3 
one. The same procedure is followed to adjust the two Y lead 
screws on a plane parallel to the reference plane. 
(c) Adjustment of the position of the two main A guide tubes, 
(d) Adjustment of the position of the two measuring X screws always 
using the same precision rod. These last two operations are 
made following criteria completely similar to the preceeding 
ones, keeping the frame fixed and moving the comparator 
equipment along a side of the reference plane. 
(e) Adjustment of the position of the A" and Y. support tubes. 
To carry out the operation regarding the X supporting tubes 
(in fig. 1 this case is reproduced) the same procedures of (c) 
and (d) are followed. To adjust the position of the two Y 
supporting tubes it is necessary to rotate by 90° the frame and 
to fit the comparator on a longer arm. 
Having carried out these operations, 
adjusting the vertic 
al 
couple 
0 f 
bearings, both the 
guides and th 
e screws will 
be on planes 
parallel 
to 
each other, and to 
the reference 
; plane. 
Then the main frame is raised 
vertical (ref. 
fig. 2) rest 
ing 
it on 
th e 
rear plane and mo 
ving the comparator 
equipped along a si 
de 
of the 
reference plane; the 
position of 
th e A 
gu ide 
and support 
tubes is 
adj 
usted by moving now the pair 
of hor: 
izontal 
bearings. Then 
after 
hav 
ing inserted the 
precision rod 
which 
t akes 
the place of 
the 
two X 
measuring screws they are also adjusted on a plane parallel to the 
reference one. Thus the general preliminary calibration is completed 
for the X guides which are thus parallel to each other in the space and 
parallel to their respective measuring screws. After having mounted the 
two photocarriages, with their call bearings in the middle position, 
using a suitable tool the comparator is fixed on the outer side of the 
plate-holder. 
By moving the carriage from the bottom to top (ref. fig.3) the 
comparator is moved along the arm of a precision square which is 
resting on the reference plane. The gliding track is then set at zero, 
adjusting the pairs of horizontal bearings of the guide tube. This 
operation, repeated naturally for „the other pi ate-holder, besides making 
the two Y. guides parallel in the space, adjusts them normal to the X 
guides. Having brought the frame back from the vertical position in which 
we were operating to the original horizontal position, the two Y support 
tubes and the Y. measuring screws are finally adjusted with relation to 
the two guide tubes. 
Therefore the comparator is placed on the inner side of the plate- 
holder and sliding it on an horizontal generatrix of the support tube