[Dexxx]

Hello people,
Somehow I've managed to unscrew the collar screw and now I cannot put it back, even though I think I screw it very tightly but it doesn't work!
I've attached photos and a video in youtube so you can see better what I am trying to explain
Do you have any suggestions hot to fix it ?
Thanks!

Youtu.be

Youtu.be

Attached Images

   

[StigVidar]

There is a small screw on the lens which you have to unscrew two or three turns. It is shown on one of the photos above.

Be careful with these collar screws and also the lock screw on the foot. They are made for light use and dont have to be forced or be used with a screwdriver.

[Dexxx]

Thanks for the info ! I've unscrew the small one but yet this didn't helped me to tighten the collar, is it possible that I've lost some part while unscrewing the big one ?

[StigVidar]

It is possible the collar have to be positioned in the right position before you mount the screw. Turn the collar and look into the hole to see if there is an obvious position to set it in.

[ramseybuckeye]

I have one but I only removed it once to look at it when I first had the lens, and I will never remove it again. So I forget what it looks like under there. Do you have the white line and white dot lined up with each other when you try to tighten it (it is not in the video)? Can you tell on the barrel where the screw hits? Is that like a bearing on the end of the screw? Does it need to fit into an indentation in the barrel?

[pschlute]

From what I recall of that lens it needs to be in one of the 4 détentes in order to lock.

[UncleVanya]

From what I recall of that lens it needs to be in one of the 4 détentes in order to lock.

On the 60-250 it will lock in any position- I would have expected the 300 to be similar.

[DonV]

Thanks for the info ! I've unscrew the small one but yet this didn't helped me to tighten the collar, is it possible that I've lost some part while unscrewing the big one ?

Yes, you likely lost a small plunger that would press against the lens so as not to scar it when turning the metal screw to lock.
The plunger was/is perhaps a plastic/polymer piece.
You can probably improvise something to put under the screw to accomplish the same purpose; like a pencil eraser or short piece of a chop stick or similar.

[kwb]

On the 60-250 it will lock in any position- I would have expected the 300 to be similar.

That's correct.

Dexx, did you inspect the collar screw hole while rotating the collar 360 degrees? Did you see anything loose that is trapped between the collar and the lens barrel? If so, it could be that the thing is supposed to be captured by the tip of the thumbscrew so it usually moves with the thumbscrew, and that the friction between the lens barrel and the thing, when you push it by thumbscrew, will provide the holding force.


I've never removed that thumbscrew from my DA* 300 so that's 100% speculation.

[alfa75ts]

is it possible that I've lost some part while unscrewing the big one ?

It looks to me like you damaged the thread in the 'sleeve'.

I believe the image below shows how it should work with the retaining pin (little screw) preventing the knob from coming out and getting lost.

What I think has happened is that as the retaining pin stopped the thread on the knob from from fully clearing the thread in the 'sleeve' and that you have used sufficient force that the steel thread has damaged the aluminium thread in the 'sleeve'.

If you try carefully you 'may' be able to get the thread started which could fix the problem otherwise, the screwdriver slots on the top of the 'sleeve' indicates that perhaps it can be removed and repaired or replaced. I don't know.

Use caution, I'm not taking any responsibility.

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