How to measure socket head shoulder screws

Tips index

To Specify Inch Shoulder Screws:

1. Call out shoulder diameter, then

2. The shoulder length

Example: 5/8" x 2" = a shoulder screw with a 5/8" diameter shoulder, 2" long.

Thread size is one standard size smaller than the shoulder diameter and needn't be specified, except for:

• A screw with a 1/2" diameter shoulder has a 3/8 - 16 thread.
• A 5/8" diameter shoulder has a 1/2 - 13 thread.

Why? 7/16" and 9/16" are not stocked shoulder diameter thread sizes.

To Specify Metric Shoulder Screws:

1. Call out shoulder diameter, then

2. The thread diameter, then

3. The shoulder length

Example: 12/M10 x 30 = a shoulder screw with a 12mm shoulder diameter, a 10mm thread diameter and a 30mm shoulder length.

With metrics, you specify shoulder and thread diameters since all dimensions are specified in whole numbers, not fractions, which can be very confusing.