Here's a picture of the beauty. This is the tool, as it should rightly be called, that makes fixing timber to steel framing a cinch. And at around 10 cents a pop they're cheap as chips.
These screws have a drill-bit-like tip that cuts easily through timber closely followed by a pair of metal wings. The metal wings make the pilot hole bigger and provide relief so that when the screw is driven home the timber will not split.
When the screw tip drills through the mild steel frame, which they do remarkably easily, the wings shear off. The countersunk head is also fitted with a cutting face that self countersinks the head.
So, in a simple single operation the clever design of this screw drills a pilot hole, opens the pilot hole for relief, drills a pilot hole in the steel and using a self tapping thread cuts a grip into the steel and finishes it all off by countersinking it's own head!
Wonderful! It may seem obvious to some but to achieve the same result using a standard countersunk self tapping screw requires the following:
1. Predrill hole through timber and metal to the correct size for the self tapping screw.
2. Oversize the hole through the timber to stop the screw thread pulling directly on the timber.
3. Countersink the timber piece.
4. Drive the screw into position for a flush finish.
This operation requires about four times as much time as using the special wing tipped screws. One word of caution though.. remember the wings shear off once the screw drives through metal. As such, a screw cannot be re-used to make a complete new hole. The cutting heads on these screws will generally make several holes and in a pinch can be used in lieu of a drill bit, for example, to drill rivet holes!
In the last article of this series we take a quick peek at the finished result.
Click to Read Part IV
p.s. Working in Brissy? You can buy your screws from Russ-All Industrial.. the local bolt bloke on Pickering Street, Enoggera. No, sorry guys, Bunnings don't stock these pearlers!
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