Options For Field Camera Focusing Hardware?

[brandon allen]

So I built my 4x5 camera using a screw mechanism (3/8" reverse-thread acme screw to be precise). I would have used racks and spur gears, but the only ones I have been able to find are ridiculously expensive (Chicago Gear, etc.) to the tune of several hundred dollars for all the parts I would have needed. I spent perhaps twenty dollars on the parts I used for the screw mechanism (and I have enough material remaining to build at least two more just like it).

For several reasons I would still like to explore the focusing rack option, as I continue daydreaming about starting on a 5x7.

Has anybody found a less expensive source for suitable gear racks and spur gears?

I just have to believe that something else exists out there.

I have even been considering buying a few of the plastic 32 pitch gear racks intended for building science projects and spur gears for R/C cars being offered on eBay. Has this been used before?

Thoughts/suggestions welcome.

[Jac@stafford.net]

Spur gears and so much more here at at McMaster-Carr.

Browse about and be happy.

[Richard Wasserman]

McMaster Carr always makes me happy. I used to have a business where I bought from them regularly. Of course there was the time I ordered 1 plastic bucket and they sent me 1,000. It was a bit like The Sorcerer's Apprentice in Fantasia with me playing the part of Mickey Mouse....

[Tin Can]

Very timely post, as I want to add mechanical focus to a Century Tailboard. The knob is not working for me.

Only last night I was considering 5 start Acme thread, which give 0.5" travel per revolution. I found McMaster to be too expensive. This maybe http://www.ebay.com/itm/141629722135 http://www.ebay.com/itm/141643805499

Now you mention spur gear and I will look into that also.


Why are you unhappy with your Acme threading?

[Peter Gomena]

My old Rochester Optical Company whole-plate camera has no tracks or threads. It's simply push-pull on the rails and is locked by a simple threaded bolt that pushes a piece of brass against the rail. It maintains good focus and is easy to fine-focus with just a little squeeze of the fingers.

[DannL]

The 8x10 that I use (Anthony & Scovill Champion) also has no gears. It's a very elegant and simple design that works quite well.The camera is a rear focus sliding design, and the rear standard locks into place with a threaded rod (not visible in picture). Small brass plates hold the standard to the rail in finely cut grooves. The intent here is to reduce weight, once touted as the world's lightest 8x10 field camera.

http://piercevaubel.com/cam/anthony/amchampl.htm

[brandon allen]

Very timely post,

...

Why are you unhappy with your Acme threading?

I'm not unhappy, it actually works very well! At 10 tpi I can move the front standard -reasonably- fast, but it does take a little time, fine focus is easy to acheive with such "precise" movement. No focus lock required - front standard stays right where you stop moving it without further input. And the system was quite easy to make.

What I don't like about it:

1) aesthetics - I just prefer the "classic" look of knobs on the sides.
2) bulk - at least the way I did it, the rear standard had to be raised 1 1/8" in order to clear the focusing mechanism and made it almost impossible to design the camera that folds up into a tidy box. And the focus knob protrudes from the back of the camera when it is folded. The design could be altered to reduce this, but max extension would probably decrease (not such a big deal).
3) weight - Kind of +/- here, I THINK focusing racks and rods with spur gears would end up being lighter, but the 8" piece of acme screw wasnt that heavy. So this may not really be the case.
4) ease of use - unless I can get an even coarser thread acme screw (I couldn't find one without going to a larger diameter screw = bulkier & heavier) it takes extra time to move the front standard long distances (~80 turns to get to full extension). Not a deal breaker, but I cant just push the standard forward and let the knob spin. It is much like opening/closing a casement window.

[Jac@stafford.net]

Why are you unhappy with your Acme threading?

Come on! Why would anyone buy from Wile E. Coyote's favorite supplier?

[Kirk Gittings]

McMaster Carr always makes me happy. I used to have a business where I bought from them regularly. Of course there was the time I ordered 1 plastic bucket and they sent me 1,000. It was a bit like The Sorcerer's Apprentice in Fantasia with me playing the part of Mickey Mouse....

[brandon allen]

Spur gears and so much more here at at McMaster-Carr.

Browse about and be happy.

I know, they have them and they are very expensive! The racks are even more!