Hand-tapping

[Philip Davies]

Surely you wouldn’t want this done to your taps?
The fact is that I’m unable to exert enough downward pressure to start the thread in these 10mm holes for 1/2” BSW (& the hole, says the tables, is supposed to be 10.5mm) Then I used a taper reamer, no.7, which might suit, though haven’t looked it up.
Still only a half-turn can be done, before moving the clamp, and I cam check each time that it’s square to the material. After 4 goes, the thread has started and little more downward force is needed. Otherwise, blood pressure shoots up!
These are first steps in metal machining, and very totters steps they are, indeed, beginning with T-nuts.

What you see here is a rehearsal in aluminium, and of course the cutter slipped down. Tapping aluminium alloy was hard enough.
You may see that I have got a second tap in the holder. That is because the starting tap has chips in it.
Do you think that this is salvageable?