Fine adjustment screw 1

[srn]

Hello,

Do you know of a supplier for a fine adjustment screw(say 100 turns per inch resolution) , that is made of brass or aluminum?

 

[steveh]

For a resolution that fine you might want to look at a differential screw. These are often used where the adjustment desired is smaller than any available pitch. This screw would consist of a shaft with two threaded diameters.
For instance, say you made up a shaft 75mm long with 30mm of M10 x 1.5 on the head end (usually the head is hex or square) and an M8 x 1.25 thread on the front. Both threads will be of the same hand but the difference in pitch is 0.25mm. Now if one part of the screw is run into a fixed member and the other part into an adjustable member, the adjustable member will move 0.25mm for each turn of the screw.
This smaller the difference between pitches the smaller the movement per turn. The movement on this type of screw is often further subdivided by using an area on the shaft that is notched parallel to the long axis with an evenly divided number of slots. A ball plunger can then be used to 'click' into the slots as the screw is turned. In this way you can divide up turns of the screw so that the above combination gives you a movement of 0.025mm per click.

 

[Dan76]

Try

http://www.micromark.com

It's a hobby supply store, but they do sell little brass machine screws (Plus they have other cool stuff like minature lathes, and drill presses, the catalog is free)

 

[OldestToolDesigner]

When using the screw adjustment and close accuracy on position is required, you will have to eliminate the inherent backlash.

Al Kirby
askkkf@avci.net

 

[13]

you can alway add a gear box. but i am not sure whether or not that would complicate or simplify things.

 

[sbc]

Steveh has a good solution if you can have someone make
it for you. Do you need br. or al. because of spark hazard,
magnetisim, or corrosion? Micrometer heads are available
graduated to .0001 in. from industrial suppliers like
msc - mscdirect.com -I have not seen any made from
non ferris matl. though. It would be too soft to use if
frequent adjustment is required. Steveh's method would
also be susceptible to wear because of the soft matl.

 

[stick1]

Here are a couple of sources;

Thorlabs has 3/16-100 adjustment screws

http://www.thorlabs.com

Newport Corporation also has 80 & 100 pitch screws

http://www.newport.com

I suspect there are quite a few more opto-mechanical suppliers that carry similar products.