Using a model mill instructions

Precautions on overtightening
As with all adjustments on any machine, overtightening can distort components or ruin
the built-in accuracy of your machine. This is particularly true on smaller machines
where the power of the operator is much greater in relation to the size of the components
than it is on larger machines. It is possible to deform the T-slot, which results in a
worktable that isn't flat. I believe that the people who damage Sherline T-slots are the
same people who break the T-slots on expensive hardened and ground tools. You have to
develop a "touch" so this doesn't happen. It is very difficult to correctly square work up
with the machine if the table is damaged and the work is "rocking".
MACHINING TIP: Use of a tooling plate (P/N 3560) is an inexpensive way to protect
the surface of your mill table while providing a flat, versatile clamping surface.
SQUARING UP YOUR MILL
Determining the level of accuracy you really need
Squaring up a multi-direction mill can be a chore if you want "perfection". It is best to
determine how accurate the setup must be before you start. The larger a close tolerance
part is the better the setup required. An error of .001" (.025mm) per inch (25.4mm) would
be a very small error on a part .4" (10mm) long. However, a part that is 5" long would
have an error of .005". The type of machining that is going to be performed also has a
bearing on the quality of the setup. As an example, a drilled hole doesn't usually require
the quality of setup that would be used for a bored hole, (assuming the hole is being
bored for accuracy rather than for lack of a drill of the proper size). The amount of work
that will be done with the setup should be considered too. If your setup is just to do one
particular job you only have to set it up close enough to do that job. If the setup will
accommodate future operations as well, it should be adjusted to the tolerances of the most
critical job. For example, squaring up a mill and vise to work on a number of precise
parts is worth more of your attention than setting up to drill one clearance hole in a non-
critical part.
Limitations of the production process
Before starting you should realize that these mills are relatively inexpensive machine
tools. They have accurately milled slides but the surfaces are not ground. To increase the
accuracy of a Sherline tool only a percentage point would dramatically increase the price.
We try to give a customer what we consider "the most bang for the buck".