Running a drill at the wrong speed is one of the fastest ways to destroy a cutting edge. Too fast in the wrong material and the edge heats up, loses hardness, and stops cutting — usually within 10 to 20 holes. Too slow wastes time and can cause work hardening in materials that harden from rubbing. The correct speed for the drill diameter and material keeps the cutting edge in its optimal temperature range and maximizes the number of holes per edge before resharpening.
The complication is that most drill press operators inherit a machine with a chart that is either missing, faded, or tuned to the original belts and pulleys which may have been changed. And calculating theoretical SFM, converting to RPM, and selecting the nearest available speed setting adds steps that slow down setup. A practical mental framework makes this faster.
Start with this simplified table, which covers the most common shop materials:
Within each material, larger drills run slower. A 1/4" drill in mild steel runs about 4× faster RPM than a 1" drill in mild steel, because both are targeting roughly the same surface footage (cutting edge speed) and the larger drill diameter covers more surface per revolution at the same RPM.
Drill press speed is set by moving the belt to different pulley steps. The belt runs between two stepped pulleys — one on the motor shaft and one on the quill spindle. Each combination of motor pulley step and spindle pulley step gives a different spindle speed. The speed chart on the machine (usually a sticker on the belt cover) shows the RPM for each combination.
If the chart is missing, measure it: install a piece of tape on the chuck and mark one revolution reference. Time 10 revolutions with a stopwatch. RPM = (10 revolutions × 60 seconds) / elapsed time in seconds. Do this for each belt position and write the results on a new sticker.
Alternatively, use a handheld optical tachometer — point it at the chuck tape mark, press the trigger, and read RPM directly. This is the fastest way to verify any belt setting.
First: not changing speed when changing drill diameter. Many operators set the belt for one size and drill the rest of the day at that speed regardless of what tool goes in next. A 3/8" bit in the same setting as a 1" bit runs at the wrong speed for at least one of them.
Second: running aluminum at mild steel speeds. Aluminum wants to run fast — 3× to 4× the RPM you would use for the same size bit in steel. Running aluminum slowly causes built-up edge (BUE), where aluminum welds to the cutting edge and the bit stops cutting cleanly.
Third: running stainless at mild steel speeds. Stainless needs to run 25–40% slower than mild steel because it work-hardens rapidly. A bit running too fast in stainless work-hardens the material ahead of the cutting edge, and the next revolution cuts harder material than the last. This is why stainless feels like it gets harder as you push harder — the rubbing at the wrong speed is creating the hardened layer.
Fourth: ignoring the speed table entirely and just "running it at whatever speed is in there." Some speeds on most machines are rarely correct for any common application — particularly the highest speed on a 12-speed machine, which may be correct only for very small drills in soft metals.
Fifth: changing only one pulley step instead of both when shifting to a very different speed range. Moving one step on the motor pulley gives a modest speed change. Moving to the opposite end of both pulleys gives the full speed range available from the machine.
Variable speed drill presses — machines with a continuously variable transmission or electronic speed control — eliminate belt changes but introduce their own complication: operators often set speed once and never touch it. The RPM display makes precise setting easy, but only if you actually use it. Treat the RPM display as a tool, not a decoration. Look up the recommended speed for each drill size and material and dial it in before the first hole of each setup.
Variable speed machines are excellent for production work with frequent size changes and for drilling into materials with strict speed requirements (thin-wall stainless, hardened bushings). They are overkill for shops that run mostly mild steel in a narrow size range — a well-tuned belt machine serves this work just as well for a fraction of the cost.
Even the correct belt setting will not save an edge that is already gone. A resharpened HSS drill running at the right speed for your material will outlast a dull one running at any speed.
Send Your Drills →