Inch drill bit size for wood
1 3/8 in drill bit
The size of a 1 3/8 in bit in both systems, how fast to run it on a drill press in softwood and hardwood for each kind of bit made in this size, and what it drills in the rest of this site’s charts.
Inch
1.375 in
1 3/8 in exactly.
Metric
34.93 mm
1 3/8 in × 25.4 = 34.925 mm.
Drill press speed by bit type
RPM in softwood (pine) and hardwood (hard maple), on face grain. The figure is the median of three charts, or the mean of two, and the lower of two that are more than twice apart. Each chart’s own figure is listed under it. A dash means fewer than two charts cover that bit at this size.
| Bit | Softwood RPM | Hardwood RPM |
|---|---|---|
| Spade (paddle) bit | 1,250 Only two sources publish this: WOOD Magazine and Grizzly WOOD Magazine 1,500 · Grizzly 1,000 | 875 Only two sources publish this: WOOD Magazine and Grizzly WOOD Magazine 1,000 · Grizzly 750 |
| Forstner bit | 800 Median of 3 sources Infinity Cutting Tools 800 · WOOD Magazine 500 · Grizzly 1,000 | 600 Median of 3 sources Infinity Cutting Tools 600 · WOOD Magazine 250 · Grizzly 750 |
| Hole saw | 500 Median of 3 sources WOOD Magazine 500 · Grizzly 400 · Exchange-A-Blade 2,400 | 400 Median of 3 sources WOOD Magazine 350 · Grizzly 400 · Exchange-A-Blade 2,400 |
Hole saws are where the charts disagree most: Exchange-A-Blade’s bimetal chart runs them several times faster than the two drill press charts, so the span is wide and the median sits with the drill press charts.
Bigger bits and hole saws run slower: every chart here steps the speed down as the size grows.
Hardwood never runs faster than softwood with the same bit, and usually slower.
The charts are a starting point: when a bit or hole saw comes with its maker’s speed, use that.
One source: Grizzly, the maker of that drill press , sources [2]
WOOD Magazine tested on face grain: slow down when drilling into end grain.
One source: WOOD Magazine, the publisher of that chart , sources [1]
Clamp the work to the drill press table: a large bit at low speed can grab it.
Sources
- WOOD Magazine, WOOD Magazine’s Drill Press Speed Chart: twist, brad-point, spade bits and hole saws in softwood (pine) and hardwood (hard maple), read 2026-11-08
- Grizzly, G7943/G7944 drill press manual (mfd. since 09/17): drill bit speed chart, p. 27 (a guide; the bit maker’s speed comes first), read 2026-11-08
- Exchange-A-Blade, Hole saw tech: bimetal hole saw recommended RPM by size, wood column, read 2026-11-08
What this size drills on this site
No screw pilot, clearance or dowel hole in this site’s charts calls for this exact size. The pilot hole chart and drill bit size chart have every size.
The same size elsewhere
Sources, read 2026-11-07/08: WOOD Magazine, WOOD Magazine’s Drill Press Speed Chart: twist, brad-point, spade bits and hole saws in softwood (pine) and hardwood (hard maple); Grizzly, G7943/G7944 drill press manual (mfd. since 09/17): drill bit speed chart, p. 27 (a guide; the bit maker’s speed comes first); Exchange-A-Blade, Hole saw tech: bimetal hole saw recommended RPM by size, wood column; Infinity Cutting Tools, Forstner Bit Speed & Feed Chart (HSS Forstner bits, hardwoods and softwoods, 3/8" to 2").