Drill Press

Part of Machine Tools

Building and operating a drill press — the essential machine for drilling accurate, perpendicular holes that hand drilling cannot achieve.

Why This Matters

Hand drilling produces holes that wander, are angled, and are difficult to locate precisely. A drill press provides three things that hand drilling cannot: rigidity (the spindle is forced perpendicular to the work regardless of operator variation), precise depth control (a depth stop limits drill travel), and the ability to apply controlled feed force while maintaining the drill geometry.

The drill press is often the second machine tool a workshop needs, after the lathe. It enables precise bearing bore holes, accurate fastener locations, and clean holes in hard materials that would destroy bits under the vibration of hand drilling. Many fitting and assembly operations that are difficult with hand tools become straightforward with a drill press.

Building a drill press from salvaged and fabricated components is achievable with basic metalworking skills. The critical components — spindle, quill, and chuck — require some precision, but the column and table are simple structural work. A functional drill press can be built in a week of concentrated effort by a competent metalworker.

Drill Press Components and Functions

Column: A vertical round or square tube, pillar, or fabricated steel structure that provides the rigid backbone. All other components mount to the column. Must be straight (within 0.5mm over its length) and rigid — flex in the column translates directly to hole inaccuracy.

Head: The casting or fabricated housing at the top of the column that contains the spindle, quill, and drive system. Must be adjustable on the column (slides up/down for different workpiece heights) and lockable.

Spindle: The rotating shaft that holds the drill chuck. Runs in two bearings (radial) and one thrust bearing. The spindle must run true (concentric with its axis) — runout greater than 0.005 inches causes oversize holes and drill breakage. Critical dimension: the spindle taper (morse taper or straight shank with chuck) must match the drill chuck.

Quill: A cylindrical sleeve surrounding the spindle, which can be moved axially (downward) to advance the drill into the work. The quill returns upward under spring tension when released. The quill feed mechanism (rack and pinion operated by a hand lever) provides controlled feed. A depth stop on the quill limits drill penetration.

Table: A flat platform mounted on the column below the head. Holds the workpiece (directly, in a vise, or in a fixture). Must be perpendicular to the spindle axis. Adjustable height and tilting for angled holes.

Drive system: Motor (or belt drive from lineshaft) transmits power to the spindle through V-belt and cone pulleys (for variable speed) or direct belt drive. Speed selection is critical: slow speeds for large drills and hard materials; high speeds for small drills in soft materials.

Building a Drill Press

Materials needed:

• Column: 100-150mm (4-6 inch) steel pipe or square tube, 1m long, wall thickness 8-10mm
• Head housing: fabricated from 12-16mm steel plate or salvaged cast iron
• Spindle: precision ground steel rod or turned bar stock, 30-50mm diameter
• Quill: steel tube bored to fit spindle, with 0.001-0.002 inch clearance on the spindle
• Table: 12-16mm steel plate, 300-400mm square
• Chuck: MT2 (Morse Taper 2) or straight-shank drill chuck — salvage from old drill press or purchase

Construction sequence:

1. Column fabrication: Cut steel tube to length. Weld a heavy base plate (250×250mm, 20mm thick) to the bottom. Ensure the column is perpendicular to the base plate (check with square; correct by grinding welds before they cool completely).

2. Head housing: Weld or bolt together the head housing from steel plate. The housing must have bored holes for the quill (must be parallel to the column) and provisions for the spindle bearings.

3. Quill and spindle: Bore the quill hole in the head housing parallel to the column axis (check with a precision square against the column). Press or slip fit the spindle bearings into the quill. Turn the spindle to fit the bearings.

4. Quill feed mechanism: A rack (gear teeth cut into the side of the quill) engaging a pinion (gear) on the hand lever shaft. Standard pitch rack and pinion can be salvaged from industrial equipment or made by milling a slot pattern into round stock.

5. Table mount: A collar that slides on the column and locks with a clamping bolt. Weld the table plate to the collar. Check table perpendicularity to column using a machinist’s square.

6. Drive: V-belt pulleys on spindle and motor (or line shaft). Cone pulley arrangement for 3-5 speed ranges. Motor mount on a pivoting plate for belt tensioning.

Speed Selection and Cutting Parameters

Speed selection:

• Small drills (under 3mm) in soft materials: 2,000-3,000 rpm
• Medium drills (6-12mm) in steel: 500-1,000 rpm
• Large drills (25mm+) in steel: 150-300 rpm
• Any drill in hardened or tough steel: half the above speeds
• Wood: 2-4x the steel speeds

Surface speed formula: V (m/min) = π × D × N / 1000

For a 12mm drill at 1,000 rpm: V = π × 12 × 1000 / 1000 = 37.7 m/min. Recommended cutting speed for HSS in mild steel is 25-35 m/min. At 1,000 rpm with 12mm drill: slightly high; use 800 rpm.

Cutting fluid: For steel, use any light oil, kerosene, or water-soluble cutting fluid. Apply to the drill point and work before drilling and during drilling. Reduces heat, improves surface finish, extends drill life. For cast iron: drill dry (cast iron produces graphite dust that acts as lubricant; cutting fluid makes a paste that clogs flutes). For aluminum: any light oil or kerosene.

Feed rate: Advance the drill at a rate that produces visible chips, not dust. Too fast: drill breaks. Too slow: drill rubs and overheats. For steel with a 12mm drill: 0.1-0.2mm per revolution. A simple feel guideline: the lever should require moderate but not excessive pressure; if you need to lean on it, reduce speed or check drill sharpness.

Operations and Accessories

Centering: A center punch mark in the work before drilling provides a starting divot that guides the drill point to the correct location. Without this, drills wander when starting. For very precise location (within 0.1mm), use a center drill (short, stiff, combined drill and countersink) before the full-size drill.

Step drilling: For large holes (over 12mm in steel), drill a pilot hole first (about 1/3 the final diameter), then the full size. This reduces the chisel-edge load and allows the drill to follow a pre-established hole rather than starting from scratch with a large point.

Reaming: After drilling, run a reamer (a multi-fluted precision cutting tool) through the hole to bring it to precise size with a smooth finish. Reamers leave holes 0.002-0.003 inch tighter tolerance than drilling alone. Use for bearing bores and precision fits.

Work holding: Never hold work by hand when drilling — the drill can catch and spin the work, causing injury. Always clamp work to the table (C-clamps or T-bolts in table slots) or hold in a drill press vise. Round stock needs a V-block to prevent rolling.

A well-built drill press serves a workshop for decades. The most important maintenance is keeping the chuck clean and tight (loose chucks cause wobble and drill breakage), lubricating the quill bearings regularly, and checking table perpendicularity annually (settling foundations can shift alignment over time).