In order to tune the lathe, three tools are needed. The first is a precision
level and the second is a spindle test bar and the third is a dial
indicator. With these tools, all measurements and adjustments can be made.
First, the level of the bed must be established. Not so much for the
operation of the lathe in this instance, but to establish a measurement
baseline. To do this correctly, be prepared to twist the bed. This sounds
impossible, but the bed is actually quite plastic and it is easy to achieve.
The bigger the lathe, the easier it is Remove everything from the bed. You
can cheat and remove everything but the saddle if you want, but it is better
to remove everything. if the lathe has an underlying bench or cabinet, you
may want to unbolt the bed, jack it up and drill and tap two holes in the
bed legs at the tail stock ends. Install two jacking bolts in these holes
and remove any shims that may exist under these legs and rebolt leaving
these new screws loose. Now level the bed horizontally at the headstock with
the cabinet feet, then level the bed longitudinally with the cabinet feet,
alternating back and forth to the best possible position. Don't worry about
the horizontal plane at the tailstock, that's why we have the jacking
screws. With the bed firmly bolted down measure the horizontal level
incrementally from the headstock end to the tailstock end and record your
readings. Now you have established the bed twist. Recheck the headstock side
and be certain it is still level. Place the level across the tailstock end
and with the jacking screws twist the bed to level, often checking that the
headstock side isn't changing. If it does, adjust with the cabinet feet (the
cabinet is twisting) Repeat this until the horizontal plane is the same at
both ends. Then with feeler gages measure the gap between the feet and the
cabinet, make a shim pack to the measured dimensions and rebolt the bed.
Check for level again and repeat 'till square. Now by measuring the
difference in level across the bed, you can establish the wear. (The level
is calibrated) Once that is accomplished, reply with your readings and we
will talk about that and perhaps the next episode, the headstock.
Steve

"Ignoramus20788" wrote in message
...
Tried to estimate the bed wear today.

I did the following: placed a digital indicator (0.001mm resolution)
with the magnetic base on the carriage. Its point was resting on the
non-worn part of the bed where the tailstock rides.

I moved it all the way away from the headstock and reset the dial to
zero.

I was hoping that as I moved the carriage along, the indicator would
show a positive number, as the bed would go lower due to its wear
closer to the tailstock.

It indeed happened. The number on the indicator started rising from
zero and rose to 0.05 millimeter (or 0.002 inch).

I repeated the procedure several times, every time the reading would
return to zero as I returned the carriage back away from the
tailstock, and the max reading was consistently 0.05 or 0.06mm, or
0.002 inch.

So, my obvious question is how to read this number, do you think that
the wear is bad or not bad?
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