MAN4MACHINE1-1/8-18 UNEF
Unified National Extra Fine
The finest of the three graduated series. The shallow thread depth suits thin-walled tubing and sheet material too thin to hold a coarser thread, and the fine pitch gives precise adjustment per turn on instrumentation and fine-mechanism hardware.
- Standard
- ASME B1.1
- Flank angle
- 60° included
- TPI
- 18
- Major diameter
- 1.1250" (basic)
- Other series, same size
Thread profile
A 60 degree included flank angle.
Basic major 1.1250", pitch diameter 1.0889", minor diameter 1.0649" -- theoretical dimensions before any tolerance class is applied.
UNEF sizes
| Size | TPI | Major Ø | Pitch Ø | Minor Ø |
|---|---|---|---|---|
| #12 | 32 | 0.2160" | 0.1957" | 0.1822" |
| 1/4 | 32 | 0.2500" | 0.2297" | 0.2162" |
| 5/16 | 32 | 0.3125" | 0.2922" | 0.2787" |
| 3/8 | 32 | 0.3750" | 0.3547" | 0.3412" |
| 7/16 | 28 | 0.4375" | 0.4143" | 0.3988" |
| 1/2 | 28 | 0.5000" | 0.4768" | 0.4613" |
| 9/16 | 24 | 0.5625" | 0.5354" | 0.5174" |
| 5/8 | 24 | 0.6250" | 0.5979" | 0.5799" |
| 11/16 | 24 | 0.6875" | 0.6604" | 0.6424" |
| 3/4 | 20 | 0.7500" | 0.7175" | 0.6959" |
| 13/16 | 20 | 0.8125" | 0.7800" | 0.7584" |
| 7/8 | 20 | 0.8750" | 0.8425" | 0.8209" |
| 15/16 | 20 | 0.9375" | 0.9050" | 0.8834" |
| 1 | 20 | 1.0000" | 0.9675" | 0.9459" |
| 1-1/16 | 18 | 1.0625" | 1.0264" | 1.0024" |
| 1-1/8 | 18 | 1.1250" | 1.0889" | 1.0649" |
| 1-3/16 | 18 | 1.1875" | 1.1514" | 1.1274" |
| 1-1/4 | 18 | 1.2500" | 1.2139" | 1.1899" |
| 1-5/16 | 18 | 1.3125" | 1.2764" | 1.2524" |
| 1-3/8 | 18 | 1.3750" | 1.3389" | 1.3149" |
| 1-7/16 | 18 | 1.4375" | 1.4014" | 1.3774" |
| 1-1/2 | 18 | 1.5000" | 1.4639" | 1.4399" |
Did you know
Why fine pitch bolts don't just work harder
A UNF bolt isn't a "better" UNC bolt -- it trades thread depth for tensile area. Cutting a shallower thread at the same nominal diameter leaves more metal at the minor diameter, which is why fine threads resist stripping and hold torque under vibration better, even though the coarser UNC thread is actually faster to run down and more tolerant of a dinged or dirty hole.
Tap drill calculator
Try “1/4-20 UNC-2A”, “#10-32 UNF”, or “1-8 UN-3A”. Add “LH” for a left-hand thread.
Basic (theoretical) dimensions and a shop tap drill only -- ASME B1.1's exact Class 1A/2A/3A pitch diameter limits depend on length of thread engagement as well as grade. Consult the standard or a calibrated thread gauge for gauge-critical work.
Calculated live
Basic dimensions
- Major diameter
- 1.1250"
- Pitch diameter
- 1.0889"
- Minor diameter
- 1.0649"
Clearance (normal)
- Clearance drill
- 1-5/32" (1.1563")
Looking for a different size or series? Open the full calculator →