Screw Thread For Camera, Camcorder And Tripod Mounts  

by Matt Hawkins, 02/11/2010

Having made a few DIY camera accessories in my time I thought I would provide some info on the screw thread used in most photographic equipment. It is important you use the correct fittings otherwise you may damage your camera mount.

The bolt that attaches to the camera (and is found on most tripods etc) is : 1/4" 20tpi UNC. In the past it was a 1/4" 20tpi BSW but at some point someone decided to create a standard and use UNC instead. Most likely so they could charge you to buy a copy of their "standard".

Here are some terms :
tpi - Threads per inch
BSW - British Standard Whitworth
UNC - Unified Thread System

Larger equipment sometimes uses : 3/8" 16tpi

BSW and UNC?

As mentioned above BSW stands for "British Standard Whitworth" and was introduced in 1841. UNC stands for "Unified Thread System" and was introduced in 1918. The number of threads per inch may be the same BUT the thread angle is different.

BSW thread angle 55 degrees
UNC thread angle 60 degrees

Apparently a 1/4" UNC bolt will fit a 1/4" BSW nut (or camera shoe) despite the thread angle difference. For camera equipment the screw length is fairly short so the thread angle doesn't make much difference.

Whatever bolts you use in your camera accessories make sure it fits correctly and don't use excessive force. Otherwise you may damage your camera shoe and repairing it may be impossible or expensive.

Unfortunately buying 1/4" bolts in the UK is not easy because most hardware stores only sell bolts in metric sizes. There is no metric equivalent to the 1/4" bolt. You may need to visit a smaller independent hardware store and speak to someone who actually knows what imperial sizes are.

So, yes, the camera mount on your shiney new HD camcorder was originally based on a bolt designed in 1841 to hold steam trains together!

Author : Matt Hawkins  Last Edit By : Matt Hawkins
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