Which Screwdriver Bit for Which Screw — Complete Reference Table
This is the definitive cross-reference for matching screw types to the correct screwdriver bit. Whether you’ve pulled a screw out of a piece of furniture and need to know what drives it, or you’re buying screws and want to make sure you have the right bit, this table covers every common screw type sold in UK hardware shops.
Master Screw-to-Bit Reference Table
| Screw Type | How to Identify | Correct Bit Type | Common Sizes | Where You’ll Find It |
|---|---|---|---|---|
| Pozidriv (PZ) | Cross recess with four extra tick marks at 45° between the cross slots | PZ1, PZ2, PZ3 | PZ2 most common | UK wood screws, chipboard screws, construction screws, drywall screws |
| Phillips (PH) | Plain cross recess — no tick marks, tapers to a point | PH0, PH1, PH2, PH3 | PH2 most common | Machine screws, electrical fittings, imported electronics, older fittings |
| Torx (TX / T) | Six-pointed star recess | Torx T10–T40 | T20, T25 most common | Decking screws, automotive, security fittings, flat-pack (IKEA) |
| Torx Security (TT) | Six-pointed star with centre pin | Security Torx TT10–TT40 | TT20, TT25 | Tamper-proof fittings, public installations, playground equipment |
| Hex Socket (Allen) | Hexagonal recess | Hex bits or Allen keys | 3mm, 4mm, 5mm, 6mm | Flat-pack furniture, machine bolts, bike parts, set screws |
| Slotted (Flat) | Single straight slot across the head | Flat / slotted bit | 4mm, 5.5mm, 6.5mm | Older fittings, electrical terminals, decorative hardware, grub screws |
| Robertson (Square) | Square recess | Square drive bits #1, #2, #3 | #2 most common | Rare in UK — Canadian/North American imports, some pocket-hole screws |
| Tri-Wing | Three-slot Y-shaped recess | Tri-wing bits | TW1–TW4 | Electronics (Nintendo, Apple), some aircraft fasteners |
| Spanner (Snake Eye) | Two small round holes | Spanner bits | Various | Tamper-proof public fittings, fire hydrants, utility covers |
Screw Gauge to Bit Size — Detailed Matching
Knowing the screw type is half the job — you also need the right size. Screw gauge (the number on the box) determines which bit size to use. Here’s how gauge numbers map to PZ and PH bit sizes.
| Screw Gauge | Screw Diameter (mm) | PZ Bit Size | PH Bit Size | Common Lengths |
|---|---|---|---|---|
| No. 2 | 2.2mm | PZ1 | PH1 | 12mm–16mm |
| No. 3 | 2.5mm | PZ1 | PH1 | 12mm–20mm |
| No. 4 | 3.0mm | PZ1 | PH1 | 12mm–30mm |
| No. 5 | 3.5mm | PZ2 | PH2 | 16mm–40mm |
| No. 6 | 3.5mm | PZ2 | PH2 | 19mm–50mm |
| No. 7 | 4.0mm | PZ2 | PH2 | 19mm–65mm |
| No. 8 | 4.2mm | PZ2 | PH2 | 19mm–75mm |
| No. 10 | 5.0mm | PZ2 | PH2 | 25mm–100mm |
| No. 12 | 5.5mm | PZ3 | PH3 | 30mm–100mm |
| No. 14 | 6.3mm | PZ3 | PH3 | 38mm–100mm |
Torx Size Guide
Torx screws are becoming more popular in the UK, especially for decking and high-torque applications. The Torx size is printed on the screw box (e.g. T25) and corresponds directly to the bit size needed. For more detail, see our dedicated Torx screw sizes guide.
| Torx Size | Screw Diameter (approx.) | Common Application |
|---|---|---|
| T10 | 2.5mm–3.0mm | Electronics, small machine screws, laptop screws |
| T15 | 3.0mm–3.5mm | Small appliances, some flat-pack furniture |
| T20 | 3.5mm–4.0mm | General woodwork, interior fittings, some IKEA furniture |
| T25 | 4.5mm–5.0mm | Decking screws, heavy-duty woodwork, automotive |
| T30 | 5.5mm–6.0mm | Heavy construction, large timber screws, automotive |
| T40 | 6.5mm+ | Heavy-duty structural fixings, coach screws |
Hex (Allen) Key Size Guide
Hex socket screws use Allen keys or hex bits. In the UK, metric sizes are standard. For a full guide including IKEA sizes, see our Allen key sizes page.
| Hex Size | Bolt Size (metric) | Common Application |
|---|---|---|
| 2mm | M2.5–M3 | Electronics, grub screws, small set screws |
| 2.5mm | M3–M4 | Small machine screws, RC models, precision equipment |
| 3mm | M4 | Furniture bolts, hinge screws, drawer handles |
| 4mm | M5 | IKEA furniture (most common size), bicycle bolts |
| 5mm | M6 | Machine bolts, automotive, structural brackets |
| 6mm | M8 | Heavy machinery, large bolts, structural steelwork |
| 8mm | M10 | Industrial equipment, large structural fixings |
Still Not Sure? Quick Decision Guide
If you’re looking at a screw and aren’t certain which type it is, ask yourself these questions in order:
Is it a cross/cruciform shape? Look for tick marks between the cross slots. Tick marks = Pozidriv. No tick marks = Phillips. When in doubt with UK wood screws, try a PZ2 first — it’s correct about 80% of the time.
Is it a star shape? That’s Torx. Count the points — there should be six. The Torx size number (T20, T25 etc.) should be on the screw packaging. If the star has a pin in the centre, you need a security Torx bit.
Is it a hexagonal hole? That’s a hex socket screw. Use a hex bit or Allen key in the matching metric size.
Is it a single straight line? That’s a slotted screw. Use a flat screwdriver bit matching the slot width.
Recommended Multi-Bit Sets
If you want to be prepared for every screw type, a comprehensive bit set is the way to go. These sets include PZ, PH, Torx, hex, and slotted bits in all common sizes.
Wera Bit-Check 30 Universal
Wera’s 30-piece set includes PZ1–PZ3, PH1–PH3, Torx T10–T40, hex 3mm–6mm, and slotted bits. Every bit is Impaktor-rated for use with impact drivers. The Rapidaptor holder with quick-release makes bit changes fast. This is the go-to set for tradespeople who need quality bits across all screw types.
DeWalt DT71572 45-Piece Screwdriver Bit Set
A solid all-round set at a lower price point than Wera. Includes PZ and PH bits in all sizes, a selection of Torx and hex bits, magnetic bit holder, and a tough case. Good for DIY users who want one set that covers everything without spending trade-level money.