HSS vs cobalt drill bits
Updated: 2026-10-23
You are looking at a packet that says HSS-R, HSS-G, M35, black oxide and a gold photo, and you need to know which word is the steel. HSS vs cobalt drill bits is three different kinds of fact, not one ladder of "better". The alloy is the word cobalt, M35, M42 or HSS-Co. The grind is R or G. The colour is a finish until the maker says otherwise. The [metal drill bit comparison](/hub/drilling-and-accessories/metal-drill-bit) ranks nine amazon.co.uk listings. A qualifying purchase can earn a commission at no extra cost to you.
You are looking at a packet that says HSS-R, HSS-G, M35, black oxide and a gold photo, and you need to know which word is the steel. HSS vs cobalt drill bits is three different kinds of fact, not one ladder of "better".
You are looking at a packet that says HSS-R, HSS-G, M35, black oxide and a gold photo, and you need to know which word is the steel. HSS vs cobalt drill bits is three different kinds of fact, not one ladder of "better". The alloy is the word cobalt, M35, M42 or HSS-Co. The grind is R or G. The colour is a finish until the maker says otherwise. The metal drill bit comparison ranks nine amazon.co.uk listings. A qualifying purchase can earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Grade | Diameters | Point | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Bosch Bosch PointTeQ 19-piece HSS set | HSS PointTeQ, not cobalt | 1.0–10.0 mm, 0.5 mm steps | n/a | 9.0 | about £14.12 | View offer |
| Best value |  Bosch Bosch PointTeQ 18-piece ToughBox | HSS PointTeQ | 1–10 mm, duplicates at 2, 3 and 4 mm | 135° | 9.0 | about £11.95 | View offer |
| Alternative |  DeWalt DeWalt DT5912 13-piece HSS-R | HSS-R black oxide in the title; material cell says chrome vanadium | 1.5–6.5 mm | 118° | 9.0 | about £9.60 | View offer |
On this page
Three different words on one packet
The making process, the alloy and the coating answer different questions. Roll-formed or ground tells you how the flute was made. Cobalt tells you the steel can keep an edge hotter. Black oxide or titanium nitride is the surface, and a nitride coat is gone from the lip once you regrind it. A gold bit can be nitride on ordinary HSS, nitride on cobalt, or an identification colour on a cobalt bit. IRWIN’s note, for IRWIN bits only, says the cobalt remains after the colour is ground off. A packet that only says cobalt may be M35, M42, or a vague claim. Claims of 68 HRC or 3× life are seller text, not a test.
HSS-R and HSS-G
HSS-R means roll-formed flutes. HSS-G means ground flutes. Neither letter means cobalt. DeWalt’s DT5912-QZ is the HSS-R example: black oxide, 118°, 1.5–6.5 mm, rated on DeWalt’s UK page to 900 N/mm². The amazon material cell says chrome vanadium steel. That clash is a conflict to report. Bosch PointTeQ in this sample is black-oxide HSS. The GB page states DIN 338 and 135°, and no cobalt. The 18-piece listing prints 135°. The 19-piece table leaves the angle blank. A 135° split point can be ground on ordinary HSS. Reading split point as cobalt is the mistake the packet invites.
M35 and M42
M35 is about 5% cobalt. M42 is about 8%. More cobalt is there for heat at the edge. It is not a reason to skip oil, and it is not automatically better in a light handheld drill. Protool’s line is that M42 is not the default just because the number is higher. Cutwel points standard HSS at mild steel and non-ferrous metal, and M35 at stainless you cut regularly. Hilti’s UK HSS-Co set states 5% cobalt up to 1100 N/mm². That description is not a row in this sample. Above about 45 HRC, Thürmer says HSS will not cut. How to keep 304 and 316 cutting is on drill bits for stainless steel.
Black oxide and a gold coat
Black oxide is a finish on HSS. Bosch PointTeQ and DeWalt’s DT5912 both carry it here. It is not a substitute for cobalt when the last bit burnt in a stainless sink. A gold colour is often titanium nitride. Once you sharpen the lip, the nitride at that lip is gone. The cobalt, if it was in the steel, is still there. Misuyue’s 1 mm pack claims M42 and a gold titanium coat in the same bullets. Reviews on that listing often name another size. Which listing aims at that reading is on best metal drill bits.
What the standard does not say
DIN 338 and BS 328 are jobber length and a straight shank. Heller’s 1 mm jobber is 34 mm overall, so a 1 mm × 34 mm title can match the standard without proving the steel. MOXPIFY claims both standards on a 1 mm pack. Those words do not assay cobalt, and BS 328 is not a Kitemark. A split point from 3 mm and above does not describe a 1 mm bit. The order for a basket of sets is the metal drill bit buying guide: metal, point, diameters, then process versus alloy, and price last.
Common questions
Is cobalt a coating or part of the steel?
In an HSS-Co, HSS-E, M35 or M42 bit, cobalt is in the alloy, about 5% or about 8%. It is still there after you grind the colour off the lip. Titanium nitride is the coat, and that coat at the tip is not. A packet that only says cobalt may be either grade, or only a claim. IRWIN’s note applies to IRWIN bits, not to every gold photo on amazon.co.uk.
What do HSS-R and HSS-G mean?
HSS-R is roll-formed. HSS-G is ground. Neither letter means cobalt. DeWalt DT5912 is HSS-R black oxide at 118°, rated to 900 N/mm² on DeWalt’s page. Bosch PointTeQ in this sample is black-oxide HSS at 135° on the GB page, not a cobalt code. The amazon cell that says chrome vanadium on the DeWalt set is a clash with the title, not a third definition of HSS-R.
Is M35 the same as 5% cobalt?
M35 is the usual name for HSS with about 5% cobalt. M42 is about 8%. HSS-E is the same family. Hilti states 5% cobalt up to 1100 N/mm² on its HSS-Co set. A listing that claims 5% and then skips a diameter, or puts Generic in the brand field, is still a claim. The percentage does not repair the listing.
When is M42 worth it over M35?
When the work is hotter and harder, and you will still use oil and a low speed. It is not automatically better for a light cordless drill in mild steel, where ordinary HSS is the right steel. Protool’s warning is not to assume M42 just because a packet says cobalt. Above about 45 HRC, Thürmer says HSS will not cut either way.
If the photo is gold, is it titanium nitride or cobalt?
You cannot tell from the photo. Gold is often titanium nitride, which can be applied to plain HSS or to cobalt. Some cobalt bits carry a dull gold as an identification colour through the steel’s heat treatment. Misuyue claims both M42 and a titanium coat. Colour does not prove either sentence. Read the grade line, and treat an untested hardness bullet as a bullet.
Related pages
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.
- Thürmer Tools, Drills FAQ (retrieved 22 October 2026)
- DeWalt UK, DT5912-QZ HSS-R set (retrieved 22 October 2026)
- Bosch Professional GB, PointTeQ HSS sets (retrieved 22 October 2026)
- Bosch Professional GB, HSS-Co twist drill bit sets (retrieved 22 October 2026)
- HSE, HSG129 health and safety in engineering workshops (retrieved 22 October 2026)
- The Personal Protective Equipment at Work Regulations 1992 (retrieved 22 October 2026)
- BSSA, speeds and feeds for drilling stainless steels (retrieved 22 October 2026)
- Heller, HSS-Co DIN 338 drill bits (retrieved 22 October 2026)