HOME MADE MACHINING CLAMP DOWN SET
I just acquired a very nice machining slide table which I use with my drill press for light to medium duty milling jobs. I do not yet own a milling machine so this has been a good temporary arrangement for my immediate milling needs. I usually rely on a very good milling vice that I have bolted to the milling slide on my small 8" bench drill press and while this arrangement serves for most instances, I sometimes need to set up something on "V" blocks, a small rotary table or simply on the slide table surface itself. The normally accepted method is to clamp the work piece to the table, supported by packing, spacers, parallels, 1-2-3 blocks and the like. The use of "T" nut bolts and rectangular slotted clamp straps secure the whole rig to the table. You can get sets of these from most every tool company and will normally include more things than you will ever need. They will run you from $40 to $80 depending on the size of the "stud" the machining table accepts. My particular table has 1" wide "T" slots and a slot width of 5/8" so I would need the larger more expensive clamping set. My clamping requirements involve medium to very small dimensioned components, mostly parts to model engines and tooling. I decided that I would do just as well if I fabricated the strap clamps myself and used carriage bolts of various lengths to hold the clamps. Pieces of key way stock are used to support the other end of the strap clamp and are chosen so the single of combined height is the same or slightly higher than the work being clamped. For the bolts, I used 1/2-13 carriage bolts, chucked on the lathe thir head diameters reduced to just under 1" so they will slide freely through my table's slots. A large washer over the strap clamp gives even clamping pressure over a wide area of the clamp. The strap clamps themselves are made of either 1/2" thick cold rolled steel plate or out of equivalent aluminum material. If you will not be subjecting them to very high stresses, you can substitute aluminum. I opted for aluminum since my work is usually a lot less stressful than most full size work and I had a ready supply of 1/2" material on hand. I sawed off a strip about 1-1/4" wide and cross cut two blanks, each about 3" long. After clamping both of them as a pair, I began to fly cut the sawn surfaces to true the pair up to 1-1/8 x 2-7/8". Maintaining them as a pair, I clamped them at a 45 degree angle and milled off the tips of both corners on one end to form a blunt point about 1/2" wide. Now I clamped them edge to edge and took a milling pass over the blunt ends with a 1/4"diameter ball mill about 1/2" from the end and finished the tips with a regular end mill to reduce the thickness to about 1/4". This gave the tips a nicer look than if I had just used the regular, square tipped end mill on them. I re-clamped them on top of each other and began to mill a 1/2" wide through slot along the mid line, about 1" long and centered along the length. After de-burring all the cut edges, I put the clamps to use. The total cost for a set of clamps plus three pair of bolts in short, medium and long length, including washers and nuts was around $6 compared to over $70. Granted, I would have also gotten a set of step blocks and many other things with the kit, I only made what I needed for my immediate needs. I use the home made " kit " for clamping down my home made rotary table, my 5C collet spin jig and index fixtures, my precision machining vice as well as any shape work piece directly to the milling table.