What size hole to drill for a #10 sheet metal screw?
Your pilot-hole drill-bit size will depend on the size of your sheet-metal screw. A size-4 screw should have a pilot-hole drill size of 3/32 inches; size 6, 7/64 inches; size 8, 1/8 inches; size 10, 9/64 inches; size 12, 5/32 inches; size 14-1/4 inches, 3/16 inches; and 5/16 inches, 1/4 inches.
US Machine Screw Diameters
- 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.
- They were one of the first international standards agreed when the International Organization for Standardization was set up in 1947. The "M" designation for metric screws indicates the nominal outer diameter of the screw, in millimeters (e.g., an M6 screw has a nominal outer diameter of 6 millimeters).
- For fasteners where the head usually sits above the surface, the measurement is from directly under the head to the end of the fastener. For fasteners that are designed to be countersunk, the measurement is made from the point on the head where the surface of the material is, to the end of the fastener.
Drill bit sizes for pre-drilling (most commonly used sizes in bold)
|Screw Size||Pilot hole size for hardwoods*||Pilot hole size for softwood**|
- First, drill a pilot hole through both boards. Pilot holes guarantee that your screw won't break off and your wood won't crack. For most hardwoods, the pilot hole should be at least as large as the screw's minor diameter. If the screw has deep threads, or the wood is very hard, the pilot hole should be another 1/64-in.
- Predrill holes for screws with countersink bits to avoid splitting the wood or snapping the screw. Wood screws are better than drywall screws for woodworking projects. Drywall screws are made of hardened, brittle steel, and the shaft will often snap during installation, especially if they're screwed into hardwoods.
- Drill bit sizes for pre-drilling (most commonly used sizes in bold)
Screw Size Pilot hole size for hardwoods* Pilot hole size for softwood** #9 1/8 3/32 #10 1/8 7/64 #11 5/32 9/64 #12 9/64 1/8
Wood Screw Pilot Hole Sizes
|Screw Size||Hard Wood|
|Tapered Bit||Straight Bit|
- Drill the tap hole: The size of the drill bit to be used is dependent on the type of spile you are using. Most spiles require either a 7/16 or 5/16 bit. Drill a hole 2 to 2 ½ inches deep.
- US Tap and Drill Bit Size Table
Tap Fractional Drill Bit Number Drill Bit #10-24 5/32" 25 #10-32 5/32" 21 #12-24 11/64" 16 1/4"-20 13/64" 7 Tap size Threads per inch Drill size w/ taper pipe reamer 1/16 27 15/64 1/8 27 21/64 1/4 18 27/64 3/8 18 9/16
Updated: 3rd December 2019