assman Loc: Grand Rapids, MI

Takumar 500mm F4.5 lens

I have acquired one of these beasts and am in the process of “restoring” it so-to-speak. This one has the “slight wobble” I have seen in the descriptions of ones for sale. I have it disassembled far enough to find the issue. There are three 2x5mm screws that hold the focusing assembly to the front part of the lens. In my case two were sheared off and the third had a damaged head. Being an old tool & die guy I have lots of experience with damaged and broken fasteners. I was able to remove the broken pieces so I am well on my way.

But I need some help.

The focusing mechanism is comprised of opposing right and left hand multi threaded helical splines that are keyed to each other so that when the cylinder housing them is rotated they move away or towards each other. I need to disassemble this mechanism for cleaning and re-lube. Taking it apart is easy. This is where I need help. What is the procedure for re-assembly ensuring I start the helical splines on the correct tooth and after that how do I make any fine adjustments? I am also in need of some screws. 2x5mm flat head screws. 2x6 will work also. I would also like to find a 1.7mm screw that's long enough to make a new pin. Probably 5mm long would work.

After all that I plan on making a drill jig to add 3 more screws to the helical assembly to help prevent this from happening again. If you were to hit the lens on it’s end about half the weight of this monster impacts the three 2mm screws. No wonder this is a common issue.

Thanks for taking the time to read this rather long note.

bleirer

I'd check mcmaster carr online for the screws. They seem to have everything. https://www.mcmaster.com/

Alafoto Loc: Montgomery, AL

I would throw up my hands and leave the room, leaving the lens in pieces for eternity. I admire you for being willing to try to complete this project. Ask me one day about my (still in pieces) field camera project.

lamiaceae Loc: San Luis Obispo County, CA

Marking splines and photographing before further disassembly not possible?

I'd just fix the screws and be done with it if that was the essential problem. And pass on the splines. Not even sure what you are actually saying. Most 35mm type lenses need little service. Perhaps cleaning iris blades if they are sticking or "slow".

assman Loc: Grand Rapids, MI

This is my first attempt at fixing a lens. Too late on "marking before dissembling". I need to tear this thing all the way down to un-do the damage from the last guy to tore it down. From what I can see ALL the lenses have cleaning marks and smears that need to be removed. It's not that bad, it's just that I have to be thorough. I have an idea it's been broke for while.

TriX Loc: Raleigh, NC

Another vote for McMaster Carr for the screws.

amfoto1 Loc: San Jose, Calif. USA

Micro-Tools.com is another good source of small parts like those screws. They are camera and lens repair specialists (though they delve into some other things, too).

I would strongly advise against fully disassembling the focusing helicoid. Those can be real buggers to ever get back together correctly.

If at all possible, it's better to remove all the optics and the lens aperture mechanism from the lens, so that all that's left is the barrel and the focusing mechanism. Then, without disassembling it, use a "flood cleaning" method to get old grease and dirt out of the helicoid. You may need to operate it a few times to do insure it's well cleared of old dried up grease and grit. Lighter fluid can be a good, cheap cleaning solvent that quickly dissolves old grease, though you obviously have to be very careful using it.... outdoors in a well ventilated area. There are other, safer to use cleaning fluids if you prefer (but the job will be messy, so I'd take it outside).

Once it's clean to your satisfaction, set the lens aside for a while to allow all the cleaning fluid to evaporate. Next extend the helicoid a bit and start to work some new grease into it. There are special "dampening" greases that can be used for this purpose... But I've often just used synthetic bicycle bearing grease and found it to work quite well. Synthetic is best because it won't dry out and harden over time and because it won't thin out or "oil off" and foul the lens aperture mechanism in hotter weather. Synthetic grease is also less likely to damage to plastics or nylon parts, if there are any inside that lens. It also usually smells a lot better than many petroleum based greases!

Work the grease down into the helicoid mechanism by extending it repeatedly. Try not to overdo it, though. And always be careful not to extend the helicoid too far, so that it comes apart. (It may have some sort of stop to prevent it, but that may have been removed when you did the rest of the disassembly.)

If, on the other hand, you've already got the helicoid disassembled.... well, good luck! At best, you'll probably have to do some trial and error to match them back up correctly. reassemble the lens, see if it focuses to infinity at to it's closest rated distance. If not, mark what you tried, disassemble and try rotating to the next logical tooth. Keep in mind, many manual focus lenses could actually focus "past infinity", had an adjustable stop that needed to be set. At worst, once taken apart, focusing helicoids can be pretty much impossible to get back together. (Been there, done that! Learned my lesson and swore I'd never, ever disassemble another focusing helicoid!)

Once you get it done, let me know if you want to work on an 800mm lens I've got here waiting for a thorough cleaning

assman Loc: Grand Rapids, MI

That's the kind of help I've been looking for. Unfortunately I did un-screw it off the helicoid. I think I got it back where it was but at the same time I disengaged the tabs that keep the LH-RH helicals in sync. I did get some information from a local repair shop that says the assembly needs to be as short as possible to focus at infinity. I am having soooooo much fun. I did find some Optical grease called HELIMAX-XP specially for heliciods.

JimH123 Loc: Morgan Hill, CA

I have the same lens and went through the same situation with the focus mechanism. I started with the problem that it was stopping just short of infinity. After taking it apart, and then reassembling, I figured out how I could adjust slightly how the two parts came together, and I was able to finally assemble it with it now able to turn slightly past infinity. All told, I probably assembled that thing some 20 to 30 times before finding the solution I wanted.

I certainly was ready to give up. But I kept trying.

assman Loc: Grand Rapids, MI

This is just an update into my Tukamar m42 500mm F4.5 lens adventure:
Well, I finally got it up and working! It took persistence and some face time with Fred at Universal Photographic in Kalamazoo, MI. He sat down with me and explained the theory behind the focus mechanism and from there it was just commitment. For this particular lens you want to have the helical splines engage in order to have the shortest over all length to enable focus past infinity. I had discovered the "person" who previously worked on this lens had engaged the helical two splines off that prevented focusing past Infinity. Once that is done it's just a matter of reassembling and focusing at infinity (the moon for me) and noting the amount of rotation from the hard stop and then making that adjustment. For me I was able to add a k-mount adapter (the one WITH the flange) from GOBE and still have plenty of room to focus past infinity by about an 1/8" looking at the markings. (the GOBE adapter stays with the lens and mounts like a regular K-mount lens - nice) I am not going to set the hard stop until I use it enough to know that's where it should be with both my bodys and teleconverter. So there you have it. One final word. If you add an adapter to your old screw mount and cannot focus to infinity there is adjustment that can be made to the stop and worse case you have to dig down to the helicals and change the engagement.