Wood Screw Sizes Chart
I'm going to be building a workbench, so I've been 'screw shopping.' I need some explanation on the sizing of screws when they are advertised as (example) 6 x 3/4'. I know that 3/4' is the length of the screw, but what does the 6 mean?
Calvin AllenCalvin AllenPilot Holes For Lag Bolts. Lag bolts are nothing more than large wood screws, as shown in Figure 1. They come in numerous diameters, the most common being 1/4, 5/16, 3/8 and 1/2 inch with the most common length in the range of 3/4 to 6 inches.
7 Answers
Common Screw Sizes
'6' is a #6-size screw. Screw gauges are a measure of the head size and shaft size, and are roughly linear but not quite a 1:1 relationship (a #8 screw is a little less than twice the diameter of a #4 screw). There isn't a good system for converting gauge to a calibrated measurement, so you're best off consulting a table like this: http://hingedummy.info/screwinfopage2.htm
Screws have three basic measurements: gauge, threads per inch, and shaft length in inches. So, you may also see a measurement like 6-32 x 1 1/2'. This means it's a #6 diameter, with 32 threads per inch (almost double the normal thread count as a standard wood screw) and an inch and a half long. When the middle number is absent (6 x 1 1/2'), the screw has the 'normal' number of threads per inch for that size and type of screw (for #6 wood screws that's 18).
KeithSKeithSYou might find this table useful as well..
See also here and the original, here.
Disclaimer: I wrote the table after more than 30 years in trade (builder/carpenter).
The sites mentioned in previous answers are nice, but are not comprehensive. There are several different ways of measuring the diameter which is critical to understand based on the application. For example, for placing a screw in a tapped hole, the important diameter is the major diameter (the largest diameter around the shank including the threads). A chart with those measurements is given here:http://www.engineersedge.com/screw_threads_chart.htmalong with explanations of the different measurements:https://en.wikipedia.org/wiki/Screw_thread#Diameters
Back in the last century when we were not sure of a screw's gauge, a reliable rule of thumb was to measure the diameter of the countersunk head in inches. Deduct from that measurement 1/16', and then count the number of 1/32' remaining. So a screw head with a diameter of 1/4' was a 6 gauge, 5/16' was an 8 gauge, 3/8' was a 10 gauge and so on.
Wood Screw Sizes Chart
McMaster-Carr also has a good description of a lot of information concerning the many kinds of threaded fasteners available. http://www.mcmaster.com/#about-machine-screws/=h8mmn6 Oblivion light armor mods.
The way I was shown was to measure across the screw head in1/16th's double it and take away 2. ie. if it is 5/16th's across double to 10 - 2 = 8
protected by StevenJan 28 '15 at 2:13
Round Head Wood Screw Size Chart
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