To make a standard (there are many ways, this is my way)
This is a standard for the flatway - on your lathe your standard might work better on another surface
Turn a piece of easily machinable material so that is round: any diameter will do.
Measure diameter (I used a micrometer).
Measure from the top of the newly machined round to the top of the carriage (If it is flat)
-your lathe may require a slightly different process if you don't have a flat topped carriage.
Now use a depth micrometer to measure from the top of the carriage to the top of the flatway.
Add the radius of the turned part to the depth-to-carriage and the depth-to-flatway.
EDIT->so it is the total distance from the top of the turned boss to the flatway minus the radius.
- by doing this several times and carefully you can easily get .001 accuracy or half that for careful measuring.
now mill a flat on you bar that will become your standard (the flat is important)
mill or turn both ends of your bar flat. and then mill it to length ( or turn it to length but that's more tricky)
Doing it quickly, you get within .001, Very carefully and with lots of trouble .00002
To Test
- set a very sharp tool to height. You can easily feel within a half-thou which is higher, the standard or the tool.
Don't use a
coated carbide tool. HSS very sharp or diamond hone a carbide to be very sharp.
Face the material that hopefully is still chucked into the lathe. You should get no leftover tip in the centre. If you do, you are either too high or too low: a loupe will help find out which. Sometimes it is a user error, but the first standard I made was .002 too short, and I had to make it over.