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SURFACE HEIGHT GAUGE
A surface gauge is a measuring tool used to transfer measurements to work by scribing a line, and to indicate the accuracy or parallelism of surfaces.

a. Description. As shown in figure 3-45, the surface gauge consists of a base with an adjustable spindle to which may be clamped a scriber or an indicator. Surface gauges are made in several sizes and are classified by the length of the spindle. The smallest spindle is 4 inches long, the average 9 to 12 inches, and the largest 18 inches. The scriber is fastened to the spindle with a clamp. The bottom and the front end of the base of the surface gauge have deep V-grooves. The grooves allow the gauge to measure from a cylindrical surface. The base has two gauge pins. They are used against the edge of a surface plate or slot to prevent movement or slippage.

b. Adjustment.
The spindle of a surface gauge may be adjusted to any position with respect to the base and tightened in place with the spindle nut. The rocker adjusting screw provides for the finer adjustment of the spindle by pivoting the spindle rocker bracket. The scriber can be positioned at any height and in any desired direction on the spindle by tightening the scriber nut. The scriber may also be mounted directly in the spindle nut mounting, in place of the spindle, and used where the working space is limited and the height of the work is within range of the scriber.


c. Setting Height on a Surface Gauge.
To set a surface gauge for height, proceed as follows:

(1) Wipe off the top of a layout table or surface plate and the bottom of the surface gauge.
(2) Place the squaring head of a combination square on a flat surface as shown in figure 3-46.

NOTE : If a combination square is not available, use a rule with a rule holder. A rule alone cannot be held securely without wobbling, and consequently an error in setting generally results.

(3) Secure the rule in the squaring head so that the end of the rule is in contact with the surface.
(4) Move the surface gauge into position, and set the scriber to the approximate height required, using the adjusting clamp that holds the scriber onto the spindle.
(5) Make the final adjustment for the exact height required with the adjusting screw on the base of the gauge.


d. Care of Surface Gauge.
Observe the following practices for the care and upkeep of surface gauges:

(1) Coat all metal parts of the gauge with a light coat of oil to prevent rust.
(2) Carefully store the gauge in the separate container provided by the manufacturer.
(3) Do not drop any surface gauge. Small nicks and scratches can result in inaccurate measurements.
(4) Protect all pointed parts from damage.