Gauge / Diameter
Thread Length
The gauge of the screw is determined by the size of the outside thread diameter.
Gauge
Metric (mm)
0g 1g 2g 3g 4g 5g 6g 7g 8g 9g 10g 12g 13g 14g 15g 16g 18g 20g 24g
1.5 1.9 2.25 2.5 3.0 3.3 3.5 3.9 4.2 4.5 4.8 5.5 6.1 6.3 6.5 6.8 7.5 8.1 9.4
Measuring Length
Screws with the following head types are measured from the top of the countersunk to the point of the screw:
Threads Per Inch (TPI)
COUNTERSUNK
DOUBLE CS
BUGLE
RAISED HEAD
DCS WITH RIBS
Screws with the following head types are measured from the underside of the head to the point of the screw:
The TPI is the number of thread crests that can be counted within 1” (25.4mm). The corser the thread the faster the insertion time but lower the holding power.
TPI PAN / ROUND
WAFER /
HEXAGON
FLANGE
Drill Tip
Metric/Imperial Size Comparison Chart
Listed beside the common imperial sizes are the metric equivalents. Also listed are common ‘even’ approximate metric equivalents in brackets. Imperial (inch)
Metric (mm)
Imperial (inch)
Metric (mm)
Imperial (inch)
Metric (mm)
Imperial (inch)
Metric (mm)
1/64” 1/32” 3/64” 1/16” 5/64” 3/32” 7/64” 1/8” 9/64” 5/32” 11/64” 3/16” 13/64” 7/32” 15/64” 1/4” 17/64” 9/32” 19/64” 5/16” 21/64” 11/32” 23/64” 3/8” 25/64”
0.40 0.79 1.19 1.59 1.98 2.38 2.78 3.17 (3.0) 3.5 3.97 (4.0) 4.5 4.76 (5.0) 5.16 5.5 5.95 6.35 (6.0) 6.75 7.14 7.54 7.94 (8.0) 8.33 8.73 9.13 9.52 (10.0) 9.92
13/32” 27/64” 7/16” 29/64” 15/32” 31/64” 1/2” 17/32” 35/64” 9/16” 37/64” 19/32” 39/64” 5/8” 41/64” 21/32” 43/64” 11/16” 45/64” 23/32” 47/64” 3/4” 49/64” 25/32” 51/64”
10.32 10.72 11.11 11.51 11.91 12.30 12.70 (13.0) 13.49 13.89 14.29 (14.0) 14.68 15.08 15.48 15.88 (16.0) 16.27 16.67 17.06 17.46 17.86 18.26 18.65 19.05 (19.0) 19.45 19.84 20.24
13/16” 53/64” 27/32” 55/64” 7/8” 57/64” 29/32” 59/64” 15/16” 61/64” 31/32” 63/64” 1” 1-1/16” 1-3/32” 1-1/8” 1-5/32” 1-3/16” 1-7/32” 1-1/4” 1-1/2” 1-3/4” 2” 2-1/4” 2-1/2”
20.64 21.03 21.43 21.83 22.23 (22.0) 22.62 23.02 23.42 23.81 24.21 24.61 25.00 25.40 (25.0) 26.99 27.78 28.58 (28.0) 29.37 30.16 (30.0) 30.96 31.75 (32.0) 38.10 (38.0) 45.45 (45.0) 50.80 (50.0) 57.15 (57.0) 63.50 (65.0)
2-3/4” 3” 3-1/4” 3-1/2” 3-3/4” 4” 4-1/2” 5” 5-1/2” 6” 6-1/2” 7” 7-1/2” 8” 8-1/2” 9” 9-1/2” 10” 11” 12” 13” 14” 15” 16” 18”
69.85 (70.0) 76.20 (75.0) 82.55 (82.0) 88.90 (90.0) 95.25 (95.0) 101.60 (100) 114.30 (115) 127.00 (125) 139.70 (140) 152.40(150) 165.10 (165) 177.80 (175) 190.50 (190) 203.20 (200) 215.90 (215) 228.60 (230) 241.30 (240) 254.00 (250/255) 279.40 (280) 304.80 (305) 330.20 (330) 335.60 (350/355) 381.00 (380) 406.40 (400/405) 457.20 (455/460)
Materials/Substrate Guide HARDWOOD
SOFTWOOD
CHIPBOARD
MDF
WOOD PANEL
GREEN OAK
KERBS/SLABS
CONCRETE PAVIORS
VITRIFIED CLAY PRODUCTS
SOFT CLAY
ENGINEERING BRICK
MEDIUM FACING BRICKS
SOFT FACING BRICK
DAMP/WET HOLES
UNDERWATER
LOW VENTILATION
HEAVY DUTY FIXING
REBAR
STEEL
ALUMINIUM
CARDBOARD
CARPET
PAINT
GLUE
SILICONE
8
BRICK
CONCRETE
STONE
HOLLOW BLOCK
BLOCK
HARD CONCRETE
CONCRETE (15-30)
CLAY PAVIORS
HARD SANDSTONE
SANDSTONE
CLAY ROOF TILES
CERAMIC TILE
GLASS
MARBLE
PORCELAIN
STAINLESS STEEL
REINFORCED CONCRETE
HARD SLATE
CONCRETE ROOFING TILES
NONFERROUS METAL
CAST IRON
THIN SHEET METAL
LEATHER
PLASTIC PLASTERBOARD