Pi Tape® precision diameter measuring tapes provide a quick, accurate and easy method of measuring the outside diameter of cylindrical, round and out-of-round parts. Also commonly called diameter tapes, diameter measuring tapes or precision vernier diameter tapes, Pi Tapes convert the circumference of a part into a direct diameter reading.
Newman Tools supplies Pi Tape® measuring tapes in inch and metric sizes, including standard outside diameter tapes, large-diameter tapes and specialty Pi Tape products. We ship worldwide, including Canada and the USA.
A Pi Tape is a precision measuring tool used to determine the diameter of a cylindrical object by measuring its circumference. The graduations on the tape are calculated so that the user can read the diameter directly rather than measuring the circumference and performing a separate calculation.
Pi Tape® periphery tapes provide a quick and accurate way of reading true diameters of both round and out-of-round forms. They are especially useful for thin- or soft-walled parts, large components and applications where a conventional outside micrometer or caliper is impractical.
Standard outside diameter Pi Tapes are supplied in 1095 clock spring steel unless another material is specified.
Stainless steel versions are available for applications where corrosion resistance is required. Ideal for oil & gas, pipeline, and marine applications.
Pi Tapes require little maintenance. After use, wipe the tape clean and apply a light rust preventive oil. Do not bend, kink or step on the tape, as damage can affect measurement accuracy.
Pi Tapes are commonly used for:
The standard inch Pi Tape range covers diameters from 1/2 inch through 144 inches. The PI-1 covers 2 to 12 inches and is one of the standard sizes commonly used for machine-shop and inspection applications.
| Part No. | Outside Diameter Measuring Range | Description |
|---|---|---|
| PI-000 | 1/2–2" | 0.500 to 2" Diameter Tape |
| PI-01 | 3/4–7" | 0.75 to 7" Diameter Tape |
| PI-1 | 2–12" | 2 to 12" Diameter Tape |
| PI-1SP | 2–24" | 2 to 24" Diameter Tape |
| PI-2 | 12–24" | 12 to 24" Diameter Tape |
| PI-2SP | 12–36" | 12 to 36" Diameter Tape |
| PI-3 | 24–36" | 24 to 36" Diameter Tape |
| PI-3SP | 24–48" | 24 to 48" Diameter Tape |
| PI-4 | 36–48" | 36 to 48" Diameter Tape |
| PI-5 | 48–60" | 48 to 60" Diameter Tape |
| PI-6 | 60–72" | 60 to 72" Diameter Tape |
| PI-7 | 72–84" | 72 to 84" Diameter Tape |
| PI-8 | 84–96" | 84 to 96" Diameter Tape |
| PI-9 | 96–108" | 96 to 108" Diameter Tape |
| PI-10 | 108–120" | 108 to 120" Diameter Tape |
| PI-11 | 120–132" | 120 to 132" Diameter Tape |
| PI-12 | 132–144" | 132 to 144" Diameter Tape |
Standard clock steel will be supplied unless specified otherwise. For current pricing and availability, see the Pi Tape Price List.
Metric Pi Tapes are available for outside diameter measurements from 28 mm through 3600 mm, with standard and extended ranges.
| Part No. | Outside Diameter Measuring Range |
|---|---|
| PI-M-0 | 28–200 mm |
| PI-M-1 | 100–300 mm |
| PI-M-1SP | 50–600 mm |
| PI-M-2 | 300–600 mm |
| PI-M-2SP | 300–900 mm |
| PI-M-3 | 600–900 mm |
| PI-M-3SP | 600–1200 mm |
| PI-M-4 | 900–1200 mm |
| PI-M-5 | 1200–1500 mm |
| PI-M-6 | 1500–1800 mm |
| PI-M-7 | 1800–2100 mm |
| PI-M-8 | 2100–2400 mm |
| PI-M-9 | 2400–2700 mm |
| PI-M-10 | 2700–3000 mm |
| PI-M-11 | 3000–3300 mm |
| PI-M-12 | 3300–3600 mm |
Standard clock steel will be supplied unless specified otherwise. Stainless steel versions may be ordered by adding SS to the part number, subject to the manufacturer's current material and size specifications.
Extra-large diameter Pi Tapes are available by special order for applications above 144 inches in outside diameter. Standard tapes are manufactured with a 1/4" wide Vernier gage, a 1/2" wide main body and a 1/4" wide gage member.
| Diameter Range O.D. | Part No. |
|---|---|
| 144–156" | P13 |
| 156–168" | PI-14 |
| 168–180" | PI-15 |
| 180–192" | PI-16 |
| 192–204" | PI-17 |
| 204–216" | PI-18 |
| 216–228" | PI-19 |
| 228–240" | PI-20 |
| 240–252" | PI-21 |
| 252–264" | PI-22 |
| 264–276" | PI-23 |
| 276–288" | PI-24 |
| 288–300" | PI-25 |
| 300–312" | PI-26 |
| 312–324" | PI-27 |
| 324–336" | PI-28 |
| 336–348" | PI-29 |
| 348–360" | PI-30 |
| 360–372" | PI-31 |
| 372–384" | PI-32 |
| 384–396" | PI-33 |
| 396–408" | PI-34 |
| 408–420" | PI-35 |
| 420–432" | PI-36 |
| 432–444" | PI-37 |
| 444–456" | PI-38 |
| 456–468" | PI-39 |
| 468–480" | PI-40 |
| 480–492" | PI-41 |
| 492–504" | PI-42 |
| 504–516" | PI-43 |
| 516–528" | PI-44 |
| 528–540" | PI-45 |
Calibration reports traceable to NIST are furnished with each new tape at no additional charge. Manufacturer calibration and tolerance specifications apply.
