2 
The general preliminary calibration in the workshop consists of 
placing, with a tolerance of a few hundredths of a millimeter, the 
guides parallel to each other and to their respective screws and of 
establishing the perpendicularity of the coordinate couples relating 
to each coordinatometer. All the components that support the guides 
and the screws are equipped with reference pins, and therefore the only 
parts which can change the position of the guides are the bearings 
supporting the tubes. 
As far as the parallelism of the guides is concerned, it is wise 
to keep in mind the following factors: the two co-ordinatometers are 
completely independent and therefore it is not important at all for the 
guides Xi and X? to be parallel to each other; the same can also be 
said about the Y guides. It is on the other hand absolutely essential 
that the guides of the same co-ordinatometer are perpendicular to each 
other and that the supporting tubes are rigorously parallel to their 
respective guides, at least as far as the horizontal components are 
concerned. 
In other words, it is only necessary for the horizontal planes 
passing through the guide tube and the support tube to be parallel 
without worrying too much so that the motion takes place without 
rotation around the guide axis. Of course we must assume that the 
guides are straight lined otherwise this calibration would not be 
possible. 
Mechanical calibration is carried out by using a reference plane, 
a square, a precision ruler and a dial comparator. 
For all measurements the base plane of the main frame and the back 
vertical plane of the same are used as reference. 
Placing the above mentioned frame on the reference plane (ref. 
fig.l) the various operations are carried out in the following order, 
making sure to keep the comparator equipped on the reference plane so 
as to be able to check those points belonging to planes parallel to the 
reference one. 
(a) 
Adj ustment 
o f 
th e 
positio 
n of 
the 
two 
main 
Y guide tubes 
, 
(b) 
Adjustment 
o f 
the 
position of 
th e 
two 
measurin 
g Y screws 
using 
a 
precision rod 
which i 
s pi 
aced 
in 
th e 
pla 
ce of the 
screws 
th 
emselves. 
To 
carry out 
the first 
of 
these 
two 
operation 
s, the 
ex 
tremi ties 
of 
a 
Y guide 
tube 
are 
che 
eked 
wi th 
the compa 
rator, 
mo 
ving the 
equipment along a s 
ide 
of 
the refer 
ence plane 
; when 
on 
the two 
ext 
rem 
e points 
the 
sam e 
re 
ading 
s ar 
e made, the 
f rame 
i s 
rotated 
by 
180°, and 
the 
extremi 
ties 
of 
the second 
guide 
tu 
be are adjus 
ted 
on the 
same 
pi an 
e, 
paral 
lei 
to the ref 
erence