- Materials for body, stop and jaws
- Which screw and flywheel to use
- Straight screw clamp
- Adjustable universal clamp
- Angle clamp
- Individual clamps for specific operations
Novice woodworking enthusiasts will benefit from our instruction with a sequentially described process for making several types of joinery clamps. In it we will tell you what materials should be used for this and how to make a device that is exactly suitable for your own needs..
Materials for body, stop and jaws
In the carpentry craft, clamps are used to securely and gently fasten several parts together during their mechanical connection or while the glue dries. The pressing force should not be colossal, it is much more important not to damage the surface of the parts to be joined. At the same time, the clamp must maintain high strength and be durable.
For the manufacture of clamp parts that are in direct contact with the workpiece, it is better to use hardwood. Ideally, these are larch, beech, hornbeam or birch bars and planks. Such a tree has a fairly high strength and at the same time is distinguished by elasticity, well restoring its shape. The hardness of such wood is usually higher than that of the processed parts, which can be compensated for by heels made of leather, light rubber, felt or softer wood..
As a frame for the clamp, you can use both hardwood and rolled metal. Corners or shaped pipes work well, but they must be thoroughly cleaned, primed and painted so that there are no traces of rust on the finished product. To prevent accidental mechanical damage or punching of the connected parts, it is recommended to glue wooden strips over the metal elements of the clamp or pull on a loose silicone hose.
Which screw and flywheel to use
Despite the not very high clamping force, conventional metric threaded studs will not be very convenient for use as a clamp screw, if only very small. A small thread pitch will make it tedious to choose a free run, among other things, the triangular profile “eats” much faster.
It would be much more correct to purchase studs with a trapezoidal or rectangular profile, otherwise called a jack thread. The optimal pitch is about 2–2.5 turns per centimeter, so good smoothness of adjustment and optimal tightening torque for wooden parts is achieved.
You can get studs, nuts and fittings of the required type, either by contacting a turner directly, or in a hardware store, including on the Internet. There is, however, one BUT: most of the factory products have a full thread, while a slightly different screw configuration is optimal for the clamp. Ideally, there are smooth pillars at the ends of the stud: about 20 mm long for the bearing (slightly thicker than the thread) and about 30-40 mm for the handle (slightly thinner or of the same diameter).
The handle or handwheel can be made either from a block of wood, or by drilling a hole in the hairpin on the side and inserting a steel bar into it as a toggle lever like in a vice.
Straight screw clamp
To make the simplest clamp, you will need a U-shaped bracket frame. There are two ways to make it. The first is to connect three bars at right angles on a groove-tenon connection, reinforcing it with glue and a pair of dowels. This option requires a fairly high qualification of the carpenter: cutting and fitting must be done with high accuracy, because the load in these nodes is very significant.
The second option is somewhat simpler, but more expensive in terms of material consumption. You can cut the staple out of thick birch plywood by gluing 3-4 pieces of 12-16 mm thick with wood glue like Titebond.
When choosing the shape of the parts, keep in mind that the most reliable structure will be with external slopes for greater rigidity. The stop of the bracket and its opposite part, in which the clamping screw will be fixed, must be trapezoidal. In this case, the inclined sides should diverge outward at an angle of about 30? more direct. Thickening in the middle of the frame is also highly desirable.
For fastening the screw, it is recommended to use fittings or nuts of the appropriate diameter, which are fixed in one of the “horns” of the clamp frame from the inside and are additionally reinforced with epoxy resin. If the bracket was assembled from bars, then the screw must be inserted into one of them before final assembly. If the frame structure is multi-layer, then the foot can be replaced with nuts that are glued into the cut of the central plywood layer. Here it is important to follow the direction of the screw axis and at the same time do not allow glue to get into the threaded connection – lubricate it well with grease.
At the point where the clamping heel is attached to the screw, a kind of swivel is needed so that the parts do not move when clamping. It is best to press a bearing matched to the diameter of the inner race onto the solid edge of the screw stud. For a secure stop, clamp the pin into the drill chuck, and then with a triangular file and a hacksaw, cut a groove for the retaining ring. Further, in a bar that serves as a support heel, you need to make a cylindrical groove with a core drill and press a bearing with a hairpin into it, strengthening the fit with varnish or epoxy resin.
