Machine Screw - Size Chart

Machine Screw Size ChartUNC · UNF · INCH & MM
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Reference only. Dimensions per ASME B18.6.3 and ASME B1.1. Verify critical dimensions against the applicable standard and product data. © Mutual Screw & Supply. Printed from mutualscrew.com/pages/machine-screw-size-chart

Machine screw sizes from #0 to 1/2" with diameter in inches and millimeters, coarse and fine threads per inch, tap and clearance drills.

Machine Screw Dimensions and Thread Chart

Size Diameter (in) Diameter (mm) Threads/Inch UNC (Coarse) Threads/Inch UNF (Fine) Tap Drill (UNC; #0 is 0-80 UNF) Clearance Drill
#0 0.0600 1.52 – 80 3/64" 1/16"
#1 0.0730 1.85 64 72 #53 5/64"
#2 0.0860 2.18 56 64 #50 3/32"
#3 0.0990 2.51 48 56 #47 7/64"
#4 0.1120 2.84 40 48 #43 1/8"
#5 0.1250 3.18 40 44 #38 9/64"
#6 0.1380 3.51 32 40 #36 5/32"
#8 0.1640 4.17 32 36 #29 11/64"
#10 0.1900 4.83 24 32 #25 13/64"
#12 0.2160 5.49 24 28 #16 7/32"
1/4" 0.2500 6.35 20 28 #7 17/64"
5/16" 0.3125 7.94 18 24 F 21/64"
3/8" 0.3750 9.53 16 24 5/16" 25/64"
7/16" 0.4375 11.11 14 20 U 29/64"
1/2" 0.5000 12.70 13 20 27/64" 33/64"

How to Read a Machine Screw Size Chart

Tap Drill Size: Use this drill bit when you plan to cut (tap) threads into the hole. The tap drill leaves just enough material for the threads to engage properly.
Clearance Drill Size: Use this drill bit when the screw must pass through freely without threading, such as through the top board in a two-piece wood joint, or through a bracket.
UNC (Coarse Thread): Unified National Coarse. Standard for most general applications. Faster to install, better in softer materials, more resistant to cross-threading.
UNF (Fine Thread): Unified National Fine. Used where greater strength, better vibration resistance, or finer adjustment is needed.
– indicates no standard thread in that series. #0 is made in fine thread (0-80) only.

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In stock from #0 to 1/2" · All head styles, grades & finishes · Serving customers since 1947

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Data based on ASME B18.6.3 standards. Always verify with product datasheets for critical applications.