping into the mast to avoid the problem with breaking the thread. To be fair I have yet to break one with the drill but a block is a much better idea!

 

[Thistle]

Linkie no workie

Try http://www.amazon.co.uk/Precision-Reference-Drawing-Toolroom-Workshop/dp/B0000CLZUO. Zeus tables = workshop bible. (But I've not actually checked my copy to see if these sizes are covered; I'd hope they are.)

 

[Thistle]

Workshop Bible?

Or a copy of The Quran in some parts of the country perhaps

I will bow (in the appropriate direction) a to your superior knowledge!

 

[nigelmercier]

I've not actually checked my copy to see if these sizes are covered; I'd hope they are.)

Mine also says "Metric revision", so I guess it hasn't been revised for a while.

 

[William_H]

Thread taps are wonderful devices to play with. The size of hole you drill first dictates how hard it is to start and cut the thread. This of course also depends on the material. So in to fibreglass you can have a smaller hole while into stainless steel you might need a larger hole. Of course a hole that is too big while making the thread easy to cut also leaves a shallow thread which might be easily stripped.
As said keeping the tap perpendicular to the material when starting is critical. If it wobbles it will just gouge out the hole bigger.
I use my drill press with the tap in the chuck. I turn the chuck by hand back and forward as said. In fibreglass on the boat I use a battery powered drill on low speed to turn the tap and it will cut in then reverse out so quickly. I find that a bolt tapped into the f/g has better sealing ability plus if i want to put a nut on the inside it will hold itself in place. (don't need a helper on the outside).
Reiterating also be careful to not snap the tap off.
Funny while Oz went to metric about 40 years ago I still buy whitworth bolts and taps die nuts etc for the boat. I have metric taps and die nuts but never use them.
good luck olewill