11. Boring long holes

Types of boring tools and uses

Although the lathe is primarily intended for turning, it can be converted into a very satisfactory horizontal drill press, with the addition of an adjustable three-jaw chuck. Most lathes, as I have already said, have the mandrel and tailstock bored to a No. 1 or No. 2 Morse taper. All that is required then, is a three-jaw chuck fitted with a Morse taper spill or shaft. The Jacobs pattern chuck is the best type to have, as the drills can be held more securely. Some lathes can be fitted with a flexible drive which will allow you to carry out drilling, buffing, etc., away from the lathe.

For drilling small holes the wood can be held in the hand and just pushed on to the drill, but for longer holes, such as for a table lamp, the tailstock can be used to feed the work on to the drill. This is not the best method for holes over 9 in. long, but it is quick and fairly accurate. Assuming that you have turned a table lamp about 7 in. long, and polished it, you will notice when it is removed from the lathe, the two centre marks at either end. Mount a three-jaw chuck in the headstock with a 5/16in. drill inserted and have the lathe rotating at about 1,000 r.p.m. Push the table lamp on to the drill, using one of the centre marks as the starting point and advance the tailstock up to the work so that it supports the table lamp on the other centre mark. Holding the work with the left hand, gradually advance the tailstock and drill about half-way through the wood. Remove the tailstock and reverse the wood so that you can bore the other end of the work, and repeat the process. Some of you may think that this is a bit of a hit or miss idea but if you have several dozen articles all to be bored out, then you will find this quite a time saver. The two holes always meet in the centre of the work, especially if you let the drill do the boring and do not apply undue pressure on the tailstock.

For those who prefer a more accurate method, then there is the long hole boring method, very accurate, but a bit long-winded if you have a lot to do. The process is as follows. Let us assume that you have turned a floor standard of about 5 ft. high, made up of two separate pieces, each of 30 in. Each separate piece should have a 1 in. diameter pin or dowel turned at one end. This will enable the two pieces to be joined together and also fixed to the base. A boring jig is now required (plate 10). Every maker differs slightly, but trie general principle in use is the same. The jig consists of an adjustable ring centre which is held in the tool rest at the tailstock end. The piece of wood to be drilled is held at the head stock end on the normal driving centre and by a plain pointed centre in the tailstock, which is passed through the ring centre. The tailstock is then advanced slightly so that the wood is held firmly on the driving centre. Switch on the lathe, so that the work rotates at about 1,200 to 1,400 r.p.m. and at the same time screw the ring centre into the work, applying a little drop of oil or grease whilst doing this. The work is now supported at the tailstock end by the ring centre so that the tailstock can be withdrawn and removed completely from the lathe bed. Some lathes, having a completely hollow tailstock, have a specially made ring centre for this process, and a separate boring jig is not required. The wood is now ready for boring. The drill used is about 24 in. long and of such a shape that it will not wander. It looks very much like a piece of tubing sealed at one end and half cut away lengthwise, and is known as a shell auger (see plate 13F).

These shell augers are made in various sizes from 1/4 in. upwards and are used with a corresponding sized ring centre. For our lamp standard use one of 5/16in. preferably, as this is the correct size to take a brass pillar nipple to screw on the lampholder. For the actual boring operation, the wood must rotate at about 1,400 r.p.m. but definitely not slower than 1,000 r.p.m. Push the auger through the ring centre and into the wood; every 2 or 3 in. remove and clear the drillings otherwise you will clog the hole and jam the drill. A spot of grease applied from time to time to the auger will make drilling comparatively easy. Do not apply undue pressure or the drill will wander. Keep it nice and sharp. This brings me to another point. