Screwdriver bit for wood screws: match recess and gauge

You have a box of woodscrews on the bench and one cross-head bit already in the chuck. The packet says No.8, the stamp on the bit is worn, and the head will shine if the fit is wrong. A screwdriver bit for wood screws has to match two things at once: the shape of the recess, and the size of that recess. Gauge, or the millimetre diameter, tells you which number to try. The recess tells you whether that number is PZ, PH or a Torx star.

This page uses public UK guides from BuildWiz, Screwfix, Wonkee Donkee and Bolts.co.uk, plus the bit sets and wood screws on the amazon.co.uk listings we checked in October 2026. We did not run a lab test. Prices are the shelf figures from those listings, in GBP. A qualifying purchase through our links can earn us a commission at no extra cost to you.

In short

Match the recess first, then the diameter. On the BuildWiz guide, Pozidriv woodscrews of about 3.5 mm to 5.0 mm usually take PZ2 and about 6 mm and up take PZ3, while a Torx size printed on the box overrules both. Those figures are guides, and the tables disagree below 3.5 mm.

Read the recess, then the diameter

Pozidriv is the common woodscrew recess on UK packets, which is the point Bolts.co.uk makes. Screwfix treats Pozidriv and Torx as the popular woodscrew drives. You can see Pozidriv as a cross plus four tick marks. Phillips is a plain cross, and Torx is a six-point star. PZ2 and PH2 are both size 2, and they seat in different recesses.

A Phillips bit in a Pozidriv screw turns while the load is light, then cams out. That tip is shaped to ride out of a cross under torque. A PZ bit in a plain Phillips cross sits proud and chews the walls. If you are unsure which cross you have, compare them on the Pozidriv and Phillips page before you lean on the trigger.

Diameter comes second, inside the right family. BuildWiz puts about 3.5 mm to 5.0 mm on PZ2, and about 6 mm and up on PZ3. A 4 mm wood screw takes PZ2 when the head has ticks, and PH2 when the cross is plain. Press the bit in by hand, with the drill stopped, and keep it only if it fills the recess. Wonkee Donkee's table covers tapered woodscrews, so machine screws, terminals and a consumer-unit plate stay on their own instructions.

A gauge guide, with the disagreements labelled

A screw gauge bit size question rarely has one answer, because UK boxes mix gauge numbers and millimetres. A No.8 Pozidriv screw is the everyday one in a household tub. On the BuildWiz band it sits with the 3.5 mm to 5.0 mm screws they put on PZ2, unless the box prints another size. The end panel of the box outranks a chart you find later.

The public tables disagree at the small end, so treat them as guides. Wonkee Donkee's example calls a 3.0 mm Pozidriv screw a PZ1 job. BuildWiz puts screws under 3.5 mm on PZ1, and puts 3.5 mm itself on PZ2. If your box is 3.5 x 40 mm and silent on the bit, try PZ2, then PZ1 if the larger tip rocks. Filing a proud tip so it almost fits splits the next head.

From about 6 mm, BuildWiz points at PZ3 for a Pozidriv woodscrew. A 6 mm star is still Torx, in the size printed on the box. A 100 mm screw and a 30 mm screw with the same recess take the same bit. Diameter and thread for those packets sit on the wood screws comparison.

Chipboard, drywall and the Phillips exception

Many UK chipboard screws are Pozidriv, so a 4 mm or 5 mm one with tick marks is a PZ2 wood screw on that 3.5 mm to 5.0 mm band. A Phillips bit for chipboard screws is right only when the head is a plain cross, or the box says PH. Using PH2 because the board is chipboard rounds the head halfway in, and the hole suffers when you extract the screw.

Drywall is the other trap in the same room. Board screws are often Phillips when the box says so, while the timber screws beside them stay on PZ2. One cross for the whole wall shines half the heads. Torx board screws are a third shape, and neither cross drives a star.

PZ2 or TX20 is a false pairing in joinery. PZ2 is the Pozidriv size for the everyday band. TX20 means a T20 bit, and only on the screw that says so. Stop when the recess is already bright, because more pressure leaves even the right bit with less wall to grip. Clutch settings for a sound head are on how to use screwdriver bits.

Torx when the box says Torx

Torx decking screws are why a PZ2 that worked indoors skates on the first board. There is no single T-number for every decking screw. BuildWiz sends you to the size printed on the box. TX20 means a T20 bit, and T25 means T25. Guessing that every deck board is T20 rounds the screws that were never that size.

An ordinary Torx bit has a solid tip. A security bit has a hole for a pin in the screw. Decking is the plain star unless the packet shows a pin. If the stamp has rubbed off, seat the Torx bits you own by hand and keep the one that fills the star.

If the head has no recess, an external hex needs a socket, and a screwdriver bit set will not supply one. A deck board you can lift is a DIY screw once the printed size is in the chuck. A stair, a balcony or a ledger with a stated torque is a different job. Leave that joint to the specification, or to someone who does this for a living.

The clutch still has to slip

Set the clutch so the drill clicks as the head meets the surface, then look at that screw before you run the box. If the head sinks and the timber mushrooms, drop a number. If it clicks while the screw is still proud, and the bit is seated, raise it one step. A correct PZ2 still cams out if you drive past flush at speed, or if the drill leans off the axis.

Wear sits on PZ2, the bit you use every Saturday on UK woodscrews. A second one is the spare you fit when the lobes go blunt. There is no reliable screw-count that names the day to bin it. The tip tells you.

Glasses are sensible when a cross-head bit can jump at chest height. A domestic bit is not insulated, and it is not a torque screwdriver. If you cannot confirm that a circuit is dead, leave the plate on a gas appliance or a consumer unit in place. Matching the recess does not make that job safe.

The set that holds spare PZ2 bits

You want PZ1 at the small end, PZ2 as the tip you wear out, and PZ3 for Pozidriv screws from about 6 mm, plus PH2 for plasterboard that is actually Phillips. Torx belongs in the case in the sizes your packets print.

The Bosch 32-piece extra-hard set, model 2607017319, lists two PZ2 bits, with PZ1 and PZ3, plus Phillips, slotted, Torx, security Torx and hex on a 1/4 inch shank. It was listed at £8.36, rated 4.7 from 26,022 reviews, with 31 bits at 25 mm and a magnetic holder. That is the top pick in our screwdriver bit set comparison for a first combi drill. The case is described as easy to crack, the warranty field says none, and the listing describes drill drivers rather than an impact rating.

The Faithfull FAISBSET61 lists three PZ2 bits, at £8.99, rated 4.6 from 240 reviews. That sample is thin next to the Bosch, some reviewers call the tips average, and one spec field says Phillips only, so read the stamps in the case. A set that leaves Pozidriv off the contents will not give you a screwdriver bit for wood screws with tick marks. Prices move on amazon.co.uk, so check £8.36 and £8.99 on the day.