NTN BEARING CORPORATION OF AMERICA - Four-Bolt Round Piloted Flange

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Four-Bolt Round Piloted Flange

detail of 4-bolt round pilot extension

the dimension "J₁" is the bolt pitch circle diameter; the dimension "J" is the distance between bolt hole centers

As with the square four-bolt, this flange is typically made of cast iron and provides the same increased rigidity when mounted over two-bolt flanges. They carry the NTN nomenclature designation FC.

As with the square flanges, the bolt holes are spaced equidistant from the shaft or bearing bore. The distance between bolt hole centers is measured from the center of one bolt hole to the center of an adjacent bolt hole. This flange also features a pilot extension on the back of the housing similar to the one described above.

When specifying this round flange another dimension must be considered—the diameter of the bolt hole center, or the bolt pitch circle diameter. This measurement is similar to that described for three-bolt round flanges.

The shaft size, the distance between bolt hole centers and the diameter at bolt hole center for four-bolt round piloted flanges are listed in the appropriate NTN catalog. Table 6 above provides a brief example of the dimensional details available. In the section listed, the details are provided for a four-bolt round piloted flange fitting a one-inch diameter shaft. From this you may select the proper distance or spacing between bolt hole centers.

Table 6: Four-bolt round piloted flanged housing variations—1" diameter

Round flange housing type	Number of bolts	Insert bearing series	Bolt center distance (in)	Pitch circle diameter (in)	Pilot diameter (in)	Housing material	Application duty
FC FC	4 4	2 2 (Adapter)	2 1/2 2 25/32	3 35/64 3 15/16	2.7559 3.1496	Cast Iron Cast Iron	Normal
FC FC	4 4	X X (Adapter)	2 9/16 2 59/64	3 5/8 4 9/64	2.9921 3.3465	Cast Iron Cast Iron	Medium

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