TS-Aligner Jr. and TS-Aligner Jr. Lite both use a standard dial indicator with 0.001" resolution for all measurements. The Angle Attachment Gage is used when making angle measurements. This device uses the change in distance over two fixed points to calculate the resulting angle. On TS-Aligner Jr. these two fixed points are precisely one inch apart. So, the theoretical measurement resolution is limited by the resolution of the dial indicator (0.001") and the distance between the two fixed points (1.000"). So, the smallest angle that can be measured is calculated by using the following formula:

Tan(0.001")/1.000" or 0.057 degrees.

Achieving this accuracy depends on careful calibration. The dial indicator must be tilted so that a square surface reads exactly one inch and a 45 degree surface reads exactly zero inches. We accomplish this at the factory by using a precision angle block and a Toolroom Grade B granite surface plate. Each and every unit is calibrated separately. A set screw limits the tilt of the dial indicator and provides a reference so that it can be removed and replaced without losing calibration.

Minor variations in parts, including the dial indicator, can affect the accuracy of TS-Aligner Jr. However, the calibration procedure compensates for these minor variations. So, once a unit is calibrated, the individual parts are no longer interchangeable. If any of the parts are replaced, the calibration procedure must be performed again to restore accuracy.

In order to characterize the accuracy of TS-Aligner Jr's angle measurement ability, I performed an experiment. It consisted of 10 trials of blade tilt settings (as shown above) using a stock TS-Aligner Jr. with the Angle Attachment Gage only (no angle blocks, just the AAG).  Actual cuts were made and error for each cut was recorded.

Experimental design:

The unit chosen for the test was randomly pulled from stock.  The angle chosen was 30 degrees so that it would be easy to measure and would not be at one of the two calibration points for the Jr. (90 and 45 degrees).  Angle measurement involved using a 30 degree angle block with less than 0.0001" error (confirmed) as a reference.  Error from each cut was measured using a Mitutoyo test indicator with 0.0001" graduations.  The saw used was a 10+ year old Unisaw that's seen heavy use.  The blade used was a Systi-Matic 10" TCG for composites and non-ferrous metals and has been used on this saw to cut thousands of pounds of aluminum.  The wood used was particle board (because it was there, it's cheap, and I don't have a huge scrap pile from doing test cuts all the time).  The board was 2.5" wide by 3/4" thick.

Experimental procedure:

Each trial started with the blade tilted to approximately 90 degrees (vertical).  TS-Aliger Jr. was then used to set the blade tilt to 30 degrees. According to the chart in the manual, this corresponds to a reading of 0.423" on the dial indicator.  No attempt was made to measure or otherwise compensate for the flatness of the blade.  Blade rotational position for each trial was not controlled (measurements were made wherever the blade happened to stop after the previous trial).  I then cut a piece of wood using my sliding table as a guide.  The resulting cut was measured and error was recorded as total deviation from 30 degrees (total indicator reading (TIR), not +/-).  The blade tilt was then returned to 90 degrees in preparation for the next trial.

Results:

 

Mean:   0.0011
Median: 0.0011
Mode:   0.0012
Range:  0.0023
Standard Deviation: 0.0007

The results are quite impressive. It demonstrates not just how accurately TS-Aligner Jr. can measure angles, but also how those measurements can translate into very precise results. Certainly, equipment and proper technique (or, lack thereof) will influence the results so your mileage may vary.