Male R-threads (tapered) can be screwed into female G or R-threads.
For full table with Thread Tolerances - rotate the screen!
|Threads per Inch|
|Outside Diameter |
d = D
d2 = D2
d1 = D1
|a||Tolerances of Internal Thread||Tolerances of|
|1/16||28||0.907||7.723||7.142||6.561||1/16||4||± 0.071||± 1 1/4||± 1||± 0.9|
|1/8||28||0.907||9.23||9.147||8.566||1/8||4||± 0.071||± 1 1/4||± 1||± 0.9|
|1/4||19||1.337||13.157||12.301||11.445||1/4||6||± 0.104||± 1 1/4||± 1||± 1.3|
|3/8||19||1.337||16.662||15.806||14.950||3/8||6.4||± 0.104||± 1 1/4||± 1||± 1.3|
|1/2||14||1.814||20.955||19.793||18.631||1/2||8.2||± 0.142||± 1 1/4||± 1||± 1.8|
|3/4||14||1.814||26.441||25.279||24.117||3/4||9.5||± 0.142||± 1 1/4||± 1||± 1.8|
|1||11||2.309||33.249||31.770||30.291||1||10.4||± 0.18||± 1 1/4||± 1||± 2.3|
|1 1/4||11||2.309||41.910||40.431||38.952||1 1/4||12.7||± 0.18||± 1 1/4||± 1||± 2.3|
|1 1/2||11||2.309||47.803||46.324||44.845||1 1/2||12.7||± 0.18||± 1 1/4||± 1||± 2.3|
|2||11||2.309||59.614||58.135||56.656||2||15.9||± 0.18||± 1 1/4||± 1||± 2.3|
|2 1/2||11||2.309||75.184||73.705||72.226||2 1/2||17.5||± 0.216||± 1 1/2||± 1 1/2||± 3.5|
|3||11||2.309||87.884||86.405||84.926||3||20.6||± 0.216||± 1 1/2||± 1 1/2||± 3.5|
The outside diameter of a pipe or fitting must be measured and compared to a table for size identification. A 3/4" ISO 7-1 pipe thread has an outside diameter - OD - of 1.060 inches. Each thread size has a defined number of threads per inch - TPI, or pitch. The 3/4" NPT pipe thread has 14 threads per inch. Both the TPI and OD of the thread are required for positive identification of thread size because more than one size have the same TPI.
ISO 7-1 threads may look similar to NPT threads. However, ISO and NPT threads should not be mixed. ISO threads have 55o taper angle versus 60o for NPT. The NPT root and crest configurations are also different from ISO. For ISO threads pitch is usually measured in millimeters ( may be expressed in Inch). The pitch are different.
|Nominal Pipe Size |
|Length of Thread |
DIN 2999 is the German version of BS 21 and BS 2779 which were the original British Whitworth screw thread pipe joint standards. DIN 2999 has been withdrawn, is obsolete and has been replaced with ISO 7 and ISO 228.
Sizes and dimensions of pipes and tubes, and their fittings - inside and outside diameter, weight and more.
Thread data - metric, unified, ACME and others.
NPS pressure tight straight pipe threads with lubricant or sealer.
NPT and NPTF pipe threads - dimensions according ANSI/ASME B1.20.1/3.
British Brass Thread is an imperial unit based screw thread.
British Standard Cycle is a British Imperial screw thread standard.
BSPT - British Standard Pipe Taper threads & BSP or BSPF - British Standard Pipe Parallel (Straight) threads.
Pipe threads where pressure tight joints are made on the threads - Part 1: Taper external threads and parallel internal threads.
International Organization for Standardization - ISO - pipe, tube and fittings standards and specifications.
Requirements for thread form, dimensions, tolerances and designation for fastening pipe threads, thread sizes.
Metric threads spark plugs according ISO 28741.
Dimensions of metric threads according ISO 724.
NPT - Briggs Standard Pipe threads - Taps and Drill Sizes.
Metric versus Imperial equivalent screw dimensions.
Applied threaded standards used for piping connections.
Piping thread standards.
ANSI/ASME B1.1 Unified National Thread - UNC Coarse series and UNF Fine series.
BSPP (G) - British Standard Pipe Parallel and BSPT (R/Rp) – British Standard Tapered Pipe for pipes and tapered threads - G/R/Rp.
Taps and drill sizes used for Whitworth - ISO 7 and ISO 228 threads.
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