In article ,
"DoN. Nichols" wrote:

On 2008-05-04, Joseph Gwinn wrote:
In article ,
Jon Elson wrote:

Joseph Gwinn wrote:

[ ... ]

[ ... ]

The ways are flame hardened, according to the nameplate on the lathe.
This means that grinding is the only way. One can do this by hand,
using coarse diamond grit embedded in a piece of aluminum as the tool.
It won't be fast, but it will work. Diamond dust cuts hard steel quite
well.

I wonder if the dovetails are also hardened. Most of the wear is in the
gibs, so one assumes that they are softer that the dovetail material.

Actually -- the wear is normally on the harder of two mating
surfaces. This is because harder objects (grit, etc) embed in the
softer surface and cut the harder. This is how a lap works.

I'm not sure that cast iron is soft enough for much embedment to happen,
unless one is using a toolpost grinder. And while the gibs are visibly
and heavily worn, the dovetails are somewhere between pristine and
lightly worn to the eye.

Anyway, the gibs both had something like 0.003" to 0.004" of wear on one
side and another 0.001" on the other side. This doesn't sound like
much, but it approaches to exceeds the adjustment range of the gib. For
example, given a taper of 5/32" per foot (0.013021" per inch), 0.003" of
wear allows the gib to move 0.003/0.013021= 0.230", a major fraction of
the adjustment range. This plus the bunged corners forced me to flip
the gib over. However, now the gib rests at an angle on the dovetail,
as the surface is stepped (the wear not being uniform, instead leaving a
step running the full length of the gib). So, I threw in the towel.

Joe Gwinn