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View Full Version : Tachihara 4x5 lock problem (now resolved!)



Ulophot
9-Aug-2017, 07:06
Hi, folks. This is a follow-on to some earlier posts. Iíve been having trouble with the front standard locks staying locked on a recently acquired Tachiara 4x5 (nickel-plated with brass toggle cam locks), especially one side. I tried replacing the old, somewhat beat-up brass shims/washers that sit topside between the bed and the cam with new steel ones in three thicknesses: 0.1, 0.2, 0.3 mm. They slip. Subsequently, I tried to get nylon ones, after reading that Tachiara had begun supplying its cameras with these as early as 1998 (1998 post on this forum). Compressible makes sense to me. The only ones I have found in the right diameters (from McMasters-Carr), however, are too thick Ė 0.5 mm, according to the description Ė though I tried them anyway. The extra thickness doesnít even allow clearance for the locks to be screwed in.
I have considered trying to sand (somehow) the steel shims with some superfine sandpaper (the gray stuff, maybe 400 grit?) to give the upper surface some friction potential, but Iím no expert in fine mechanisms and metals, and Iíd rather get proper guidance from someone who knows.
Therefore, I am seeking either/both a source for thinner nylon washers and/or some expertise from someone with experience with this camera, preferably with this particular problem, who can help me get it operating properly. Itís frustrating to have gotten the camera and not be able to use it!

Thanks.

xkaes
9-Aug-2017, 09:23
Can you move a shim/washer, temporarily, from another lock -- in order to determine if the problem is, in fact, the shim/washer?

Ulophot
9-Aug-2017, 10:27
I replaced all four shims with the new steel ones, after discovering that the one was missing on the front left side. The new, thinner steel ones freed up the back, which was moving only with difficulty with the old ones, which were too thick to allow free movement. The back ones lock fine, but this is a different mechanism, in that there are two plates drawn together. Nonetheless, the cams do hold there quite well with the new shims. And one side of the front holds better than the other, though still prone to releasing. As I had mused in an earlier post, it may be that I have to disassemble the rails and see if there is some cause of instability in the base of the pins that the cams screw into. I was hoping there might be a simpler solution.

Doremus Scudder
9-Aug-2017, 11:03
You might try brass or bronze washers instead of steel. They are a bit softer and may have more "grab" than steel. Also, you may be able to source some sheet nylon that you could make your own washers from in the right thickness if you can't find a source for washers in the appropriate thickness. Just brainstorming here, but that's what I'd try.

Best,

Doremus

xkaes
9-Aug-2017, 13:24
Before going nuts and taking every thing apart, I'd take a CLOSE look at the locks that work and figure out what the difference is between them and the one that does not work.

Ulophot
10-Aug-2017, 15:43
Thanks to all. I'm going to post over at APUG and see if anyone has any ideas.

Ulophot
10-Aug-2017, 19:14
Problem resolved. Please see separate post, if interested.

Ulophot
10-Aug-2017, 19:33
This is a resolution to the previous thread, Tachihara lock problem.

No one ever accused me of mechanical genius, so this is only a bit embarrassing. I discovered that the problem lies not in the shims but in the screw holding the cam to the pin, namely, the screw needed tightening. For those who know the mechanism, enough said. For anyone else who may be interested, the following brief explanation, as well as I can elaborate.

The cam is made as a sort of yoke that fits over the tightening pin; the two are held together by a very small screw that passes from outside one side of the yoke, through the center pin, and through the other side of the yoke. Picture an upside-down, 3-dimensional U pulled down like a hat over a 3-D I (it's sides are flat), with a screw passing horizontally through all three to hold them together. As the screw is tightened into the far side of the cam yoke, the two sides of the yoke are pulled together, creating friction with the sides of the pin. If the friction is just right, the cam, which has a pole coming out of the top that looks like a toggle switch, can still be moved but is held more firmly in place as the cam is rotated to make pressure against camera rail in the bed.

As I said, these are small screws, and in my concern not to over-tighten them, I was leaving them too loose, and they lacked the friction to "lock."

Live and learn. If anyone knows who might source these (presumably Japanese) screws, please let me know. I'd like to have a few extras on hand for the long run.

Oren Grad
10-Aug-2017, 19:58
Threads merged.