This month's topic is clamps, or as the British say, cramps. Never a truer woodworking word was spoken than you can never have enough clamps, although I'm not sure the same could be said for cramps. We use them in every project, making jigs, used as jigs, basically for everything and you will find your are always one short. For ease of description, I'm going to group them into four categories: bar clamps, hand clamps, mitre/picture clamps and specialty clamps. Clamps have one basic function, which is to temporarily hold one or more pieces of material together. However, I've seen clamps being used for jobs, which they were not designed for and doing them well. This will not cover every clamp, there are just too many versions, and every year there are new clamps coming on the market, plus there are those homemade ones, which work perfectly but unfortunately no one will ever see.

Bar Clamps
Within this category I'm grouping the standard bar clamps, along with pipe, and quick action clamps.

	Standard bar clamps can come in lengths from 4" to as long as 96" and with jaw lengths from 3" to 12". The basic design is a bar with one fixed and one sliding jaw. The jaws themselves are almost always a cast iron with a screw adjustment for tightening. Handles can be a simple wood grip, a rubberized one, a steel toggle, wing nut or even a crank style handle. An older, but lesser known design used a wooden cam lever for clamping. Bars can be extruded aluminum or various qualities of steel. Sizes can range from 3/16" x ½" to ½" x 1-1/2" and there are metal working bar clamps I've seen which are ¾" x 1-1/2". Although the aluminum clamps do not have the same clamping strength, they are light and easier to handle, especially in the longer lengths. They often have stops cut into the bar to ensure the sliding jaw stays in position. Many steel bars have serrated edges for better gripping and less slippage of the moveable jaw. The heavy-duty steel bars can also be designed like an "I" beam for added strength and reduced flexing.

Pipe clamps work in the same manner as bar clamps but use a standard black pipe with a threaded end instead of a bar. The fixed end is threaded on the end of the pipe and the sliding end uses a series of steel rings which grip by biting into the pipe. Most jaw depths on pipe clamps are shallow, about 1-3/4", but deep throat designs are available which have a throat of about 7". The most common pipe size is ¾", but there are also clamps for ½" pipe. Lengths are up to you, just keep in mind that the pipes flex easier the longer they are.

Quick action clamps tend to be lighter duty but are great for single-handed use. The sliding jaw is pistol grip shaped which moves forward as you squeeze the handle and a pressure release trigger. It is amazing how useful these clamps are. They do not take the place of bar clamps, but help to make clamping easier especially when working alone. I use them constantly to get large and small projects held in place and then add the heavier clamps afterwards.

Quick Tips - Buying Clamps. It's very hard to judge the quality of cast iron, which has been painted. For heavy-duty use you need to rely on brand and your own observations. If the brand is unknown to you, look at the edges of the casting to see if they were ground smooth before painting. If the casting was in two halves, see how well the sides match up. Check to see how easy the screw action works and if the sliding jaw slips when pressure is added. There is nothing wrong with buying a cheaper clamp if it suits the purpose. Just don't expect it to act and stand up like a heavy-duty one. I have clamps from all price ranges and quality. They all do the job they were

Hand Clamps
In this section I've put "C" clamps, hand screws and spring clamps.

	"C" clamps are used in both metalworking and woodworking and come in a variety of sizes and shapes. Metalworking "C" clamps usually have a metal sleeve cover over the screw threads to protect them from spark damage. Sizes range from 1" jaw opening to over 18" and a jaw depth from 1" to 8-1/2". There are also some deep-throated varieties, which have a jaw depth of 12" or more. As with all clamps there is a large range of quality. Many of the cheaper clamps have a light duty casting, so care must be taken not to over tighten them or they will snap. Those clamps marked as forged are stronger than cast. Prices reflect the difference in quality. As with bar clamps, you can get away with cheap "C" clamps as long as you don't over stress them. Hand screws are a very old form of clamp. They consist of two blocks of wood held together by two threaded rods. Originally the rods were wooden as well. The central rod acted as a pivot and initial sizing, then the outer rod was used to tighten the clamp. Normally the sizes range from 2" to 17" jaw opening with a jaw depth of 2" to 12". I've seen antique versions used in boat construction, which were over three feet long and had a depth of throat of almost 24", and I'm sure there are even larger ones out there. These clamps allow for very even clamping pressure over the jaw length, plus they can be adjusted to match odd angled material. These can be expensive clamps but kits are available with everything but the wooden jaws, so you can keep costs down by making your own. This also allows you to increase the jaw length by about ¼ to 1/3, any more and they loose too much strength. Spring clamps are very handy in any shop. They act like giant alligator clips and range in size from a micro version with ½" jaw opening up to 4". They can be made of steel or high-density plastic and have straight or pivoting jaws. Some of the newer versions have adjustable clamping pressure and even a second spring, which allows you to use it as an edge clamp. These clamps are reasonably priced often in packs of various sizes and it pays to have a number. I have twenty of various sizes and there have been gluing operations where I have used all of them. I've even used them to hold a heavy bar clamps in place until I could align and tighten them.

