What size drill

[JasonBModerator @jasonb]

I too have always read that the shanks are unhardened HSS rather than welded on materail

[HopperParticipant @hopper]

Posted by Ian Phillips on 11/09/2016 19:50:46:

Posted by Hopper on 10/09/2016 14:44:31:

It is interesting to note too that the shanks of most drills beside being smaller diameter than the fluted section, are not made of HSS but of a softer, more flexible grade of steel welded on to the end of the HSS blank. You can easily turn the shank of a 3/4" drill bit down to fit in your 1/2" drill chuck if needed.

 

I have turned shanks of large drills down, but I always assumed that the shank was a soft form of HSS.

Do you know that they are welded on extensions?

Ian

No, don't know for sure. Just remembering what I was taught as an apprentice 40 something years ago. The old grey cells, well they could be unreliable. And manufacturing techinques could have changed I suppose. HSS is not as exotic or expensive as it used to be, so it might make more sense these days to make the whole drill out of HSS but harden only the working section.

I do remember being taught to grip the drill in the chuck leaving plenty of gap between the end of the flutes and the chuck jaws so the unhardened section of shank would be allowed to flex and so would not snap the drill bit off at the weld. Maybe it was just a toolmaker's old wives' tale.

 

Edited By Hopper on 12/09/2016 05:46:11

Edited By Hopper on 12/09/2016 06:02:51

[HopperParticipant @hopper]

PS from what I remember, I was told the HSS section and the carbon steel shank were welded together using friction and or pressure welding, ie forcing them together and rotating them in opposite directions. Going back a long time now though.

[HopperParticipant @hopper]

Well I just had to find out if I was remembering right. Couple of interesting videos on Youtube about drill bit manufacture. A couple of the older firms, Titex and Dormer, mention welding a softer section on the shanks of their drill bits. Others seem to just use great coils of HSS wire to spit the drill bits out like cookies.

Mention of it at 3:12 in this video

The whole video is worth a watch, 1967 manufacturing technology seems so primitive today.

This one is more modern, showing rolls of 1/2" HSS like wire being fed into CNC machinery. Friction welding the HSS section to the carbon steel shank is shown at about 2:10. Interesting stuff.

[stewart woodParticipant @stewartwood82335]

Hi Further to the discussion on drill manufacture .If we look at what's known as a Jobber drill 1/64 – 1/2 " and metric up to 13mm these are solid HIGHSPEED STEEL (HSS) not welded ( hardened for about 2/3rds of it length) Next you have what would be known as a par shank ( a drill up to 3/4" I think) with a parallel shank of 1/2" solid HSS not welded . Then we have taper shanks starting at No1 MTS through to No 6 MTS , used to be Carbon shanks welded to HSS . As the cost of welding increased and machines developed, it was more cost effective to make No1 and No2 MTS from solid HSS . A point of interest ,the smallest drill might be a number drill through to say 6" MTS and everything in between going up in 1/64s or metric equivalents , that's quite a range of drills to stock and a lot of money not making money ,the accountants didn't like it , and as they say that was the beginning of the end.

Stewart

[stewart woodParticipant @stewartwood82335]

There may have been one or two other reasons as well Smiley face in a strange place (what y gunna do). Stewart

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