In the first article we looked at some basics of screw technology. Next up we need some equipment to put them in. The trusty handpowered screwdriver just will not do with our high-tech screws.
Drills
Self drilling screws are designed to be driven at about 1000 revs per minute (rpm).
Most electric drills range between 1500 and 3000 rpm. An electric drill with a variable speed trigger can work, HOWEVER, be warned! An electric drill will not stop turning when you release the trigger like a cordless drill. This can make the job of driving screws quite dangerous. You've been warned. Please be careful.
Cordless drills are usually the best device to drive screws; they run at the right speed and have adjustable torque settings. However, drilling through wood, into metal and countersinking the screw head is tough even for the toughest cordless drills.
The absolute best idea is to hire a Tec-Gun. A Tec-Gun is an electric drill that only takes screwdriver bits (i.e. no drilling) runs at a close to optimum drive speed around 1200 rpm and has an electric brake. That means when you let the trigger go the spindle stops turning.
Driver Bits
Just about anyone can and has used a cordless drill.
The bits we're talking about (so you can ask for them at the hardware) are 6mm hexagonal driver bits. These bits interchange easily with various heads, to suit various screw heads. You may be familiar with the Flat Head bit for a slotted head, a Phillips Head bit, sometimes called a cross point as well as some of the newer styles such as Torx and Pozi-Drive bits.
For the special wing-tipped self-drilling self-tapping screws we will be using we need a phillips head No.2 driver bit. This is the most common size of phillips head bit in use today.
The reason for the different driver bits is that they are used for different purposes and generally the more complex patterns provide a more positive driving experience. This means the bit is less likely to slip and damage the head. It also makes their manufacture more expensive.
As an interesting aside, I recently bought a pack of outdoor timber screws made by Buildex that included a square driver bit! It seems ironic to me that we went from flat to cross to several variations of hexagonal design before coming back to a simple square. And it actually drives long screws into hard wood exceptionally well.
Buying the right driver bits involves a little understanding. In the next article we are going to see just how easy it is to put some of this screw technology to good use. For now we need to make sure we have the right tools.
Cheap bits are a waste of time and money, even though they look the same as expensive bits. Fancy coatings do help but in general good quality bits will advertise quality forging with an added bonus of a special shiny coating. For driving self-drilling, self-tapping screws into metal, buy the best driver bit you can get.
As a rule, spend about five dollars per bit (c2011). A five dollar bit will outlast at least five one dollar bits. Then again, the odds are good you will break one or two so I'd suggest buying at least two good quality bits for the job you're about to undertake.
For a good education, buy a cheap bit while you're there, no, get two! When you see in practice how long the cheap bits stand up to real work you will never waste your money again.
In Europe bits are graded according to quality. Five star bits are the right temper with a high quality coating. Here in Australia we currently do not have such a grading system. The best idea is to try one or two bits from Bunnings (mid-range quality bits) and then track down your local tool stockist. They can usually point you towards the quality you need for frustration free work.
Remember that the harder a metal is the more brittle it becomes. Drilling into steel tube, through hard timbers like Merbau is a shocking series of stop/start drill work and your drill bit needs a bit of flexibility. Inevitably though, even your best bits will succumb to breakage after a while.
Right!
Now we're armed with the right driver bit in our tec-gun we're ready to take a look at this modern wing-tipped marvel.
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