Best Practice for Using Metal Cutting Tools with an Impact Wrench

Most steel erectors and installers already carry a 1/2" or 3/4" impact wrench. With impact-rated tooling, the same wrench will drill, step, ream, tap and deburr connection holes as well as run bolts. When a cutter snags, the hammer mechanism stops the rotation, so there is far less kickback than with a drill, though you still need a firm grip and good footing.

This is the practical detail: which tools, what torque, and where impact cutting stops being the right answer. It applies whatever brand of wrench you run.

One thing first: a hammer drill is not an impact wrench. Hammer action drives the bit forwards for masonry, and on steel it wrecks cutters. Why the difference matters.

What an impact wrench can do

Torque: too little breaks more tools than too much

A tool that stalls mid-cut takes the full shock on its cutting edges, with nothing driving it through. So:

• If your wrench has no exact match for the chart figure, use the setting above it, not below. The exception is blind-hole tapping with a clutched adapter: use the lower settings the Clutched Tapping guide gives for smaller taps, and never use Nutbuster.
• Pull the trigger fully. Feathering it costs you torque.
• Swap the battery before it fades. Torque drops with charge.

Settings vary a lot by job. An M10 ImpactaTap in 10 mm plate wants 280–300 Nm; a 10 mm TurboTip in the same plate wants 395–430 Nm. One setting for everything doesn't work. The torque tables are in each HMT technical guide.

Tooling and adapters

Standard bits and taps aren't built for repeated rotary blows: shanks twist and edges chip. VersaDrive tools share one hex shank and run in VersaDrive impact adapters, and the same tool moves to a drill chuck or mag drill when the job needs it. Not everything in the range is for impact use, though. Cobalt drill bits are rotary only.

Drilling

• Use TurboTip Drill Bits (209015) for impact drilling.
• No pilot hole is needed up to 13 mm. Above that, pilot at about 70% of the finished size.
• TurboTips are for through holes. Drill blind holes with Cobalt split-point bits on a rotary machine.
• In box section, ease off before breakthrough so the tip doesn't hit the far wall.

Enlarging and reaming

Sheet and plate: TurboTip ImpactaStep Cutters handle plate up to 12 mm. Use Step Drills for thinner sheet. Cone Cutters stop at about 2–3 mm, so don't push them into anything thicker.

Connection holes: misaligned holes, and holes choked with paint or galvanising, are where a reamer earns its keep. A larger drill bit grabs the edge of the existing hole; a reamer is built to follow it.

• Take 1–2 mm per pass at most. For a bigger correction, step up through the sizes.
• Never start a reamer in reverse.
• Run high torque. Reamers stall easily.
• For heavy plate, use MAX Impact Reamers, which have a heavier shank.

Details are in the Reamer guide and the Step Drill guide.

Tapping

Through holes: ImpactaTaps will only cut a good thread in the correct tapping-size hole. Use SpeedLube and finish each thread in one pass where you can. Reversing and re-entering is where cross-threading starts. See the ImpactaTap guide.

Blind holes: standard ImpactaTaps are for through holes only. For blind holes, fit a 131-series Clutched Tapping Adapter, drill the pilot to exact size and depth, and keep the Nutbuster setting off. When the clutch slips, stop within a few seconds, because prolonged slipping heats the tap and breaks it. Then reverse out.

Drill and tap in one: Combi DrillTaps save a tool change on repeat holes. Spiral-flute versions need no pilot; heavy-duty versions need a pilot of about 70%. The drill and tap sections need different torque settings, so check both in the DrillTap guide.

Countersinking

On impact, use VersaDrive Countersinks and DrillSinks for light chamfering and deburring, up to about 16 mm. A full-depth seat for a countersunk bolt needs a rotary drill or mag drill at low speed. A piloted MultiSink gives the cleanest finish. See the Countersink guide.

When not to use impact

• Stainless steel: impact builds heat and work-hardens it. Use a rotary drill at reduced speed with Cobalt bits (202050 or 209010).
• Hardened steel: most impact tooling won't cope. Look at HMT Ultra tooling on a rotary machine.
• Flame-cut, plasma-cut and punched holes: the edges are often harder than the parent metal. A powerful rotary or mag drill at reduced speed does the job better.
• Heavy section or high volume: a mag drill is more accurate and saves the operator, including from the hand-arm vibration of long impact sessions.

Lubricant

SpeedLube for tapping and general work. BioCut Paste overhead, where liquids run off. BioCut Blue where the steel is going to be welded or galvanised, but not for blind-hole tapping. See the full range.

If it goes wrong

Watch: VersaDrive impact cutting best practice

The full Impact Training Video Series covers each tool in about two minutes.

Technical guides

Drill Bits · Step Drills & Cutters · Reamers · ImpactaTaps · Clutched Tapping · DrillTaps · Countersinks

Safety: Wear eye and hearing protection. If a tool stalls, release the trigger, and take the battery out before changing tools or clearing a jam. Cutters, swarf and slugs will be hot and sharp.