Square Head Tool Post Screws

At Tanner Bolt & Not, we field a lot of calls from customers trying to find the right bit or screw type.

To help, we prepared this guide to screw head types and drives.

Click on the image that looks most like the top of the screwhead to see the bit you need.

Always use the right driver for the screwhead you are working on. I know some of these look the same (can you tell the difference between a Pozidriv and a Phillips from 10 feet away?) but they are not – and you risk damaging the screw and ending up taking a lot of time to extract it if it gets damaged.

Slotted

This is the original screw drive. You find these everywhere, though the practice of using screws with slotted drives is on the decline because the screwdriver slips out of the slot, particularly when you are applying heavy torque to really tighten down (or loosen, for that matter) these types of screws.

Phillips

This screw drive type is very popular – and again, you find them in a very wide range of applications. Common sizes are Phillips #1, #2 and #3. The most common Phillips size is #2.

Phillips Tamper-resistant

Not very common, but when you need one, you need one. Same shape and sizing as Phillips, but the screw includes a tamper-resistant pin in the middle. This screw is not used in high torque applications as the design is not very strong and the bits cannot be manufactured to high strength specifications.

Quadrex

A combined Phillips and square recess drive.

Pozidriv®

This screwhead isn’t seen very often in the U.S.A., though it is very common in Europe. It looks a lot like a Phillips screwhead, but it includes 4 more contact points. Common sizes are Pozidriv #1, #2 and #3.

Square Recess

Square recess are being used more and more as they are very resistant to cam-out, which is a fancy way of saying the tip of the tool does not slip out and mar the screwhead very easily. Commonly found in two sizes: Square #2 and #3.

Square Recess Tamper-resistant

Same design and sizing as square recess, but includes a centered tamper-resistant pin.

TORX®

TORX, the funny looking screw drive. Well, you see them in a lot of electronics here in the US, and they are gaining ground in a variety of ther applications. They range in size from T5 through T55 in 1/4″ insert bits and powerdrive bits.

Tamper-resistant TORX

Tamper-resistant TORX has a small post in the middle of the drive that prevents a regular TORX driver from working.

TORX Plus

TORX Plus is an enhanced TORX design that allows more contact area between the driver and the screwhead allowing more torque to be applied, even at high driving speeds. This is a fairly new design.