Fig. 488.
To clamp two or more flat pieces together, as in making a "glue-joint," or in clamping framework, as a door or picture-frame, lay the work across the horses, which should be so placed that their tops will be as nearly level, or in the same plane, as possible, and apply the clamps as shown in Fig. 488, always putting pieces of waste wood between the edges of the work and the clamps. Place the clamps so that either the flat side of the bar or the corner, as shown, will lie against the surface of the work, thus keeping it from bending towards the bar when the screw is tightened. The number of clamps to be used must depend on the size of the work, but there is not usually much danger of an amateur's work being clamped too securely.[42]
If you have to glue a flexible strip, put a stiff piece outside between it and the clamp to distribute the pressure.
You will often find by sighting across the surface of the work as you tighten the clamps, particularly in the case of door-frames, picture-frames, and the like, that the surface is winding. When this happens, move one or more corners of the work up or down, as the case may be, in the clamps, and thus take out the winding. A little experimenting will show how to do this. In the case of framed work, such as doors or picture-frames, test the angles with the square as soon as the joints are brought to a bearing. If the angles are not right, as will often be the case, move one end of either one or both of the clamps to the right or left, as the case may be, and you can easily change the angle until the square shows it to be right, when the screws can be tightened and the joints should close accurately. In clamping nearly all kinds of "case" work, such as bookcases, cabinets, boxes, and the like, these directions about moving the clamps until the angles are correct and the work free from winding are applicable.
In such cases as that shown in Fig. 488, waste no time in trying to get the surfaces exactly flush with each other at the joint before partially tightening the clamps, lest the glue become set. Any slight alteration can best then be made by tapping with the hammer near the joint, whenever either piece needs to be raised or lowered, putting a block under the hammer if the dent will not be removed by planing (see Gluing). The clamps can then be screwed tighter.
Fig. 489.
In such cases as gluing the joints of a box, put stout blocks or cleats over the joints before tightening the clamps (Fig. 489), to distribute the pressure. This applies to all cases of clamping where the pieces to be glued are not heavy enough to resist the change of shape from the pressure of the clamps, and pieces of waste wood are almost always required in any case to prevent bruising of the work.
