GB/T 11917-2009Terms in timber sawing technology (English PDF)

Foreword

GB/T 11917-2009 was issued on 23 February 2009 by the General Administration of Quality Supervision, Inspection and Quarantine and the Standardization Administration of the People's Republic of China, and has been in force since 1 August 2009. It replaces GB/T 11917-1989.

The document is a recommended national standard: the /T in the designation marks it as recommended rather than compulsory.

1 Scope

China's national vocabulary for the sawmilling trade - the terms for the sizes and shapes of sawn products and for the operations that produce them. A sawmill is where a round, tapered, irregular natural object is turned into rectangular pieces, and almost every decision in it is a trade-off between yield and grade: cut a log one way and you get more boards, cut it another and you get better ones. That negotiation cannot be conducted without exact words. A cant and a blank are both intermediate pieces but they are not the same thing; breakdown and rip sawing are consecutive operations, not synonyms; a heart board and a half heart board differ by where the pith falls, which decides how the piece will move as it dries. This standard defines the terms used for the dimensions, the shapes and the production technology of sawn timber, and applies to timber manufacturing processes. It is a vocabulary rather than a specification: no normative references, no limits, only the definitions - some two hundred of them - each given in Chinese and English with figures where the shape matters.

This standard defines the terms concerning the dimensions, the shapes and the production technology of sawn timber products.

This standard applies to timber manufacturing processes.

2 Terms and definitions

The standard gives roughly two hundred numbered entries, each with the Chinese term, its English equivalent and a definition, with figures where the cross-section has to be seen. The opening entries define the raw material and the product: log, a length of wood cut from a stem to meet the requirements of the standard; butt log, top log and second log, according to which part of the stem it is cut from; saw log, a log used for producing sawn timber; and sawn timber, the product obtained by working a log.

The next entries classify sawn timber by what has been done to it: dried sawn timber, brought to the specified moisture content by air drying or kiln drying; planed sawn timber, planed to meet the technical requirements; preserved sawn timber, treated to resist decay; fire-retarding sawn timber, treated to resist ignition and burning; and square-edged sawn timber, whose opposite wide faces are parallel and whose adjacent faces are perpendicular, with any wane on the arris within the permitted limit.

Further entries name the pieces produced by cutting the log up: half log, sawn timber produced by splitting a log along its diameter into two equal or nearly equal parts; quarter log, split along the radius into four; heart board, a radially cut board containing the pith; and half heart board, a board split along the pith so that the pith is exposed.

The operations themselves are distinguished carefully: breakdown, the sawing process in which a log is ripped into cants and blanks working from a reference face; rip sawing, the process in which cants and blanks are sawn into boards and squares from a reference face; and feed, the collective name for breakdown and rip sawing together.

Finally the intermediate and by-products are defined: cant, the rough-edged square timber left after the slabs have been sawn off a log, either one-faced or two-faced, illustrated in Figures 1 and 2; blank, the various shapes of stock produced by the large bandsaw or the breakdown headsaw and supplied to the other rip sawing machines; and slab, the curved outer piece sawn from a log, whose cross-section is bounded by the tangential cut plane and the curve of the log's outside.