Shoulder diameter, thread size, head size and hex key for inch socket shoulder screws, 1/4″ to 2″. ASME B18.3.
A shoulder screw (“stripper bolt” or “shoulder bolt”) has a socket head, a smooth, close-tolerance shoulder, and a smaller thread on the end. It is sized by the shoulder: a 1/4″ × 7/8″ shoulder screw has a 1/4″ shoulder, 7/8″ long, and a #10-24 thread. The length is the shoulder length — from under the head to the end of the shoulder — and does not include the thread. D is the shoulder diameter, A the head diameter, H the head height, J the hex key. Inches throughout.
Letters match the table. Socket shown dashed.
| Shoulder | D max | D min | Thread | Head A max | A min | Head H max | H min | Key J |
|---|---|---|---|---|---|---|---|---|
| 1/4″ | 0.2480 | 0.2460 | #10-24 | 0.375 | 0.357 | 0.188 | 0.177 | 1/8″ |
| 5/16″ | 0.3105 | 0.3085 | 1/4″-20 | 0.438 | 0.419 | 0.219 | 0.209 | 5/32″ |
| 3/8″ | 0.3730 | 0.3710 | 5/16″-18 | 0.562 | 0.543 | 0.250 | 0.240 | 3/16″ |
| 1/2″ | 0.4980 | 0.4960 | 3/8″-16 | 0.750 | 0.729 | 0.312 | 0.302 | 1/4″ |
| 5/8″ | 0.6230 | 0.6210 | 1/2″-13 | 0.875 | 0.853 | 0.375 | 0.365 | 5/16″ |
| 3/4″ | 0.7480 | 0.7460 | 5/8″-11 | 1.000 | 0.977 | 0.500 | 0.490 | 3/8″ |
| 1″ | 0.9980 | 0.9960 | 3/4″-10 | 1.312 | 1.287 | 0.625 | 0.610 | 1/2″ |
| 1-1/4″ | 1.2480 | 1.2460 | 7/8″-9 | 1.750 | 1.723 | 0.750 | 0.735 | 5/8″ |
| 1-1/2″ | 1.4980 | 1.4960 | 1-1/8″-7 | 2.125 | 2.095 | 1.000 | 0.980 | 7/8″ |
| 1-3/4″ | 1.7480 | 1.7460 | 1-1/4″-7 | 2.375 | 2.345 | 1.125 | 1.105 | 1″ |
| 2″ | 1.9980 | 1.9960 | 1-1/2″-6 | 2.750 | 2.720 | 1.250 | 1.230 | 1-1/4″ |
The thread is smaller than the shoulder, coarse (UNC). Thread pitches are on the thread pitch chart.
Where you’ll see them
Punch and die work — locating and holding stripper plates (hence “stripper bolt”) — and as guides, pivots and pulley shafts.
Quick answers
- How are shoulder screws measured?
- By the shoulder: its diameter and its length, measured from under the head to the end of the shoulder. The thread is not included.
- What thread is on a 1/2" shoulder screw?
- A 1/2″ shoulder screw has a 3/8″-16 thread and takes a 1/4″ hex key.
- What thread goes with each shoulder size?
- 1/4″ shoulder – #10-24, 5/16″ shoulder – 1/4″-20, 3/8″ shoulder – 5/16″-18, 1/2″ shoulder – 3/8″-16, 5/8″ shoulder – 1/2″-13, 3/4″ shoulder – 5/8″-11, 1″ shoulder – 3/4″-10, 1-1/4″ shoulder – 7/8″-9, 1-1/2″ shoulder – 1-1/8″-7, 1-3/4″ shoulder – 1-1/4″-7, 2″ shoulder – 1-1/2″-6.
- What is another name for a shoulder screw?
- Stripper bolt, or shoulder bolt. The name comes from holding stripper plates in punch and die work.