The various standards for taps give certain allowances or tolerances for manufacture. Taps are generally manufactured to take advantage of these tolerances, so that as they wear their life is extended. The closest tolerances are applied to Class 1 taps, and the most generous to Class 3. Standard, off the shelf taps are manufactured to Class 2, which applies to all taps listed in this catalogue. Classes 1 and 3 can be manufactured to order.
Classes of fit apply to all thread forms:-
Information on tolerances and fits for individual threads is available on request.
ACME-C |
Acme Thread-Centralizing |
ACME-G |
Acme Thread-General Purpose |
AMO |
American Standard Microscope Objective Thread |
ANPT |
Aeronautical National Form Taper Pipe Thread |
BA |
British Association Standard Thread |
BSF |
British Standard Fine Thread Series |
BSPP |
British Standard Pipe (Parallel) Thread |
BSPT |
British Standard Taper Pipe Thread |
BSW |
British Standard Whitworth Coarse Thread Series |
M |
Metric ScrewThread Series |
N |
American National 8, 12 and 16 Thread Series (8N, 12N, 16N) |
N BUTT |
American Buttress Screw Thread |
NC |
American National Coarse Thread Series |
NEF |
American National Extra Fine Thread Series |
NF |
American National Fine Thread Series |
NGO |
National Gas Outlet Thread |
NGT |
National Gas Taper Thread (see "SGT") |
NH |
American National Hose Coupling and Fire Hose Coupling Threads |
NPS |
For tap marking only (See NPSC, NPSM) |
NPSC |
American National Standard Straight Pipe Thread in Pipe Couplings (Tap marked NPS) |
NPSF |
Dryseal American National Standard Fuel Internal Straight Pipe Thread |
NPSH |
American National Standard Straight Pipe Thread for Hose Couplings |
NPSI |
Dryseal American National Standard Intermediate Internal Straight Pipe Thread |
NPSL |
American National Standard Straight Pipe Thread for Loose Fitting Mechanical Joints with Locknuts |
NPSM |
American National Standard Straight Pipe Threads for Free-Fitting Mechanical Joints for Fixtures (Tap marked NPS) |
NPT |
American National Standard Taper Pipe Thread (See ANPT, NPTR) |
NPTF |
Dryseal American National Standard Taper Pipe Thread |
NPTR |
American National Standard Taper Pipe Thread for Railing Joints (Tap marked NPT) |
NS |
American National Thread-Special |
PTF |
Dryseal SAE Short Taper Pipe Thread |
SGT |
Special Gas Taper Thread |
SPL-PTF |
Dryseal Special Taper Pipe Thread |
STI |
Special Thread for Helical Coil Wire Screw Thread Inserts |
Stub Acme |
Stub Acme Thread |
*UN |
Unified Constant Pitch Thread Series |
*UNC |
Unified Coarse Thread Series |
*UNEF |
Unified Extra Fine Thread Series |
*UNF |
Unified Fine Thread Series |
UNJ |
Unified Thread Series with a 0.15011P to 0.18042P Controlled Root Radius on External Thread only. |
UNJC |
Unified Coarse Thread Series with a 0.15011P to 0.18042P Controlled Root Radius on External Thread only. |
UNJF |
Unified Fine Thread Series with a 0.15011P to 0.18042P Controlled Root Radius on External Thread only. |
UNM |
Unified Miniature Thread Series |
UNR |
Unified Constant Pitch Thread Series with a 0.108P to 0.144P Controlled Root Radius; Ext. thread only. |
UNRC |
Unified Coarse Thread Series with a 0.108P to 0.144P Controlled Root Radius; Ext. thread only. |
UNRF |
Unified Fine Thread Series with a 0.108P to 0.144P Controlled Root Radius; External thread only. |
*UNS |
Unified Thread-Special |
V |
A 60¡ "V" thread with Truncated Crest and Root. The theoretical "V" Form is usually flatted to the user's specifications. |
WHIT |
British Standard Whitworth Special Thread |