Grease

[AlistairW]

Hello,

Should I grease the rack on a rack and pinion focuser - or leave it alone ?

Thanks

Alistair

[Uranium235]

Depends if your focuser has a problem in the first place (if its ok, leave it alone). But whatever you use, make sure its goopy - you dont want stuff that migrates when it gets a bit warm. And if you do use some, just a little is all thats needed (dont go mad with it!).

[damnut]

A tad of molyslip works well. But as above gently does it.

[AlistairW]

thanks

[ronin]

A small amount over the bits. You do not want the two intermeshing items to be dry as they do not operate on a friction basis as do the Crayfords

[Bizibilder]

Our rack and pinion focussers are used for very slow and small movements and then only on very rare occasions - maybe only a fraction of a turn a few times a night and then only a few nights (or days) in a week.  I suspect that the greatest enemy they have is dust and grit that settles on them during the 99.99% of the time that they are not being operated.

Grease in any form will only act as a glue to hold that dust and grit in place.  So there is a good argument for not using any grease at all and running a rack and pinion focusser bone dry (and clean!).  The amount of wear over its lifetime will be minimal if it is kept clean and dust free.

One of my other hobby's is clocks (brass ones with real gears, springs and/or pendulums etc) - if you look at an old clock it is always the hardened steel pivots that are worn away rather than the soft brass of the clock frames / bearings that they run in.  This seems to be "wrong"  until you realise that any grit that gets into the bearing will embed itself in the soft brass and will then act as a very efficient cutting tool on the hardened steel pivot.

This process will also occur in a focusser where the rack is often brass or bronze (in high class ones) and the pinion is probably only "normal" soft steel.  Some of the cheaper ones are made of very low quality metals of dubious chemical composition and are often plated with some sort of "chrome" to make them shiny and attractive to buyers rather than being functional scientific instruments.

Grease will make two meshing gears seem to be smooth but this can simply be hiding a multitude of other issues that are being hidden from your "feel" on the focusser knob.

I'm not saying that you should not use grease, just that you should consider the mechanism that you are using and how best to ensure that it works and is likely to continue to do so for a reasonable length of time.

[Dannae]

I agree with Bizi,

I feel the build up of grit and muck on something like a lithium or silicone grease might outway the benefits. I would suggest a light wipe (not spray) of something like a glass cutting oil or wd40 on the focusser wheel and the tightening grub screws to keep the area rust free (from dew) and moving nicely.

Regards

Dannae