Everything you never knew you needed to know about Recessed Screw Drives
This started as a simple idea to start creating more blocks for download. Unfortunately once I realised how many screw drives there were available, my obsessive compulsive side kicked in and I had to document them all! If you see any you think I’ve missed, please let me know ;-)
Screw heads come in a range of sizes. A screw ‘Drive’ is the system used to turn a screw. The drive is a feature on the screw that allows it to be turned. The ‘Driver’ is a mating tool, which is used to turn the screw
A little bit of Screw history
The idea of the screw was first explored by the Greek mathematician Archyta. Wooden screws were used in early machinery such as wine presses.
The first documented use of a metal machine screw was by a German clock maker in 1513. The head was made by flattening one end of a wire and the threads and slot were hand cut with a file.
Screws weren’t machine made until Henry Maudslay, a British engineer, Invented the Screw lathe in 1797. Another British Engineer, Jesse Ramsden continued to develop the screw Lathe to make mass Production possible.
Screws with tapered points (‘Gimlet’ Points) weren’t mass manufactured until George Nettlefield started making them in the 1840s
Common Wood Screw Recessed Drives
Every woodworker should have a set of Bits in his kit for these drives.
Slotted, Flat, Straight
The traditional wood screw has a single slot in the fastener head and is driven by a flat-bladed screwdriver. Driving by hand or using a ‘Yankee’ pump action driver is recommended due to the tendency of a power driver to slip out of the head and damage the surrounding material.
Frearson, Cross Head, BS ‘Type H’ , ANSI ‘Type II’, Reed & Prince, (R&P)
The Frearson screw drive was developed by an English inventor named John Frearson in the 1870’s . It was produced from the late 1930s to the mid-1970s by the former Reed & Prince Manufacturing Company of Worcester, Massachusetts.
The Frearson pre-dates the Phillips and has a more pointed 75° V shaped recess. The tool recess is a perfect cross and allows mechanical driving without ‘Cam-ing Out’ (slipping). In theory one driver or bit fits all screw sizes, although different sizes are recommended.
The ‘Phillips’ Head was invented by John P Thompson, who sold his self-centring design to Henry F Phillips after failing to interest other manufacturers. Henry Phillips is credited with developing the idea to the point that it was adopted by major manufacturers, such as General Motors.
Unlike the Frearson, The self centring Phillips is Designed to ‘Cam-Out’ when the driver reaches maximum torque. This saves the screw from being over tightened or the head from being damaged or broken off.
This might be frustrating on the bench, but it was a design feature when used on the production line. It is important not to mix up Phillips Heads with ‘Pozidriv’ Heads because the drivers are not compatible and you can damage the screw head.
Pozidriv (PZ), Pozidrive, BS ‘Type Z’, ANSI Type 1A
The Pozidriv Recess was also designed by the Phillips company, and is designed not to Cam-Out. The distinctive ‘Cross’ mark is used to distinguish between the two. The Pozidrive system is compatible with the Supadriv system.
Next – Less common recessed drives…