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Hollis
14-Oct-2008, 08:29
Hey all, I have a large petzval brass lens, unmarked, that I am trying to get the front (or rear) group off so that I can have it mounted into a combo flange/lensboard (all one piece). It appears that someone has used a liberal amount of polish on it at some point in its recent life and it has locked the threads tight and I cant get them off. Does anyone have any suggestions as to how to get these to turn?


Hollis

vinny
14-Oct-2008, 08:45
Something like this will help.
http://www.cookmatesouthwest.co.uk/acatalog/Jar_Opener_Ratchet_Strap.html
Or saw the lens board down the middle on 2 sides with a coping saw and split it in half.

John Schneider
14-Oct-2008, 09:40
Two small strap wrenches should make quick work of it.

Gordon Moat
14-Oct-2008, 10:09
Sorbothane pad against which you can apply leverage by twisting, without causing any crushing force nor pressure on the barrel. You can find something similar in an art store in the screen printing supplies, in the form of a braying pad, which is a type of rubbery pad.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

W K Longcor
14-Oct-2008, 10:48
Since you have some "polish" goop that is down in the threads, you might need more than a strap wrench will do. Stop at an auto spply store for a spray can of "PB BLASTER" -- DO NOT spray it on the lens. (The stuff is great , but SMELLS really bad)Spray some in a can or small jar. Use a small brush to apply right on the thread area. Allow several hours to soak in. Apply several times. Then try the strap wrench. As long as the threads are not crossed -- it should come right off. Unless it is aluminum against aluminum -- then you are out of luck.

Hollis
14-Oct-2008, 11:47
ill give it a try. No, it is brass on brass. I tried a little WD 40 in the threads over the weekend but that didn't work.

H.

Chauncey Walden
14-Oct-2008, 12:46
I've had real good luck with running a drop of Break Free CLP around the joint followed by gentle tapping all the way around with the butt end of a plastic screwdriver. You might have to repeat over the course of a couple of days but it usually only takes hand pressure to unscrew it after that. The tapping is the key.

Keith Pitman
14-Oct-2008, 13:49
I have had good luck separating stuck components by placing the lens in the freezer for a half hour, then carefully heating one of the elements. Use something dry like a heating pad or hot towel for heat. The freezing/heating causes one side to contract and the other to expand.

goamules
14-Oct-2008, 13:58
I had trouble getting my brass Vitax apart for cleaning. CLP Breakfree is great, let it soak in for a few hours, add more, etc. The problem was gripping the 3 inch diameter lens. It just kept slipping in our hands. We also needed more leverage or torque.

So what worked for me: Cut two semicircles in the edges of two 2x4s or similar small boards, slightly larger than the lens body. You're basically going to make a hand vise. Line the cuts with inner tube to protect the brass. You want the cut to fit snug, but with a little gap between the boards so you can grip them together tightly. Make another set, of thinner wood to fit just the element section. Get a partner to hold the barrel tight with one set, as you grip the other and unscrew.

Skorzen
14-Oct-2008, 14:54
I have had good luck separating stuck components by placing the lens in the freezer for a half hour, then carefully heating one of the elements. Use something dry like a heating pad or hot towel for heat. The freezing/heating causes one side to contract and the other to expand.

This scares me, I don't know just how sensitive the glass in lenses is, but I know glass does not like rapid temperature changes.

lenser
14-Oct-2008, 15:29
My machinist buddy uses automotive brake cleaning spray to freee up almost anything. I would never allow it near a shutter, but letting it soak in to frozen threads for awhile and then using the previously mentioned strap wrenches should work just fine. If you don't want to risk overspray, just spray some into the cap and apply with a modeler's paint brush.

Keith Pitman
14-Oct-2008, 16:08
This scares me, I don't know just how sensitive the glass in lenses is, but I know glass does not like rapid temperature changes.


I knew it would scare you!

I'm not taking about "rapid" temperature changes, nor am I talking about extreme cold: my freezer is about zero degrees F. The heat is applied to the metal lens barrel, not the glass, and it's pretty moderate heat. The idea is to have one side expand while the other is contracted, and provide some room to turn them. I've done this with lenses, but also with glass bottles with stuck glass stoppers with no ill effects and quick separation of the stuck parts.

seawolf66
14-Oct-2008, 20:05
Also a pair of mgloves that have latex rubber on the palms, make holding thosed old big lenses and give you better grip than one Might think : Lauren

Jim Galli
14-Oct-2008, 21:40
I make "grips" out of cut pieces of old inner tube. At the auto parts store I buy a product called "rubber buffer." It is tri chloroethylene or something that sounds just as cancer causing. I pour it in the crack, then grab with the grips and apply a frighteneing amount of torque. This usually works.

Paul Fitzgerald
14-Oct-2008, 22:27
Hollis,

all of the above but try tightening - then loosening, all you need to do is break it free, it should unscrew after that.

good luck with it.

Hollis
15-Oct-2008, 18:06
Victory is mine! I was able to get the front and rear elements separated fairly easy once I went and bought a pair of rubber strap wrenches. It had soaked over the weekend with a bit of WD-40 so i guess that helped too. Once I had both the front and rear groups off, I decided to go one better and get the actual glass out of their captive state. Right as rain they came right out although one end needed a tiny tiny dab of PB blaster on the threads and 10 sec. later it was like silk. While I had it all apart I took a brass brush to the threads and got all the polish (looked like car wax) out of them and put it back together the correct way. Someone had the elements reversed at some point. Also, I found the only markings I have seen on this lens. They are on the sides of the glass and in handwritten pencil and are the letters 'R G'

Any ideas???

goamules
16-Oct-2008, 06:47
I knew you would eventually get it apart. The discovery of lettering is a fun find, but I cannot think of any RG meaning. Any other indications of age, or quality? This one has a waterhouse slot, right? Beading around the rims? Belled or straight shade? I think most makers put their mark, but this one could have been for "outsourcing" and never marked.