Stripped copal retaining thread

Discussion in 'Large Format Cameras and Accessories' started by watanabe`, Aug 20, 2011.

  1. watanabe`

    watanabe` Member

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    I received a pretty Nikon 65mm sw (for use w/rollfilm back) today that was in great condition, except for a pretty beatup Wista lensboard, took it off the board it came with to put it in a new chinese recessed board and despite having done this many times I managed to muck it up, apply too much force, and stripped(wrong word?) the threads on the copal shutter as well as the retaining ring.

    Is there any easy (cheap) way to fix this? Maybe take it to a local machinist/lathe? I can't be the first one to make this stupid mistake.

    Sorry if this is a common question, tried to search but only got results of people trying to fix old wooden cameras with stripped screws... learned the neat toothpick fix for that scenario but nothing in this one.
     
  2. Jon Shiu

    Jon Shiu Subscriber

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    Could it be that the threads on the back of the shutter are still usable and you just need a new retaining ring?

    Jon
     
  3. watanabe`

    watanabe` Member

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    Nope I hamhandedly forced it and upon inspection both the ring and copal 0 jave their threads smashed. Tried putting the ring on my 90sw's copal 0 and ut didnt work, and the 90's ring couldnt go on the shutter in question.
     
  4. SMBooth

    SMBooth Member

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    I would get a couple of new retaining rings and try to carefully use one as a die to realign the thread.
     
  5. watanabe`

    watanabe` Member

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    by realign does that mean just forcing the new retaining ring onto the shutter and using it to "cut" / clear the threads of the shutter? Sorry not the most mechanically inclined...

    edit: so after some reading the basics of thread repair (for auto restoration) it seems I want a thread chaser or die? However given the relatively large diameter and small pitch of these delicate threads finding something to straighten the threads out would be pretty difficult, hence your suggestion to just buy a few retaining rings and use them to "recut" the threads on the copal shutter?
     
    Last edited by a moderator: Aug 20, 2011
  6. Ian C

    Ian C Member

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    The Copal 0 shutter uses 32.5mm x 0.5mm mounting thread. The threads on the shutter body and the retaining ring are relatively soft aluminum.

    You cannot reform the male thread on the shutter by forcing a new ring onto it. The thread of the new ring is far too soft. That will only ruin the thread of the ring.

    I suggest emailing SK Grimes for advice. That is one of the few places with experience in such matters and it might have a chasing die or a lathe setup for holding the shutter body as the threads are refreshed.

    You won’t find such a special tool or a shop with that type of special experience in SE Michigan and any machine shop that could do the work would have to charge you far more than the entire lens and shutter together are worth.

    Further tampering will only make matters worse. By discussing this with SKG you’ll have the best advice and possibly, a practical solution.

    http://www.skgrimes.com/home
     
  7. Jon Shiu

    Jon Shiu Subscriber

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    Usually the shutter body is steel and the ring is aluminum.

    Jon
     
  8. John Koehrer

    John Koehrer Subscriber

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    I've used dental probes with a sharpened edge/point for this sort of "adjustment"
    Carving knives(wood) can work very well too. A cheap set the good ones are too good(?). I'll use the non-sharpened edge to do the work
    they have corners that work very well.
     
  9. Sirius Glass

    Sirius Glass Subscriber

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    In the future getting a lens spanner from S. K. Grimes for $30 to $40 with shipping will be cheaper than fixing the damage caused by not having the right tools.
     
  10. Leigh B

    Leigh B Member

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  11. watanabe`

    watanabe` Member

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    Thanks for all the advice will give sk a call.

    Also, I have one of the square metal lenswrench stamped spanners, however the lens in question had one of those small set screws to prevent it from spinning in the lens board. When I received it thelens had some wobble on the board so I took it off. Found 2 grooves in the hole on the board that looked like one of them would hold the screw so realigned the front element with that and started cranking on the ring when after a turn it wouldn't go any further. Stupidly thought I was pulling the lens into it's proper place when in fact I was just pulling the threads out. Let that be a lesson to you that you probably already knew: don't force anything camera related when it won't move.
     
  12. Ian C

    Ian C Member

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    With respect to #7

    I examined my late model 135mm f/5.6 Nikkor W to determine what metal the threaded mounting sleeve of its Copal 0 shutter is made of.

    The mounting sleeve is finished black except for the unfinished end. That’s machined square and left unfinished to form a seat for the shoulder of the rear unit.

    I brought a small magnet slowly to the end and outside diameter of the sleeve until the magnet touched. I tried this in a number of places. I couldn’t detect any magnetic attraction.

    Austenitic stainless steel is known to have little or no ferromagnetic attraction, but the unfinished end doesn’t look like steel or stainless steel. It looks like aluminum.

    Older shutters might well have steel shanks, but this Copal 0 shutter appears to have an aluminum mounting sleeve.
     
  13. Neanderman

    Neanderman Member

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    Don't force anything, period, when it won't move. It is a sign that something is wrong.

    Ed, son of a mechanical designer.
     
  14. jeffreyg

    jeffreyg Subscriber

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    If all else fails or is not feasible could he get the next larger size retaining ring and lubricate it and the lens board and VERY carefully place a bead of epoxy resin around the shutter threads then place the larger ring. If all works well then he will have made a new set of threads.

    http://www.jeffreyglasser.com/
     
  15. paul_c5x4

    paul_c5x4 Subscriber

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    If by "specialized tooling", you mean full form indexable carbide inserts, you'd probably be right. However, any decent machine shop worth their salt should be able to grind a cutting tool to do the job - For a 0.5mm pitch, a stub of 1/8" square HSS would be ideal.

    If the OP had been closer to me, I'd have offered to do the job for him.
     
  16. Jon Shiu

    Jon Shiu Subscriber

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    Thanks, you are correct. I don't think he could have stripped steel threads with a small aluminum ring.

    Jon
     
  17. watanabe`

    watanabe` Member

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    Just to let you/anyone else who has this problem know: Bob at precisioncameraworks was able to take care of it for cheap. Apparently he didn't need to resort to putting it on a lathe and could use a chaser to repair the threads.

    Thanks for the help