Saturday, March 7, 2020

Tumico Disassembly

Had some extra attention to apply to the Tumicos.  And the soaking time has mostly done it's thing.

For working in the house on stuff, I built this little table to hold my projects.  I painted it with Ford Gray implement paint from Tractor Supply.  That puts a nice hard shell finish on that is like the s,W&W commercial.

It's a 2x2 piece of 3/4 inch plywood, BC sanded.  I got some quarter round, glued and nailed around the edge for a fence.  I find it easy to clean off any mess that gets on it, since it's so slick.  That can cause some of it's own issues, though.  So I used pot scrubbers as pads to keep small objects from running away.  I get them at a restaurant supply house in town.  Way cheaper than name brand Sctochbrite pads and they double as abrasives.  They even have some really coarse ones for digging out hard pack goop.

So, the disassembly went well, except for a few little issues:  The ratchet on the 3 inch is stuck fast, and the spindle won't thread back in on the 2 inch.  They are heading back to the can for an extended soak, so maybe that will help on the ratchet.  I may need to work up a 40TPI tap for the spindle.

Cleaned up, out and a bit of polishing on the spindle

The lighter fluid was a pretty good, light solvent.  I like it better than alcohol or acetone.  The smell reminds me of my 8th grade science teacher.  Mr. Hale had been a Marine tanker in Korea.  He could flip-light his zippo with ease.  He walked out side on the porch to smoke between classes.  I really enjoyed his company.  He was a real man you could look up to, emulate, even.  Good memories.

The ratchet mechanism on the two I got apart kept the spring.  I don't know if it's supposed to be captive, but it is.  I had a sewing needle for a proboscis to try and ease them out.  No dice.

Slime in the tapped hole, and a captive spring in the recess to the left

That little steel pin is amazingly tiny, and the end is shaped to work on the saw tooth on the bottom of the ratchet.  Neat in concept and execution. 

There was some real pitting and corrosion on one spindle.  I worked it on the pot scrubbers a bit, light pressure, until it smoothed out to the touch.

I didn't notice any drag when I disassembled them, but the one inch felt tight only .200" inch from closed.  I cleaned it out again, and it went easy.  It's close to being on the spot.

About .0005" off.  That knurled ring on the left is supposed to allow you to adjust the mic to zero.  But on all three mics, they aren't moving very much and the tubes are stuck in the frames.  It may take heat, or John in Philly said I should consider freezing cycles.  I can get dry ice down the street at the grocer, so that may be the next go round.  I figure it'd be pretty cool to try... I couldn't resist.

So back in the bath for a few days.  And then we'll start working on the rest of the stuck parts.

For your edification, I present a film.... with these exact models of mic.  I love how things come together like this. 


  1. Measure the OD of the thread the best you can and I'll check my tap supplier and see if I have something in stock you can use to chase the threads with.

    1. Spartan-C I really appreciate the offer.

      Near as I can tell, the minor diameter is .270" and the major is .285" Looks like a 5/16 - 40??

      Again, thanks for checking for me.

    2. The next dozen attempts ran from .260" to .265". Ugh....

  2. I went downstairs to check my memory, and I found that the knurl you referred to in the lower photo isn't in the same location on the two mics that have knurls, and on my mics the knurl is to temporarily lock a reading.
    I know there is a process for resetting the mic, but I would have to blow a bunch of cobwebs away, and probably end up looking it up online.