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HSS or cobalt drill bits

Updated: 2026-10-23

You are holding a gold bit in one hand and a stainless bracket in the other, hoping the colour is enough to finish the hole. It is not. HSS or cobalt drill bits is one decision: high-speed steel for mild steel and aluminium, a titanium nitride coat still counted as HSS, and the M42 listing only when the hole is stainless, at low speed and with oil. Prices are the amazon.co.uk lines in the [drill bit comparison](/hub/drilling-and-accessories/drill-bit). Products Compared used those listings and UK trade guides on 22 October 2026, and did not run a lab test. A qualifying purchase can earn a commission at no extra cost to you.

You are holding a gold bit in one hand and a stainless bracket in the other, hoping the colour is enough to finish the hole. It is not.

Our top picks

Bosch Bosch PointTeQ 19-piece HSS

Best overall

Bosch Bosch PointTeQ 19-piece HSS
8.4/10about £14.12
View offer
Amazon Basics Amazon Basics 14-piece HSS

Alternative

Amazon Basics Amazon Basics 14-piece HSS
7.7/10about £9.12
View offer
STROTON STROTON M42 cobalt 19-piece

Alternative

STROTON STROTON M42 cobalt 19-piece
6.8/10about £37.89
View offer
On this page
  1. 1.HSS for mild steel, aluminium and plastic
  2. 2.A titanium nitride coat is still HSS
  3. 3.Cobalt when the listing says M42 and the job is stainless
  4. 4.Low speed and oil, or the bit is wasted

HSS for mild steel, aluminium and plastic

High-speed steel covers mild steel, aluminium, copper and plastic if you stop before the tip turns blue. PointTeQ at £14.12, 4.5 from 5,060 reviews, is black-oxide HSS from 1.0 to 10.0 mm in 0.5 mm steps. The bullets name mild steel, cast iron and plastic, and not stainless. The piece-count field says 1 against a 19-piece title. Amazon Basics at £9.12 runs 1.5 to 10 mm, with 1.5 mm and 3.2 mm repeated, and the usage note excludes stainless. The title says titanium and the finish field says polished. None of these sets says DIN 338 or H8.

A titanium nitride coat is still HSS

Screwfix splits the steel from the coating. Titanium nitride, which that guide also types as titanium nitrate, slows wear on HSS. It is not cobalt. The 50-piece and 70-piece say HSS-TiN and stop at 6.5 mm. The 34-piece metal bits stop at 5 mm. A 4.7-star line does not make them stainless bits. LSLANSOON prints 118 degrees in a bullet and 1183 degrees in the spec. Amtech says titanium-nitride HSS in the title and alloy steel in the spec. Grind a TiN tip back and the coat is gone. Cobalt runs through the steel.
Bosch Bosch PointTeQ 19-piece HSS

Testsieger

Bosch Bosch PointTeQ 19-piece HSS
8.4/10about £14.12
View offer

Cobalt when the listing says M42 and the job is stainless

UK Drills puts cobalt in the 5–8% band on stainless, cast iron and hard alloy steels, and notes that it is harder and more brittle. Protool puts M35 around 5% cobalt and M42 around 8%. A box that only says cobalt might be either. The only grade here is M42: STROTON at £37.89, 4.3 from 4,756 reviews, 1 to 10 mm. The bullets say 135 degrees. The spec says 90 degrees. The shank is not stated. Reviews that praise stainless, and reviews that report a snap, are comments, not a timed test. Skip it for brick, on the masonry drill bit page, and for mild steel that PointTeQ already covers.

Low speed and oil, or the bit is wasted

Use a lower speed for a large bit in hard material, and cutting fluid, before the tip turns blue. UK Drills' chart, as theirs and not a test of these bits, suggests about 1,500 rpm for 6 mm HSS in mild steel and about 650 rpm for 6 mm in stainless. Powder instead of a chip means you are rubbing, and stainless work-hardens if it rubs. Use the lower gear on a cordless drill and peck the bit out. Cables and dust are on the how to use a drill bit page. Mild steel takes HSS. Stainless takes the M42 listing, slow and oiled. Brick takes neither. The mixed 4.7-star cases are on the best drill bits page.

Common questions

Should I buy HSS or cobalt drill bits?
Buy HSS for mild steel, aluminium, copper and plastic. Buy the M42 cobalt set when the hole is stainless. In this comparison that is PointTeQ or Amazon Basics on one side, and STROTON at £37.89 on the other. A gold mixed set stays on the HSS side. Cobalt is the wrong spend for brick, and HSS is the wrong spend once stainless has already blued a tip.
Is a gold titanium drill bit cobalt?
No. Titanium nitride is a coating on high-speed steel. The Bosch 34-piece, 50-piece and 70-piece metal bits, the LSLANSOON step bits and the Amtech title are in that group, with the listing clashes left as they are. Cobalt is in the steel. The only listing here that says M42 8% cobalt is STROTON, and the bullets there name stainless.
What is M42, and which listing here says it?
Trade explainers put M42 at about 8% cobalt and M35 at about 5%. A box that only says cobalt could be either, which is why this page trusts the letters on the listing. STROTON is the listing that says M42 8% cobalt, nineteen bits from 1 to 10 mm. No set here says M35, so this page does not recommend one.
Can HSS drill stainless steel?
Sometimes, for a single shallow hole, and often it rubs, blues and work-hardens the surface. Amazon Basics excludes stainless in the usage note. The gold X-Line bits are still HSS-TiN. If the job is stainless, or HSS has already failed, the listing to open is STROTON, used slowly with cutting fluid. Reviews that mention snaps are comments, not a promise the bit will or will not break.
Why do the STROTON angle lines disagree?
The bullets say a 135 degree split point. The cutting-angle field says 90 degrees. Both are on the amazon.co.uk listing, and this comparison does not pick a winner or treat either figure as a measured test. The shank is not stated. You can still use the set for the steel it names, and you should not quote a single tip angle as if the page had one.

Related pages

Drill bit buying guide

Drill bit

Best drill bits for brick, steel or stainless steel

Masonry drill bit for brick plugs, hammer and dust

How to use a drill bit: speed, oil, dust and cables

Sources

Public UK sources from the research digest. Shelf prices and star lines are the amazon.co.uk figures in the display file.

  1. HSE CN3: silica dust and APF 20 (retrieved 22 October 2026)
  2. HSE CIS36: drilling and respirable crystalline silica (retrieved 22 October 2026)
  3. HSE: electricity, drilling near cables (retrieved 22 October 2026)
  4. HSE CIS65: power off if cable routes are unknown (retrieved 22 October 2026)
  5. Bosch DIY UK: guide to drills (retrieved 22 October 2026)
  6. Screwfix: guide to types of drill bits (retrieved 22 October 2026)
  7. Rawlplug UNO universal plug (retrieved 22 October 2026)
  8. CMT: standard plastic wall plugs (retrieved 22 October 2026)