BS 4235-1:1972

What is BS 4235-1 – Metric parallel and taper keys specifications about?

Parallel keys are the most widely used keys. The tapered key is tapered only on the side that engages the hub. BS 4235-1 is a British Standard that discusses specifications for metric keys and keyways.

BS 4235-1 is the first part of the BS 4235 multi-series, and relates to the following types of keys and keyways with dimensions in millimetres:

• Square parallel
• Rectangular parallel
• Square taper, gib-head, and plain
• Rectangular taper, gib-head, and plain

Who is BS 4235-1 - Metric parallel and taper keys specifications for?

BS 4235-1 on metric parallel and taper keys specifications is useful for:

• Manufacturers and suppliers of keys and keyways
• Product designers
• Quality control personnel
• The automobile industry
• The manufacturing industry
• Agencies involved in keys and keyways

Why should you use BS 4235-1 - Metric parallel and taper keys specifications?

The purpose of the taper is to secure the key itself, as well as, to firmly engage the shaft to the hub without the need for a set screw.

In addition, the fourth class of fit is provided in BS 4235-1 to give an interference fit.

Three classes of fit are provided for the square and rectangular parallel keys and keyways, namely “free”, “normal” and “close”, and the dimensions and tolerances specified are in accordance with ISO Recommendations R 7733 and R 7744).

BS 4235-1 walks you through the fits, material, dimensions, and tolerances of metric keys and keyways.

The three classes of fit dealt with in BS 4235-1 are intended to meet varying requirements as follows:

• Free, where the hub is required to slide over the key when in use
• Normal, where the key is to be inserted in the keyway with minimum fitting, as is required for mass production assembly
• Close, where an accurate fit of the key is required. In this class, the fitting will be required under maximum material conditions, and if it is required to obtain these conditions some selection of components may be necessary
• Interference, where a fit is required such that there is no possibility of play between the key and keyway in the shaft and hub. In this class of fit, hand-fitting will be necessary

Detailed diagrams and tables have been provided in BS 4235-1 to illustrate the shapes and dimensions of parallel and taper keys.

BS 4235-1 assists you in securing the hub and shaft to prevent relative movement between a power transmitting shaft and a connected component.