Driving brass countersunk screws using a slotted screwdriver bit How To'sHow To's section icon
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There isn’t much call these days in the normal run of events to use an old fashioned, steel, countersunk screw, let alone brass screws, so much so that over the last few years, the steel variety has completely disappeared. The reason is the rise and rise of the ever popular drill driver (in all its forms) that requires a different sort of screw compared to the old, slotted steel one.


When I first started making sawdust in the early 1970s, any screws that had to be driven were done laboriously by hand using an ‘egg beater’ drill for the various holes and the appropriate sized screwdriver to wind them in. Life now, in many ways, is much easier and far quicker using a drill driver with a box full of Woodspur screws. But despite being something from a bygone age, brass countersunk screws are still in use, albeit now only in the best quality cabinet work.

Whereas steel screws are no more, you can still obtain the brass variety, but you may need to hunt through t’interweb for some considerable time to find a decent range of sizes and when you do, prepare to dig deep into your pockets!

It always has, and still is, a lengthy business to fit brass screws because the heads have the not unreasonable habit of shearing off at the drop of the proverbial chapeau. That said, a row of polished brass screw heads, with the slots ‘clocked’ in line certainly adds a little something to a decent piece of furniture. Over the years, this is the way I’ve fitted them; it takes time, but the result is worth it.

Firstly, mark out the positions of the screws and prick their centres with an awl.

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Then, drill the correct sized pilot hole through both pieces. The next step in the process is to enlarge the upper section with a clearance drill so that the plain shank of the screw drops neatly through the hole. After the clearance hole, drill the countersink with a really good quality bit so that the edge is sharp and crisp.

Drilled pilot holes
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When tested for a fit, the screw head should fit just below the surface of the wood.

Even with the right sized pilot hole, it’s still a dicey business to drive a brass screw without first cutting the thread. This is where the long defunct and totally redundant steel screw gains a new lease of life.

If you ever see an old box of different sized steel screws, for example at a boot fair, snap them up and hoard them away for the day in the ‘shop when you need to drive a few brass ones. I have a tobacco tin in the workshop with a selection of different sized steel screws which I keep for this very purpose.

You don’t need an identical steel screw, but one with the same thread, so you can use a 50mm No.8 steel screw to cut the thread for a 25mm No.8 brass screw. Drive the steel screw into the pilot hole to the right depth and lubricate it with either petroleum jelly, furniture wax, or scrape it across a candle; it doesn’t matter as long as you lubricate the threaded hole.

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Polishing brass screws for a better finish

Brass screws always look better if the heads are mirror polished before they’re driven and this is easy to do by rubbing across a worn piece of 320g sandpaper or in this instance, a ‘scary sharp’ honing film lubricated with a squirt of WD40.

mirror polishing screw heads using sandpaper and a honing film lubricated with WD40.

 

Apart from trying to ensure that the heads don’t shear, the other vital thing to do is to drive them flush, avoiding at all cost any damage to the sides of the slot. To do this, the screwdriver bit should be a perfect fit; the slightest play or sloppiness will instantly mangle the sides of the slot making the screw fit only for the waste bin.

As long as you’re cautious, driving brass screws doesn’t have to be an insurmountable problem. However bitter experience over a few decades of work teaches me that although it can be a long process, it’s really the only way to do it.

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