Need a flange or retaining ring for Compur shutter

[durr3]

I have a Steinheil Munchen 165mm f4.5 lens mounted on a Compur shutter, but I cannot find a flange or retaining ring to mount it with.

Does anybody have one or know where I can go to find one? I tried S K Grimes and they did not have one.

OR, if you know what size threads it uses, that may help.

The lens is very clean and the shutter works great, so I want to give it a try.

Thanks for your help.

[Andrew]

maybe try an alternative method of securing the shutter to the lens board ?

[Emmanuel BIGLER]

Hello from France

The retaining ring diameter & thread pitch depends of course on which shutter size you have.
You can roughly estimate the inside ring diameter by applying a caliper on the rear lens mounting threads.
Compur shutters, unlike Compounds, have metric thread specifications.

For the Compur#0 the ring specifications are: ring outer diameter to seat inside the board hole = 34.6 mm - ring inside thread = M32.5x0.5
For the Compur#1 the ring specifications are: ring outer diameter to seat inside the board hole = 41.6 mm - ring inside thread = M39x0.75
For (certain) Compur#2 the ring specifications are: ring outer diameter to seat inside the board hole = 52.2mm - ring inside thread = M50x0.9
For the Compur#3 the ring specifications are: ring outer diameter to seat inside the board hole = 65.1 mm - ring inside thread = M62x0.75

M62x0.75 means : metric thread, nominal diameter = 62 mm, thread pitch = 0.75 mm.
The nominal diameter of a thread can be estimated by applyning a caliper to an outer thread, the nominal thread diameter is just slightly bigger than what the caliper measures.
The nominal pitch can be easily measured with a comb-shaped tool which is very inexpensive ; some even exist combining metric and imperial threads. The right pitch is as important as the right thread diameter! For example, M39x0.75 is not the Leica Thread Mount (LTM), the #1 compur's pitch of 0.75 mm is finer than for the LTM (close to 1mm)

The nominal lens board hole diameter is equal to the outer ring diameter plus 0.2 or 0.3 mm to allow some amount of play.


Your lens is certainly not mounted on a #0, may be a #1 shutter, to be checked; the thread diameter for the mounting ring could be something like 39 mm for a #1, 50 mm for a #2 or 62 mm for a #3.

If by chance, your shutter is a compur#3 with a retaining ring threaded as M62x075, this thread size is easily avalaible for filter mounts.
So you can find such a filter ring, an empty filter mount or a step-down ring from something bigger down to M62x0.75 (a step-down ring is required, not a step-up, in order to get an inside thread M62x0.75)
But such a filter ring will not exhibit the flat outer ring of diameter 65.1 mm which in principle touches the inside of the lens board hole, diameter 65.3 or 65.4 mm (this size for the lens board hole is not really very critical).
In principle, the mounting threads of the lens should not directly touch the lens boad hole, hence the special shape of the lens retaining ring.
But if your thread sze is M62x0.75, you can certainly mount your lens with the help of a filter ring without having to order custom-made ring.

[durr3]

Emmanuel, thank you for the information. I will try to get the measurements and post later today. A quick measure, I came up with 48-49 mm.

[IanG]

That assumes the Compur is the later Rim-set variety. Dial-set flange sizes were different.

Ian

[durr3]

IanG-mine IS the dial set type.

[Regular Rod]

Widepan make them for a few sizes. Put a search on eBay for Widepan retaining ring.

Here's on eBay item number: 151242677226

RR

[Emmanuel BIGLER]

IanG-mine IS the dial set type.

Hence, as Ian said, the specifications above, are for modern compurs and copals ; unfortunateley they might be irrelevant to your case. Sorry, I do not have the specs for old compurs in my files.

A quick measure, I came up with 48-49 mm.
Could be something like a compur#2 with a M50 thread, but here I doubt that you'll find a modern replacement ring for this compur, since modern compur#2 were discontinued in the sixties, and your Compur was discontinued ... probably before WW-II.
S.K. Grimes otherwise mention on their web site that they have measured different compur#2 with different specifications.

