Four-Bolt Square Piloted
Flange
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the dashed lines highlight the raised pilot extension of
this four-bolt square flange
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Although these flanges have the same face dimensions as the four-bolt
flanges described above, they have little else in common. The four-bolt
square piloted flange is offered only in a heavy-duty series and uses
series 3 insert bearings. (Additional information
on insert bearings and series sizing will follow later in the guide.)
The NTN nomenclature designation for this housing is FS.
The back of the square four-bolt piloted flange is machined to
set flush against the mounting surface. In addition, a cylindrical
pilot section extends from the back face
of the housing. This pilot, when inserted through a corresponding
hole in the mounting surface, helps to locate the unit during installation.
The pilot extension is machined to tight tolerances to ensure a
close fit, resulting in greater placement accuracy and additional
rigidity of the flange unit.
When specifying four-bolt piloted flanges an additional dimension
is required—the outside diameter of the pilot extension, which
can only be measured from the back of the flange.
The shaft size and the distance between bolt hole centers for four-bolt
piloted flanges are measured exactly like the four-bolt square flanges,
and are listed in the appropriate NTN catalog. Table
5 below provides a brief example of the dimensional
details available. In the section listed, the details are provided
for a four-bolt square piloted flange fitting a one-inch diameter
shaft. From this you may select the proper distance or spacing between
bolt hole centers.
| Table 5: Four-bolt squared piloted flange housing
variations—1" diameter |
Square
piloted
flange housing |
Number
of
bolts |
Insert
bearing
series |
Bolt
center
distance (inch) |
Pilot
diameter
(inch) |
Housing
material |
Application
duty |
FS
FS |
4
4 |
3
3 (Adapter) |
3 5/32
3 47/64 |
3.1496
3.5433 |
Cast Iron
Cast Iron |
Heavy
Heavy |
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