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

Joseph Gwinn wrote:

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.


That sounds like a decent setup. My 6903 is sporting an Aloris AXA on a spacer block
which is too small for the lathe. I've been holding off on more holders as not to get
locked into something I'd rather change to BXA.

Parting is where my set up is weak. Making it to 3" would satisfy most of my needs.

Now if only some extra money would stay in the budget, I'd be upgrading.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

In article ,
Wes wrote:

Joseph Gwinn wrote:

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.

It turns out that it chatters with the D30BXA-71-26 SGIH blade holder, but not
with the smaller SGOH blade and holder I had been using. I had theorized that
the thick washer wasn't quite flat enough, allowing slight rocking, so I
undercut both faces so the toolpost and compound would rest firmly on rings at
the outer diameter. Made no difference.

Research continues. This with an upsidedown blade and reverse rotation, so
static stiffness is not the issue. That leaves dynamic stiffness. So, ways to
increase both stiffness and damping are needed. Maybe a piece of sheet lead in
a critical spot.

Actually, this toolholder will accept a HSS T-section cutoff blade, if I recall,
so there is an experiment to try.


That sounds like a decent setup. My 6903 is sporting an Aloris AXA on a
spacer block
which is too small for the lathe. I've been holding off on more holders as
not to get
locked into something I'd rather change to BXA.

Parting is where my set up is weak. Making it to 3" would satisfy most of my
needs.

Now if only some extra money would stay in the budget, I'd be upgrading.

For a 6900-series lathe, an AXA is far too small. Which you already know.
Aloris recommended the BXA without spacer for my 5900-series lathe, and it does
fit well, except for this larger Dorian toolholder.

If the 6900-series lathe works with a CXA toolpost, as seems plausible, the big
Dorian D30BXA-71-26 toolholder and blades would just fit.

Joe Gwinn