Adjustable universal clamp
Clamps with variable width of the solution are more versatile in use, most often they are used when joining furniture boards. To make such a clamp, you will need a calibrated rail made of dry hardwood, ideally beech or ash. A constant profile size along the entire length and the complete absence of any defects are required. The clamping force that the clamp can withstand directly depends on the thickness and width of the rail.
So, manufacturing should begin by fixing a perpendicular stop at one end of the longitudinal rail. It is better to make it from two bars, which fold and clamp the rail in two symmetrical grooves, or fill it in the manner of a hammer. Thus, the workpiece for a clamp with a fixed stop takes on a T-shape, and the length of the stop on the working side should be no more than 3 times the overhang from the back side. The connection of the stop with the rail can be strengthened with furniture ties, it is also possible to connect with 2-3 dowels and PVA glue.
The back part of the stop is designed to secure the bowstring. A straight steel bar with a diameter of 10–12 mm is ideal for it. At the end of the bar, cut a thread and spread it between the end stops with nuts on the inside. The holes for the bowstring should be drilled as close as possible to the opposite edge of the stop. In this case, the indent from the edge should be sufficient so that the wood does not split. After installing the bowstring, it is necessary to mark on the end of the strip facing the clamped part, a number of notches with a step of 15-20 mm, make according to this marking slots up to 2 mm deep with a hacksaw and cut the notches with a knife.
Next, you should make a movable clamp block. In it, a through eye of a rectangular section is made, the dimensions of which exactly correspond to the thickness and width of the longitudinal bar. Ideally, gouge a groove 2–3 mm smaller and then use a square rasp to make the desired shape. The bar should sit tightly in the block, but at the same time allow relatively free movement along the clamp and its inclination to lock on the notches. Under the bowstring, you also need to make a through hole so that the bar is located strictly perpendicular to the rail, and the block freely slides along it with a slight backlash.
On the reverse side of the hard stop, you need to fill another block, which will fasten the bar with the string parallel to each other. To do this, you can use a small piece of a bar in which a groove is made with a chisel for the bar and an incomplete hole for the string is drilled. Dowels or bolts are used to fix the shoe. As for the clamping screw and heel, they are installed by analogy with a conventional clamp. It is enough to drill a through hole in the movable block not too close to the edge and glue a nut or a nut into it from the inside. So when clamping the part, the nut of the screw mechanism will abut against the wood and sit even tighter.
The most difficult to manufacture can be called a clamp, which provides fixation of two parts at right angles. At the same time, it is the most useful and demanded tool in the carpenter’s workshop..
The corner clamp will be based on a piece of thick plywood. It is better to take a square plank of about 300×300 mm with a thickness of at least 14 mm. In the corner of the base, you need to fix two blocks of hardwood, which for convenience we will call the reference. These blocks must converge at right angles facing the center of the plywood board, the thickness of the bars is at least 25×25 mm. Their fastening should be as rigid as possible: it is recommended to first glue the bars, ensuring their perpendicularity using a plumbing square, and then strengthen the connection with ties or bolts.
From the center of each block, you need to draw a perpendicular line, coaxial with which the screw pins will be located. It is necessary to retreat from the bars a distance of 20-30 mm more than the maximum thickness of the parts to be pulled together. After that, two more bars are rigidly attached to the base parallel to the previous ones. It is advisable to glue the nuts immediately, and then proceed with the thrust bars in the same way as with the reference bars: first position them on the glued joint, and then strengthen them with ties. For more convenience, you can immediately screw the screw studs into the nuts.
After fixing the thrust bars, it remains only to press on the bearings fixed in the movable blocks. The cross section, dimensions and material of the latter should be similar to the reference bars. In conclusion, you need to stuff the handles or insert the rocker levers and cut off the excess base of the clamp, removing the protruding corners for free rotation by the handles of the screws
Individual clamps for specific operations
In any carpentry workshop, homemade clamps prove to be more adapted to local working conditions than purchased in a store. A wide variety of variations of the three designs described above can be used.
For example, on one rail, you can fix not one, but two adjustable jaws for positioning parts at a great distance. Such a tool will be very useful, for example, when assembling door blocks..
Instead of a handle, you can weld a regular hex head from the bolt onto the stud. This is important if, when assembling parts, several clamps need to be frequently clamped, released and rearranged. At the same time, it will be convenient to rotate the clamping screw using a ratchet socket or even a screwdriver.
For assembling products of complex shape, it is possible to make clamps stops and movable blocks of a more complex configuration, which are well suited for working with parts of irregular shape.