The results over time of over oiling a rotary dial

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If anyone is still working on dials, cleaning and re-lubricating them, this will show why putting too much oil on the dial mechanism, or just adding oil to a slow dial, is not the best thing to do.

I just opened up this WE 500 from the early 1960's that has a 7D dial. From markings on the dial, it was field serviced in the late 1960's. Upon testing as removed from its storage box, it was running at 9.3 PPS.

After removing the plastics and the leaf pile up, first thing I noticed during a visual inspection was the pile of oily crud that was case off of a large diameter middle gear onto the brass spacer/ferrule holding the top and bottom gear cage apart, the red circle in the image below. There was so much extra oil added to the dial that the centrifugal force of the gear spun the excess crud off of the gear.

Looking closer, it was seen that every gear was filled with the black oily crud (yellow arrows) and the surfaces of non-gear parts were covered with the greasy, black crud (blue arrows).

If you look at the top cage plate, at the green/white arrow, you can see a piece of dust or lint that was captured by the oily surface crud. This is what happens with the gear teeth, they collect the lint if the oily crud and the adjacent gear pushes it deep into the mating gear. That creates, over time, a buildup in the root of each gear tooth and gets so thick and hard that it can prevent the gear train from moving, it stops the gear.

As the crud in the root builds up, the dial speed slows down. Thinking that adding more oil to the gear mechanism will increase the speed is wrong. In fact, adding more oil to a crudded up gear train will create more crud in the root over time.

The only way to get hard crud out of every gear root is to use a round tooth pick, or similar item (not metal), to break up the hard, packed crud followed by cleaning with lacquer thinner (and a brush, like a tooth brush) to fully clean the the gear surfaces and teeth. Then, the dial can be lubricated and the dial speed checked. Cleaning and lubricating usually brings the dial speed back into spec without having to adjust the governor.

After cleaning and re-lubricating this dial, I will post a reply with the "clean" dial speed.

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Took the dial apart for thorough cleaning. That black clump of cast off oil turned to tar. The clump was similar to axle grease and it didn't dissolve in lacquer thinner.

Actually, the plates and gears were covered with the same stuff. Every part I picked up literally stuck to my fingers.

Needed to use a round toothpick to clean out all of the gear roots before using an old tooth brush and lacquer thinner to nicely clean all parts.

These are the parts before cleaning. I'll put it back together tomorrow and check its speed.

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I forgot about posting an update on this dial so here it is.

After taking the dial apart, cleaning it and properly lubricating the dial parts during re-assembly, the dial speed came in at 10.63 PPS. That's typical of a dirty, slow dial that was field serviced by adding lubrication and speeding up the governor. This dial was adjusted to a dial speed of 10.01 PPS.

This is usually the case when cleaning a dirty, slow dial (a slow dial that is not dirty usually indicates a dial in which its lubricants have dried up over time - this type of slow dial after cleaning and proper lubrication will speed up to about 10 PPS, no governor adjustment will be needed).

Adjusting the governor without removing the gunk that is slowing it down will result in a dial speed greater than 10 after the dial is cleaned and lubricated.

I just cleaned another dial (a very dirty 1940 5H dial that had a 56L field lubrication yellow stamp on the Governor case) that as found was testing slow at 9.25 PPS. Complete disassembly, cleaning and proper lubrication on re-assembly resulted in a dial speed of 10.64 PPS. Adjusting the governor resulted in a good dial speed of 10.05 PPS.

This is the 5H dial as found, full of crud.