BS 1660-1:1992

This standard BS 1660-1:1992 Machine tapers is classified in these ICS categories:

• 25.060.20 Dividing and tool-workpiece holding devices

This International Standard specifies the dimensions of self-holding tapers for tool shanks with a small taper of about 4 % to 5 %, classified, according to their use, into the three following catergories:

1. tapers for general use;
2. smaller tapers;
3. larger tapers.

For the first category, tapers recommended by ISO are Nos. 1 to 6 Morse tapers. Their standard sizes in millimetres are given in Table 2, and the corresponding sizes in inches are given in Table 3.

For smaller and larger tapers, those recommended by ISO are, on the one hand, Nos. 4 and 6 metric 5 % tapers and No. 0 Morse taper, and on the other hand, Nos. 80 to 200 metric 5 % tapers, the sizes of which, in millimetres only, are given in Table 2. However, it was agreed to include in parallel, in the category of small tapers, Nos. 1 to 3 Brown & Sharpe tapers, the sizes of which, in inches only, are given in Table 3.

Consequently, as shown in Table 1, the self-holding tapers dealt with in this International Standard include

1. for general use, only Nos. 1 to 6 Morse tapers;
2. for sizes below No. 1 Morse taper, two solutions, i.e. either Nos. 4 and 6 metric tapers and No. 0 Morse taper (without corresponding tapers in inches in Table 3) or, alternatively, Nos. 1 to 3 Brown & Sharpe tapers (without corresponding tapers in millimetres in Table 2);
3. for sizes above No. 6 Morse taper, only Nos. 80 to 200 metric tapers (without corresponding tapers in inches in Table 3).

Table 1 – Tapers

Designation	Sizes in millimetres	Sizes in inches
Small tapers	Nos. 4 and 6 metric and No. 0 Morse	Nos. 1 to 3 Brown & Sharpe
Tapers for general use	Nos. 1 to 6 Morsea
Large tapers	Nos. 80 to 200 metric	–
a Except for threads, Nos. 1 to 6 Morse tapers, manufactured either to metric values or to inch values, are strictly interchangeable, though not absolutely identical.

This International Standard provides, for those elements which are threaded, two entirely distinct types of product according to the type of thread, M or UNC.

In order to distinguish between those two types, it is important that the element itself be marked with the corresponding thread symbol and the type of taper symbol, as shown in the figures in clause 4. Lastly, this International Standard specifies the dimensions of grooves and holes necessary for the design of tapers for applications where coolant supply is required.

Specifies dimensions of tapers for use on small tools where the tools may be used in applications with or without coolant supplies.