Cleaning and lube for DAR Helical Focusers?

I have 2 DAR Double Helical 2" Focusers, which I like very well.
What is the best way to clean and lubricate them?
They are getting stiffer to rotate, especially when further into the barrel.
I enjoy these 'built like a battleship' focusers as they don't care how heavy
the eyepiece or camera is.
I am not getting any answer back from Joe O'Neil who sells them, nor Dave Rubenhagen who makes them.
FYI, they are made of aluminum running on phosphor bronze on aluminum which tend to self lubricate but need cleaning. WD40 is used as a cutting oil to lap these together so is not suitable as a cleaner/lubricant.
Thanks
Mike 10" f4.5 home made Dob

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I notice that your focuser looks similar to my LUNT Pressure Tuners (all 5 of them!). And indeed one has gotten frightenly stiff when turned in far. I have always assumed they are brass on brass and just greased up. These tuners have 4 identical threads phased 0, 90, 180, 270 (of course). Especially stiff when it gets cold - I assumed it was the non-synthetic grease viscosity climbing. I keep planning on at least cleaning and regreasing them but never get around to it. But here's a thought: if the M, F are of different BASE materials, then their different CTEs would result in best match pitches and diameters at the original lapping ambient. Anything other temp would result in a mismatch...which need not be much at all, considering the close tolerance of lapped threads. And THAT would be a function of how much engagement is involved. My inclination would be to disasemble (if easy), clean, re-lap, clean, grease, reassemble and use. Risk is that further abrading surface-hardened materials can subject them to galling...disasterous. At work we more than once ruined surfaces by breaking thru the anodized surface of aluminum. Al is notorious for galling unless it's the cast stuff. It astounds me that our hardware works as good as it does, considering all the little gremlins that affect performance.

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