Sunday, February 19, 2012

McNally's Justin Clamp Modification

Well, thanks to Joe McNally, everybody knows about Justin Clamps. Well, almost everybody.

This  Justin Spring Clamp can attach itself to pipes up to 1.6" in diameter and has a cold flash shoe mounted on miniature ball head for easy positioning. It can also attach itself to the top of any lightstand or clamp equipped with a 5/8 stud.

Perfect? As clamps go, yes. But a bone of contention has been the plastic cold shoe on the end of the ball head. Manfrotto sells the shoe itself as an accessory, and it's a handy for attaching a speedlight to anything with a 1/4 x 20 female thread. You see, unlike most cold shoes, it has a threaded shaft rather than the usual threaded hole.

The biggest problem is that the plastic shoe sometimes breaks free from the metal shaft. This has happened to me several times. Also, the original shoes could not accommodate the thicker-than-normal feet of the Nikon SB-900 speed light. So the ideal solution to this problem is to install a replacement cold shoe that will accommodate the SB-900. McNally has done this on his own clamps, I noticed. But here's my solution. You'll need:
  • 1-cold shoe. I used the Stroboframe Flash Mount Adapter. It is all metal and has a 1/4 x 20 threaded hole that passes completely through the base of the adapter. While any threaded cold shoe will do, I prefer this one because it utilizes a clamp rather than a setscrew arrangement. The Frio Cold Shoe works, too.
  • A section of 1-1/4 x 20 threaded steel rod. You can buy them in 3' lengths, or you can simply buy any 1/4 x 20 machine screw and saw off a piece between 1/2" and 3/4". For this project, I thought I'd be clever and purchased some 1/4 x 20 x 1/2" hex head set screws. Boy, the lengths I'll go to avoid using a hacksaw!
To attach the cold shoe, you must:
  • Tighten the ball head on your Justin Clamp so the shaft won't turn.
  • Unscrew the plastic shoe and remove it, along with the threaded thumbwheel. Keep the pieces, as the shoe could be used to attach something that weighs less than a speeedlight. (Photo 1).
  • Using your fingers, thread the  threaded rod section (or setscrew) into the hole in the shaft until it bottoms out. If you cut the rod to a length of 1/2", there will be enough excess to properly secure the cold shoe. (Photo 2).
  • Now thread the flash adapter onto the protruding end of the screw and firmly hand-tighten. (Photo 3). 
The change went well, and appears to be quite functional. I may consider changing the aforementioned Stroboframe Adapter to a Nikon AS-10 knockoff. While I don't generally trust Chinese knockoffs, they will probably do in this application, since shoe doesn't do anything except hold the flash and they can be had for about $15. Genuine AS-10s are selling for $40 to $50 each. But the AS-10 is much more convenient because the speedlight is retained using the retractable retaining pin found on Nikon speedlights starting with the SB-80DX instead of the clamp of the Stroboframe unit.

Now that should do it.

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