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SDS max drill bit size: shank, diameter and length

Updated: 2026-10-23

Your SDS max hammer's next job is one hole. Match the shank to the chuck, then the cutting diameter to the fixing sheet, then a length you can interpret. The large number in an amazon.co.uk title is often the whole bit, and the hole you can drill is shorter. The five kept listings, from £9.99 to £26.99, are on the [SDS max drill bit comparison](/hub/drilling-and-accessories/sds-max-drill-bit). If the chuck is SDS plus, or the housing only says SDS, read [SDS max vs SDS plus](/hub/drilling-and-accessories/sds-max-drill-bit/sub/sds-max-drill-bit-vs-sds-plus) before you look at a diameter.

Your SDS max hammer's next job is one hole. Match the shank to the chuck, then the cutting diameter to the fixing sheet, then a length you can interpret.

Our top picks

Keewaki Keewaki 20 x 400 mm

Best overall

Keewaki Keewaki 20 x 400 mm
6.8/10about £17.99
View offer
UK Drills UK Drills 18 x 330 mm

Best value

UK Drills UK Drills 18 x 330 mm
5.6/10about £14.89
View offer
UK Drills UK Drills 10 x 280 mm

Alternative

UK Drills UK Drills 10 x 280 mm
5.6/10about £9.99
View offer
On this page
  1. 1.Match the shank before the diameter
  2. 2.Pick the diameter from the fixing
  3. 3.Read working length and total length apart
  4. 4.What these five listings leave blank

Match the shank before the diameter

Heller's shank page puts SDS max at about 18 mm, for rotary hammers over about 5 kg, and SDS plus at about 10 mm. GTSE's buyers' guide states the same split: one chuck will not take the other shank. Every listing kept here prints an 18 mm SDS max shank, including UK Drills B01N410BGL, 10 × 280 mm at £9.99. The 10 mm is the hole, not the steel that enters the chuck. On an SDS plus hammer it will not seat. The best SDS max drill bit page says when that row is still the wrong basket.

Pick the diameter from the fixing

The hole follows the anchor, plug or sleeve, not the largest bit in the photograph. A sheet that says 18 mm does not become a 20 mm hole because 20 mm was in the basket. An oversized hole leaves a sleeve loose. This set covers 10 mm at £9.99, 18 × 330 mm at £14.89, 18 × 400 mm at £15.99, the only 20 mm at £17.99, and 25 × 550 mm at £26.99. There is no 12 mm, 16 mm or 22 mm. If the sheet asks for one of those, none of these five is the honest buy. The UK Drills bullets say these bits are not for wood or metal.
Keewaki Keewaki 20 x 400 mm

Testsieger

Keewaki Keewaki 20 x 400 mm
6.8/10about £17.99
View offer

Read working length and total length apart

Working length is the flute you can send into the wall. Total length is the whole bit, shank included. JCP's 12 mm example, part MAX12340, is 188 mm working and 340 mm overall. That pair is JCP's table, not a UK Drills ASIN. UK Drills titles print one number, 280 mm, 330 mm, 400 mm or 550 mm. A 280 mm bit with its shank in the chuck will not give you a 280 mm hole. Keewaki's title is 20 × 400 mm, one bullet says 340 mm, and a highlight says 400 mm working depth. Do not state one working length for B0GVMJM9HP. Dust clearance is on the how to use an SDS max drill bit page.

What these five listings leave blank

Keewaki omits a flute count. UK Drills describes 4 cutting edges and, in the spec, 2 spiral flutes. PGM is not stated on any of these five. Water cooling is asked on the UK Drills pages and left unanswered. If the sheet is not 10, 18, 20 or 25 mm, skip all five. We compared these amazon.co.uk listings with Heller, GTSE, JCP and the Bosch Professional GB catalogue page. We did not drill the bits in a lab. A qualifying purchase through our links can earn a commission at no extra cost to you. Updated 22 October 2026.

Common questions

Does an SDS max bit fit an SDS plus drill?
No. An SDS max bit uses a shank of about 18 mm, and an SDS plus chuck is made for a shank of about 10 mm. Heller and GTSE both describe that split, and GTSE is clear that the chuck will not accept the other system. Every listing in this comparison states SDS max, including the 10 mm cutting diameter at £9.99.
Is the number in the title the depth of the hole?
Usually it is one length for the whole bit, and you should not treat it as hole depth. Part of an SDS max shank sits in the chuck, so a 280 mm or 400 mm title is longer than the hole you can drill. Mark the depth on the fixing sheet and stop when that mark meets the wall.
What diameter should match the fixing?
Use the drill diameter and the minimum hole depth on the anchor, plug or sleeve sheet. In this set the cutting diameters are 10 mm, 18 mm, 20 mm and 25 mm, with 18 mm at a 330 mm title and a 400 mm title. There is no 12 mm or 16 mm listing. A near size is still the wrong hole: 20 mm is not a substitute for an 18 mm sleeve.
Is a 10 mm SDS max bit the right bit for a 10 mm plug?
Only if the hammer is SDS max. UK Drills B01N410BGL is a 10 mm cutting diameter on an 18 mm SDS max shank, at £9.99 and a 280 mm title length. The 10 mm matches a 10 mm plug hole. It does not match an SDS plus chuck, and it does not become a 10 mm shank.
What does the Keewaki listing say about 400 mm and 340 mm?
The title is 20 × 400 mm, at £17.99. One bullet says 340 mm, and a highlight says 400 mm working depth. The page does not reconcile those lines, so you cannot take either number as the working length of B0GVMJM9HP. It is the only 20 mm bit in this set, which matters if the sheet asks for 20 mm, and the length clash still stands.

Related pages

SDS max drill bit for reinforced concrete

SDS max drill bit

Best SDS max drill bit: which listing fits the hole

How to use an SDS max drill bit in brick or concrete

SDS max vs SDS plus: the shanks do not interchange

Sources

Public UK and manufacturer pages used for shank, dust, vibration and anchor-bit geometry, plus the amazon.co.uk listings for the five ASINs. Last checked on 22 October 2026.

  1. Heller Tools, Shanks (retrieved 22 October 2026)
  2. HSE CN3, Construction dust: drilling (retrieved 22 October 2026)
  3. HSE CIS36, Construction dust (retrieved 22 October 2026)
  4. HSE, Hand-arm vibration: assess the risks (retrieved 22 October 2026)
  5. HSE INDG175, Hand-arm vibration (retrieved 22 October 2026)
  6. HSE, Electrical systems on construction sites (retrieved 22 October 2026)
  7. Bosch Professional GB, PRO SDS max-7 drill bit (retrieved 22 October 2026)
  8. PGM, Check of standard drill bits (retrieved 22 October 2026)
  9. PGM, Marking of drill bits (retrieved 22 October 2026)