Unused square HSS tools come with each end cut off at an angle, 60deg sounds about right. My understanding is that this is to facilitate sharpening the end before mounting it in a tool holder of the Jones and Shipman type, which holds the whole tool at an angle below the horizontal, automatically giving a top rake angle without grinding away the top surface of the tool blank.

Other explanations may abound!

Simon

Dave, the toolbit in your photo looks pretty much the same as the ones I have.

Thor

As Simon suggests the angled cut off is provided to reduce the amount of grinding needed to produce a typical tool.

Works for conventional lay flat and boring bar tool holders as well as the Armstrong, J&S et al "up kicked" variety. The proper clearance angle for the material being cut only needs to be applied to a narrow land below the cutting edge. Think typical insert tooling. Once you have clearance between tool and cut surface the HSS is in the wind and air cares not a jot about what the angle is. So long as there is sufficient support for the cutting edge and adequate metal to take the heat away detail shape beyond the active cutting part is unimportant.

Pretty much stuck with a full grind on the flat top as the swarf needs to flow over it. Pro users tended to grind a chipbreaker there anyway.

I have an orphan tangential type cutting tool holder which takes truncated triangle shaped HSS exploiting the same ideas to minimise waste.

Got a cheap chainsaw sharpener on the shelf waiting to be converted into an HSS bit end chopper off. Plan is to fit a 1 mm cutting disk and arrange a suitable adjustable bit holder to put a similar over clearance angle on well used bits so only a narrow land has to be ground or touched up when re-sharpening. As one side of my DE grinder carries a wire brush cutting thus saves swopping between coarse and fine wheels or wasting the fine one on bulk grinding. Doing it by hand is less than accurate.

Clive.

Grind the tool for a purpose, dont worry about what is there now. Grind the tool to the angles YOU want for standard turning or a rounded point. Cut back as far as necessary for internal cutting. You will end up with a selection of tooling for most purposes.

Clive

There is an analysis of presenting the work to the grinding wheel above centre height to achieve a predictable clearance angle in the book of the Quorn. IIRR it crops up in the setting instructions for grinding reamer flutes, also for putting clearance on the perphery of a side and face cutter.