Mitre/Picture Clamps
There are many clamps on the market for making mitre joints and pictures. Some are designed to hold a single corner in place while it's glued and pinned and others are meant for clamping the entire frame all at once.

	Those clamps designed for one corner have one main prerequisite, and that is to be a perfect 90 degrees. There are some cheaper, light duty clamps, which are adjustable and clamp 90 to 180 degrees, but they can be very frustrating. If you intend on making anything other than a four-corner 90degree frame they may be of use. If you mainly want a standard four-corner frame get a good 90degree clamp. Some are a heavy cast and are designed for shop use and others are a lighter cast but are still good for home use plus they are more portable. The last clamps in this group are the spring steel "C" clamps. These clamps are 1/8" to 3/16" steel rods formed in a "C" with sharpened ends. Using a pair of pliers like applicators you spread the jaw and place them over the joint, then release. The spring steel holds the joint in place. The clamps have been used in Europe for decades and still have a place in the shop. The only draw back is that they can leave a small dent in the work material and the kits tend to be expensive. To clamp the entire picture all at once there are two stiles of clamp. Band clamps and rigid frame clamps. Band clamps have a band of steel or reinforced fabric which when tightened pulls evenly around the material. These clamps can also be used on box, carcass, chair, etc, construction. If over tightened even slightly, these clamps can rack the material and two opposite corners will often pop up. This pop up can also happen with the rigid clamps. These clamps use threaded rods or extruded aluminum to provide the clamping pressure. With the threaded rods they have brass or steel couplers/nuts, which tighten the clamp. I've had the best luck with the aluminum design. With these clamps instead of tightening four nuts you only tighten one in the center, which means more even pressure. To prevent the pop up of the corners with these clamps I often weight down all four corners.

	Edge clamps, like their name states, are used for attaching an edge to another surface such as a table or panel. They are used more and more these days as so much is made from laminates and melamine. They grip the flat surface and then a second jaw push outward holding the edging into the main body. These clamps can be economical at about $10.00 up to elaborate high quality units at $80.00. Cabinet clamps are similar to edging clamps in that they apply pressure in two directions. The difference is that these are designed specifically for applying face frames to cabinets, which tend to be wider than the body material. The jaws must compensate for this. When gluing up boards to create a broad flat surface, the boards can buckle when clamping pressure is added to the sides. A four-way clamp prevents this by clamping the edges and the flat surface at the same time. The boards slip into the clamp like a sandwich. When the clamp is tightened it squashes the boards flat while adding pressure to the edges. Hold fasts are one of the oldest forms of clamps and also the simplest. It is designed to hold material "fast" to the workbench so you can cut, plane, chisel, or sand it without its' moving. Usually cast iron, these clamps have a swan like neck attached to a steel rod. Just drill a hole in your bench slightly larger than the rod diameter, slide the rod in until the pad touches the material, then tap if with a mallet and the material is secure. There is now a modern version made from high-density plastic designed to attach to portable folding benches like the Black & Decker Workmates. These use a cam lock to add pressure. Toggle clamps are similar to hold fasts but use a mechanical cam leverage to provide amazing clamping pressure in very small clamps. They can clamp downward like a hold fast or in-line. These clamps are usually used in jigs, as stops or holding material while it is milled or worked on. They are not usually used in the gluing process, except in more production, oriented jigs. I use one attached to a mitre gauge for making style & rail cuts at the router table.