For cutting bars off in the Clausing 5914 lathe, I have been using a
up-side-down SGIH19-2 blade in a up-side-down Dorian D30BXA-7-71C holder, which
fits a Aloris BXA toolpost. The lathe is run in reverse, so the cutoff blade
will not self feed into the groove.

This works quite well, up to maybe 1.5" diameter steel, but at the larger
workpiece diameters the surface finish deteriorates markedly. What I think is
happening is that the blade is on the verge of elastic (sideways) buckling, and
is vibrating laterally. I have been using it anyway, manually and with care. I
had read that using a heavy feed helps, and it does, at least to control chatter
(where the vibration is vertically). But one must be too careful.

The Dorian catalog states (on page P-23) that the maximum workpiece diameter for
a SGIH19-2 blade is 1.57", which is consistent with my experience.

Clearly I needed a beefier cutoff blade if I was to cut larger steel workpieces
off.

So, I got a Dorian D30BXA-71-26 holder with SGIH26-3 blade. The blade is rated
for up to 3.00" diameter workpieces, which will cover most of what I do.

This made a big difference. Cutting a 2.5" diameter 12L14 bar off left a mirror
finish under power feed when flooded with soluble-oil coolant. Coolant is
essential, and one can hear the difference if there is too little coolant.

The only problem was that it turned out that the Dorian D30BXA-71-26 holder with
SGIH26-3 blade is slightly oversize for the BXA toolpost, requiring the
D30BXA-71-26 holder to be about 0.2" above the top of the BXA toolpost. My
current solution is a 0.25" thick heavy steel spacer washer 2.5" in diameter
with a 5/8" hole that goes between lathe compound and BXA toolpost. We'll see
how well this works.

As for toolpost rotation under cutting force, there is a 0.25" diameter blind
hole in the bottom of the BXA toolpost that looks perfect for an anti-rotation
pin, so I may make an adapter plate with a ridge to fit into the compound's
T-slot on the bottom and has the anti-rotation pin on the top.

Joe Gwinn