Steel Tape Line Accuracy

Lufkin steel tapes are made to government standards. Our bench standards for the Unites States are certified accurate by the United States Department of Commerce, National Bureau of Standards, and Washington D.C. Tapes for Canada are made to Canadian government standards.

Temperature standard for steel tapes is 68°F, which equals 20°C. Coefficient of expansion of steel tapes is 0.000645 foot per degree F; 0.0000116 foot per degree C. This amounts to 0.000645 foot or 0.00774 inch per degree F. on a 100-foot tape, and one-half as much on a 50-foot tape. As a figure that is reasonably accurate and also easy to handle, it is customary on very long runs of pipe to allow 1/10” per 100 feet for each 10° change.

The above illustration shows, for a 100-foot tape, the actual length variations of temperature within the range of 20° below to 120° above zero F. The terminal graduation on the lower edge is at 68°, this being standard temperature. Furnished only when specified and at additional cost. Standard tension for steel tapes 25 to 100’ long (10 to 30m) supported entire length on a horizontal, flat surface, is 10 pounds (4.5 kg.); for all tapes over 100’, 20 lbs., (9kg.). For steel tapes suspended horizontally and supported only at ends, there can be no set or standard tension for accuracy because of weight and other variations.

The following listings are averages of many tests made by the Bureau of Standards of Lufkin steel tapes supported ends only. These averages are taken from the experience of tests and should be used as a working basis only, and not to replace the test of any individual tape. All tape lengths are 100’.