Choosing the right bit diameter and length is just as important as choosing between Bosch and budget alternatives. The wrong size wastes time, damages fasteners, and produces crooked holes. This guide shows you exactly which diameter and length you need for every common fastening job.
SDS-Plus Available Sizes
SDS-Plus bits cover most common drilling needs for DIY and trade work. Available diameters range from 4mm to 30mm, with lengths from 110mm to 1000mm.
The most common sizes you’ll encounter:
- Diameters: 4, 5, 6, 8, 10, 12, 14, 16, 18, 20, 22, 25, 28, 30mm
- Standard lengths: 110, 160, 210, 310, 460, 600, 1000mm
Longer bits are available but increasingly rare — for holes deeper than 600mm, consider renting an SDS-Max tool or using a core bit.
SDS-Max Available Sizes
SDS-Max bits are for larger-diameter work on heavy mains-powered or industrial tools. Available diameters range from 12mm to 52mm, with lengths from 340mm to 1320mm.
- Diameters: 12, 14, 16, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 42, 45, 50, 52mm
- Standard lengths: 340, 450, 540, 740, 1000, 1320mm
SDS-Max tools are overkill for small wall plugs — they’re designed for structural bolting, through-holes, and heavy demolition drilling.
Quick Size Reference — Plugs & Anchors
| Fastening Job | Fastener Size | Bit Diameter | Bit Length | SDS System |
|---|---|---|---|---|
| Wall plugs (small) | Rawlplug No. 6 | 5mm | 110–160mm | SDS-Plus |
| Wall plugs (medium) | Rawlplug No. 8 | 6mm | 110–160mm | SDS-Plus |
| Wall plugs (large) | Rawlplug No. 10 | 8mm | 110–160mm | SDS-Plus |
| Anchor bolt M6 | M6 | 8mm | 160–210mm | SDS-Plus |
| Anchor bolt M8 | M8 | 10mm | 160–210mm | SDS-Plus |
| Anchor bolt M10 | M10 | 12mm | 210–310mm | SDS-Plus |
| Anchor bolt M12 | M12 | 14–16mm | 210–310mm | SDS-Plus or SDS-Max |
| Chemical anchor M12 | M12 | 14mm | 210–310mm | SDS-Plus |
| Through-bolt M10 (clearance) | M10 | 11mm | 210–460mm | SDS-Plus |
| Through-bolt M12 (clearance) | M12 | 13mm | 210–460mm | SDS-Plus |
| Large structural bolt | M16+ | 18–25mm+ | 300–1000mm+ | SDS-Max or core bit |
Bit Length Guide for Common Applications
Always calculate: Bit length = Working depth + 30mm minimum clearance.
110–160mm Bits (Shallow Work)
Use for: Hanging pictures, light shelves, small wall plugs on interior walls.
Typical depth: 50–100mm (into blockwork or concrete).
Common sizes: 5, 6, 8mm (Rawlplugs Nos. 6–10).
210mm Bits (Standard Wall Depth)
Use for: Most wall-mounted fixings — shelves, radiators, mirrors, heavy items on interior blockwork or cavity walls.
Typical depth: 150–180mm (block + cavity consideration).
Common sizes: 6, 8, 10, 12mm anchor bolts.
Why 210mm? Interior blockwork walls (typically 100mm block) + plaster (10mm) + cavity (50–100mm, if cavity exists) = 160–180mm working depth. 210mm gives you 30mm of safe clearance.
310–460mm Bits (Deep/Through Cavity)
Use for: Through-bolts on cavity walls, deep fixing into solid concrete, attaching to external masonry walls with internal cavity.
Typical depth: 250–400mm.
Common sizes: 10, 12, 14, 16mm.
Example: External stone wall (200mm) + cavity (50–100mm) + internal blockwork (100mm) = 350–400mm total. You’d want a 460mm bit.
600mm Bits (Very Deep Work)
Use for: Structural bolting, deep anchoring into concrete beams, through thick masonry.
Typical depth: 500–550mm.
Common sizes: 12, 14, 16, 18mm (SDS-Plus or SDS-Max depending on hole size).
1000mm Bits (Extreme Depth)
Use for: Rare — drilling through full structural elements, deep pile work, or specialist applications.
Typical depth: 900–950mm.
Note: Very long bits (900mm+) require careful technique — they flex more and are harder to keep straight. Professional drills and guides are recommended.
Hole Diameter Reference
Small Holes (4–8mm)
Wall plugs, picture hooks, light shelving. Quick and easy work. Available in all lengths.
Medium Holes (10–16mm)
Heavy shelves, radiators, mechanical anchors. This is the sweet spot for most DIY and trade work. Maximum availability in all lengths and both SDS systems.
Large Holes (18–30mm)
Structural bolting, heavy machinery, large-diameter anchors. Longer bits become scarcer — 460mm+ may not be readily available in 25mm+ sizes. Consider SDS-Max for holes above 25mm.
Extra-Large Holes (32–52mm+)
Requires SDS-Max or core bits. 32–52mm SDS-Max bits are available but specialised — expect to order online. For very large clean holes (50–150mm), core bits (annular cutters) are faster and create less mess.
Core Bits for Large Clean Holes
If you need a very large, clean hole (25–150mm diameter), a core bit (annular cutter) is often better than a standard twist drill or SDS bit.
Advantages:
- Cuts a clean, precise hole with no chatter or bounce-out
- Produces a plug of material that ejects easily (no dust accumulation)
- Much faster than SDS bits for holes above 32mm
Disadvantages:
- More expensive than standard bits
- Requires a drill with depth stops or a rotary table
- Cuts only about 50–100mm deep before requiring re-sharpening or replacement
Typical use: Drilling through structural beams for large bolts, cable entries through concrete, large-diameter pipe penetrations.
Watch: Video Guide
Frequently Asked Questions
Why can’t I just buy a 1000mm bit for everything?
Long bits are harder to keep straight and control, especially on shorter holes — they flex more and the drill bounces around more easily. Use the shortest bit that reaches your target depth. For a 150mm hole, a 210mm bit gives you much better control than a 600mm bit.
Can I use a 10mm bit for an M8 bolt?
A 10mm bit is slightly oversize for M8 (which normally uses an 8mm bit). The bolt will fit but with excessive clearance — the anchor may not grip properly. Always use the correct size for the fastener. If you only have a 10mm bit, drill an 8mm hole first, then enlarge if absolutely necessary.
What if the hole needs to be deeper than my longest bit?
You have three options: (1) rent an SDS-Max rotary hammer and use a longer bit; (2) drill in stages — drill to your bit’s max depth, withdraw the bit, clear the debris, and continue; (3) use a core bit with a depth stop to avoid overheating. Option 3 is fastest for very deep work.
Why do I need 30mm extra clearance?
This accounts for bit drift, the depth you can’t measure precisely, and ensures the chisel/flute point doesn’t break through and bind on the far side of the hole. It’s also a safety margin — bits can jam if they break through into an unexpected void or cavity.
Do SDS-Plus bits fit in SDS-Max hammers?
No. The shank types are completely different — SDS-Plus won’t fit in SDS-Max sockets. You need to use the correct shank type for your hammer. Check your drill or hammer manual if you’re unsure.
Related Guides
For bit recommendations, see our guide to best SDS drill bits for concrete. For chiselling work, see SDS chisel bits compatibility.
