Linear stage without a micrometer

[martincito]

I'm putting together a macro rig but my funds are running low. Would it be false economy to buy a Newport 420 stage without a micrometer? I wondered if I could just forward the actuator little by little by "feel"...

Martin

[enricosavazzi]

I'm putting together a macro rig but my funds are running low. Would it be false economy to buy a Newport 420 stage without a micrometer? I wondered if I could just forward the actuator little by little by "feel"...

Martin

First of all, these stages usually have springs that press the slider against the micrometer. Using the slider as you plan requires the springs to be removed (but see below).

These stages usually have a low friction, so the slider will likely not stay put (even in a horizontal orientation) but may easily slide either direction with vibrations. Some stages have a locking screw, but locking it may also disturb the position of the slider.

Depending on your metal working skills and/or available parts, you may replace the micrometer with a nut-and-screw mechanism. This allows a better use of the slider (and requires the springs to be in place). Some linear stages come in fact equipped with just this type of mechanism (e.g. eBay item 110979368902). This mechanism may allow small enough steps to be performed, if you plan to work at low magnifications and don't need very small and precise steps. You do need to add a scale or ruler on the stage to estimate the step size.

[martincito]

Thanks Enrico.
I thought the actuator was a screw, but I think you are saying it just pushes the slider along. The item I was looking at is eBay 111005742779. So that rod doesn't advance the stage as it is turned, rather it just pushes it along as it, in turn, is pushed by the spindle of a micrometer. Is that right?
Martin

[enricosavazzi]

As far as I can see, eBay item 111005742779 is a linear stage that has a screw actuator instead of a micrometer. The main difference between a screw actuator and a micrometer is that only the latter has a scale (and the micrometer usually is also machined to tighter mechanical tolerances).

In both cases, the stage slider is pushed in one direction by the end of the screw/micrometer screw, and in the opposite direction by the springs that push the slider against the end of the screw. So with this specific item the only thing you need to add is a linear scale along the stage and/or an indexed round scale around the knob that turns the screw. The precision will be less than with a proper micrometer, but still enough for low-mag work, depending on the pitch of the actuator screw.

My first reply was made on the assumption that you had selected a stage entirely without an actuator, like e.g. eBay item 261176963813.

[martincito]

Thanks! I think I understand now.

Martin