Harold Hall

Workshop Processes


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.