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Drill bit for stainless steel sheet

Updated: October 2026

You are putting a hole in a stainless sink rim, a 1 mm panel or a thin bracket, and the 10 mm twist bit grabbed as the point broke through. In thin stainless the risk is snatch at breakthrough, not a long chip from deep bar. This page is the drill bit for stainless steel sheet: when the stepped cone is the tool, and when the metal is already too thick. Twist-set prices stay on the [stainless steel drill bit comparison](/hub/drilling-and-accessories/stainless-steel-drill-bit). Products Compared used the single step bit on the amazon.co.uk shelf from 15 October 2026, with no lab test. A qualifying purchase can earn a commission at no extra cost to you.

You are putting a hole in a stainless sink rim, a 1 mm panel or a thin bracket, and the 10 mm twist bit grabbed as the point broke through.

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
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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KASAFE KASAFE M35 step bit, 3–13 mm

Alternative

KASAFE KASAFE M35 step bit, 3–13 mm
7.3/10about £7.99
View offer
On this page
  1. 1.Why a twist bit grabs sheet
  2. 2.What the step bit on this shelf is
  3. 3.Where it stops
  4. 4.Clamp, oil, and the chuck

Why a twist bit grabs sheet

A twist bit is a point and two lips. In thick bar the point is supported by the hole it has already cut. In sheet, the point crowns through while the lips still meet a thin wall, and the bit screws itself in. An unclamped sheet climbs the flutes, and a round mark becomes a triangle. ITS describes step and cone bits for that problem, because each step cuts a short ring instead of one large point breaking through at full diameter. A 3 mm or 4 mm pilot is less violent than a 10 mm bit in 1 mm steel if you clamp and back the exit. It is still the wrong finished tool once the hole must grow. A step bit opens a small hole, then lets the next land enlarge it, and you stop when the land you want is through. That shape is a poor way to drill deep bar, because the large steps never get a full flute of support.

What the step bit on this shelf is

The only step bit in this comparison is KASAFE, at £7.99 on 15 October 2026, scored 4.3 from 84 ratings. It has 11 steps from 3 mm to 13 mm, an uncoated finish and a 118° split point on a 1/4 inch hex. The bullets say 5% cobalt M35. Hardness lines in the bullets are claims, and the file contains no test of them. Do not copy an 8% line from another brand onto this ASIN. BSSA’s 135° note is for twist bits. Do not correct this step bit to 135°. Coat versus alloy is on the cobalt versus HSS page.
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

Where it stops

The listing claims 1 mm foil to 5 mm stainless plate. That is the seller’s sentence, not a lab maximum. One review reports 14 holes of 13 mm in 6 mm steel. Another reports a snapped hex when it was not fully chucked. Do not plan past 5 mm. A 35 mm monobloc tap hole is a punch. Wolfcraft’s sink cutter is stated up to about 2 mm sheet. This 3–13 mm cone will not finish it. A 10 mm or 13 mm bracket hole is the shape this shelf stocks. Twist-set diameters, when one size is safer, are on the buying guide.

Clamp, oil, and the chuck

Clamp the sheet to a backing board so it cannot climb the cone, and support the exit. Start at the 3 mm pilot and let each land cut. Forcing 13 mm in one squeeze burns the edge in 1 mm stainless. Seat the full 1/4 inch hex in the chuck. A short grip bends the shank. Use rotary gear and cutting fluid. Hammer mode is the wrong setting. Oil and rpm are on the how to drill page. A curl means the step is cutting. A blue land means heat.

Common questions

Should you use a twist bit or a step bit in thin stainless?
Use the step bit when the sheet is thin and the hole may grow through several diameters up to 13 mm. The stepped lands cut a short ring and reduce the snatch ITS describes for a large point breaking through. A small twist bit can still start a pilot if you clamp and back the sheet. A 10 mm twist bit in 1 mm steel is the grab you are trying to avoid.
How thick can this step bit go?
The KASAFE listing claims 1 mm foil up to 5 mm stainless plate. That is the seller’s sentence, not a measured maximum. One review reports 14 holes in 6 mm steel, and another reports a snapped shank on a 6 mm section when the hex was not fully chucked. Plan to stay within the 5 mm claim. Treat anything thicker as twist-bit work, or as a job for a workshop if the part is structural.
Can it cut a tap hole in a sink?
It can cut a hole up to 13 mm, which may be a draw-bolt or a bracket hole. A 35 mm monobloc tap hole is a punch, and Wolfcraft’s sink cutter is stated up to about 2 mm sheet on that set. RUKO uses a step drill for the small hole and a punch for the fitting. This comparison does not sell that punch. If the fitting is 35 mm, the 13 mm cone will not finish the job.
When is the metal too thick for a step bit?
Plan to stop at the listing’s 5 mm stainless claim, sooner if the edge is already burning. A 6 mm section appears in reviews both as a success and as a snapped shank, so it is past the claim. Deep bar and a 35 mm sink hole are different tools.
Why is this step bit 118° when twist bits are 135°?
The KASAFE listing prints 118°. BSSA’s 135° note is written for twist bits in ordinary stainless. Do not correct this step bit to 135° in your notes. A gold step bit on another site may only be a coat. This listing says uncoated M35.

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

How to drill stainless steel: speeds, feed and oil

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)