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How to drill stainless steel

Updated: October 2026

The hole in the 304 bracket has gone shiny, the bit is blue at the tip, and the cordless drill has no tachometer. That shiny spot is the failure. Grades 304 (1.4301) and 316 (1.4401) work-harden when a drill rubs instead of cutting a chip. How to drill stainless steel, once a bit is in the chuck, is the feed, the oil and the moment you stop. Which box to buy stays on the [stainless steel drill bit comparison](/hub/drilling-and-accessories/stainless-steel-drill-bit). Products Compared set this procedure against the British Stainless Steel Association’s drilling note, with no lab test. A qualifying purchase can earn a commission at no extra cost to you.

The hole in the 304 bracket has gone shiny, the bit is blue at the tip, and the cordless drill has no tachometer. That shiny spot is the failure.

Our top picks

Bosch Bosch PRO HSS-Co set, 19 pieces, 1–10 mm

Best overall

Bosch Bosch PRO HSS-Co set, 19 pieces, 1–10 mm
8.4/10about £34.52
View offer
Bosch Bosch HSS PointTeQ 18-piece metal set

Alternative

Bosch Bosch HSS PointTeQ 18-piece metal set
5.6/10about £11.95
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Rennie Tool Company Rennie Tools 5-piece cobalt set, 4–10 mm

Best value

Rennie Tool Company Rennie Tools 5-piece cobalt set, 4–10 mm
8.3/10about £13.99
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On this page
  1. 1.Why the surface goes hard
  2. 2.Set up the hole
  3. 3.Speed, feed and oil
  4. 4.Peck, breakthrough, and when to stop

Why the surface goes hard

Stainless work-hardens if you dwell with no chip. BSSA’s warning still applies to a cobalt bit. Thyssenkrupp Materials UK asks for cutting fluid. A curl means you are cutting. Dust and a blue tip mean heat. A polished disc with no chip will get worse if you lean harder. Grade choice is on the cobalt versus HSS page.

Set up the hole

Clamp the work and back the exit with timber or scrap mild steel. Eye protection is the HSE baseline for flying chips. On a pillar drill, leave gloves off so a glove cannot wind into the chuck. Use rotary gear only, with hammer and SDS action off. Mark the hole with a light three-corner punch. A deep conical punch work-hardens the spot you need to cut.
Bosch Bosch PRO HSS-Co set, 19 pieces, 1–10 mm

Testsieger

Bosch Bosch PRO HSS-Co set, 19 pieces, 1–10 mm
8.4/10about £34.52
View offer

Speed, feed and oil

There is no single rpm you can treat as law. At 6 mm, Armeg’s free-cutting column is about 530 rpm, David Harries about 849 rpm, and metaldrilling.co.uk about 640 rpm near 12 metres per minute. Thürmer’s 8–12 metres per minute is a rule of thumb, not a British standard. BSSA says small bits must not run too slowly, so “slow” is the chart for that diameter, not the lowest tick on a 3 mm bit. On a cordless drill, a curl is the check you can see. Dust and a blue tip means stop. Do not average 530 and 849 into a third speed. A household oil may wet the hole. It is not the sulphurised cutting oil metaldrilling.co.uk names. Check the bit on the buying guide before oil is asked to save a blunt edge.

Peck, breakthrough, and when to stop

Withdraw after about three to four diameters, then after about two, then after about one, and do not dwell with the bit spinning. A 6 mm bit takes the first peck after roughly 18–24 mm. Ease the feed as the point breaks through. Thin sheet is on the sheet page. In bar, keep the bit square. Side load snaps 1–3 mm bits. Feed bends a chip. It is not a lean on the web. Stop for a workshop on a deep or very small hole in 316 or duplex, a reamed size, a loaded thread, or a part that is already glazed. A blue spot that has stopped cutting will harden further on the next pass.

Common questions

What speed do you use if the drill has no tachometer?
Use the chip, because the charts disagree. At 6 mm, Armeg’s free-cutting column is about 530 rpm, David Harries about 849 rpm, and metaldrilling.co.uk about 640 rpm near 12 metres per minute. On a cordless drill, low gear plus a visible curl is the check you can actually see. A blue tip and fine dust mean you are too hot. Do not treat the slowest tick as correct for a 3 mm bit. BSSA warns that small bits must not run too slowly.
Do you need cutting oil, and what if you only have a household oil?
The UK charts ask for a cutting lubricant. Metaldrilling.co.uk names sulphurised cutting oil, and thyssenkrupp asks for cutting fluid. Reviewers mention oil and cutting compound as the reason a bit kept cutting. A household oil is a wetting agent you happen to own. It is not the named cutting fluid. If the edge still polishes the steel, fluid of any kind will not restore a burnt tip.
What does a blue tip or a shiny spot mean?
A blue tip means the edge has run hot. A shiny spot with no chip means the surface has been rubbed and is likely work-hardened. A curl means you are cutting. Mixed chip sizes can mean unequal lips. Stop when you see blue or a polish, let the bit cool in the air, and correct the speed or the grind. Quenching a hot HSS bit in water is a reviewer’s habit on one listing. It is not a manufacturer instruction in these files.
Can you use hammer mode on a combi drill?
Leave hammer mode and SDS action off. The hole wants a steady rotary cut. Hammering the point chips the edge and bruises stainless that is already ready to harden. Set a combi drill to rotary, in a low gear, and use eye protection. If the drill cannot hold a low speed without stalling, it is the wrong machine for a larger diameter.
When should you stop and take the job to a workshop?
Stop when the hole is deep or very small in 316 or duplex, when you need a reamed diameter, or when a loaded thread or a glazed structural part is involved. A one-off bracket that still produces a chip can stay on the bench. Punching a run of enclosure holes is Ritherdon’s production limit, outside this set of twist bits.

Related pages

Stainless steel drill bits

Best drill bits for stainless steel: match the hole

Cobalt drill bit set for stainless steel: listings

Cobalt vs HSS drill bits: which side of this shelf

Drill bit for stainless steel sheet, step or twist

Sources

Public UK sources and the amazon.co.uk listings captured on 15 October 2026. The 8–12 m/min cutting-speed band is a rule of thumb, not a British standard.

  1. British Stainless Steel Association — Speeds and feeds for drilling and reaming stainless steels (retrieved 15 October 2026)
  2. Health and Safety Executive — PUWER overview (retrieved 15 October 2026)
  3. Health and Safety Executive — Using the right type of PPE (retrieved 15 October 2026)
  4. legislation.gov.uk — Consumer Rights Act 2015 (retrieved 15 October 2026)
  5. Armeg — Twister impact-rated HSS cobalt drill bits (retrieved 15 October 2026)
  6. Dormer Pramet A777 — jobber drill data sheet (BS 328, DIN 338, ISO 235) (retrieved 15 October 2026)
  7. David Harries — cobalt drill technical sheet (retrieved 15 October 2026)
  8. Thürmer Tools — drill FAQ (8–12 m/min is a rule of thumb, not a British standard) (retrieved 15 October 2026)