Cableaddict
Offline
• • • •
Upload & Sell: Off
|
Wow, it's been a whole 12 hrs and I don't see 20 replies. Is this really FM forums?
OK, I've been doing some research (Ughh...) and the answer seems to be complicated.
Here's what I have gleaned so far:
================================
The "best" helical grease will vary depending upon the lens, but several factors are important.
1: it must not be prone to oil separation. Many automotive greases fail in this regard.
2: It must be fairly temperature stabile.
3: It must not be prone to collecting dust.
A lot of people recommend synthetic bicycle grease (no specific brand, but the RED colored stuff is recommended.)
-------------------------
The required thickness of grease is affected by several factors:
1: The courseness of the gears. - Fine gears need thinner grease.
2: Condition of the teeth:
- Worn teeth can be helped with thicker grease.
note: "The focusing mounts on the very best lenses (Leica, Zeiss, and a few others) are hand-lapped, and most good lenses use dissimilar metals in the helicals because these bind a lot less than pairs of similar metals. A hard light alloy and brass should not wear significantly in normal use, but if both components are made of soft light alloy (East German lenses from the 40s and 50s, cheap Japanese lenses from the 60s) it's possible that they used LOTS of grease to disguise sloppiness from new."
note also: "the rough feel of a cheap lens can be masked, to some degree, by a generous application of thick grease, but this will lead to problems of high torque when subjected to cold temperatures or migration at high temperatures.
3: type of lens. Large zoom lenses need heavier damping-grease, to keep the focus from slipping. One such product is Nyogel 774. (medium silicone grease)
4: ## HOW YOU PACK: The standard method is to fill-in only the front & back races, keeping the parts separated. However, most folks here seem to prefer to pack the entire helical. This then requires a much thinner grease.
Application of the 3/4 dabs of the heavier greases: (suggested by a pro lens restorer, specifically for old & heavy lenses like the Jena 120 and 180.)
The ideal is to fill all the 'lead ins' ie a strip of approx 1/2" completely round the top circumference, and the same for the bottom 'lead outs' of the helix. The mating surfaces of the helix are thus held apart by the grease film, the un-greased portions never touchings.
However, If you like to fully pack the helix, so the 'recommended' products often give unsatisfactory results. My £3.00 pot of Paragon silicone has performed flawlessly over the years, on all but a few medium format lenses.
======================================================
The "medium" Japanese tub sold by Micro tools is evidently way too thick for a small, quality prime. (and way overpriced as well) The lighter Nyogel may work, but again is serously overpriced, and could cost a fortune if you need to experiment with different grades.
If I could find a cheap source for Nyogel damping grease, in an assortment of grades, (774VL - 779) that would be the way to go, but not from Micro Tools!
The silicone bicycle grease is looking pretty good to me right now. I think I'll buy a few different types and experiment.
- But I am puzzled about the Nye "Damping" grease. Worth the exorbitant price? see:
http://www.nyelubricants.com/pdf/DampGrease/DampGrease_Broch_English.pd
Here's the pertinent paragraph from that article:
"The difference between standard grease and damping grease is shear resistance. Damping greases are formulated with viscous (high-molecular-weight) synthetic oils, giving them a high internal shear resistance. While standard greases are slick, almost like cream cheese, damping greases are more like sticky peanut butter. When damping grease is applied to mated, moving parts, it’s difficult for parts to come into physical contact. It also takes a degree of force to move through the grease. Since moving parts do not come into contact, there is little, if any noise and wear. And because a force is required to move the parts, there is little chance of free motion when the force is removed."
Is this some special characteristic, or just a marketing gimmick? If this "damping" is so important, how can folks be happy with plain old silicone grease? Perhaps all modern synthetic greases meet this "damping" description?
Not having an answer, I'm also ordering the Nyogel #744, as it's the one Micro tools specifically lists for helical gears. They also sell #767A but that is for heavier damping (probably zoom lenses)
-------------------------------------------------------------------
I'm diving in this weekend. Starting on a few cheapo small primes, but then on to the Rokkor 58/1.2's. (I desperately need to sell them) Any thoughts or quick suggestions?
(I just wanna get back to taking photos!  )
|
