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Wild M5 focus mechanism service advice

 
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viktor j nilsson



Joined: 01 Mar 2013
Posts: 14
Location: Gothenburg, Sweden

PostPosted: Sat Dec 16, 2017 3:20 pm    Post subject: Wild M5 focus mechanism service advice Reply with quote

Long time since I posted on the forums.

I hope to attract the attention from g4lab, Ichthyophthirius and others who service stereo microscopes.

I have a nice old Wild M5 that I got for free from a University. Optically it is perfect, but the focus mechanism is not. It's not stuck, but the friction changes as you change the focus. It feels good at first, but as I shift the assembly downwards, it suddenly becomes much looser. The grease has definitely started to age.

I really hope to get the focus mechanism buttery smooth again. I've read everything I could find online about greases and focus blocks, but I'd love some feedback before I start.

First, am I correct that it should be safe to take apart the M5's focus mechanism before cleaning and re-greasing it? I've read that g4lab prefers to keep focus mechanisms intact whenever possible due to problems with "factory calibration" of some focus blocks, but I believe that this only applies to more complicated designs? Or could the teeth of the rack and pinion somehow become 'mismatched' if I take it apart?

Second, is it correct that I should only re-apply grease to the flat, sliding surfaces, not the rack and pinion? Should I apply any type of lubricant to the rack and pinion, or should they be kept completely clean and dry?

Third, do you think that the Nye 362HB general purpose grease would do a good job for the sliding surfaces? I've also considered damping greases such as Nye 868 and Nye 795A, but after reading lots of different opinions it seems as if that these might be a bit too sticky. I really like a smooth, buttery focus mechanism. Could it be worth trying the very light or ultra light grades of Nye's damping grease?

That's it I think. Many thanks in advance!

/Viktor
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viktor j nilsson



Joined: 01 Mar 2013
Posts: 14
Location: Gothenburg, Sweden

PostPosted: Sun Jan 14, 2018 5:02 am    Post subject: Reply with quote

I've went ahead and ordered some Nye 795A lubricant. It was quite cheap at Newgate Simms (£18.75 for 50 grams) compared to the alternatives, and seems to have a good reputation online for similar applications. I'll try it out to see how it feels, and take it from there.

I would still appreciate input on whether I should put any grease or oil in the rack and pinion.

I've also realized that I have a "new old stock" spare set of rack and pinion for the M5 in my drawer. I'm guessing that those parts are almost worth their weight in gold...
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