Post by PeterW on Dec 24, 2006 12:07:09 GMT -5
Hi all,
Just finished repairing a quite nice little 6x6 folding Balda Baldix from the early 1950s. Its got an f/4.5 Baltar len, obviously bought-in but I don’t know who made it. The shutter is a Prontor S, 1 sec to 1/300 sec. When I got it the shutter dragged on its slow speeds, nothing unusual, and a CLA cured it. Cosmetically the camera’s very nice, hardly a mark.
BUT, and this is why only some nut like me would take it on, the rivets holding the shutter mounting panel to the lens standard uprights had been removed and replaced with nuts and bolts that were far too small. The shutter wobbled all over the place. Don’t ask me why the rivets were removed, I’ve no idea. Everything looks square, no signs of the lens standard having been bent and straightened, and the door closes easily and sits square. I don’t think it has been dropped and damaged, so the reason remains a mystery.
Rivets in this position on folders are almost always shouldered. The holes in the shutter panel are smaller than those in the uprights, so a shouldered rivet can be clinched up tight without squashing the two pieces of metal so tight that they don’t move freely. After all, the panel’s got to swing to fold and unfold the camera.
I pondered over turning up some new rivets from a piece of *nickel-copper-zinc alloy bar, but the shoulder would have to be so narrow, 1mm plus a thou or two for clearance, and I don’t think the headstock bearings on my rather ancient instrument lathe are not quite up to minus 0 plus 2 thou sort of precision nowadays, and my Boley watchmaker’s lathe won’t take anything approaching that sort of diameter.
So I cheated. The larger holes in the uprights were just a shade under the diameter of a 4BA bolt, and the smaller holes in the shutter panel were just a shade under the tapping size for 4BA. Aha! I opened up the holes in the uprights with a reaming broach till a 4BA bolt was a nice snug fit, then opened out the holes in the shutter panel to 4BA tapping size and cut a 4BA thread in them. Only enough metal to get about two threads, but enough to help lock a nut on the inside.
There wasn’t enough clearance between the panel and the shutter to fit a full width nut, so I filed a couple of nuts down to half thickness and screwed it all together. It felt fine, so I undid it and put some two-pack epoxy inside the nuts, did them up and backed off the bolts just enough to let the panel swing. I waited till the epoxy had set and put the shutter back on. The shutter feels nice and firm, the self erecting mechanism works a treat and the lens looks nice and square to the body. I haven’t run a film through to check it, but the lens checks out OK on infinity. Yes, I know that the panel is pivoting on the bolt threads inside the uprights and not a plain shoulder, and that’s not ideal engineering, but with the amount of use its likely to get I don’t think wear on the bolts is going to be an issue. Total cost about 15p (roughly 30 cents), and although it’s not original it looks quite smart. Maybe it would have looked a shade better if I’d used bolts with a thin cheese-head and not domed, but I hadn’t got any in my box.
Tip: In case anyone ever needs to thin down a nut or a washer there’s an ancient and very simple way to hold the nut or washer and keep the file square. Take a small block of soft wood, pine or similar, squash the nut or washer halfway into it in the vice, then clamp the block of wood in the vice with the nut or washer on the top. It will stay there while you file it down, and if you hit the wood one side with the file you’re rocking it instead of holding it flat. See my little sketch.
*Nickel-copper-zinc alloy is commonly known as nickel-silver. Very useful stuff for making bits for vintage and antique cameras. It’s easy to work and polishes up just like nickel plate.
Here’s a pic of the job and a sketch about thinning nuts or washers.
PeterW
Just finished repairing a quite nice little 6x6 folding Balda Baldix from the early 1950s. Its got an f/4.5 Baltar len, obviously bought-in but I don’t know who made it. The shutter is a Prontor S, 1 sec to 1/300 sec. When I got it the shutter dragged on its slow speeds, nothing unusual, and a CLA cured it. Cosmetically the camera’s very nice, hardly a mark.
BUT, and this is why only some nut like me would take it on, the rivets holding the shutter mounting panel to the lens standard uprights had been removed and replaced with nuts and bolts that were far too small. The shutter wobbled all over the place. Don’t ask me why the rivets were removed, I’ve no idea. Everything looks square, no signs of the lens standard having been bent and straightened, and the door closes easily and sits square. I don’t think it has been dropped and damaged, so the reason remains a mystery.
Rivets in this position on folders are almost always shouldered. The holes in the shutter panel are smaller than those in the uprights, so a shouldered rivet can be clinched up tight without squashing the two pieces of metal so tight that they don’t move freely. After all, the panel’s got to swing to fold and unfold the camera.
I pondered over turning up some new rivets from a piece of *nickel-copper-zinc alloy bar, but the shoulder would have to be so narrow, 1mm plus a thou or two for clearance, and I don’t think the headstock bearings on my rather ancient instrument lathe are not quite up to minus 0 plus 2 thou sort of precision nowadays, and my Boley watchmaker’s lathe won’t take anything approaching that sort of diameter.
So I cheated. The larger holes in the uprights were just a shade under the diameter of a 4BA bolt, and the smaller holes in the shutter panel were just a shade under the tapping size for 4BA. Aha! I opened up the holes in the uprights with a reaming broach till a 4BA bolt was a nice snug fit, then opened out the holes in the shutter panel to 4BA tapping size and cut a 4BA thread in them. Only enough metal to get about two threads, but enough to help lock a nut on the inside.
There wasn’t enough clearance between the panel and the shutter to fit a full width nut, so I filed a couple of nuts down to half thickness and screwed it all together. It felt fine, so I undid it and put some two-pack epoxy inside the nuts, did them up and backed off the bolts just enough to let the panel swing. I waited till the epoxy had set and put the shutter back on. The shutter feels nice and firm, the self erecting mechanism works a treat and the lens looks nice and square to the body. I haven’t run a film through to check it, but the lens checks out OK on infinity. Yes, I know that the panel is pivoting on the bolt threads inside the uprights and not a plain shoulder, and that’s not ideal engineering, but with the amount of use its likely to get I don’t think wear on the bolts is going to be an issue. Total cost about 15p (roughly 30 cents), and although it’s not original it looks quite smart. Maybe it would have looked a shade better if I’d used bolts with a thin cheese-head and not domed, but I hadn’t got any in my box.
Tip: In case anyone ever needs to thin down a nut or a washer there’s an ancient and very simple way to hold the nut or washer and keep the file square. Take a small block of soft wood, pine or similar, squash the nut or washer halfway into it in the vice, then clamp the block of wood in the vice with the nut or washer on the top. It will stay there while you file it down, and if you hit the wood one side with the file you’re rocking it instead of holding it flat. See my little sketch.
*Nickel-copper-zinc alloy is commonly known as nickel-silver. Very useful stuff for making bits for vintage and antique cameras. It’s easy to work and polishes up just like nickel plate.
Here’s a pic of the job and a sketch about thinning nuts or washers.
PeterW
