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== Model Pipe Threads == | == Model Pipe Threads == | ||
=== NPT American National Standard Tapered Pipe Thread == | === NPT American National Standard Tapered Pipe Thread === | ||
NPT is a North American tapered pipe standard. | NPT is a North American tapered pipe standard. |
Revision as of 16:00, 2 June 2015
Standard Screw Threads and Tap Drill Sizes
American Threads
No. | Thread | Tap Drill | Clear Drill |
---|---|---|---|
0 | 80 | 56 | 52 |
1 | 72 | 53 | 48 |
2 | 56 | 49 | 43 |
3 | 48 | 47 | 39 |
4 | 40 | 44 | 32 |
5 | 40 | 39 | 30 |
6 | 32 | 36 | 28 |
8 | 36 | 29 | 19 |
10 | 32 | 21 | 11 |
12 | 24 | 16 | 2 |
Size | Thread | Tap Drill |
---|---|---|
1/4 | 28 | 3 |
5/16 | 24 | I |
3/8 | 24 | Q |
7/16 | 20 | 25/64 |
1/2 | 20 | 29/64 |
Size | Thread | Tap Drill |
---|---|---|
1/4 | 20 | 7 |
5/16 | 18 | F |
3/8 | 16 | 5/16 |
7/16 | 14 | U |
1/2 | 13 | 27/64 |
9/16 | 12 | 31/64 |
5/8 | 11 | 17/32 |
British Threads
Size | Thread | Tap Drill |
---|---|---|
5/32 | 40 | #30 |
3/16 | 40 | 5/32 |
7/32 | 40 | 3/16 |
1/4 | 40 | 7/32 |
5/16 | 32 | J |
3/8 | 32 | Q |
3/8 | 40 | 11/32 |
Size | Diameter mm | Diameter inch | Tap Drill | Clear Drill |
---|---|---|---|---|
0 | 6.0 | 0.2362 | 10 | C |
1 | 5.3 | 0.2087 | 17 | 2 |
2 | 4.7 | 0.1851 | 24 | 12 |
3 | 4.1 | 0.1614 | 29 | 19 |
4 | 3.6 | 0.1417 | 32 | 27 |
5 | 3.2 | 0.1260 | 37 | 30 |
6 | 2.8 | 0.1102 | 43 | 34 |
7 | 2.5 | 0.0984 | 46 | 38 |
8 | 2.2 | 0.0866 | 50 | 43 |
9 | 1.9 | 0.0748 | 53 | 47 |
10 | 1.7 | 0.0670 | 55 | 50 |
11 | 1.5 | 0.0591 | 56 | 52 |
12 | 1.3 | 0.0512 | 60 | 54 |
14 | 1.0 | 0.0394 | 70 | 59 |
Machine Screw Diameters
The Miniature Locomotive, July-August 1954
Machine screws are numbered as distinct from Cap Screws, Bolts, etc, and range usually from #0 to #12. A convenient method of finding the exact diameter if a table is not handy is as follows:
- Multiply the number of 13 and add sixty thousandths. The answer will be thousandths.
Examples:
- #0 -- 0 multiplied by 13 equals 0, plus 0.060 equals 0.060
- #3 -- 3 multiplied by 13 equals 39, plus 0.060 equals 0.099
- #5 -- 5 multiplied by 13 equals 65, plus 0.060 equals 0.125
- #10 -- 10 multiplied by 13 equals 0.130, plus 0.060 equals 0.190
Model Pipe Threads
NPT American National Standard Tapered Pipe Thread
NPT is a North American tapered pipe standard.
MTP Model Taper Pipe
MTP is a North American tapered pipe standard designed specifically for small live steam models.
METP Model Engineer Taper Pipe
METP is the British equivalent of the North American MTP.
ME Model Engineering (British Straight Thread)
ME is a British, non-tapered (straight) thread.
UNS American National Standard Unified Special
UNS is a non-tapered (straight) thread.
UST Universal Straight and Taper
UST is a proprietry tapered thread designed by PM Research.
Comments
Ciszewski posted on PracticalMachinist.com:
- You can tap NPT without taper reaming. Morse Cutting Tools recommends:
- 1/4 NPT - drill with a 7/16 bit to a minimum depth of 0.78125 & tap to a depth of 0.72525
- 3/8 NPT - drill with a 37/64 bit to a minimum depth of 0.8125 & tap to a depth of 0.7565
- 1/2 NPT - drill with a 45/64 bit to a minimum depth of 1.03125 & tap to a depth of 0.96025
- Following these recommendations will only give you a full thread for the first 2 to 3 threads.