Whilst the condition in SK.1 B would probably clamp adequately the part being held,
the fact that the clamp can easily swing from side to side could as a result create
a dangerous situation, especially if being used on a machine tool. Where the clamping
force is distributed evenly along the length of the jaw "C" then the clamp will become
rigidly coupled to the workpiece.
Setting a clamp
Setting the clamp is not difficult but must be done with care. Hold the two jaws
manually against the part to be held and run both screws finger tight. Then, tighten
the outer screw finger tight as far as can be done, there being no need to use a
Tommy bar. Now attempt to move the clamp side to side at the outer end observing
at what point it pivots, workpiece's edge or jaw end. If the clamp pivots at the
edge of the part being clamped then the jaws are too close, loosen the outer screw
and then open up the jaws very slightly using the central screw and tighten once
more using the outer screw. Check once more and if still too close repeat the procedure.
If however the clamp pivots at the jaw ends then the jaws are too far apart. The
clamp therefore has to be loosened and the central screw wound in a little and the
clamp tightened again.
Once it becomes impossible to move the clamp side to side having tightened the clamp
generously finger tight using only the outer screw then the clamp can be finally
tightened using a Tommy bar, again using the outer screw only. If however you find
that the clamp can be moved side to side again the centre screw can also be tightened
using a Tommy bar, though this should not really be necessary once you become experienced
in setting the clamp in the initial stages.
Considering experience, why not place a piece of flat steel in the vice and practice
adding the toolmakers clamp to it. When this becomes an easy operation then you are
in a position to use the clamps in more critical applications.
In theory, applications where two flat parallel surfaces are available for the clamp
jaws to make contact with are the only ones where a toolmakers clamp should be used,
typically that in Sk.1 C. However, some leeway on this condition can be accepted
in some cases, though careful consideration to the application should be given.