One of the pieces of equipment I built when setting up my optical shoo
was a Pitch Hardness tester. Thougn it looks no different to other testers
it differs in detail ono is simpler to use. The illustrations below
show its outside appearance an inside detail.
Referring to the drawing:- The spring (7) is slipped over the (8) and
the pin inserted in the sleeve (3). The collar (5) is a light press
fit in the sleeve and is pushed down until the spring is compressed
a little. This assembly is then inserted through the top frame and the
pin through the weight until the sleeve (3) bottoms in the hole in the
weight. The weight is then locked to the pin with the grub screw. Sleeve
(4) is Loctited in the upper frame. The locking screw (10) clamps onto
the sleeve (3). The dial gauge is a firm push fit in sleeve (3) and
is pushed in untl the needle has made two to three revolutions of the
dial. Do this so the needle and the zero are at the top of the dial.
It looks better.
In operation the dial gauge is first set at zero. Once set it needs
no further adjustment. The weight is raise with the fingers and the
sample of pitch to be tested is placed under the needle. The weight
is let down so that the point touches the pitch, and the screw is tightened.
The dial gauge then reads the distance the point sinks into the pitch.
I measure this over a minute. The point will start to sink as soon as
the needle touches the surface of the pitch. but the gauge will not
start reading until the screw is tightened. I dribble pitch off the
stirrer to fill a bottle cap. I allow this to cool to room temperature
even cooling it under a water tap before conducting a test. I use it
as a comparitor having found from experience how hard I want the pitch.
Click image to view larger picture.