However, M49x0.75 is a standard filter thread, so you could give it a try with a step-down ring, one never knows. Aluminum step-down rings are quite cheap. Just try it very gently, never attempt to apply too much torque/force if the diameter or the pitch are not good, you would jam the ring on the lens thread.

If this fails, I'm afraid that you'll have to order a custom-made ring or try the infamous method of "paper-thread-mount" which is not rock-solid but will not damage the original lens threads. The idea is to insert some amount of paper between the lens threads and another threaded ring sligthly bigger in order to be able to lock the ring on the lens.
Next to M49x0.75 comes M52x0.75, one of the most common filter sizes, but probably already too big for the paper insert.
I have a Compound#3 with a missing ring like you, the shutter came with this horrible "paper mount" and if I want to remount it properly, I'll have to order a custom-made ring. In the past I have ordered a custom-made ring to mount a M39 enlarger lens on a #1 shutter, from SRB Griturn in the UK and the price was fair if I accepted a long delay for delivery.
The specifications for compounds are known, they have been posted here by Ole Tjungen from an old catalogue, may be somebody here has the specs for old compurs?

[Emmanuel BIGLER]

Just after I finished my post, I remembered this French web page by M. Suaudeau which is a nice compilation of thread sizes for leaf shutters.

http://www.suaudeau.eu/memo/pratique/Les_obturateurs_centraux.html

The compur that comes closest to your measurement (in this list, which is probably not comprehensive) is named : Compur 2 tube 5/I.
But yours could be another, not listed.

However, the specs are here for the Compur 2 tube 5/I
overall diameter 78 mm
speeds BT 1s to 1/150s
iris diameter 30.5 mm
front cell thread 45.8 mm x 40 TPI
rear cell thread 45.8 mm x 40 TPI
lens retaining ring thread 50 mm x 40 TPI

40 TPI converted to metric is 25.4/40 = 0.635 mm.
So if the thread is actualy 50 mm x 40 TPI, you can forget about modern filter rings ...

A thread gauge looks like this and is easy to find. A serious LFer cannot live without a set of specialized tools, first of all the special key/wrench to mount retaining rings and second, a set of thread gauges, metric and imperial, to identify exotic thread pitches ;)
This is the Imperial/US version : http://shop.grfasteners.com/Draper-Imperial-UNC/UNF-Thread-Gauge

Good luck !

[Regular Rod]

Widepan make bigger sizes too. It must be worth you measuring your threads and asking Widepan if they have something that fits. http://i.ebayimg.com/00/s/NTAxWDc1MA==/z/k1sAAOSw7I5TuVfn/$_12.JPG

RR

[durr3]

I took the shutter to Graingers and they measured it for me...they guy said the threads were very close to 28 threads per inch and measured 49.9 mm or 1.9625 inches.

[Emmanuel BIGLER]

threads were very close to 28 threads per inch and measured 49.9 mm

Good. Hence we are very close to something that would read, in metric : M50x0.9 i.e. one of the specifications for one of the modern Compur#2 that I have in my files (those specs for some compur#2 were simply cut-pasted from S.K. Grimes' web site).
And this is definitely not 40 TPI like some other compur#2 mentioned in Mr. Suaudeau's web site.
Some compounds have threads specified as 29-1/3 TPI which corresponds to 0.86 mm, not exactly 0.9 but for a small number of threads, some deviations could be acceptable if the diameter is right.
The problem is still far from being solved, but at least we know precisely what we need ;)

After all this effort to find the specifications of the retaining ring, may be it is time to remember what Andrew suggested very early in this discussion (hello, Andrew, form the other side of the planet ;-) ) and follow another route:
maybe try an alternative method of securing the shutter to the lens board ?

One could think of using small screws that would hold the shutter back directly to the lens board?
I have no idea if this could be done or not, it involves opening the shutter and see how its box could be modified and directly attached tothe board.
Or securing the shutter as a whole, from its outside diameter, with somethink like a split, adjustable metal collar and some rubber insert; a fixture that should, of course, allow to operate the tensioning lever and other controls!

[IanG]

My experience is the threads with some Dial set Compurs are very close to Rim set Compurs but just no quite close enough for the retaining rings to be inter-changeable.

Good luck.

