Tell me more ×
Home Improvement Stack Exchange is a question and answer site for contractors and serious DIYers. It's 100% free, no registration required.
up vote 25 down vote favorite
4

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?

share|improve this question

4 Answers

up vote 31 down vote accepted

"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).

share|improve this answer
2  
Good answer. Only thing I could add is that some "normal" thread screws can come in both fine and coarse thread varieties, so you could have "6 x 1 1/2" coarse" or "6 1 1/2" fine". – Tester101♦ Apr 23 '12 at 16:19
Fantastic explanation, thanks! – Calvin.Allen Apr 23 '12 at 16:21
Also, I usually see screw gauges for sizes less than 1/4". Above that I see fractions. – Jay Bazuzi Apr 23 '12 at 21:06
up vote 1 down vote

6 refers to the size of the screw - diameter, threads, etc

http://www.wlfuller.com/html/wood_screw_chart.html

http://www.csgnetwork.com/screwinfo.html

share|improve this answer
up vote 1 down vote

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.htm along with explanations of the different measurements: https://en.wikipedia.org/wiki/Screw_thread#Diameters

share|improve this answer
up vote 0 down vote

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

share|improve this answer
Good summary, but they omit PoziDrive and Hex-insert for the heads. – staticsan Apr 26 '12 at 6:56

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.