Fastener Sizes

As you build your robot, you will be drilling and tapping hundreds of holes. A reference that you will always want to have handy is a Tap and Clearance Drill Chart. This document will provide a typical chart, as well as explain how SolidWorks standard fasteners are dimensioned.

(Reference) Tap and Clearance Drill Chart

The chart[^1] below can be a valuable resource in helping to quickly determine the proper Tap Drill or Clearance Drill to use for various fasteners indicated in the Input-Inc. CAD releases.

Screw	O.D.	Tap		Close Fit		Free Fit
Size/Thread	Decimal	Size *	Decimal	Size	Decimal	Size	Decimal
000-120	0.0340"	71	0.0260"	65	0.0350"	62	0.0380"
00-90	0.0440	65	0.0350	3/64"	0.0469	55	0.0520
0-80	0.0600	3/64" (56)	0.0469	52	0.0635	50	0.0700
1-72	0.0730	53	0.0595	48	0.0760	46	0.0810
2-56	0.0860	50	0.0700	43	0.0890	41	0.0960
3-48	0.099	47	0.0790	37	0.1040	36	0.1065
4-40	0.1120	43	0.0890	32	0.1160	30	0.1285
5-40	0.125	38	0.102	29	0.1360	28 (9/64)	0.1405
6-32	0.1380	36	0.1065	27	0.1440	25	0.1495
8-32	0.1640	29	0.1360	18 (11/64)	0.1695	16	0.1770
10-24	0.190	25	0.150	9	0.196	7 (13/64)	0.2010
10-32	0.1900	21	0.1590	9	0.1960	7 (13/64)	0.2010
1/4-20	0.2500	7	0.2010	F	0.2570	H (17/64)	0.2660
1/4-28	0.2500	3	0.2130	F	0.2570	H (17/64)	0.2660
5/16-18	0.3125	F	0.2570	P	0.3230	Q	0.3320
3/8-16	0.3750	5/16"	0.3125	W	0.3860	X	0.3970
1/2-13	0.5000	27/64"	0.4219	33/64"	0.5156	17/32"	0.5312

• For copper, aluminum, cast iron, bakelite, or very thin materials, use one drill size larger (i.e. a slightly smaller diameter).

Standard SolidWorks fastener dimensions

Fasteners will appear in the Input-Inc. CAD in a few different ways:

• standard fasteners from SolidWorks' internal fastener library
• imported geometry from a fastener vendor, such as McMaster

For SolidWorks' standard fasteners, SolidWorks will show you the fastener diameter (in inches) as opposed to the gauge number of the fastener. The above Tap and Clearance Drill Chart is therefore also handy to aid in the conversion.

See the image below as an example:

The highlighted screw is indicated as a 0.138" diameter x 32 pitch fastener, 0.25" long, where "SBHCSCREW" means Socket Button Head Cap SCREW.

Using the above Tap and Clearance Drill Chart, we can see that a fastener of 0.138" is a #6 gauge screw by looking up 0.1380 in the "O.D" (Outer Diameter) column:

Screw	O.D.	Tap		Close Fit		Free Fit
Size/Thread	Decimal	Size *	Decimal	Size	Decimal	Size	Decimal
6-32	0.1380	36	0.1065	27	0.1440	25	0.1495

Therefore, for this particular fastener, we will need a 6-32 x 0.25" long screw.

[^1]: The information in the provided chart is copied from here. All credit goes to the original author.