Don’t get too excited – this isn’t an article on porn or sex, but only about making holes in wood! There are times when you need a hole in wood which becomes a challenge, even with the right sort and size bit. Here’s how to deal with some of the more common challenges:
1. Drilling long holes accurately:
A. By far the easiest way is by making a shallow saw kerf in the “Faying Surface”①. These are then joined together by glueing or other means, with the kerfs mirroring each other, i.e., face to face. After joining, the hole is made using a spiral auger with a lead screw entering the saw kerfs. The lead screw will follow the kerf unless it encounters a knot or irregular spot. Needless to say, you must go slowly and carefully and clear the chips often. If the bit starts to bind it may mean it is getting off track. This works with brad point bits too up to a point (pardon the pun!), but these are more likely to wander since the bit is not supported on its sides its full length, which seems to be an important requirement for any tool drilling long, deep holes. Regular machinist type twist bits do not work nearly as well as augers unless the saw kerfs are quite wide.
B. Of course there are times you must drill a long, deep hole when you don’t have the option of glueing two pieces together with sawn kerfs. Here, you might use a ‘Barefoot Auger’; A barefoot auger is a special bit used by shipwrights and is similar to a spiral auger with no lead screw. These can drill quite long holes, but must be very carefully started in exactly the right direction. Even then, it the bit hits a knot or hard place it can change direction on you. Shipwrights often make a special ‘guides’ to get the bits started in the proper direction usually consisting of two pieces of wood at right angles to each other and squared at the bottom (or beveled, if the hole is to be at an angle). Other sorts of guides ‘sandwich’ the part to be drilled with drill guides to keep the bit centered along its length. You can make a sort of barefoot auger from an old auger by cutting off the lead screw, but it will not have the same ‘foot’ as a bit intended and manufactured as barefoot, and therefore will not work nearly as well.
C. Use a ‘Spoon Bit’ or ‘Shell Auger’; A spoon bit is an ancient type still used by chair, lamp, and instrument makers to bore long holes in things like chair backs, lamps and flutes. These are usually carefully hand driven with a bit stock, or twist handle. Spoon bits today are fairly expensive. Lee Valley sells one type.② You can also make your own and here is an article which shows how in detail.③ If you find yourself making a lot of long, deep holes it would be worthwhile to explore this type of bit. Obviously, there is some skill and patience required to use these accurately.
D. There are also a number of speciality (and expensive) bits used with lathes to make long holes in gun barrels, lamps, etc. These are somewhat similar to shell bits and are called ‘D’ bits. Those are beyond the scope of what I am trying to present here.And, just for giggles, I’ll mention something called a ‘boring bar’ which boatbuilders use to drill out for propeller shafts, but these are not properly drill bits in themselves as they need a pilot hole which must first be drilled with one of the above mentioned type bits.
2. Drilling ‘part of a hole’:
Here are some common-sense tips for drilling ‘parts’ of a hole, i.e. half or other fraction of a hole’s diameter at the edge of something. For example, you may need a series of half circles in the edge of a plank to hold bottle necks in a wine rack or something like that. You can use a jig saw, or band saw and try to deal with the irregular hole which results, Or,
You can cut or drill your holes down the middle of a plank and then cut that through the holes into two equal width pieces with a saw; Or you can,
Clamp a piece of waste material of the same thickness next to your stock, locate the center of your hole so your drill cuts away as much as you need for the partial hole in your stock. This works with augers, twist drill bits, Forstner bits, hole saws or whatever and is very accurate. See illustration and photos following:
If you need to make ‘part holes’ of longer lengths, you can use the same method at the edges of your working stock. The nice thing about this is you can produce partial holes limited only by the depth capacity of your bit or hole saw. See illustration and photos following:
Links to pertinent information:
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