Measure Distance/Angle

Two axis readouts give you the two legs of a right triangle. The numbers a print is usually dimensioned in are the other two: the straight-line distance between the features, and the angle of the line joining them. Getting from one pair to the other is a square root and an arctangent, which is not work to be doing at the machine with a part clamped up.

The "Measure Distance/Angle" function does that arithmetic and keeps doing it as you move. It is available on a milling machine and on a lathe, and reads the two axes that lie in the machine's working plane: X and Y on a mill, X and Z on a lathe.

Taking a Measurement

The dialog measures from the current origin to the current position. It has no capture buttons and holds no stored points, so the origin is what marks the first end of the measurement.

  1. Position the machine at the first feature and zero the axes.
  2. Move to the second feature.
  3. To open the dialog, press the "Measure Distance/Angle" button in the function strip.

The order does not matter, and the dialog can be left open while you move. Every number in it will follow the machine live, which makes it usable the other way round as well: open it first, then jog until the distance or the angle reads what the print calls for.

Because the origin is one end of the measurement, an active sub-datum is a convenient first point. Activating a saved hole puts the origin at its center, and the dialog then reads the distance and angle from that hole to wherever the spindle is.

What the Dialog Shows

The dialog is a list of five values beside an illustration of the triangle they describe, with a units selector underneath. The illustration follows the machine type, so it is drawn against a mill's table or a lathe's spindle axis.

The Two Legs

The first two rows are the axis distances, labelled "X" and "Y" on a mill and "X" and "Z" on a lathe. They are the same numbers the axis rows behind the dialog are showing.

Distance

The row labelled "Distance (d)" is the straight-line distance between the two points, which is the hypotenuse of the triangle the two legs make.

The Two Angles

The two angle rows describe the same line measured from either leg, so they always add up to 90 degrees. On a milling machine, "Angle ɑ" is measured up from the X axis and "Angle θ" from the Y axis. On a lathe, "Angle ɑ" is measured from the Z axis, which makes it the half angle of a taper between the two points, and "Angle θ" is measured from the cross slide.

The lathe reading is directly useful for setting the compound. A taper cut between two known diameters gives an "Angle ɑ" that can be typed into the "Compound Slide Angle Compensation" dialog.

Units

The "Units" selector switches the three distance rows between inches and millimeters. It belongs to the dialog and does not change the units the axis rows are displaying, so you can check a metric drawing on an imperial machine without disturbing the readout. It starts on whichever units the application is configured to default to.

Diameter Mode on a Lathe

On a lathe with the X axis in diameter mode, the "X" row in this dialog shows the diameter reading, matching the axis row behind it. The distance and the two angles are worked out from the actual cross slide travel instead.

The two have to differ, because a diameter reading is the cross slide movement doubled, and doubling one leg of a triangle and not the other does not turn the triangle. It produces a different triangle. Two points a tenth apart in each axis would measure 0.2236" and 63.43 degrees instead of 0.1414" and 45 degrees, and the 63.43 degrees would correspond to no angle on the part at all.

The legs stay as the readout shows them so the dialog agrees with the numbers you have been reading, and the geometry is computed from what the scales actually measured so the angle is the angle on the part.