What is the difference between Pozidriv and Torx?
Telling the drive types apart, why a Phillips bit ruins a Pozidriv screw, and which to use for what.
- Difficulty
- beginner
- Time
- 15 min
- Read
- 3 min
Short answer
Pozidriv has four extra small lines between the cross arms; Phillips does not. Using a Phillips bit in a Pozidriv screw is the single most common cause of chewed screw heads. Torx is the six-pointed star and grips best of all — use it for anything driven hard.
Most stripped screws are not a strength problem. They are the wrong bit sitting loosely in the head and camming out under load.
Step by step
- Learn the two crosses apart.Look at the head. A plain cross is Phillips (PH). A cross with four fine lines at 45 degrees between the arms is Pozidriv (PZ). Almost every screw sold in the UK for woodwork is PZ.
- Never put a Phillips bit in a Pozidriv screw.Phillips is designed to cam out under torque — that was the original point of it. In a PZ head it sits shallow, slips and destroys the recess. This is the most common cause of a ruined screw.
- Use Torx for anything driven hard.The six-point star transmits far more torque without camming out. Decking screws, structural screws and most modern flat-pack use it, and it is genuinely easier to drive.
- Match the size as well as the type.PZ2 fits most 4 to 5mm screws; PZ1 is for small ones and PZ3 for large. A PZ1 bit in a PZ2 screw strips it as reliably as the wrong type.
- Recognise the others you will meet.Slotted on old work and electrical accessories. Hex or Allen on furniture and machinery. Square drive occasionally. Security types with a pin in the centre need a matching bit.
- Push hard, drive slowly.Most cam-out is insufficient axial pressure. Firm pressure straight down the axis, and a slower speed, does more than any bit upgrade.
- Keep the driver square to the screw.Any angle concentrates the load on one side of the recess and rounds it. Line the drill up along the screw's axis before pulling the trigger.
- Buy decent bits and replace them.Bits wear. A rounded tip strips heads regardless of technique, and the wear is not obvious until you look. They cost very little.
- Pilot hard or dense material.Hardwood, chipboard edges and anything near the end of a board. A pilot hole removes most of the torque that causes cam-out and splitting.
- Set the clutch on a drill-driver.It slips before the screw does. Start low and work up until it drives the screw home without over-driving it.
Tips
- If the cross has four extra fine lines, it is Pozidriv and needs a PZ bit. That one check prevents most stripped screws.
- Torx wherever you have the choice. It holds the bit, resists cam-out, and lets you drive one-handed.
- Replace worn bits. A rounded PZ2 will chew every screw you use it on.
Common mistakes
- Using PH bits on PZ screws — Phillips is designed to cam out under torque. In a Pozidriv recess it sits shallow, slips and destroys the head.
- Driving fast with light pressure — Cam-out is caused by the bit lifting out of the recess. Slower speed with firm axial pressure prevents it.
If it doesn't work
Screw head chewing out
Cause: Wrong bit type or size, or worn bit — Fix: Check for the four fine lines, match PZ to PZ, and replace the bit.
Bit keeps jumping out
Cause: Not enough axial pressure or driver off-axis — Fix: Push harder, slow down, and line the driver up square with the screw.
Screw snapped rather than stripped
Cause: No pilot hole in dense material — Fix: Pilot hardwood and chipboard, and use the drill's clutch.
Cannot identify the drive type
Cause: Uncommon or security head — Fix: Compare against a bit set. Security types have a pin in the centre and need the matching bit.