The part at _r_ should be about 3/16" long and only
reduced in size enough to fully remove the screw threads shown at _t_.
[Illustration: Fig. 174]
[Illustration: Fig. 175]
[Illustration: Fig. 176]
[Illustration: Fig. 177]
We next provide a sleeve or guard for our gage. To do this we take a
piece of hard brass bushing wire about 1/2" long and, placing it in a
wire chuck, center and drill it nearly the entire length, leaving, say,
1/10" at one end to be carried through with a small drill. We show at
_F_, Fig. 174, a magnified longitudinal section of such a sleeve. The
piece _F_ is drilled from the end _l_ up to the line _q_ with a drill of
such a size that a female screw can be cut in it to fit the screw on the
needle, and _F_ is tapped out to fit such a screw from _l_ up to the
dotted line _p_. The sleeve _F_ is run on the screw _t_ and now appears
as shown at Fig. 175, with the addition of a handle shown at _G G'_. It
is evident that we can allow the pivot _s_ to protrude from the sleeve
_F_ any portion of its length, and regulate such protrusion by the screw
_t_.
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