regreasing helicoids on longer MF (200mm) lens results in binding when focusing?

[whatdoido]

A question for folks who maintain / service their own helicoids.

I have regreased shorter focal lens with no issues but on a 200mm f/4 AI I have cleaned, regreased. remated and reassembled the lens.  However when I turn the focus ring it feels like its "bnding" as I turn the focus ring in the horizontal position- if i support the front for the extending lens then thers no binding and its nice and smooth and similarly front downon table, focus from infinity to MFD its nice. Can anyone suggest why this would be the cause of the apparent binding?

Individually, the regreased helicoids (before the helicoid key is reattached) turn very smoothly with no resistance so I don't beleive that I've over-lubed the helicoids - when attaching the helicoid key I also added grease to the key and the "notch" where it sits.

thanks in advance

[Birna Rørslett]

To my ears it sounds there is too much grease -- a very minute amount is what is needed.

The lens hasn't received knocks from the side?

[whatdoido]

I only regreased this 200mm as it had some spots where it felt like it was slipping when focusing (I'd turn the ring and it took a moment for the focus to start adjusting)  but otherwise it was nothing wrong.  In the years I've owned it, its never had a knock but I got it 2nd hand in immactulate condition from a colelctor.

When I regreased it (i've made the too much grease mistake before) I made sure i could turn the helicoids and they were very smooth and light with no binding feel - I've wiped off more grease (its Japan Hobby Tool #10) from the helicoids and its the same binding feel.

The binding feel is only after I fully reassembled.  Without the helicoid key, all the helicoids turn in place very smooth.

[Erik Lund]

Sounds like the key is binding,,, or too heavy/Thick grease.

[whatdoido]

I finally had some time to re-look at this lens and conclude that it was the helicoid key rubbing up against the slots due to gravity when lens held normally/shooting horizontally.

I found that if i sat this on my desk, front element down, the lens is very smooth to focus.  I proceded to strip it down to the helicoids without the (single) helicoid key - with the front optical group attached turning the helicoids there was no bnding.  This made me think that the problem was they key.

And when reassembling, and securing the key i noticed this problem.  Normally for the long helicoid keys, I slide it into position, focus half way out away from infinity (so I dont secure the key askew at infnity and then drag when going to MFD) and stand the lens on a table to try to get the key hang neutrally before lightly securing the middle (of three), check theres not drag and then add the outer screws .  If theres a better, solution, it'd be great to learn.

I had previously greased the side of the helicoid key as well as the side of the slots but perhaps the helicoid was secured too close to one slot.  Its much better but still some binding so i'll experiment.