Ian

[durr3]

Pics

[Emmanuel BIGLER]

Thanks for the pictures.
At the first glance, although there are some small screws accessible from the back, I do not see how one could easily attach the shutter to a lens board using those small screws or their tiny threads. At least, I would not change anything to this venerable compur shutter.

The lens looks reasonably compact and not very heavy, hence, at least to get one image and see how it looks, you might give a try to the infamous "paper insert" method.
The next standard filter thread above 50 mm is M52x0.75, so once you've got a step-down filter ring down to M52x0.75 (step-down in order to get a inside thread) you need about one millimeter of paper insert in order to hold the two parts together.
Well, a gap of 1 mm to fill is quite thick for paper, so I do not know if the method can work or not.
A gaffer-tape insert might be useful as well. Real good gaffer-tape, in principle, can be safely removed without any glue left of the surfaces.
And a sufficient provision of gaffer-tape could also be useful, between the shutter and the lens board, to prevent the lens from falling down in case the paper of gaffer-tape insert would not hold the lens strongly enough.
So this would be my approach, trying to attach by the rear thread, using a crude method that I would not disclose publicly here ;) at least to take one or two pictures and know if the lens is worth using.

An idea for a **really crude** attaching method; crude but harmless for the lens and its attaching thread.
I would apply a few turns of gaffer-tape around the threads.
I would find a board through which the gaffered lens thread would pass-through, with as little amount of play as possible, and I would tighten a clamping collar (one of those inexpensive pipe clamps) (http://www.hiwtc.com/photo/products/19/00/13/1359.jpg) directly to the gaffer-protected threads, behind te lens board. Hence no need for a threaded retaining ring at all!!

Eventually, if I like the lens very much I would order a custom-made ring, but for a mail-order, I would send the whole lens or at least the shutter so that the machinist can measure himself the required thread and diameter.

[Old-N-Feeble]

I may have a flange that would work but I can't find my calipers and thread gauges to check. I know that's not very helpful but I can't afford to buy any tools at the moment.

[durr3]

I may have a flange that would work but I can't find my calipers and thread gauges to check. I know that's not very helpful but I can't afford to buy any tools at the moment. Can you get a diameter measurement ? Thanks

[durr3]

Thanks for the pictures.
At the first glance, although there are some small screws accessible from the back, I do not see how one could easily attach the shutter to a lens board using those small screws or their tiny threads. At least, I would not change anything to this venerable compur shutter.

The lens looks reasonably compact and not very heavy, hence, at least to get one image and see how it looks, you might give a try to the infamous "paper insert" method.
The next standard filter thread above 50 mm is M52x0.75, so once you've got a step-down filter ring down to M52x0.75 (step-down in order to get a inside thread) you need about one millimeter of paper insert in order to hold the two parts together.
Well, a gap of 1 mm to fill is quite thick for paper, so I do not know if the method can work or not.
A gaffer-tape insert might be useful as well. Real good gaffer-tape, in principle, can be safely removed without any glue left of the surfaces.
And a sufficient provision of gaffer-tape could also be useful, between the shutter and the lens board, to prevent the lens from falling down in case the paper of gaffer-tape insert would not hold the lens strongly enough.
So this would be my approach, trying to attach by the rear thread, using a crude method that I would not disclose publicly here ;) at least to take one or two pictures and know if the lens is worth using.

An idea for a **really crude** attaching method; crude but harmless for the lens and its attaching thread.
I would apply a few turns of gaffer-tape around the threads.
I would find a board through which the gaffered lens thread would pass-through, with as little amount of play as possible, and I would tighten a clamping collar (one of those inexpensive pipe clamps) (http://www.hiwtc.com/photo/products/19/00/13/1359.jpg) directly to the gaffer-protected threads, behind te lens board. Hence no need for a threaded retaining ring at all!!

Eventually, if I like the lens very much I would order a custom-made ring, but for a mail-order, I would send the whole lens or at least the shutter so that the machinist can measure himself the required thread and diameter.

Thanks for the help. I want to mount the lens and shoot with it to see what it renders. Something about these OLD lens! You are right, if it looks good to me, I would get a flange made. But I do not want to go to that expense until I see how it does.

I will let you know.

thanks again