Industar 61 recalibration question

[blockend]

This question might be a long shot, but maybe someone who's dismantled an FSU rangefinder lens can help. I took an LTM Industar 61LD apart to clean out the waxy gunk (whale blubber?) and put it together with fresh lube. All seems fine except the focus is slightly out, not greatly, but not focused exactly to the lens scale, for example 1 metre looks to be about 6 inches out tested on a digital camera with a tap measure, I haven't put it on a film rangefinder camera since reassembly or tested for infinity (it's night time here).

Following instructions on the internet http://mattsclassiccameras.com/industar_relubing/index.html the author says there is more than one starting thread position to re-fit the helicoid, which is true but I photographed each stage of disassembly and the reassembled position is the same as the previous one. The other possible variable is the locking sleeve behind the lens assembly, a threaded collar that adjusts the height of the complete lens assembly.

I'm not sure if my helicoid thread starting position was incorrect, or the rear threaded column position is wrong. I appreciate this will be gibberish to anyone who hasn't taken a similar lens apart, but someone out there may know the answer. The link above is good so far as it goes but there's no advice on fine tuning, and I may be expecting too much accuracy from the distance scale.

 

[Ko.Fe.]

Keep trying. It always helps for me.

http://lens-club.ru/public/files/pdfs/abf57839610ed1ea9f254a4e179ae593.pdf

 

[Gerald C Koch]

If the lens design is typical then you have 6 possible starting points for the threads. Just keep trying. Professional repairmen make a scratch on the lens barrel to show the original start position.

 

[RSalles]

Check also if only the scale ring can be correctly positioned in the barrel when the infinity is at the correct stop point. I have dis-assembled 2 of this lens in the last year, but can't recall the details no more - I used to scan with it and my EOSMkII before concluded that a enlarger lens is much better,

Cheers,

Renato

 

[blockend]

Thanks for the replies. I've reassembled the lens three times but each one is incorrect. I don't want to spend too much longer repairing it so I have ordered another and will see mess around with it when I have more time.

My other thought is that because I'm testing it on a digital camera (crop sensor), the distances indicated on the barrel may not be those on the film plane.

 

[02Pilot]

My money's on the helicoid being off as well, but also double-check to make sure you didn't lose any shims that might have been in there. It can be frustrating to get lenses back together correctly; only practice will help to ease the process.