This is the most common screw style; it is used for general work and has the widest range of sizes. The countersunk head allows the screw to be sunk into the timber or fitting for a flat surface.
Finish is clear (silver) zinc plating; ideal for matching hardware hinges gate fittings etc. It is moderately corrosion resistant, but the finish is primarily decorative so should only be used in sheltered exterior applications if necessary. This finish is denoted by the -Z shown at the end of the product code.
Where zinc is not available, the standard steel "Lube" finish is offered, which has a bronze/Grey colour. The colour of the screw comes from the heat treatment after which a dry wax is applied to prevent corrosion and ease driving. If there is no suffix shown on the product code, this is the finish the screws will be supplied in.
If you require the lube finish in the popular 8G x 25 - 75mm screw sizes, we recommend purchasing the Particleboard Screws which are identical in colour and design but also include the four lugs for gripping the surface in man-made board which will not affect their ability in normal timbers.
Origin of the Robertson square drive screws
The "Robertson" screws were invented in Canada by Peter Robertson in 1908. Due to patent restrictions they stayed in Canada for many years and became the standard screw in that country. They are now spreading rapidly through the US and other countries. It is a far superior system and we are sure you will agree “once you use them you don't want to use anything else”.
Not only is the drive system better than the conventional drives, the actual quality of the screws is superb. The screws are extremely strong and the square drive means the driver doesn't jump out and the screw does not break under heavy load.