When is a new 90 degree drill not 90 degrees?

[Bill PhinnParticipant @billphinn90025]

I recently bought a new spot drill (pictured) off ebay.

Can anyone explain the lack of correspondence between the marked tip angle and the actual one?2

[DiogenesParticipant @diogenes]

Used, reground, put back in it’s packet, and sold? ..the box looks a bit ‘handled’..

[Bill PhinnParticipant @billphinn90025]

I think that’s unlikely, Diogenes, though I understand your cynicism; the drill is its full 75mm in length, the tip grind looks factory-like for its evenness and smoothness, there are no signs of use on the shank or the lands, and the seller tells me all the stock of these drills he has have visibly the same tip angle.

82 degree spotting drills do exist (presumably in both LH and RH), but I’d expect them to be marked as such, not marked 90 degrees. I can only assume this was a batch that got marked 90 but was ground to 82 degrees.

It can be used for screw extraction and to countersink for UNC/UNF screws if nothing else.

Now I just want some 140 degree spot drills, which seem to be rare as hen’s teeth in HSS, and ludicrously expensive in carbide.

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