Civil Engineering Reference
In-Depth Information
Fig. 5.13. If you wobble off the bar through the main bearing hole you can find its
centre.
Toolmaker's buttons
Another method of setting the datum of a workpiece is by using toolmaker's
buttons. Toolmaker's buttons are readily available on places like eBay, but
they are also easy to make.
They are literally a turned tube counterbored to take a screw to screw them
to the workpiece. You set the buttons using micrometers and/or spacers so
they are the correct distance apart or from one edge of the workpiece. Then
you put the workpiece into the milling machine vice and clock up the outside
of the button with a lever dial test indicator. Then you can proceed to drill,
bore or whatever at the position of the toolmaker's button, and then move to
the next button and so on.
Hollow toolmaker's buttons are similar to normal toolmaker's buttons, but
they are longer and the internal counterbore is dead true to the outside of the
button. These are useful when the buttons are placed too close together to
allow a clock stylus between buttons, as they allow you to clock the inside
diameter of the button.
