L.A.Van Royen Twist Drills and their Grinding

[Anonymous]

Posted by SillyOldDuffer on 10/01/2019 11:24:41:

Now I wonder where I got that from? I was confident it was a fact but now my reputation is on the line I can't find anything authoritative to support it.

It has cropped up every now and again for as long as I can remember. It might possibly have been true, to some extent, in the early days of HSS in the 1900s. But not now with more complex types of HSS with better heat treatment and understanding of the metallurgy.

Whatever the answer, I use carbon steel, HSS and carbide tooling as needed to suit the job and machine.

Andrew

[jacques maurelParticipant @jacquesmaurel42310]

You can read my articles in MEW about drill sharpening (the Van Royen is discribed as conical clearance). Issues N° 245, 246, 247. Issue 251 for small drills, and issue 256 for web spitting. I'm still working on the subject for further articles.

J Maurel

[IanTParticipant @iant]

I have quite a collection of 'carbon' tools and often use them in preference to HSS tooling when working brass – either on my smaller lathes or the hand shaper. They take a very good edge where fine cuts are required and many are forged to particular shapes that can be convenient on the shaper. They don't get hot enough to lose their hardness, which is more than sufficient for non-ferrous work.

As always these things depend on the context – horses for courses.. If I'm roughing out mild steel then obviously HSS holds up much better – but for shaving thous off brass, then a nicely honed carbon tool works very nicely and I've never had to worry about its "Rc" value!

I haven't got the math to understand most of the discussion here – but when those who 'do have' decide what's best – a simple "do it this way" would be quite good enough for me. All I want is something that drills to size and produces those lovely twin spirals of swarf. Sounds simple enough…

Regards,

IanT

[John BatesParticipant @johnbates63489]

A really great discussion on sharpening and carbon tool steel vs HSS.

But (there is always a but) when doing comparisons we always need to be clear about the items being compared. There are many “types” of carbon tool steels and many more types of HSS. The “original” HSSs now known as T-1 and T-2 were 18%W 4%Cr 1% Vanadium and 14%W 4% Cr and 2% Vanadium respectively. In 1921 the addition of 12% Cobalt to T-2 gave us T-6 the first Super HSS. Ellwood Haynes invented Stellite in 1922 and the needs of war production saw these cast alloy cutting tools made from W, Cr and Cobalt developed from 1939.

However, the tensile strength of the material to be cut is one of the most important factors to be considered when making a choice of the best type of cutting tool material. It largely determines the degree of cold hardness, red hardness, and toughness required to machine the part efficiently. We can divide material into low tensile and high tensile but the dividing line comes at a tensile strength of about 40,000 lbs/sq.in the approximate point where cold hardness gives way to red hardness and toughness as the most important quality that a tool should have.

John

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