Haltbare Rollen für Jobo CPA/CPP

The Jobo CPA/CPP processors are good devices for developing photographic papers and films. I bought one second-hand many years ago and use it to develop colour films and sheet films. The processor is largely plastic, but solidly built and does its job without major problems.

However, the unit is not sufficiently dimensioned for the large and heavy drums in two respects. The first is the lever of the lift with which the drum is lifted for emptying. The second weak point is the rollers that support the drum. They have no real bearing but only two plastic pins that turn in the roller bracket. The heavy weight of the drums cannot be withstood by the axle support of the roller block and it increasingly loses its shape.

There are replacements for the lever and the roller block, but they are not permanent solutions. You can prevent damage to the lever by taking hold of the end of the drum and lifting it. To find a better solution for the roller block as well, I replaced the plastic rollers with ball bearings with a steel axle.

For a first attempt I used ball bearings, screws and nuts made of industrial steel. I expected everything to rust quickly, and already after the first use it did. The rust made the drums run a bit rough, but against all expectations I was able to work with it for one and a half years before one of the bearings started to jam. This is probably caused by rusting balls in the bearing.

I therefore bought stainless steel ball bearings, screws and nuts some time ago. Unfortunately I didn't find any stainless steel bearings with a small inner diameter, so I had to mount them on an M8 bolt. The bearings are held by narrow stainless steel nuts, so the whole bearing still fits into the roller block. Because of the thick screws it was necessary to mill out the recess in the roller block a bit.

For the production you need

  • 4 Stainless steel ball bearings, 8x19x6 mm
    (The dimensions of the ball bearings are inside diameter x outside diameter x width)
  • 2 Stainless steel screws M8x30
  • 6 narrow stainless steel nuts M8
  • a small hand mill for expanding the roller block

The cost of materials is about 25 €.

Wider bearings would actually be better, but narrow ball bearings are easier to find. Probably two of them are enough, but at the low cost you don't save much.

I have been using these rollers for half a year now. They do not rust and run smoother than the castors of my first solution. They are a little louder than the plastic castors, but you don't have to worry about them wearing out.


Have fun putting it together!

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