92 CLASSIC BOAT SEPTEMBER 2016Boatbuilder’s Notes
CRAFTSMANSHIP
Slow-moving
snail countersink
TEXT AND PHOTOGRAPH ROBIN GATESThe purpose of the cone-shaped countersink bit is to
cut a recess for a countersunk screw head so that it lies
flush with the surrounding timber. More than just
looking pretty, this increases the area of contact
between screw head and timber making the screw more
effective in pulling components together.
There are several designs of countersink bit, the
umbrella-shaped rose bit being the most common, but a
blunt one in a power drill can do a lot of damage fast,
leaving over-sized craters with ragged edges.
This snail pattern bit is for use in a slow-turning
brace, offering excellent control, and is a favourite
among hand tool workers. Its volute structure with single
cutting edge – indeed resembling a mollusc shell, more
particularly a conch – gives a crisp and circular result. It
works by taking small shavings, not merely abrading the
wood, but it must be kept sharp. It is sharpened on the
inside of the cutting edge only, using a fine hone or
small rat’s tail file, so as not to reduce the bit’s diameter.
Some timbers are trickier to countersink than others.
Turning in the coarse, long grain of a fast-grown
softwood, the cutting edge, if not razor-sharp, may
lever up the surface fibres instead of slicing cleanly
through them. But in the more even-grained and
workable mahogany pictured here, the snail bit
rolls like a conch on a south-seas beach, throwing up
a froth of tissue-thin shavings.Spend a little... live a lot!
Without losing sight of the fact that it’s the quality of the
blade which is paramount, there’s no denying that a
screwdriver with a plastic handle doesn’t look or feel as
good as its wood-handled counterpart. This set of three
slotted and three Phillips screwdrivers with beech handles
under the Workzone brand at Aldi Stores is a real bargain
at an RRP of £8.99, and you may find them for even less
when the store is rotating stock; Aldi’s tools come and go
on a seasonal basis like big spring tides.
The hexagonal handle which provides a sure and
comfortable grip also prevents the tool rolling off the
bench. The chromed-steel shank is hexagonal too so you
can grip it with an adjustable wrench to increase leverage.
Steel caps permit the gentle persuasion of a hammer
without splitting the wood, should the situation be that
desperate. The set comprises 5, 6 and 8mm flat blades,
and PH1, PH2 and PH3 Phillips cross-heads – all well-
formed and sturdy. Robin Gates
A wrench on the hexagonal shank increases leverage