# SDS drill bits explained: types, lengths and tips

Source: https://drillandbit.co.uk/blog/sds-drill-bits-explained
Published: 2026-10-12
Publisher: Drill and Bit

**In short:** SDS bits have a slotted shank that slides in the chuck so the piston can hammer them. SDS plus bits have a 10 mm shank and suit most drills; SDS max bits have an 18 mm shank for heavy drills. Choose by diameter, working length and tip: four cutter tips drill rounder holes and handle rebar better than two cutter tips. Replace bits when the tip is worn.

SDS drill bits look simple, but packs list cutters, flute types, working length and overall length, and prices vary widely. Knowing what each feature does helps you buy bits that drill clean, accurately sized holes and last. This guide explains SDS plus and SDS max shanks, tip designs, lengths, chisels and when a bit is worn out.

## SDS plus and SDS max shanks

**SDS plus** bits have a 10 mm shank with two open and two closed grooves. They fit almost every SDS drill sold for home and light trade use. **SDS max** bits have an 18 mm shank and fit heavy combination hammers and breakers. The two are not interchangeable without special adapters.

See [what is an SDS drill](https://drillandbit.co.uk/blog/what-is-an-sds-drill) for the drills themselves.

## Tip designs

The carbide tip does the cutting. **Two cutter** tips have a single flat blade and are common on smaller, budget bits. **Four cutter** or cross tips have four carbide edges, which centre better, drill rounder holes and are less likely to jam on steel reinforcement. Many trade bits use four cutter tips from about 6 mm upwards.

| Feature | What it does |
| --- | --- |
| Two cutter tip | Simple, good for brick and block |
| Four cutter tip | Rounder holes, better in concrete with rebar |
| Centre point | Accurate start without wandering |
| Wide flutes | Clears dust faster, less binding |
| Hollow bit with extraction | Removes dust as you drill |

Tip and flute features

## Working length and overall length

Bit packs list overall length, such as 160 mm, and working length, such as 100 mm. The working length is what can enter the hole; the rest sits in the chuck. For a wall plug, choose a working length a bit longer than the plug plus any plaster or tile. For through holes in cavity walls, long bits of 300 mm to 600 mm and more are available.

Long thin bits flex, so start slowly and keep the drill straight. Use the depth rod on the side handle to avoid drilling too deep.

[See SDS drills](https://drillandbit.co.uk/best/best-cordless-sds-drills)

## Common sizes

Wall plug sizes set the bit diameter. Brown plugs often take 7 mm, red plugs 6 mm and yellow plugs 5 mm, but always check the packet. Larger anchors and resin fixings need 10 mm to 16 mm bits. See [which drill bit for wall plugs](https://drillandbit.co.uk/blog/which-drill-bit-for-wall-plugs) for a full chart.

A set with 5, 6, 8, 10 and 12 mm bits covers most home jobs. Add long bits and larger sizes as you need them.

Some masonry anchors and resin fixings specify an exact bit size and depth on the packet. Follow it closely, as a hole only a millimetre too big can greatly reduce the holding power of a fixing in soft brick.

## Chisels and special bits

SDS drills with a hammer only mode take chisels: point, flat, wide tile and channel chisels. There are also SDS core bits for large holes and SDS adapter chucks for normal bits. See [how to break up concrete with an SDS drill](https://drillandbit.co.uk/blog/how-to-break-up-concrete-with-an-sds-drill) and [how to core drill with an SDS drill](https://drillandbit.co.uk/blog/how-to-core-drill-with-an-sds-drill).

Hollow extraction bits connected to an M class dust extractor reduce silica dust and leave a clean hole for resin anchors.

## When to replace a bit

Check the tip. When the carbide corners are rounded, the hole becomes undersize and plugs spin or anchors fail. A chipped or cracked tip should be replaced at once. Bits with worn shanks or bent bodies can damage the chuck.

Keep bits clean and lightly greased at the shank, and store them in a case so tips are not knocked. A cheap bit that wears quickly can cost more in failed fixings than a quality bit that keeps its size for hundreds of holes, so buy better bits in the sizes you use most.

Note: Wear eye protection when drilling and never touch a bit straight after use; it gets very hot. Use dust control for silica dust from concrete and brick.

## Frequently asked questions

**Do SDS bits fit a normal drill?** No. They need an SDS chuck. Some combi drills accept SDS bits through an adapter, but the hammer action is weak.

**Are four cutter SDS bits worth it?** For concrete and frequent use, yes. They drill rounder holes and cope better with rebar.

**What is the difference between SDS plus and SDS max?** SDS plus has a 10 mm shank for most drills; SDS max an 18 mm shank for heavy drills.

**How long should an SDS bit be?** Choose a working length a little longer than the hole depth you need.

## Buying guides on this topic

- https://drillandbit.co.uk/best/best-cordless-sds-drills
- https://drillandbit.co.uk/best/best-power-tool-kits
- https://drillandbit.co.uk/best/best-combi-drill-kits