Ok, first off for reference you can see Matt Blaze's picture of this type of tension wrench here:
http://www.crypto.com/photos/misc/picks ... iable.htmlThat should give you a general idea of the construction.
You'll need:
-A bench grinder
-A dremel tool (with cut-off wheels)
-A drill (preferably a drill press, but a power drill can work if you're steady with it)
-Drill bits (3mm and 3.5mm diameter bits.)
-2 nuts, 2 bolts, and two washers to hold the two pieces of metal together (preferably the bolts should have a diameter of 3mm so they'll fit through the pieces snugly.)
-A pliers
Procedure:
1.) Print out the template I provided on lockpicking101.com and make sure it's printed out to scale, I've provided the measurments right on the template so you can just line it up with a ruler to see if it is coming out right.
2.) Grind out the two pieces using your bench grinder to rough out the eliptical shape, and your dremel tool+cutoff wheels to shape both ends of both pieces (Top and Bottom.) Basically you're trying to copy that shape exactly onto your metal.
3.) After shaping the pieces, you'll notice there are holes in the middle of the Top and Bottom parts. Using your drill (and the template you printed out as a guide) mark and drill the required holes. On the Top piece with the oblong holes, you can make a series of holes with your drill and then file down the inside so it creates one larger oblong hole. Do this on both ends that are marked.
4.) After you've completely cut out the two metal pieces to scale, sand them smooth and have a drink - the hard part is done.
5.) If you look at the picture I provided in this post from Matt Blaze - you'll notice that either end needs to have the prongs bent down. You can pretty much eye-ball where this should be from the picture, so go ahead and do this now. Make sure to bend them the right way! Again use Matt Blaze's picture as a reference.
6.) Put the Top piece on top of the Bottom piece. On each oblong hole place a washer so that it rests on the Top piece. Insert a your bolts through the small holes on the Bottom piece so that they come up through the Top piece and washers. Screw your corresponding nuts on each bolt - the nuts should be tightened against the Top piece now. (See picture for reference.)
The two pieces should now be sandwiched firmly together by your nut and bolt assembly.
You've now built your Falle Variable Torque Wrench. Here's how to use it.
-By loosening the nuts, you will be able to slide the Top piece with the oblong holes back and forth so the prongs adjust to the size of the keyway.
-Tighten the nuts back down to hold the wrench spacing in place.
-The opposing ends of the tension wrench allow you use the wrench from the bottom of the keyway, or from the top.
-If the head of the bolts on the Bottom piece are too thick, feel free to grind the heads down a little. The ones on the store-bought wrenches are almost flush with the tool.
Any questions - or if you need any further clarification - let me know. I'll be glad to help.
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