We are going to show you how to measure imperial (non-metric) turnbuckle swage stud sizes for standing rigging (shrouds, forestays, backstays…) and life line terminations. The following will be measured and used to specify replacement studs or turnbuckles:
- Stud diameter
- Wire diameter
- Thread Length
- Thread Count
- Right or Left hand threads
The only tool you will need is a set of calipers. Using a ruler to measure is not accurate enough if you want to be 100% sure.
- Diameter is measured with your calipers running across the rows of threads.
- Thread count is the number of threads over a one inch range and will be 20, 24, 28, 32…
- Hand is the slant of the threads either to the left or the right when looking at the stud side on. Right-Hand (RH) studs tighten clockwise, and Left-Hand (LH) studs tighten counter-clockwise.
- Thread length is the length of the stud that is threaded. Generally you will find that life line studs are considerably shorter than standing rigging turnbuckle studs.
- Wire size is the diameter of the wire and is measured with your calipers. Be sure to measure the wire at its largest diameter (correct orientation to the surface of the calipers). See illustrations above. Wire sizes are generally 3/32”, 1/8”, 5/32”, 3/16”, 1/4”, 9/32”. 5/16”, 3/8”…
Now string all of your measurements into a specification using the following example:
Hand: Right Hand
Thread Length: 3-1/2”
Wire Size: 5/16”
The stud size in this example is expressed as: ½-20 R.H. x 3-1/2” for 5/16” wire
Note: Be sure when ordering replacement threaded studs or turnbuckles that you do not choose life line fittings for standing rigging. Life line studs and fittings are not appropriate for standing rigging (mast) loads.
FYI: Most U.S. turnbuckles use swage studs that are left handed. This way the threads are opposite the lay/twist of the wire.
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