Worm Clearance & Adjustment
Fig.1
WORM CLEARANCE - This is a very hot topic. How much clearance? This is what has been gleaned from much experience: "Loose is good". That may sound contrary to good guiding but it turns out that in solving other annoyances, loosening the worm clearance actually improved tracking!Here is what to do: With the clutch knob snug, grab the counter shaft and jiggle it, rock it back & forth ever slightly. You WANT to be able to feel a slight clunking or hear it. If you don't, then you are too tight and will stall a motor or even burn it. Get it to feel a little clunky. Do this by loosening the two socket screws under the worm block and move the block in or out. Maintain the same clearance at each end of the block with an automotive type feeler (see Fig.1). Snug each of the two wing adjusters which push against the screws moving the worm into the gear. Do this slightly and maintain even feeler sizes at both ends. The feeler size should be recorded. Later, you may want to loosen the clearance or tighten it a bit and knowing what size you had set it to will enable you to make accurate adjustments if desired. It may take a little self developed technique to do this adjustment efficiently. Snug the screws. Check for the clunk. Redo if no clunk. As the night air cools, the worm clearance gets smaller so if you start out without that clunk, you will end up with some binding due to interference between the worm and gear.
After the worms are adjusted, you should remove the motor and the small gearbox located on the end of the worm block. This is very easy to do (See Gearbox). Now you can see a gear sticking out of the worm box. Rotate the gear with your fingers so that the Ra or Dec axis makes a complete turn (360 deg). It should turn easily all the way around, If you find a place that feels tight, you will need to loosen the worm block some. This is the location where the clearance should be set. The reason that one particular location is tighter than elsewhere is due to eccentricity. The gear form is slightly out of round or out of concentricity with the rotating axis. I did this rotation and found a snug place. So I increased the worm clearance such that my feeler size was now .001 thicker than I previously had. Then I rotated the little gear again for another complete turn (360 deg). No more snug place. Record the new feeler size. Using the feeler this way provides a way to make accurate clearance adjustments and also to keep the worm tangent to the gear and parallel to the opposing housing faces. (equal feeler size at both ends of worm block)
Remember, as the temperature lowers, the clearance will decrease. If you set the clearance in a warmer temperature than it will be when in use, allow for that and provide additional clearance.
If the clearance is not sufficient, the motor will heat up, stall, or even burn.
Apply this to both worms.