8/21/2019

Machine Screw Thread Sizes

  1. Small Machine Screw Thread Sizes
  2. Screw Size Chart Diameter
  3. Screw Thread Size Chart
  4. Machine Screw Thread Sizes Chart
Active1 year, 6 months ago

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 Allen

Screw Designation Tap Drill Size Close Fit Loose Fit Number Diameter Pitch Tap Size Drill Diameter Drill Diameter Drill Diameter or dia. (inch) (threads/inch) Size (inch) Size (inch) Size (inch) #0 0.06 80 0-80 3/64 0.0469 52 0.0635 50 0.07. 95 rows  ANSI/ ASME EXTERNAL Screw Thread Size Chart. All units are in inches. Unified Screw Threads per. ANSI/ASME B1.1-1989 (R2001), R2001) Nomenclature, are used. Acceptability criteria are described in ANSI/ASME B1.3M-1992 (R2001). Note: This screw chart is not comprehensive of all available standard threads as provided by the standard.

Calvin Allen
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7 Answers

'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).

KeithSKeithS
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You might find this table useful as well..

Small Machine Screw Thread Sizes

See also here and the original, here.

Disclaimer: I wrote the table after more than 30 years in trade (builder/carpenter).

handymanhandyman

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

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Peter DPeter D

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.

Screw Size Chart Diameter

John DavidsonJohn Davidson

Screw Thread Size 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

whatsisnamewhatsisname
JasonJason

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

John BignellJohn Bignell

Machine Screw Thread Sizes Chart

protected by StevenJan 28 '15 at 2:13

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