Attaching focusing rack to rails?

Discussion in 'Camera Building, Repairs & Modification' started by Curtis Nelson, Jul 21, 2005.

  1. Curtis Nelson

    Curtis Nelson Member

    Messages:
    21
    Joined:
    Sep 7, 2002
    Location:
    Lehi, UT
    Shooter:
    4x5 Format
    OK, I'm stuck.

    I'm building an 8x10 camera, and I'm using a brass rack & pinions to serve as the focusing mechanism. The problem is, I'm not quite sure how to attach the rack to the focusing rails. The rack is 1/8" wide & high. I'm thinking my options are:

    1. Drill VERY tiny holes (<= 1/16") in the rack and attach it to the focusing rails with really tiny pins.

    2. Gorilla glue.

    3. rout a 1/8" channel down the middle of the focusing rail (as opposed to the edge) and let friction do the rest.

    Am I in the ballpark on this, or is the a better way?

    Thanks for all your help.

    Curtis
     
  2. r0l4nd

    r0l4nd Member

    Messages:
    4
    Joined:
    Jul 1, 2005
    Shooter:
    4x5 Format
    I have tried all three methods.

    1. Didnt work. Either the pins were too small to hold the rack on securely or they were too big and interfered with the spur gear.

    2. Worked fine for about a month. Then I started to get play in the rack.

    3. Worked fine for about a week. Then the rack moved without moving the rails.

    In the end I went for a combination of 2 and 3. A routed channel with glue to hold the rack in place (I used araldite impact adhesive). Worked perfectly. You just have to watch that you get the channel perfectly level. I couldn't do this with my hand router and ended up milling it out on the lathe with a small routing cutter.

    PS Where did you get the rack and pinions from?
    After seeing the prices everyone seems to want for them I made my own.
    Next time I will DEFINATELY buy them!
     
  3. Curtis Nelson

    Curtis Nelson Member

    Messages:
    21
    Joined:
    Sep 7, 2002
    Location:
    Lehi, UT
    Shooter:
    4x5 Format
    r0l4nd,

    Thanks for the feedback.

    I bought my rack and gears from McMaster-Carr (www.mcmaster.com). I paid $25 for a 2' brass rack and $7 each for the pinion gears.
     
  4. Greg Davis

    Greg Davis Member

    Messages:
    2,057
    Joined:
    Feb 4, 2004
    Location:
    Nicholasvill
    Shooter:
    8x10 Format
    I drilled through the rack and the rail it was to sit on. The hole in the rail was large enough for a #2 machine screw to fit through. The hole in the rack was smaller and then threaded for a #2 screw. Then I screwed the rack to the rail from underneath. If the screw was too long, I shortened it so it would not interfere with the spur gear, but was long enough to be held in place. My racks are 12 inches long and are held by four screws each. It works fine.