Remounting a barrel lens into a shutter.

[Wolfram Malukker]

Bought a 14" Goerz Red Dot Artar the other day for far less than they seem to be listed for, in the box, in a barrel. It arrived almost translucent, it was so full of fungus. I spent the time to clean it carefully, and the result is a nearly undamaged lens-the coating has a tiny etched spot on the very edge of one of the center lenses, and I doubt it will be a problem.

But, then I mentioned it at work and my co-worker brought me another! This one is the 9.5" F9 RDA, and fit into one of the Ilex #3 shutters with a little room to go. It came to me mounted on a horseman lens board, but I don't have a horseman, so I figured I'll remount this one into the shutter.

I managed to get the front bushing on the first try, and set the front lens to iris distance to exactly the same as the original barrel. I neglected to take photos of it, but I'll make a few more sets of bushings now that I know what their approximate dimensions will need to be. I was doing good with the photos, and then I managed to delete the in-process pictures. The rear bushing, which should have been easier, I managed to scrap 3 times before I made one that placed the rear lens cell the correct distance from the front cell.

So, here's the finished lens mounted in one of my rough looking, but nicely timed and working, Ilex #3 shutters:

I will need to find some replacement front plate screws for this shutter, the ones that came in it are obviously not the correct screws, and they're flat-head countersunk types to boot, so the front cover shifts very slightly. You can see where I put a new dot and an "F9" mark on the front plate with a sharpie, after measuring the original barrel to start working out the F-stop markings. The shutter hits the end stop for the aperture at 0.132" diameter, and the F64 aperture would be at 0.123" diameter. I do not know if I can get it all the way there.

 

[Sirius Glass]

Looks as though you have collected, cleaned and set up a very nice camera. Enjoy.

 

[Wolfram Malukker]

Still working on the rest of it. I have to fit a new bellows into my Toyo 45A, and may need to fix some of the friction locks that are a bit worn.

I'll get there.

 

[David Lindquist]

Very nice work. Would have liked to have seen some "in process" photos. Thinking you must have or have access to a lathe.

As you may know back in the day Goerz mounted these in either the No. 3 Acme or the No. 1 Compur. (A 1970 price list shows them adding the No. 1 Copal and the No. 1 Prontor).

David

 

[Wolfram Malukker]

Yes, I have my own machine shop, and teach machine tool at work. I was having some problems with my threading bar, the inserts were not fitting correctly and I was getting stuck into that instead of taking photos of what I was doing. Finally figured out that I was trying to fit the wrong insert into the bar, I've got three that will physically fit in the pocket but only one of those three positions the cutting edge correctly!

I have an Ilex #4 and the 14" Goerz Artar to mount next, plus I want to make a few more sets of bushings to put in back-stock for future acquisitions. The Ilex shutters might only be good within one stop but they're inexpensive and very easy to work on, at least for me.

 

[Patrick Robert James]

You should offer this service to others if you have the time.

That 9 1/2 lens can go into a smaller shutter. I have a 10 3/4 RDA that is factory mounted in a regular ol' Synchro Compur #1. I used to have a 24" that was mounted in a Copal #3. Love me some RDAs! Wish I had a complete set.

 

[Wolfram Malukker]

I would not have any problem mounting these barrel lenses into shutters, except that a lot of lenses/shutters are metric threads. All my lathes have imperial leadscrews, which means when I cut metric threads on them I cannot disengage the carriage to make the next pass-I have to use the emergency stop and spindle brake, then throw the thing in reverse and back up, then reset the cut and make the next pass. It's rough on the spindle brake.

For metric threading, I would need to set up and threadmill the bushings. I can do that, but I'd need to buy some more tooling. I guess if anyone asks and has a complete barrel lens, I might be willing to do the job.

Loose lens cells into a shutter? Not something I can do without having a customer-supplied blueprint.

 

[Wolfram Malukker]

There was a request for photos.

Machining another set of bushings, starting with the rear bushing. Boring out the ID to 1.596", the minor thread diameter.

After that, I set up the most annoying threading bar that I own. This one has to tilt the insert to gain clearance, because it's made to fit into a small hole diameter, but it's the only one that I own a fine enough threading insert to cut these 1.600-36TPI threads with.

Next up, turning the OD down to the major bushing diameter and the major thread diameter for the shutter. The bushing diameter needs to be larger than the thread major so there is a positive stop against the shutter barrel, but small enough that the shutter retaining ring will thread on over it. I chose 1.825", it's a nice round number and the 1.915"-40TPI threads will slide over it.

It's a thousandth oversize...that's OK. Will just need the thread crests filed a smidge to bring them down after cutting the thread, it'll come off during the deburring.

Time to set up the OD threading tool, it's kind of a pain because we're threading up to a shoulder and the thread infeed depth is really tiny for these 1.775-48TPI threads. My eyes are starting to go the other way from my -5.50 prescription, I'm down to -5.25 and as I loose some more weight I figure they'll keep changing, so I kinda did this half blind.

Not too bad, the shutter starts to thread on here. Needed another 0.002" from here to thread on fully.

And there it goes. Nice and smooth, and locks up nice when the shoulder bottoms out. Much nicer than I figured the old crusty aluminum threads in the back of the shutter led me to believe it would fit, these old cast aluminum shutters don't thread that nice.

Next I need to measure and part off the bushing the correct length plus a few thousandths that I'll lap out, the parting tool sometimes will wander a smidge of a degree and leave a tapered face, so it's easier to just correct that taper than scrap the whole part.

Then, after parting of about 90% of the way through, I'll switch back to the threading bar and chamfer the inside thread, and then I'll finish that parting cut with the bar from the inside. That will help prevent the bushing from getting flung across the shop when the parting blade cuts through, and getting mangled in the process.

As another internet machinist says often, "Yahtzee!"

Next, I'll turn the front bushing. There's enough internal threads inside what's left to finish up the front bushing from here.

 

[David Lindquist]

Thank you very much!

David