stiff focus

[MISH]

Hi Brian & everyone
I have a screwmount Summicron 50mm collapsible that the focus turns rather hard on, is this something that I could address (RE without taking the lens apart) or would I be better off sending it to someone that knows what they are doing? If it is something I could tackle what kind of lubricant should be used?

thanks

[ferider]

It's easy to relube. You can open the focus mount by hand - just twist the curled ring on top of the mount.

[ed1234]

What kind of grease should be use to lube the lens? Can we use automobile silicone grease?

[ferider]

Medium to high viscosity oil, silicon grease or graphite. Not so critical with the collapsible since the optical barrel is completely separate of the focus mount, so focus lube will not make it even close to the optics/aperture, etc.

[ed1234]

Thanks, I felt safer now.

[sanmich]

Originally Posted by ferider

It's easy to relube. You can open the focus mount by hand - just twist the curled ring on top of the mount.

I'm not pretending to really know how to work on lenses, but my experience with a collapsible cron was a bit more complicated.
I received mine after a relube from Youxin and it was still a bit sticky, so I tried to solve the issue. I opened the three screws on the lens flange, then unscrewing the flange (make a sign where it disengages). I cleaned what I could, but it still wasn't good. I asked DAG about his opinion, and he told me that there is another area of friction, and if cleaning the helical wasn't enough, a more advanced dismantle was necessary. I decided to send it to Don and (after a loooonnnnng wait) got it back.... perfect.

The thing is with these lenses that the focus movement may seem ok, but it really needs to be super smooth for the user to make small focus adjustments.

Good luck!

[Brian Sweeney]

The Thread mount version comes apart with the three screws in the back as Sanmich states, the M-Mount is different and the front ring must be undone, as Roland states. I've not tried taking an LTM version apart as Roland describes.

I received a Thorium LTM Summicron that had been "Sun bleached" to get rid of the Yellowing. It also cooked the grease into wax. The focus was extremely stiff. I took the three screws out the back, helical came apart. The helical has Multiple Starting Points, and only one is correct. mark the lens if you decide to do it yourself. Note the extension of the RF Cam at infinity. It will be at this extstion when the screws line up properly un re-assembly. I did not take pictures, was more like a random walk until i got it reassembled. I used a Little Vacuum Pump grease on mine, because I wanted it damped. I also use White Lithium grease for a looser focus.

[ferider]

Interesting. Mine (shown in the above pic) was a late LTM coming apart as described.

[Brian Sweeney]

at this point- both of my LTM Summicrons are Thorium. I'm careful not to bring them too close together. Unless the power is out in the house...