Independent comparisons. We may earn from shop links. More info

How to drill metal

Updated: 2026-10-23

You are about to put a hole through a mild-steel bracket or a piece of aluminium with a cordless drill or a pillar drill. The hole is finished when the bit is still sharp, the work is still in the clamp, and the exit is a burr you can file, not a torn sheet or a blue tip. This is the sequence for that job. The sets are ranked in the [metal drill bit comparison](/hub/drilling-and-accessories/metal-drill-bit). If the metal is 304 or 316, stop after the clamp section, because rubbing there work-hardens the hole. A qualifying purchase can earn a commission at no extra cost to you.

You are about to put a hole through a mild-steel bracket or a piece of aluminium with a cordless drill or a pillar drill.

Our top picks

Bosch Bosch PointTeQ 19-piece HSS set

Best overall

Bosch Bosch PointTeQ 19-piece HSS set
9.0/10about £14.12
View offer
Bosch Bosch PointTeQ 18-piece ToughBox

Best value

Bosch Bosch PointTeQ 18-piece ToughBox
9.0/10about £11.95
View offer
DeWalt DeWalt DT5912 13-piece HSS-R

Alternative

DeWalt DeWalt DT5912 13-piece HSS-R
9.0/10about £9.60
View offer
On this page
  1. 1.Clamp it and cover your eyes
  2. 2.Start the hole without skating
  3. 3.Speed, oil, and feed
  4. 4.Breakthrough and the burr
  5. 5.When to stop

Clamp it and cover your eyes

HSE’s HSG129 is blunt: hair and clothing in the chuck, gloves at the tip, an unclamped part that spins, and swarf in the eye. Wear impact eye protection. Clamp the work so a bracket cannot orbit the bit. Keep gloves off an open chuck. The PPE at Work Regulations 1992 bind employers. The hazard is the same at home. If you cannot clamp a small offcut, do not drill it. Rotary only. Hammer mode will destroy a twist drill in steel.

Start the hole without skating

On mild steel, a centre punch gives the point a dimple so a 118° or 135° tip does not walk. A blunt bit skates and overheats. If the edge polished the last hole instead of cutting a chip, change it. Start perpendicular. A bit that enters at an angle can snap a small diameter on the way out. Let the point cut. A heavy conical punch can itself harden 304 or 316, so do not copy a mild-steel punch habit onto a sink. Those rules are on drill bits for stainless steel. Which set to chuck is the metal drill bit buying guide.
Bosch Bosch PointTeQ 19-piece HSS set

Testsieger

Bosch Bosch PointTeQ 19-piece HSS set
9.0/10about £14.12
View offer

Speed, oil, and feed

Revolutions follow rpm = (m/min × 1000) ÷ (π × mm). A larger diameter means fewer revolutions. This comparison does not crown one mild-steel chart. For stainless, Thürmer specifies HSS-E, a 135° split point, cutting oil, no dwell, and about 8–12 m/min. About 320 rpm is the 10 m/min figure for a 10 mm bit. On a cordless drill, use low gear: a scream, smoke or a blue tip means you are too fast or the edge is rubbing. Use a cutting oil on steel and back the bit out when chips pack. WD-40 is not a cutting fluid. A packed flute is what turns the margin blue.

Breakthrough and the burr

As the point breaks through, the bit can grab and a hand drill twists in your wrist. Ease the feed for the last millimetre. On thin sheet, scrap wood behind the metal supports the exit. When the bit is through, stop. Spinning with no feed only polishes the margin. Withdraw while the drill is still turning slowly. Take the exit burr off with a file or a countersink used lightly.

When to stop

Stop, or do not start, when the hole is structural or in a pressure pipe, when a file will not touch the steel, when you cannot clamp the part, or when the drilling is at work and nobody has assessed eyes, fluid or vibration. Above about 45 HRC, HSS will not cut. DeWalt’s 900 N/mm² figure is a rating for one HSS-R set, not permission to drill a hardened pin. Do not finish the hole by leaning on a blunt bit.

Common questions

Do I have to clamp a small piece of steel?
Yes. A small offcut is the part that spins. HSG129 treats an unclamped workpiece as a chuck hazard, along with hair, clothing and swarf in the eye. If the piece is too awkward for a vice, clamp it to a board or do not drill it. Hand pressure is not a clamp.
Should I wear gloves while drilling metal?
Not at an open chuck. A glove caught in the flutes pulls your hand in. Impact eye protection is the protection HSG129 puts on this job, and swarf is still sharp when it lands on a bare hand after the drill stops. The PPE regulations bind employers. The snag hazard does not change in a home workshop.
Do I need cutting oil on aluminium?
Aluminium is less demanding than steel, and a light oil is sometimes used as a stand-in on thin aluminium. Steel wants a cutting oil, reapplied when you peck. WD-40 and similar penetrating oils are not cutting fluids. This page does not name a brand. Dry drilling in steel is what blues the bit.
How fast should a cordless drill run in mild steel?
Use low gear and a feed that produces a chip, not a polish. Revolutions fall as the diameter rises, from rpm = (m/min × 1000) ÷ (π × mm). This comparison does not fix one mild-steel rpm, because the published charts disagree and a cordless drill rarely holds a single number. If the bit squeals or turns blue, you are too fast or the edge is rubbing.
Why did the bit turn blue?
The edge overheated. Speed was too high, the bit was blunt and rubbing, or chips packed in the flute and you kept feeding. Ease off, add cutting oil, and clear the swarf. A blue HSS bit may already have lost its temper at the lip. Do not cure it by pushing harder on the next hole.
When should I stop and get a machinist?
When the hole is structural or in a pressure pipe, when a file will not mark the steel, when you cannot clamp the part, or when you are drilling at work with no assessment of eyes, cutting fluid or vibration. Above about 45 HRC, HSS will not cut. Leaning harder snaps the bit and does not make a hole.

Related pages

HSS vs cobalt drill bits

Best metal drill bits

Metal drill bit

Metal drill bit set: check the grade, point and size

Drill bit for stainless steel: keep 304 and 316 cutting

Sources

Public sources from the research digest, dated 22 October 2026. Shelf prices, stars and review counts are the amazon.co.uk figures saved on 19 October 2026.

  1. Thürmer Tools, Drills FAQ (retrieved 22 October 2026)
  2. DeWalt UK, DT5912-QZ HSS-R set (retrieved 22 October 2026)
  3. Bosch Professional GB, PointTeQ HSS sets (retrieved 22 October 2026)
  4. Bosch Professional GB, HSS-Co twist drill bit sets (retrieved 22 October 2026)
  5. HSE, HSG129 health and safety in engineering workshops (retrieved 22 October 2026)
  6. The Personal Protective Equipment at Work Regulations 1992 (retrieved 22 October 2026)
  7. BSSA, speeds and feeds for drilling stainless steels (retrieved 22 October 2026)
  8. Heller, HSS-Co DIN 338 drill bits (retrieved 22 October 2026)