The quill is the moving sleeve that carries the drill chuck and spindle downward when you pull the feed handle. The depth stop is a mechanical limit that prevents the quill from traveling below a set depth. When the quill reaches the stop, you feel solid resistance and the quill does not travel further regardless of how hard you pull the handle.
This gives you a mechanical depth limit that is repeatable hole to hole, part to part, without having to watch a scale or guess. For through-holes it is less critical — the drill exits the bottom and you stop. For blind holes — holes that do not go all the way through — the depth stop is what makes consistent depth possible at production rates.
Most drill presses use a nut-and-collar system on the quill rod or quill rack. The most common arrangement: a threaded rod runs alongside the quill housing. As the quill feeds down, the rod moves with it. A nut on the rod can be set to contact a fixed stop on the housing, arresting quill travel. Turning the nut adjusts depth in small increments, typically 0.05"–0.1" per turn depending on the thread pitch.
Some machines use a scale with a locking collar instead of a threaded stop. The collar slides on the rod and locks with a set screw. These are faster to set but less precise and can slip in heavy use. On production work, threaded-nut depth stops are preferred.
Know which style your machine has before trying to set it. Both work; the adjustment procedure is slightly different.
This is where most people get confused. The depth stop controls where the quill stops, but the usable hole depth depends on what the drill tip does. A standard 118° drill point has a significant taper. If you set the stop so the cutting edges reach 1" below the work surface, the drill tip extends an additional 0.29 × diameter below the cutting edges — for a 1/2" drill, that is about 0.145" of taper below the "full diameter" depth.
For a true blind hole where the full diameter must be 1" deep, you need the cutting edges (the full-diameter portion) to reach 1" depth, not the tip. The tip will be 1.145" below the surface. Set the stop for 1.145", not 1".
The formula: tip extension ≈ 0.29 × drill diameter for a 118° point. For a 135° point: tip extension ≈ 0.21 × diameter. If you need a specific full-diameter depth, add the tip extension to get the stop setting.
If the full-diameter requirement does not matter — if you just need the hole to be "at least 1" deep" — set the stop so the tip reaches 1". The taper below the cutting edges is counted as part of the hole depth for clearance purposes.
Start with the drill installed and the workpiece fixtured in its normal drilling position. Lower the quill until the drill tip touches the work surface — just barely contacts it, no feed pressure. Lock the quill at this position. Now read the depth scale on the machine, or note the position of the depth stop nut. This is your zero reference for this drill-part combination.
Calculate the stop setting from zero: desired depth plus the tip extension if you need true full-diameter depth. Set the depth stop nut to this value from your zero reference. Double-check by lowering the quill to the stop with no part in place and measuring the distance the tip travels from its touch-off position — this should match your target depth.
Drill a test hole in scrap material of the same thickness as your workpiece. Measure the actual depth with a depth micrometer or telescoping gauge and scale. Compare to the target. Adjust the stop nut as needed. A half-turn on most drill presses is 0.025"–0.05" of depth change.
The stop setting is specific to the combination of drill, chuck, and part position. If you change drills — even to a drill of the same nominal size — you must reset the stop. A freshly resharpened drill is shorter than a new drill. A drill of the same size from a different manufacturer may have a different flute length or shank depth. Any of these changes the touch-off position and invalidates the previous stop setting.
Get in the habit: install new drill, touch off, set stop, drill test hole, confirm. This takes two minutes and prevents scrapped blind holes. Skipping it causes short holes that require rework or deep holes that break through.
Sensitive drill presses — the smaller bench-top machines used for precise work in instrument making and light machining — often have more precise depth stops than floor-standing production presses. Some use a micrometer-style depth collar with 0.001" resolution. The procedure is the same, but the resolution allows setting blind hole depths to tight tolerances that production machines cannot match without additional tooling.
For precision blind holes on a sensitive press, use the micrometer collar for initial setup and confirm with a depth mic on the first hole. Do not assume the scale is calibrated — use a direct measurement to establish your baseline and work from there.
A resharpened drill that comes back shorter than it left throws off your depth stop setting. We document point geometry so you know exactly what you are working with after resharpening.
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