Tap-End Studs
A short interference-fit thread one end, nut thread the other.
Tap-end studs to AWEM and API 6A patterns for tapped-hole installation.
Specifications & technical data.
Tap-end studs to ASME B18.31.2 — a Class 5 interference-fit tap end that seats permanently in the tapped hole, and a nut end that does the clamping.
Download our tap-end stud dimensioning table (PDF)| Nominal Size | BM — Tap-End Thread Length | U max — Chamfered Thread Distance | B min — Nut-End Full Thread Length | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Nominal | Min. | Max. | UNC | UNF | 8UN | L < 10 | 10 ≤ L ≤ 16 | L > 16 | |
| 1/4" | 0.375 | 0.350 | 0.400 | 0.100 | 0.071 | … | 0.750 | 1.000 | 1.500 |
| 5/16" | 0.469 | 0.440 | 0.498 | 0.111 | 0.083 | … | 0.875 | 1.125 | 1.625 |
| 3/8" | 0.563 | 0.532 | 0.594 | 0.125 | 0.083 | … | 1.000 | 1.250 | 1.750 |
| 7/16" | 0.656 | 0.620 | 0.692 | 0.143 | 0.100 | … | 1.125 | 1.375 | 1.875 |
| 1/2" | 0.750 | 0.708 | 0.792 | 0.154 | 0.100 | … | 1.250 | 1.500 | 2.000 |
| 9/16" | 0.844 | 0.802 | 0.896 | 0.167 | 0.111 | … | 1.375 | 1.625 | 2.125 |
| 5/8" | 0.938 | 0.892 | 0.983 | 0.182 | 0.111 | … | 1.500 | 1.750 | 2.250 |
| 3/4" | 1.125 | 1.075 | 1.175 | 0.200 | 0.125 | … | 1.750 | 2.000 | 2.500 |
| 7/8" | 1.313 | 1.258 | 1.368 | 0.222 | 0.143 | … | 2.000 | 2.250 | 2.750 |
| 1" | 1.500 | 1.438 | 1.562 | 0.250 | 0.167 | … | 2.250 | 2.500 | 3.000 |
| 1-1/8" | 1.688 | 1.625 | 1.750 | 0.286 | 0.167 | 0.250 | 2.500 | 2.750 | 3.250 |
| 1-1/4" | 1.875 | 1.813 | 1.938 | 0.286 | 0.167 | 0.250 | 2.750 | 3.000 | 3.500 |
| 1-3/8" | 2.063 | 2.000 | 2.125 | 0.333 | 0.167 | 0.250 | 3.000 | 3.250 | 3.750 |
| 1-1/2" | 2.250 | 2.188 | 2.313 | 0.333 | 0.167 | 0.250 | 3.250 | 3.500 | 4.000 |
| 1-5/8" | 2.438 | 2.375 | 2.500 | … | … | 0.250 | 3.500 | 3.750 | 4.250 |
| 1-3/4" | 2.625 | 2.563 | 2.688 | 0.400 | … | 0.250 | 3.750 | 4.000 | 4.500 |
| 1-7/8" | 2.813 | 2.750 | 2.875 | … | … | 0.250 | 4.000 | 4.250 | 4.750 |
| 2" | 3.000 | 2.925 | 3.075 | 0.444 | … | 0.250 | 4.250 | 4.500 | 5.000 |
| 2-1/4" | 3.375 | 3.300 | 3.450 | 0.444 | … | 0.250 | 4.750 | 5.000 | 5.500 |
| 2-1/2" | 3.750 | 3.675 | 3.825 | 0.500 | … | 0.250 | 5.250 | 5.500 | 6.000 |
| 2-3/4" | 4.125 | 4.050 | 4.200 | 0.500 | … | 0.250 | 5.750 | 6.000 | 6.500 |
| 3" | 4.500 | 4.425 | 4.575 | 0.500 | … | 0.250 | … | 6.500 | 7.000 |
| 3-1/4" | 4.875 | 4.775 | 4.975 | 0.500 | … | 0.250 | … | 7.000 | 7.500 |
| 3-1/2" | 5.250 | 5.150 | 5.350 | 0.500 | … | 0.250 | … | 7.500 | 8.000 |
| 3-3/4" | 5.625 | 5.525 | 5.725 | 0.500 | … | 0.250 | … | 8.000 | 8.500 |
| 4" | 6.000 | 5.900 | 6.100 | 0.500 | … | 0.250 | … | 8.500 | 9.000 |
All dimensions in inches, per ASME B18.31.2-2014. BM = tap-end thread length (Class 5 interference fit); U max = 2P. Confirm requirements with our estimating team.
Standards.
What are tap-end studs?
A tap-end stud screws permanently into a tapped hole: the short tap end carries a Class 5 interference-fit thread that seats tight and stays put, while the longer nut end takes the working nut. Pumps, compressors, engine blocks and machine housings run on them.
- Class 5 interference-fit tap end
- Nut end sized for standard heavy hex nuts
- Tap-end length ≈ 1.5 × diameter
- Any length, machined in-house
Other names
- Tap end studs
- Interference-fit studs
- Engine studs (loosely)
- Shoulder studs (incorrectly)
Tips for purchasing
- Tell us the tapped-hole spec — the Class 5 fit is matched to the hole, not just the size.
- Nut-end thread length follows the table by stud length.
- Removal and reuse of interference studs is a repair decision — ask us about oversize tap ends.
- MTRs and traceability come standard.
Materials.
Representative capabilities — every item is manufactured or certified to your specification. Confirm requirements with our estimating team.
