Ive got some metric taps labelled as "tapered", "second" and "bottom" all for the same size.

My big box of taps and dies has one tap for each size, which I presume are all "tapered".

When does one use these different taps?

Tapered taps are the starter tap to help align the tap and doesnt cut that deep, then you go down with the second then the bottom/plug tap to finish the thread, and you need the bottom/plug tap to get the thread right to the bottom of a blind hole, hope this helps m8.

Further to the above, when using taps, run them in about a turn (360 degrees), out a half, in a turn, out a half...

This lifts the swarf out of the hole, which makes your job easier, and helps to avoid breaking the tap, which you really, really do not want to do!!

Further to the above, when using taps, run them in about a turn (360 degrees), out a half, in a turn, out a half...

This lifts the swarf out of the hole, which makes your job easier, and helps to avoid breaking the tap, which you really, really do not want to do!!

That is what I was taught and do as well. Use the same method with Dies as well. 1 full turn then quarter to a half back. Cutting compound/paste (eg. Rocol) helps but if you don't have any WD-40 does just as well.

Further to the above, when using taps, run them in about a turn (360 degrees), out a half, in a turn, out a half...

This lifts the swarf out of the hole, which makes your job easier, and helps to avoid breaking the tap, which you really, really do not want to do!!

well you lads are brave I usually go +1/2 and back 1/4 to be safe. more than approx 2 diam's deep (with a tap) remove and clean, don't lube' very small sizes and watch out for Metric fine ie; 8x1mm pitch 10x1.25mm and 12x1.25 often used in cars also brake fittings seem to be 10x1mm which is 10mill spark plug size here endeth the lesson:rolleyes: