Drill speed chart by material

Run a drill too fast and the bit's cutting edge overheats, goes blue, and dulls in a single hole. Too slow on stainless and the material work-hardens ahead of the cut until even a fresh cobalt bit just polishes instead of drilling. The right RPM depends on exactly two things: the material and the diameter of the bit. Below is a speed chart for steel, stainless, aluminum and wood, the formula behind every number so you can calculate any combination yourself, and the feed and depth adjustments that separate a clean hole from a burned bit.

Why one RPM number is never enough

What a material can actually tolerate is surface speed, usually quoted in surface feet per minute (SFM): how fast the cutting edge sweeps across the work. A 1 inch bit's rim travels four times as far per revolution as a 1/4 inch bit's rim, so to keep the same surface speed the big bit must turn at a quarter of the RPM. That is the whole logic of every drill speed chart: small bits fast, large bits slow, hard materials slower still. BuildToolHQ's drill bit speed guide and the WorkshopCalc drill speed chart both build their tables on this principle, and the University of Florida manufacturing lab's speeds and feeds reference derives it from the standard spindle speed equation.

The drill speed formula (do it yourself calculator)

Any chart value can be recomputed from one formula:

RPM = (SFM x 3.82) / bit diameter in inches

The 3.82 is 12 divided by pi, converting surface feet per minute into revolutions per minute for a diameter in inches. In metric units the same relationship is RPM = (cutting speed in m/min x 318.3) / diameter in mm. Gera Tools' drilling calculator and the Mech Codex speeds and feeds reference publish both forms of the identical equation. Worked examples:

• Mild steel, 1/4 inch HSS bit, 80 SFM: (80 x 3.82) / 0.25 = about 1,220 RPM.
• 304 stainless, 1/2 inch cobalt bit, 45 SFM: (45 x 3.82) / 0.5 = about 344 RPM.
• Aluminum, 1/8 inch bit, 250 SFM: (250 x 3.82) / 0.125 = 7,640 RPM, far beyond any cordless drill or common drill press, which is why small bits in aluminum simply run at your tool's top speed.

The SFM inputs come from published cutting speed tables for high-speed steel (HSS) tooling:

Cutting speed basis: WorkshopCalc drill speed chart and Gera Tools drill feed and RPM calculator, which agree on aluminum 200 to 300 SFM and cast iron near 70 to 90 SFM; Mech Codex publishes the same aluminum range (200 to 300 SFM) from the Norseman and Viking drill speed charts. Stainless runs slow because it work-hardens; cobalt M35/M42 bits tolerate the heat better than plain HSS.

Drill speed chart: steel, stainless, aluminum

RPM for HSS twist bits, given as ranges where reputable tables disagree slightly. Start at the low end on a hand drill, where you have less rigidity than a drill press.

• Use cutting oil on steel and stainless. Both the BuildToolHQ and WorkshopCalc guides make oil mandatory for ferrous metal; stainless additionally demands constant feed pressure, because stopping mid-hole lets the material work-harden and the bit then skids instead of cutting.
• Aluminum wants fluid too, for a different reason: the soft chips weld themselves to the bit's flutes (built-up edge). Cutting fluid, wax, or even a squirt of a light penetrating oil prevents the galling; Gera Tools and BuildToolHQ both flag this.
• Read the chips: long silvery spirals mean the speed and feed are right; blue chips mean too fast. BuildToolHQ and Gera Tools both use chip color as the go/no-go check.

Chart basis: BuildToolHQ drill bit speed chart and the WorkshopCalc metal speeds table; the two agree within about 25 percent at every cell, and the ranges above span both. Cross-checked against DrillBitsWorld's RPM calculator (304 stainless, 1/4 inch cobalt: about 690 RPM).

Drill speed chart: wood

Wood forgives more than metal, but the same diameter rule applies, and overheating shows up as burn marks around the hole instead of blue chips.

Large boring bits are a different category: Forstner bits, spade bits, and hole saws remove a lot of material per revolution and should run roughly 250 to 750 RPM depending on diameter, per WorkshopCalc's Forstner and spade chart and the Zhonghuan Tools large-bit table (a 2 inch hole saw in softwood: about 450 RPM). For the bit-family comparison at these diameters see our wood boring bits compared page; for hole diameters and arbor sizes see our hole saw size chart; for which bit type to pick in the first place see drill bits by material.

Chart basis: WorkshopCalc wood speeds table and BuildToolHQ; large-bit guidance cross-checked against Zhonghuan Tools' RPM chart.

Using this on a cordless drill

A drill press has labeled pulley speeds; a cordless drill has a trigger and a two-speed gearbox and no RPM readout, so you work in bands. High gear on modern cordless drills tops out around 2,000 to 2,500 RPM (2,100 on the Milwaukee 2904 and Flex FX1271T, 2,000 on the Hercules 59420 in our comparison dataset), which covers everything in the wood table and the small-bit metal rows. Low gear is for the bottom of the metal table: half-inch steel at 600 to 750 RPM means low gear, half trigger, and steady pressure. For the machine that does hold exact speeds, our drill press speed chart maps these numbers onto real pulley steps. The gearbox and clutch live on separate rings; our torque settings chart covers the clutch side, and if your drilling has graduated to hundreds of holes, the bit, not the speed, is usually what needs upgrading; a dull bit at the correct RPM still burns up. See drill bit sharpening before replacing it.

Speeds and feeds: the other half of the equation

Speed is how fast the bit spins; feed is how hard you push it into the work, measured in inches per revolution (IPR). The consensus rule of thumb is feed equal to 1 to 2 percent of the bit diameter per revolution: a 1/2 inch bit wants about 0.005 to 0.010 IPR. The University of Florida lab reference publishes the same idea as diameter bands: under 1/8 inch up to 0.002 IPR, 1/8 to 1/4 inch 0.002 to 0.004, 1/4 to 1/2 inch 0.004 to 0.008, and 1/2 to 1 inch 0.008 to 0.016. Feed too light and the bit rubs instead of cutting, which generates exactly the heat you were avoiding by slowing down. On a hand drill you cannot measure IPR; the translation is simply firm, steady pressure and letting the bit make chips.

Deep holes change the math. Past about three times the bit diameter, chips pack the flutes and heat builds at the tip, so the standard advice is to reduce speed 10 to 30 percent and peck: drill a bit, retract to clear chips and let oil reach the tip, repeat. The Zhonghuan chart says 20 to 30 percent for deep holes; the UF reference gives peck depth guidance of about one bit diameter per peck with good coolant flow. For a listing of what the published specs on a drill actually mean, see specs explained.

Related

For bit selection by material and coating, see drill bits by material; for the full walkthrough of the metal side, how to drill through metal covers lubrication, feed, and the stainless work-hardening trap. For the fixed-speed machine side of these numbers, the drill press speed chart maps RPM onto real pulley steps and covers speed reducers. For chuck capacity limits on larger bits, see drill chuck sizes explained. For driving screws rather than drilling holes, the clutch chart at drill torque settings is the companion piece to this page.