HEX HEAD THREAD LENGTHS
Earnest Machine Products line of "Inch Series" cap screws are made to the dimensional requirements specified in ANSI B18.2.1. This standard defines the lengths of product that are manufactured as Threaded to the Head and the sizes that are manufactured with a Full Body Diameter.
Lengths that are "Threaded to the Head" (TTH)
Table 1 lists the maximum length for each diameter that is threaded to
the head per ANSI B18.2.1.
The "Thread Transition Length" can be calculated by the formula:
Thread Transition Length* = 2.5 x (1/ Threads per Inch)
*Transition lengths for cap screws with lengths of less than 2 x Dia are slightly shorter
Lengths with "Full Body Diameters"
Cap Screws with full body diameters (also called the shoulder or shank) start at the next length increment longer than the lengths listed in Table 1. As the cap screw's length increases the thread length stays the same and the length of the full body becomes longer.
The minimum thread length (for lengths longer than the lengths listed in
Table 1) are based on the formulas:
For Lengths up to 6" Long: 2 x Diameter + 1/4"
For Lengths Longer than 6": 2 x Diameter + 1/2"
| Diameter |
1/4 |
5/16 |
3/8 |
7/16 |
1/2 |
9/16 |
5/8 |
3/4 |
| Lengths Threaded to Head |
3/8 to 1 1/8 |
1/2 to 1 1/4 |
1/2 to 1 1/2 |
3/4 to 1 5/8 |
3/4 to 1 3/4 |
3/4 to 2 |
1 to 2 1/8 |
1 to 2 1/2 |
| Diameter |
7/8 |
1 |
1 1/8 |
1 1/4 |
1 3/8 |
1 1/2 |
1 3/4 |
2 |
| Lengths Threaded to Head |
1 1/2 to 2 7/8 |
1 1/2 to 3 1/4 |
2 to 3 5/8 |
2 to 3 7/8 |
2 1/2 to 4 1/4 |
2 to 4 1/2 |
3 to 5 1/8 |
4 to 5 3/4 |
Lengths that are Threaded to the Head
(minimum lengths shown represent lengths that are commercially available)
Diameter
Overall Lengths
|
1/4
1 1/4 to 6
|
5/16
1 5/16 to 6 |
3/8
1 5/8 to 6 |
7/16
1 3/4 to 6 |
1/2
1 7/8 to 6 |
9/16
2 1/8 to 6 |
5/8
2 1/4 to 6 |
3/4
2 5/8 to 6 |
| Thread Length |
3/4 |
7/8 |
1 |
1 1/8 |
1 1/4 |
1 3/8 |
1 1/2 |
1 3/4 |
| Max Trans. Length |
.250 |
.278 |
.312 |
.357 |
.385 |
.417 |
.455 |
.500 |
Thread Lengths with Full Body Diameter to 6" Long
| Diameter |
7/8
3 to 6 |
1
3 1/2 to 6 |
1 1/8
3 3/4 to 6 |
1 1/4
4 to 6 |
1 3/8
4 1/2 to 6 |
1 1/2
4 3/4 to 6 |
1 3/4
5 1/4 to 6 |
2
6 |
| Lengths Threaded to Head |
2 |
2 1/4 |
2 1/2 |
2 3/4 |
3 |
3 1/4 |
3 3/4 |
4 1/4 |
| Lengths Threaded to Head |
.556 |
.625 |
.714 |
.714 |
.833 |
.833 |
1.000 |
1.111 |