Dial Indicator Myths


I was surprised at the reaction to yesterday's dial indicator ruminations by Erik and myself.  At first, I figured the critics might have thought they were visiting the Neanderthal Haven.  Then I remembered that dial indicators aren't power tools, and their invention was roughly contemporary with the invention of the Bailey pattern plane, though the AGD standard was not set until 1945.  Dial indicators have long been the measurement workhorses of industrial production.  They are accurate, rugged, versatile, convenient to use, and relatively inexpensive.  The transfer of indicators from industry to home use is no more surprising than the fact that high quality table saws are now affordable (and owned by most posters in this group).

It is not my purpose to convince anyone to run out and buy a dial indicator.  There is no woodworking end they assist that cannot be accomplished by other means.  Mine only sees occasional use.  There seems to be a fair amount of misunderstanding about their use, so I offer the following myths and reality checks to the open-minded and patient.

Myth:  Indicators are expensive.
Reality:  Many indicator/jig assemblies designed for woodworking are quite expensive, but you can accomplish the same tasks with a $15 Chinese indicator and jigs cobbled together from the scrap pile.  Accurate vernier calipers are available for as little as $20.

Myth:  It would be stupid to measure the length of a board to .001" accuracy.
Reality:  Indicators are not used to measure board length or width; that would be stupid.  Indicators are used for machine adjustment and the occasional tight tolerance set up.  Sometimes small errors in table saw, jointer, and planer settings cause large errors in your work.  People who use non-indicator methods to properly set up their machines have already achieved .001" accuracy (without being aware that they were anal retentive); they just took longer to do it.

Myth:  Indicators are a waste of time.
Reality:  Indicators save time and wood.  For example, you don't need to mill extra stock for the tap dance required to properly set up cheek cuts on the table saw.  You can just cut the first tenon intentionally thick, measure it and your (presumably) consistent mortise cuts with the caliper, use the indicator to reset the fence, and cut all your tenons with confidence.

Myth:  Minor misalignments don't matter since I sand or plane joints flush anyway.
Reality:  You would be surprised at how much faster assembly and finishing goes when all the pieces fit together smoothly and align properly.

Myth:  Accuracy isn't important since wood moves with moisture changes anyway.
Reality:  The goal isn't control of short or long-term workpiece thickness or width.  The goal is easy and quick achievement of tight joint tolerances at assembly time.

Myth:  Ultimate accuracy doesn't matter; it is only important that multiple pieces be cut at the same time with the same machine setting to ensure matching dimensions.
Reality:  Anyone who hasn't come across the need to repeat a machine setting later in a project either has too many machines lying around or hasn't been working wood for long.

Myth:  The methods I use are the only proper way to work wood.
Reality:  Get a life.  I would rather spend time expanding my knowledge of woodworking instead of converting others to my narrow-minded methods.  If you think you've learned everything there is to know, stop visiting this forum.

Myth:  The discussion of esoteric woodworking or engineering minutia is a waste of time.
Reality:  People who can identify and avoid information that will never be of use to them should use their time machines and omniscient powers to stop war and solve world hunger.

Sorry about the last two; it's late.  I mean no offense.  Happy woodworking, however you prefer to do it!

Dave Wright -


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