The depth mic: Another multi-anvil tool

Despite the very different uses for a depth mic as opposed to an outside mandrel mic, the depth mic also needs a specific procedure in order to be set up properly.   The picture at left shows the three main parts of the mic, all of which need to be cleaned.  Pay special attention to the black collar at the top of the thimble (left) and the bottom of the collar on the anvil (or rod) on the right.  They’ll be in full contact with each other, so they have to be totally clean.

The second picture shows how you hold the mic assembly when you’re putting it together.  As you screw the cap down over the rod collar, rotate the rod with your bottom hand.  As the cap tightens, the rod will become more difficult to turn in some spots, but slightly easier in others.  That’s because the two collars aren’t perfectly flat.  What you’re after is to find the last spot in the rotation that tightens up.   Once you do, tighten the cap the rest of the way so the rod won’t rotate any more — but don’t over-tighten it.  Snug, or a little past snug, is just fine.  This procedure will line up the two collars the same way every time.

Finally, check the face of the mic (click the pic).  Make sure it’s clean and free of nicks or burrs, especially on the edges.  Once that’s done, the mic is ready to use.

Next time:  Indicators


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