Best Practice for Using Metal Cutting Tools with a Handheld Rotary Drill

A good two-speed pistol drill will do far more than drill holes. With the right tooling it will cut large holes, step, ream, tap and countersink, and on stainless steel it is often the better choice over an impact wrench.

The trade-off is control. A rotary drill puts its full reaction torque into your wrist, and spindle speed matters far more than it does on impact. This covers the settings and techniques that make the difference, whatever brand of drill you run.

Set the drill up properly

• Use the gearbox. Low gear is for large cutters, reamers, taps and countersinks; high gear is for small drill bits. Select the gear first, then pull the trigger fully. Feathering a variable-speed trigger gives inconsistent speed and torque, which is hard on cutting edges.
• Rotary mode only. Hammer mode on steel damages cutters and the drill.
• Fit the side handle. It is your main defence against kickback when a cutter grabs.
• Keep the battery fresh. Torque drops as charge fades, and that is when tools snag and chip.

The VersaDrive V18-120 is set up for this work: a brushless motor, an all-metal 2-speed gearbox (500 / 2,200 rpm), 120 Nm, a metal 13 mm chuck and a side handle, and it runs on Makita LXT 18V batteries. Any professional two-speed drill with similar figures will do the same jobs.

Speed is the setting that matters

On a rotary drill, the wrong RPM wears out more cutters than anything else. Larger diameters and harder materials both need lower speeds. Stainless typically needs less than half the RPM of structural steel at the same size. Running flat out burns the edges; running too slowly with light feed just rubs.

Figures for HMT tooling, taken from the HMT technical guides, which give the full tables by size and material.

Drilling

• All HMT drill bits run in a pistol drill. TurboTips are the choice for structural steel and through holes. Cobalt bits (202050 or 209010) are the choice for stainless steel.
• TurboTips need no pilot hole up to 13 mm. Cobalt split-point bits need a pilot above 10 mm. Above 13 mm, pilot everything at about 70% of the finished size.
• For blind holes, use 209010 Cobalt split-point drills.
• Ease off before breakthrough. That is where a drill bit grabs and the reaction torque arrives.

Large holes: HoleCutters and SheetCutters

A pistol drill is the recommended machine for VersaDrive TCT HoleCutters, run at the lower speed settings.

• Pre-drill the pilot. The integral pilot drill can catch and twist the drill when it breaks through. Drill a 6.35 mm (1/4") pilot hole first, then refit the pilot drill or use a solid 101030P-0003 pilot pin as a guide.
• Thick steel. Above 20 mm, back the rotating cutter out periodically to clear swarf.
• Sheet up to 4 mm. Use 101050 TCT SheetCutters, which also handle stainless sheet.
• Above about 50 mm diameter, move to a mag drill or pillar drill.

See the HoleCutter guide.

Enlarging and reaming

Sheet and plate: Step Drills suit thin sheet, but go carefully on the 4 mm tip while starting. Cone Cutters stop at about 2–3 mm. TurboTip ImpactaStep Cutters take plate up to 12 mm. Pilot drilling helps above 13 mm.

Reaming: VersaDrive Reamers up to about 30 mm can be used in a pistol drill at low speed. Take 1–2 mm per pass at most, step up through the sizes for bigger corrections, and never start a reamer in reverse. In stainless, rotary reaming at reduced speed is recommended over impact.

See the Step Drill guide and the Reamer guide.

Tapping

• ImpactaTaps run in a pistol drill in a correctly sized tapping hole, using SpeedLube. Larger sizes build serious resistance and kickback.
• Combi DrillTaps are suitable in a pistol drill up to around M20. Above that, the resistance and kickback make an impact wrench the better tool, because it doesn't throw the reaction into your arm.
• Blind holes: clutched tapping adapters are not suitable for pistol drills. Use an impact wrench with a 131-series clutched adapter, or a reversing mag or pillar drill.
• Let the spindle stop before switching to reverse, then back the tap out under control.

See the ImpactaTap guide and the DrillTap guide.

Countersinking

VersaDrive Countersinks and DrillSinks work well in a pistol drill at low speed. Chatter usually comes from running too fast or letting the countersink bounce over swarf in the hole, so clear the hole and keep the speed down. A piloted MultiSink stops the cutter wandering and gives the cleanest seat. For larger countersinks, a mag or pillar drill gives more control. See the Countersink guide.

Stainless steel

This is where a rotary drill beats an impact wrench. Stainless work-hardens if the cutter rubs, so:

• reduce the speed (see the table above);
• increase the feed pressure, so the cutter keeps cutting rather than polishing;
• use plenty of coolant, with BioCut Blue where heat control matters.

Lubricant

SpeedLube for tapping and general drilling. BioCut Blue for stainless and hard steels, and where the work will be welded or galvanised. BioCut Paste overhead. See the full range.

If it goes wrong

Watch: rotary cutting tool training

The Rotary Training Video Series also covers countersinks, TCT HoleCutters and SheetCutters.

Technical guides

Drill Bits · HoleCutters · Step Drills & Cutters · Reamers · ImpactaTaps · DrillTaps · Countersinks