Accessing helicoid in 1939 Elmar 9cm?

[mystichobo]

Hi guys!

How do I access the helicoid for relubricating on an '39 Elmar 9cm? I've tried the stuff mentioned in the image with no luck; I'm wondering if maybe I need to remove the silver mount part but I'm not so sure, and really don't want to force it.

The lens works fine, optically it's beautiful even though there's a tonne of wear on the outside, but it's making a bit of a rasping sound when focusing, which indicates to me that it's probably metal on metal somewhere, and I'd like to fix that before something internally gets worn down.

 

[mystichobo]

If anyone is curious, the silver mount comes off after removing those screws, along with the rangefinder coupling tube. in my example, it was actually the helicoid between this tube and the mount that needed cleaning, the grease in there was basically solid, which is why it was hard to get off.

 

[Ko.Fe.]

Do you unscrew the mount ACW to remove it?

 

[mystichobo]

Do you unscrew the mount ACW to remove it?

I did, but I'm not sure it was necessary; there's no actual threading on the silver mount part (except for on the helical threads to the coupling tube, which is attached to the main helicoid by two slotted sections). It's a very tight fit, but I think you could just pull it backwards without any issue.

I'll try to draw a diagram of how it fits together tonight!

 

[Ko.Fe.]

Thank you, this will help. Common problem with these old lenses, it seems.

 

[mystichobo]

Hopefully this makes sense!

 

[Ko.Fe.]

Nice 3D modeling! I could get another 90mm now.

 

[Turtlewits]

Hopefully this makes sense!

Hi!
Thank you so much for these explanations. By any chance, did you clean the helicoid in the red part? Would you know how to dismount this part as well?

All the best,
Ph