G Cramps are an essential tool in the workshop and they come
in a range of sizes and are generally used for clamping work securely to a
surface/workbench top. They can also be used to hold parts together whilst glue
is drying.
The clamp is tightened by turning the small tommy bar which turns the threaded
rod. Some G Cramps have a wing nut in place of the bar making it easier to turn
by hand. However, if a tommy bar is used more pressure can be applied to the
thread in order to tighten the clamp.
The thread of a G Cramp is made from hardened and tempered steel which means it
is quite resistant to wear. The frame is normally made from drop-forged steel.
Sash clamps are used to clamp work together when it is glued. They vary in size and are normally used in pairs. The lengths are normally from 460mm to 1370mm. The bar is made from cold drawn mild steel and the head and slides made from malleable iron.
When in use, the sash clamp is placed below the work to be glued / assembled. The slides are arranged on either side and scrap wood is placed between each face and the work. This protects the work when the thread is tightened. The tommy bar is used to tighten the thread and pressure is increased slowly.
After clamping a frame, the 'squareness' of the frame should be tested and adjustments made to the position of the clamps if necessary. The internal angles of the corners should be 90 degrees. The 90 degree angle is checked with a try square or a rule. A long ruler is used to check large frames and a try square is used on smaller ones. When using a ruler the diagonal distances are measured. If both measurements are the same, the angles at each corner are correct. If the two measurements differ, the clamps need adjusting until the measurements are the same.
A RULER BEING USED TO CHECK
FOR 90 DEGREE ANGLES
A try square is pushed into the each corner of a smaller frame / box, to check that the 90 degrees internal angle is correct.
