Cramping

CRAMPING

Whether you require to hold a workpiece securely in place while cutting, drilling or chiselling, or you need to hold an assembled model under pressure while the glue is setting, you will need to use some sort of holding device. A well-equipped workshop will have a collection of cramps, often called clamps, to m eet each of these operations. A selection of commonly used cramps is shown below.

SASH CRAMP

The sash cramp is used when large boxes or frames such as doors or window frames are assembled. To adjust a sash cramp when gluing up a frame, the back jaw rests against the locking pin which is in one of the holes that run along the bar of the cramp, and the head jaw is screwed into place using the tommy bar to tighten the head jaw securely against the frame to hold it in place.

G-CRAMP

The G-Cramp is used to hold a workpiece securely in place while cutting, drilling or chiselling, and to hold glued components together while the glue sets.

MITRE CRAMP

The mitre cramp is mainly used to cramp up mitre joints in picture frames or trinket boxes. It's designed in such a way that the jaws of the cramp hold the joint in place at an exact angle of 90°. Although the main use of the mitre cramp is to cramp up mitre joints for picture frames, it can also be used to cramp other joints at 90°.

BAND CRAMP

Band cramps use large straps and corner brackets to hold large, irregular frames in place and apply pressure while the glue has time to set. As the straps are tightened, they provide an equally distributed amount of pressure which helps prevent any distortion in the frame.

checking for squareness

Once you have dry cramped your model, as well as checking all the joints fit together properly, you should check the assembly for squareness. There are two main techniques for checking the assembly for squareness.

A try square should be placed in each corner to check all corners are 90°.
Measure the distance between the diagonals. If both diagonals are the same, the frame is square.

dry CRAMPing

One of the most important stages of assembling any model is to dry cramp it. Dry cramping is when you cramp up your model without applying any glue. The purpose of dry cramping is to make sure that all the joints fit together properly and there are no mistakes before applying the glue. It also gives you an opportunity to check you have all the required cramps set up in the correct position and that they are in good working order.

THINGS TO DO AND THINK ABOUT

State two adjustments that can be made to a sash cramp
Describe how to avoid damage to your workpiece when using cramps.
Explain what is meant by the term 'dry cramping'
Describe 2 ways to check a model for squareness.

For more information, see the Cramping notes in the practical tab.

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