Do remember to allow for the diameter of the cutter being used when setting the mill
to the required radius. Traverse the table by the calculated value plus half the
cutter diameter for the outer curve and the other calculated value minus half the
cutter diameter for the inner curve. Do make sure that you use the correct values
for each side of the tooth. Do not forget that the inside of the tooth is machined
with the largest radius
Use only the fence to make adjustments to the position of the groove within the jaw
remembering that the milling machine table's traverse is only used to set the radius
Machining the side groves
The groves in the side of the jaws must be a close fit on the rails on which they
are to move. If typically the groove measures 6mm then using a 6mm end mill may seem
the obvious choice, but should the cutter be running a little off centre then the
result may be oversize. However, in many cases, the load on the cutter will constrain
it to run true and cut size, it is therefore worth trying on a test piece first,
Even so, do only run the cutter through again as it will increase the width if it
is passed through the groove a second time. If this approach is not possible then
it will be necessary to cut the groove in two stages with a smaller cutter.
First, set up the vice on the table such that its fixed jaw is perfectly in line
with the table's cross traverse. This is vital so using a dial test indicator to
test this requirement is essential. With the vice positioned fix the first jaw in
this with its teeth against the fixed jaw.
Now machine one side of the jaw and to the depth required setting the position such
that the lower side of the groove is the correct distance from the base of the jaw.
With that done, remove the jaw, turn over and machine the other side similarly. This
will ensure that the two groves are exactly opposite, any error though in the setting
of the vice relative to the tables traverse and they will end up with an X formation.
Repeat for jaws 2 and 3. If you are machining the groove in two stages, machine all
the grooves first at the cutter's width then return them a second time to increase
Do aim for a width of groove that is a little on the tight side requiring a little
hand fitting. Remember, it is relatively easy to remove a little and almost impossible
to add some metal.