Thread Gage Finder
Enter a thread callout. Get its basic dimensions, the pitch-diameter limits for the bolt and the nut, and the GO / NO GO gages that check them.
Don't know the thread? Identify it from a measurement
Basic profile
60° form. Pitch diameter is where thread and groove widths are equal; it's the dimension a thread gage checks.
Bolt
External thread limits
| Max | Min |
|---|
Nut
Internal thread limits
| Min | Max |
|---|
How these numbers are calculated
Unified inch (UNC, UNF, UNEF, UN, UNS): ASME B1.1, Classes 2A / 2B (standard) and 3A / 3B (closer fit). Pitch-diameter tolerance for Class 2A = 0.0015∛D + 0.0015√LE + 0.015∛P², with length of engagement LE taken as one nominal diameter. Other classes are multiples of it (3A 0.75×, 2B 1.3×, 3B 0.975×). Class 2A carries an allowance of 0.3 × the 2A tolerance; 3A has none.
ISO metric (M): ISO 965-1/-2 at the standard 6g bolt / 6H nut tolerance classes, normal length of engagement.
Tap drill: sizes and percent of thread from WESTport's tap drill charts. Where a size isn't on the chart, the estimate is the drill that leaves 75% of the basic thread depth.
Gage members are made to the product limits shown, with gagemaker's tolerances (ASME B1.2 / ISO 1502) applied inside them. Long engagement lengths, coated threads and special classes change these limits. For anything outside the standard, call 1-888-400-4243.
Disclaimer
This calculator is a reference tool. Results are calculated from published ASME and ISO formulas and tables, but they are not a substitute for the applicable standard, your drawing or your customer's requirements.
You are solely responsible for checking every value before you use it to make, buy, inspect or accept parts or gages. WESTport Corporation provides this tool "as is" and makes no warranty, express or implied, as to the accuracy, completeness or fitness for a particular purpose of any result. WESTport is not liable for any loss, damage, scrap, rework or other cost arising from the use of, or reliance on, this tool.
For certified gage dimensions, or if you're unsure which gage you need, call 1-888-400-4243.