Converting to the metric system

THE odd thing about the increasI ingly frequent talk about converting lumber sizes to the metric system is that while experts see no immediate or general benefit to the lumber industry, virtually all of them concede that the change is inevitable.

That same kind of thinking shows up in other industries and observers feel that most people recognize the superiority of metrics over the inchpound system and are aware that the United States is the last great holdout from the otherwise universally used system of metric measurement. About the only other countries on inches and pounds are such industrial giants as Gambia, Trinidad and Tonga.

The U.S. has been slipping into more and more metric use in the last two decades and the process is accelerating. Fifteen years ago the pharmaceutical industry dropped drams and grains for milligrams and grams. Last year General Motors said all its new products from here on would be metric and Ford is now building the U.S.'s first massproduced metric system auto engine at its new plant in Lima, Ohio, a 2.3 liter engine used in the I974 Mustang II. Camera film everywhere is sold in 35 millimeter sizes.

Assuming that the Congress officially ordains a national changeover, what happens then?

Good question, and not one, it seems, that is capable of an easY answer. As even the most cursory examination of factors involved in a conversion show, the switch to meters, grams and liters can raise some devilishly complex problems.

One of the best summations is in a paper by Gerald F. Prange, v.p.technical services, of the National Forest Products Assn. that he Presented to the Construction Industry National Metric Study Conference at the National Bureau of Standards in 1970. It says in part:

"Should a coordinated program to increase the use of the metric sYstem by the wood products industries be undertaken, additional information in the following areas would appear to be essential.

"(l\ Unit Conuersion

or Size

Ad,justmenr - The question of whether metrication in the wood products industry should be one of simple adaptation of present standard sizes to the nearest metric equivalent or whether product size changes (conversion) should be made to capitalize upon the simplicity of the metric system is highlY significant. Adaptation, for example, to the nearest millimeter, would undoubtedly be the least complicated. It would involve a minimum of machine adjustment and require minor education of mill

Chorl A STRAIGHT CONVERSION

The sizes of dimension and board lumber here have been directly converted to metric sizes by multiplying inches by 2.54 to gain the equivalent size in millimeters, .rounded off to 6ne olacd. Wtrite this ivould involve the least amount of change, most observers feel further'rounding off, as in Chart B, would be generally preferable.

personnel. This procedure, particularly in the case of lumber, would require that a similar direct adaptation be made by regulatory, design and construction services in spacing of members and assignment of design criteria.

"Should change to the metric system be accompanied by a substantive modification of actual product sizes (conversion), then the added delays of commodity and product standards development can be anticipated. For example, the recently approved size standard for softwood lumber, which involved a rather minor adjustment in dimensions, required more than ten years to develop and implement.

"(3) Estimating Log YieldThe current method of determining log yield for its various product possibilities is through application of experience factors to a standard unit of tally called the board foot. This is an arbitrary unit I"xI2"xl2" or I/12 cubic foot. Considerable experience is required to be able to determine the value of a log on the basis of its product yield related to its volumetric content in board feet. While similar experience would be required for the metric system, the units of volume in this system are

Story at a Glance

"(2)Metric Uniformity _If metric conversion is to be a simple transposition to metric units, the international uniformity benefits attributed to the metric system may not be readily apparent, since domestic and foreign lumber dimensions presently do not coincide, irrespective of the units of measure. It can be argued, however, that adoption of the metric system can be a force for securing international lumber size uniformity.

As Congress inches its way towards a decision on converting the U.S. to metric measurement, experts argue over how best to make the conversion despite problems and little if any benefit to many sections of the lumber and building materials business, most observers see the changeover as inevitable.

limited to the cubic centimeter, the cubic decimeter and the cubic meter. Although the cubic decimeter approaches the size of the American board foot (being approximately

Chort B

Rounded Off

This chart shows proposed sizes in millimeters that have been rounded o,ff to even numbers for greater convenience. Advocates of a larger degree of change feel further rounding olf, such-.as having as. many numbers as technicaiiy possible e-nd in 0, would optimizd the benefits of any changeover.

equal to three board feet) the standard metric measure of log volume is the cubic meter. This unit equals 424 board feet or 35.3 cubic feet. lt seems likely, therefore, that a major program of indoctrination and experience will be required before buyers and sellers of logs can achieve their present skills in determining log product yield in the absence of a ready metric approximation of the board foot or cubic foot.

"(4) Initiation of Conaersion ProgramIn contrast with other industries, engineering design, construction and product manufacture in the construction industry involves independent disciplines. Thus, for the wood products industry to consider conversion of its product to metric sizes will also require the modular planning of the architect and the engineering calculations of the designer to be based upon metric units. Each of these disciplines, in turn, will probably be confronted with problems similar to that experienced in the previous discussion of the board foot. For the architect or builder the standard 16inch spacing of wood members becomes 40.6 centimeters and the engineeros pound-per-square inch becomes 0.0703 kilograms per sguare centimeter. In each case requiring conceptual adjustments on the part of the user.

"Preceding utilization of metric units by the architect, engineer and building contractor; the specifications and standards for use ofbuilding products will require conversion and building codes must be revised to reflect such changes. In this latter category, perhaps the most extensive educational program required will be the indoctrination of the building official who presently must be conversant with quantitative factors applicable to a broad range of building products. The substitution of a completely new schedule of units, standards, design criteria and engineering data at this level may constitute the major area of educational need in any metric conversion effort.

"(5) Effect Upon Land MeasurententsMetric conversion will (Please turn to page 34)