Found my "Report of Calibration" for my 100 Foot Lufkin Steel Tape and thought I would share the results with all interested.
I have had this tape since around 1970 and would compare it with a calibrated tape (it was close as will be shown).
In 1991 I was at NIST (National Institute of Standards and Technology) to get my tape calibrated. The tape is calibrated on a flat surface
with (then) a HP Interferometer (now a Renishaw XL-80 Interferometer) at 68 degree Fahrenheit (20 degree Celsius).
At a Tension of 10 pounds at 68 F on the flat the tape was 100.0045 feet with a Uncertainty of +/- 0.0010 feet.
Other tables supplied with the report are calculated results.
0 to 10 foot interval with a temperature in 2 degree interval and a Tension at 10,15,20,25,30 lbs. This table was supported at 2 points.
Then there is a table with 3 point support, 4 point support, 5 point support and then a table supported on a flat.
Here are some results for the 10 foot interval on the FLAT. 42Deg.F, 10 lbs pull, distance 10.0000 feet (at 68 deg., 10 lbs pull, dist. 10.0017
At 34 Deg. F, 15 lbs pull, dist. 10.0000 (too cold for me).
Now for 0-50 foot on the FLAT
Temp. 56 Deg. F., 10 lbs pull, dist. 49.9998, with a 15 lbs pull at 50 Deg. F. , dist. 50.0002
Now for 0-100 Foot on the FLAT
Temp. 61 Deg F., dist. 100.0000 and at 54 Deg. F., 15 lbs pull, dist 100.0002 feet.
Now for 0-100 foot supported at 2 points
Temp. 68 Deg. F. , 10 lbs pull dist. 99.9368, at 15 lbs pull dist. 99.9791, at 20 lbs pull 99.9969 , at 25 lbs pull, dist 100.0077
If the tape was supported at 5 points ( 0,25,50,75 100 feet then at 68 Deg. F. the tape would be 100.0003
The last table in the REPORT is for different supports ( 2 points, 3, 4, 5 and FLAT support) for the tape to be 100.000 feet.
So lets look at 68 Deg. F. 2Pt. Supp. 21.23 lbs,, 3 Pt. Supp. 14.18 lbs, 4 Pt. Supp. 11.39 lbs,5 Pt. Supp. 9.85 lbs and on the FLAT 5.20 lbs.
The Temp. in the table goes from 14 Deg. F. to 104 Deg. F. at 2 degree intervals.
I only wish I had calibrated this tape when I first got it.
JOHN NOLTON
We used a 300' tape for years.
Calibrating it, like above, must be a real bear!
I'm sure that accounts for some of the typical errors we have fd. when retracing our own work. 0.15' per 1/4 mi. to 0.30' per 1/4 mi.
