Digital height gauge.
Digital calipers are very cheap these days. I paid £6.99 for a set from Arc Eurotrade. At this price it is worth considering adapting them for other uses. In this project they are converted into a digital height gauge. I use it quite often rather than using a scribing block since it is easier to set and more accurate in use.
It is easy to dismantle these calipers. There are just 4 screws on the back of the display panel and two screws on the end stop. Once the end stop is removed the jaws with the scale can be slid off. There is a bronze spring strip that will then drop out of the display panel.
It is easy to dismantle these calipers. There are just 4 screws on the back of the display panel and two screws on the end stop. Once the end stop is removed the jaws with the scale can be slid off. There is a bronze spring strip that will then drop out of the display panel.
This photo shows the parts after dismantling and after cutting the jaws off. These jaws are hardened but not so hard that they cannot be cut with a junior hacksaw and filed with needle files. For this project it is important not to destroy or damage the machined face on the jaw attached to the display. This is the leftmost face of the cut off jaw in the above photo. This machined face is a reference face to which a new jaw will be clamped. Most of the depth gauge part of the scale has also been cut off but leave a little since this centres and guides the display on the scale.
This is the base. It was machined from 15 mm hot rolled steel. Hot rolled steel is better for this sort of application than bright mild steel since it is much less likely to distort when the block is machined. A 3 mm slot has been milled, as shown, to accept the end of the caliper scale.
The scale is assembled to the base using epoxy resin. The scale must be assembled exactly perpendicular to the base. Note the protruding tang. The bottom surface of this tang is the original surface of the caliper jaw that has not been cut or machined.
This photo shows the new jaw and clamp. The jaw was cut from 1/8" x 2" mild steel and then case hardened. The upper surface of the protruding tang must be exactly parallel to the bottom surface of the jaw. The tip of the jaw is sharpened to a knife edge so that it can be used as a scriber.
The completed height gauge. The upper surface of the tang on the jaw must be placed against the lower surface of the tang protruding from the display. When the jaw is lowered onto the surface plate then there should be no gap.