FSN / Mafell-pattern rail key for Jorgensen E-Z Hold (or similar flat-bar) clamps

Parts per key

• 2 x M5 pan-head screws, 25 mm, with nuts (plain or nyloc; set nut_t/nut_clr to suit)

• 1 x M6 bolt, 25-30 mm, with nyloc and two washers (the bar pin). M5 works at a push also.

Print

Lie the block on the face WITH the bar opening upwards. Use  PETG or PLA, 5-6 walls, 0.2 mm layers.  Go for strong rather than fine.

Assembly

1. Fit the bar and pin; confirm the pin passes through the bar's own hole.

2. Drop the nuts in, run the M5s in from the top, and set both heads to the same stand-off using a drill bit or allen key laid across the block as a gauge (not too tight)

3. Grind or sand the TOP of each pan head only, keeping the flat underside, until the head is 1.1-1.2 mm thick. With both screws fitted, the block held face-down on abrasive on a flat surface does both at once and keeps them coplanar. The test is the rail: the key should slide freely from the rail end with no play you can feel. Slightly over-ground is better than tight; too thin and the bolt-heads will bend and can get locked into the rail. Polish the heads and remove any metal/abrasive dust.

4. Remove the gauge if you left it in during grinding.

Important!

Clamp to snug only: Each pan head bears on about 15 mm2 of aluminium per side of the rail - far less than a commercial steel clamp head, so excess force will distort the rail before anything in the block gives. You should be able to operate tools with enough tension on the clamps with a snug fit, given the non-slip base of these rules.  Treat your expensive kit with care!  

Safety is a premium.  This model offers no guarantees nor warranties regarding you or your equipment. Use at your own risk.

OpenSCAD file is included - this is really useful for your own tweaks, or if you want to fit to your own bar.