scope:

FOREWORD

For many years, roller chain manufacturers have furnished a substantial volume of chains consisting of link plates assembled on pins without the use of bushings and rollers. These chains provide relatively high strength per unit of weight and have found wide usage where sprockets are not required and high-speed power transmission characteristics are not needed.

Previously, variation in link plate thickness, link plate contour, diameter of pins, and the method of lacing limited its interchangeability and restricted its use. For these reasons the Association of Roller and Silent Chain Manufacturers appointed a task subcommittee on September 21, 1951 to develop this Standard.

The scope of the resultant Standard covers the lacing, pin diameter, diameter of link plate holes, link plate contour and thickness, chain widths, and minimum ultimate tensile strengths. The Standard also recommends clevis and sheave design. Supplementary information to guide users in the application of these chains appeared in the 1958 edition and was deleted in 1960.

The 1971 reaffirmation was approved by the American National Standards Institute on September 10, 1971.

Prior to 1975, all B29.8 leaf chain standards included both Type A and Type B leaf chain designs. Type A, the lighter series, was characterized by even or balanced lacing, while Type B, the heavier series, was shown only with uneven or unbalanced lacing of chain links.

During the decade preceding 1975, it became increasingly apparent that the use of Type A leaf chain was declining and that it was being used primarily for replacement. Most new design applications used the heavier Type B design either with the standard uneven lacing or with even lacing, which was shown as standard only for Type A leaf chain. The increased use of Type B chain and the desire to simplify chain standards led the American Chain Association to undertake a revision of B29.8 to:

(a) eliminate Type A leaf chain from the standard;

(b) add even lacing (balanced) to the Type B chain series;

(c) include a 2½ in. pitch chain to the list of Type B chain.

These revisions were subsequently included in ANSI B29.8-1977 and approved by the American National Standards Institute on May 4, 1977.

In tabulating dimensional information in this Standard, customary inch-pound units have been used. Additionally, companion tabulations have been included that provide metric (S.I.) unit conversions of these values in accordance with SI-I, ASME Orientation and Guide for Use of Metric Units. Certain formulas and relationships have intentionally been presented only in customary units to eliminate ambiguity between them and the tabulated values.

Revisions incorporated in ANSI/ASME B29.8M-1985 provided additional information on clevises, clevis pins, minimum sheave size, and lubrication.

Revisions incorporated in ASME B29.8M-1993 included changes in format, restatement of the definition of Minimum Ultimate Tensile Strength and, most notably, minor changes in the standard values for maximum pin diameter and the minimum hole diameter. The dimensional changes were required to allow a direct, error-free conversion between conventional units (inches) and metric units (millimeters).

Revisions incorporated in ASME B29.8-2002 include the elimination of 88 lacing. Tables 1A and 1B have been revised to show minimum width between outside plates (L_m) and Tables 3A and 3B have been revised to show the dimensions for an inside clevis. An appendix has been added that contains information on lubrication and maintenance, connect and disconnect, and general inspection criteria. Preload and manufacturer's identification marking have been added in compliance with the requirements of ISO 4347.

This Standard was approved by the American National Standards Institute on March 27, 2002.