as promised…
the main triangle jig, complete so far as i know. the angle stock is 1/8″, mostly 1.5″ on a side, but somebody stole my DT piece so that’s 2″ on a side. i ground the corners down because i kept hitting them. the bolts are all 1/4-20.
the procedure for getting all this aligned and locked down tight: position the angle stock, with two 1/4″ holes pre-drilled per piece, along the proper line on the drawing, using the actual tube as a guide. clamp down the ends, checking while you tighten that everything’s still aligned. drill through the holes, through the plywood backboard, with a cordless drill and a 1/4″ twist bit. with the clamps still tight, set up the bolts, nuts, and washers. tighten down, again checking alignment with the actual tube. remove clamps.
the hold-down bit. material is 1/2″ 4130 hex stock cut from a 6″ sample piece from McMaster-Carr. turned down to fit inside the fork blade by chucking into a massive drill and taking it to the bench grinder. finished up by chucking into the drill press and filing. really wish i had a lathe.
the bit essentially replaces e-RITCHIE’s sacrificial front dropout. the 4130 was cheap and easier to get and hopefully will work at least as well.
the complete hold-down setup. material for the hold-down is 3/16″ x 1.5″ (?) flat mild steel stock. MIG welded–i’m still learning so they’re kinda sloppy. it’s not especially precise, as you can see, but it seems like it’ll do. the next step is to drill through the hold-down sides and run bolts through to secure it to the bender.
the nut and bolt were in a box of random hardware. i had to grind off the galvanized surface of the nut. they’re 1/2″-13 tpi. i pre-drilled a 1/2″ hole in the top horizontal piece and reamed it out a little, but the nut ended up a little off-center so i ran a tap through to put some threads in the mild steel piece.
pictured is my 3rd bender, 8″ radius. i plan to re-cut the groove using a V-shaped router bit from Grizzly. if i can, i’ll sand flat the part that contacts the hold-down bit so it has a nice stable surface to sit on.
i’m also planning to make a 6″ radius bender. the idea is to use the 6″ bender to start for a tight bend near the tip, then switch to the 8″ for the upper part. i’ll try some test bends on the 8″ and see how it looks first.
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