Topcor lens, help

Lightshow · Joined: 04 Nov 2011 Posts: 3666 Location: Calgary

Anyone recently open up one of the 3 Topcor lenses that have the arm? 3.5cm, 5.8cm,& 100cm.
I'm about to dig in to my new 3.5cm and it's been a while since I opened up the 5.8cm, and it's not separating like I was expecting, so rather than going in blind, I'm pausing in the hope of get an idea of how both ends come apart, it's in better shape than I thought and don't want to make things worse.
Thanks in advance.

tomasg · Expire: 2014-04-28

Unfortunately i have no experience with those variants of the Topcors, but i wanted to say kudos to you, an experienced lens tinkerer stopping and asking for help.

Tomas

Lightshow · Joined: 04 Nov 2011 Posts: 3666 Location: Calgary

Lightshow · Joined: 04 Nov 2011 Posts: 3666 Location: Calgary

vivaldibow · Expire: 2021-03-09

tomasg · Expire: 2014-04-28

visualopsins · Expire: 2025-04-11

Make a tool using pvc pipe & some rod stock?

fiftyonepointsix · Joined: 30 Apr 2017 Posts: 292

The Nikkor-SC 5cm F2 in Leica Thread Mount requires a tool similar to this to remove the rear group.

I cut up an old Tripod Tubular Leg (broken), the folding legs gave different sizes. One of them worked.

Look around the house, or in the hardware shop.

Lightshow · Joined: 04 Nov 2011 Posts: 3666 Location: Calgary

tomasg · Expire: 2014-04-28

John Shriver · Joined: 24 Dec 2009 Posts: 199

The RE Auto-Topcors up to 100mm focal length are all similar. The focusing helical is all aluminum. The aperture mechanism is in the form of a cup, with the bottom near the rear of the lens. It is made of black anodized aluminum. The front and rear optical blocks are connected to the aperture mechanism. The rear optical block screws into the aperture mechanism. The front optical block is held by a retaining ring.

The aperture mechanism and the two optical blocks are held into the focusing helical by an outer retaining ring. You want to remove the rear lens mount before you pull the aperture and optical block. That's because it has a fork and rod that engage with the aperture mechanism. You also want to remove the filter ring first, and perhaps the front sleeve, to get better access to that retaining ring.

If you have to disassemble the aperture mechanism to clean the leaves, make a scribe mark on the front ring and side of barrel, as the exact rotation of that front ring calibrates the aperture. It's held by three set-screws.

Infinity focus is collimated by a selected (and possibly hand-filed) spacing ring between the aperture mechanism and the focusing mount.

Lightshow · Joined: 04 Nov 2011 Posts: 3666 Location: Calgary

My request has nothing to do with the RE series, thanks anyways for the effort.

John Shriver · Joined: 24 Dec 2009 Posts: 199

Oh, I didn't see "with the arm". The original Auto-Topcors.

I've done some work on the R. Topcor 135/2.0 and 300/5.6, and you just start taking things off starting at the rear. They don't have modular optical blocks like the F. Auto-Topcors and RE. Auto-Topcors. But the Auto-Topcors may still have that modular design, since they need to be able to quickly release the aperture when the plunger is pushed.

If it's easy to remove the rear mount, have a look in from that point of view. You would see the bottom of the cup of the aperture mechanism if they are similar. There's a keyway that controls it's alignment in the focusing helical.

Lightshow · Joined: 04 Nov 2011 Posts: 3666 Location: Calgary

I've already removed all the visible screwson the mount and it's still not budging, I'm sure the optics have to be removed from the front which will expose internal screws that secure the mount to the body. I just have to come up with a way to remove the optics without damaging anything.