SHEDNOTES 74: Some notes on screws

For years, The Shed has operated mainly on inherited, left-over or reclaimed screws – most of them single-slot originally, although we have moved as far as having a range of crosshead screwdrivers, imperfectly understood, in order to deal with flat-pack standards.
But having had our lives changed by a battery-powered impact driver, we have been trying to catch up.
The power driver works best with Pozidriv-type screws, which are slightly different from the original Phillips crossheads, with a thin X cut in above the central +. By hand, you can turn a Pozi with a Phillips driver or a Phillips with a Pozi bit, but for motorised screwing, you want the best possible match, or you will tend to slip out and strip the heads. There are other screwheads but most of them are designed for engineering or industrialised construction.
The same goes for the baffling array of thread options to some extent. Twin-thread screws will cut faster but require more torque to turn, so they suit a powered driver and soft wood for fast work such as studding. For particle boards, however, you want a chipboard screw, which has a single thread, don’t ask us why yet.
The DIYer does have to pay attention to whether the threading runs all the way up the screw or leaves a smooth neck below the head. If you are screwing one piece of wood to another, or a bracket to a wall, you might want a neck, so you can screw the face item down tight without turning it. If you are screwing tight up against a wall plug, though, you want the whole length of the screw to be gripping the plug so you do not want a quarter-inch of unthreaded neck in the front of the hole.
The Shed has also recently learned a little lesson about plugs. Most of them come with a collar but The Shed’s new plumbing and general consultant buys collarless, or cuts the collars off, because it is easier to get a tight fit against tiling – an obvious point which The Shed has failed to take into consideration over decades of fitting slightly wobbly toilet-roll holders.
Finally for now, The Shed wishes it had earlier come across the advice to always prepare the way for a brass screw by using a steel one of the same size to make the thread. Brass just rips and breaks too easily.

moresomeday …

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