Maryland Metrics Technical Data Chart:
Squares for Operating Spindles and Operating Parts
to DIN 79 extract
Type A Shaft square Type I bore square
* Internal squares are allowed to be recessed (relieved) in the middle third of each side.
s
d
e1
e1
e2
H11/h11
max.*
max.
min.**
min.
4
4.2
5
4.8
5.3
5
5.3
6.5
6
6.6
5.5
5.8
7
6.6
7.2
6
6.3
8
7.2
8.1
7
7.3
9
8.4
9.1
8
8.4
10
9.6
10.1
9
9.5
12
10.8
12.1
10
10.5
13
12
13.1
11
11.6
14
13.2
14.1
12
12.6
16
14.4
16.1
13
13.7
17
15.6
17.1
14
14.7
18
16.8
18.1
16
16.8
21
19.2
21.2
17
17.9
22
20.4
22.2
19
20
25
22.8
25.2
22
23.1
28
26.4
28.2
24
25.3
32
28.8
32.2
27
28.4
36
32.4
36.2
30
31.7
40
36
40.2
32
33.7
42
38.4
42.2
36
38
48
43.3
48.2
41
43.2
54
49.3
54.2
46
48.5
60
55.2
60.2
50
52.7
65
60
65.2
55
57.9
72
66
72.2
'd max' defines the recommended bore hole diameter which leaves an appropriate clearance when
positioned concentrically to the internal square.
** External squares made on round steel bar may fall below the minimum size by the amount of
tolerance on the steel bar, i.e. by h11.
all dimensions in mm