| Diameter Range O.D. | Part No. |
|---|---|
| 3600–3900 mm | PI-M-13 |
| 3900–4200 mm | PI-M-14 |
| 4200–4500 mm | PI-M-15 |
| 4500–4800 mm | PI-M-16 |
| 4800–5100 mm | PI-M-17 |
| 5100–5400 mm | PI-M-18 |
| 5400–5700 mm | PI-M-19 |
| 5700–6000 mm | PI-M-20 |
| 6000–6300 mm | PI-M-21 |
| 6300–6600 mm | PI-M-22 |
| 6600–6900 mm | PI-M-23 |
| 6900–7200 mm | PI-M-24 |
| 7200–7500 mm | PI-M-25 |
| 7500–7800 mm | PI-M-26 |
| 7800–8100 mm | PI-M-27 |
| 8100–8400 mm | PI-M-28 |
| 8400–8700 mm | PI-M-29 |
| 8700–9000 mm | PI-M-30 |
| 9000–9300 mm | PI-M-31 |
| 9300–9600 mm | PI-M-32 |
| 9600–9900 mm | PI-M-33 |
| 9900–10,200 mm | PI-M-34 |
| 10,200–10,500 mm | PI-M-35 |
| 10,500–10,800 mm | PI-M-36 |
| 10,800–11,100 mm | PI-M-37 |
| 11,100–11,400 mm | PI-M-38 |
| 11,400–11,700 mm | PI-M-39 |
| 11,700–12,000 mm | PI-M-40 |
| 12,000–12,300 mm | PI-M-41 |
| 12,300–12,600 mm | PI-M-42 |
| 12,600–12,900 mm | PI-M-43 |
| 12,900–13,200 mm | PI-M-44 |
| 13,200–13,500 mm | PI-M-45 |
The Vernier scale allows the Pi Tape to provide a direct diameter reading. For the most accurate result, clean both the tape and the part before measuring and use the specified measuring tension.
The standard gage member is 1/4" wide. Optional 1/8", 3/8" and 1/2" widths are available for certain applications.
The Vernier scale divides each graduation on the tape body into 25 parts, allowing readings to .001 inch.
Example: if the divisions to the left of the Vernier zero indicate 20.025 inches and the 15th Vernier line coincides with a line on the gage member, the reading is 20.040 inches.
When reading a standard O.D. tape, apply a snug pull of approximately 5 lb. tension after properly cleaning the tape and part.
The standard metric gage member is 6.35 mm wide. Optional 4.76, 9.53 and 12.70 mm widths are available for certain applications.
Each line on the gage member represents 0.5 mm of diameter, while each line on the Vernier represents 0.01 mm. For example, if the Vernier zero is past the 661.5 mm line and the 23rd Vernier line coincides, the diameter reading is 661.73 mm.
When reading the metric O.D. tape, apply a snug pull of approximately 2.25 kg tension after properly cleaning the tape and part.
A standard O.D. Pi Tape can be used for certain inside-diameter measurements by accounting for the tape thickness and using zero tension. However, for the most accurate direct inside-diameter measurement, a dedicated Pi Tape Inside Diameter or O-Ring Tape is recommended.
For a standard metric O.D. tape, the current published procedure specifies adding twice the tape thickness to the reading. Standard tapes are 0.25 mm thick, so 0.50 mm is added when using the standard O.D. tape for this type of I.D. measurement.
For large diameters, small pieces of masking tape can be used to help hold the Pi Tape parallel to the component while taking the measurement.
Pi Tape® specialty products are available for applications that cannot be handled by a standard outside diameter tape.
Easy-read, stainless steel, inside diameter, narrow or wider width, special thickness, Go/No-Go inspection, extra-capacity and intermediate-range Pi Tapes.
Precision tapes specifically designed for quick and accurate inside diameter measurement of O-rings and other soft-walled parts.
Custom and special Pi Tapes can be manufactured to suit particular measuring requirements. Contact Newman Tools if you need a diameter range, width, thickness, material or inspection configuration that is not listed here.
Newman Tools has supplied high-quality tools and supplies to machine shops, plant engineering and maintenance since 1955. We supply Pi Tape® precision diameter measuring tapes in inch and metric sizes and can assist with standard, large-diameter and specialty applications.
We ship worldwide, including Canada and the USA. For current pricing or help selecting a Pi Tape, please contact Newman Tools.
Trademarks are the properties of their respective owner(s).
The descriptions, illustrations, specifications, dimensions, and part numbers are subject to change without notice.
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