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Unusual drills

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Maurice30/03/2019 18:31:51
460 forum posts
50 photos

I was sorting though some bits and pieces that came from an old friend's workshop. Still sealed in a packet are what at first sight looked like a couple of 1/8" drills. However, looking more closely, the last 5/32" of the shank on the cutting end has no flutes, and the cutting face on one is like a pyramid, the other is chisel like, i.e. a straight line across the centre and an inclined face at about forty-five degrees on either side. As they are packed together I assume they are intended to be used together, perhaps for drilling hard material in a two stage process. Can anyone tell me what they are really for, and how they are used please?


David Standing 130/03/2019 18:53:39
1288 forum posts
48 photos

A photograph would help smiley

Maurice31/03/2019 00:13:39
460 forum posts
50 photos

Yes; I'm working on that. My camera is on the blink at the moment; I am trying to borrow one. I'll post pictures as soon as I get it.


robjon4431/03/2019 09:34:46
119 forum posts

Hi, I think that what you have there are drills for armour plate, think wear plates on blades of motor graders & similar earthmoving machines, made from Stellite modus operandi under very heavy drilling pressure the drill itself & the material rise to red heat, anneals & then allows the drill to pass through, a classic case of brute force & ignorance! not really the sort of thing you need in a your shed. Naturally I have some that I acquired years ago, around half inch diameter, I would not subject any of my own equipment to that kind of abuse BUT Stellite can be ground with green grit or diamond wheels into lathe or shaper tools that will withstand large amounts of abuse without flinching.


David George 131/03/2019 09:55:32
1193 forum posts
409 photos

Are they flow drill drills I used them in the past to make panels for machines from thin steel plate. They heated the steel by rotational friction in a drill or mill and forced the steel through hole to make a boss which you could tap because of the thickness if the material increase.


mark costello 131/03/2019 18:46:24
586 forum posts
12 photos

Any idea what the friend did for a living?

PekkaNF01/04/2019 10:44:24
96 forum posts
12 photos


I (mis)used one to drill into hardened steel pin.

Edited By PekkaNF on 01/04/2019 10:45:05

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