mike_j
Established
I have just made another bad ebay purchase, a Takumar 50mm f1.4. It has clearly been dropped and the manual/auto switch was damaged. When I investigated the lens further it found it had been partly, and badly, dismantled up to the focus ring level at which point a screw had sheared and dismantling stopped. On the plus side the lens elements were in first class condition and the main lens barrel seemed undamaged.
As an occasional amateur repairer and model engineer I decided to give it a go and went on to totally dismantle the lens, helped by a couple of websites showing the procedure.
The cause of the problem was the internal brass aperture ring, to which the auto/manual switch is screwed. This ring rotates in the lens barrel. I assume it was bent when the auto/manual switch was damaged and was about 0.15mm out of true, just enough to make movement extremely difficult. I couldn't true it up by bending so skimmed it on the lathe. After various tribulations like dealing with the sheared screw stub I got the lens back together, thoroughly cleaned and relubricated. It now is as smooth as silk though I haven't done anything to improve the battered exterior yet.
I don't know how to patch the satin finish black enamel on the lens or how to recolour the engraving so any help with this would be welcome.
As an occasional amateur repairer and model engineer I decided to give it a go and went on to totally dismantle the lens, helped by a couple of websites showing the procedure.
The cause of the problem was the internal brass aperture ring, to which the auto/manual switch is screwed. This ring rotates in the lens barrel. I assume it was bent when the auto/manual switch was damaged and was about 0.15mm out of true, just enough to make movement extremely difficult. I couldn't true it up by bending so skimmed it on the lathe. After various tribulations like dealing with the sheared screw stub I got the lens back together, thoroughly cleaned and relubricated. It now is as smooth as silk though I haven't done anything to improve the battered exterior yet.
I don't know how to patch the satin finish black enamel on the lens or how to recolour the engraving so any help with this would be welcome.
Ronald M
Veteran
Check with Micro tools and a few gun smiths. You already did the hard part
peterm1
Veteran
I would be interested to know if there are any "chemical" solutions to this problem also. I have thought of the gunsmith option also but when I last looked (a few years back) only found bass blackening chemicals, nothing for aluminium alloys or other alloys. A few years ago I had an otherwise nice 50mm f 4 Macro Takumar which had a bright spot and ended up very carefully spraying the bright area with several coats of a good quality spray paint after carefully matching it to the same colour and satin sheen as the original anodizing (or whatever it is on the lens.) It is hardly noticeable but took quite a bit of work to match up and I dare say it is not as durable as the original. So I would love to hear about any alternatives. Recolouring of the engraving is a little easier. There are a few paint sticks I am told and these apparently work OK. (I have thought of the type available from auto parts stores and used to mark car tyre lettering but have not tried it yet.)
charjohncarter
Veteran
You might try having the ring CAD plated. Ask a 'hot rodder' where they get their cad plating in your area. There are many colors and shades to choose from. Of course, you will have to remove the ring again.