Washer between front cell and shutter

[Songyun]

I know that the washer/spacer is creating the proper distance between front cell and shutter (or say the rear cell)
I was trying to change a shutter (modern copal), but when I unscrew the front cell (with the washer), and put it on another shutter(modern copal). The letter on the barrel turned a certain degree clockwise/counter clockwise. Does that mean the space between the front cell and shutter changed a little bit? (both are modern copal shutters made in the late 90s), Will that change the distance between front and rear cell?

[Paul Ewins]

It might, or it might mean that the thread starts in a different place. You really need to measure the overall length of the lens in the old shutter and then again with both cells installed in the new shutter. A cheap plastic micrometer should be good enough for this, but not a ruler or tape measure.

If the combination in the new shutter is longer than in the old shutter then the chances are that the front cell isn't going in far enough, possibly due to grit or thread damage. In that case try removing the shim washer and see if that gives you the correct overall length.

If the reverse is true, then its is possible that threads on the new shutter are machined a little longer, allowing the front cell to go too far into the shutter. Or indeed that there was a problem with the old shutter and that everything is OK with the new one.

[mrossano]

Measure the distance between the lens cell seating surfaces on either end of the shutter, using a hub micrometer. Compare the two shutters. If they haven't been screwed-with since manufacture, the measurements should be the same. The tolerances of late model Copal shutters are closer than your ability to measure, and much closer than the thickness of even the thinnest shims used by Rodenstock or Schneider.

To answer your original question, the change in position of the lettering means nothing.

[Songyun]

Measure the distance between the lens cell seating surfaces on either end of the shutter, using a hub micrometer. Compare the two shutters. If they haven't been screwed-with since manufacture, the measurements should be the same. The tolerances of late model Copal shutters are closer than your ability to measure, and much closer than the thickness of even the thinnest shims used by Rodenstock or Schneider.

To answer your original question, the change in position of the lettering means nothing.

Thanks!

[Ernest Purdum]

A machine shop can compare the two assemblies and remove all doubt.