The intent of this document is to offer designers and users standard dimensions and tolerances for inch bores,
keys and keyways for flexible couplings. In general, the dimensions contained in this Standard represent the dimen-
sions and tolerances used within the industry for pre-engineered couplings. It may prove useful in establishing
dimensions and tolerances for custom engineered coupling products.
This Standard was developed after intensive study of existing standards, literature, design practices, and
manufacturing procedures for bores and keyways of unmounted flexible coupling hubs and similar components.
The study revealed that much of the data contained in existing standards and specifications is predicated upon prac-
tice and procedures that pertain more to keyways in the shaft members than to keyways in coupling hub bores. The
information contained within this Standard does not necessarily agree with some commonly used existing specifica-
tions. This Standard is based upon the design criteria related to bores and keyways in coupling hubs that have
evolved over many years of successful industry practice.
This Standard presents pertinent data on dimensions, tolerances, and sizes for straight bores, tapered bores,
keys, and keyways for unmounted industrial flexible couplings. Decimal equivalents of fractions are shown to a
maximum of four decimal places and are not meant to imply tolerances.Inspection methods for tapered bores and
keyways are included in the appendices. The appendices also include the recommended design practice for tapered
shafts for use with flexible couplings.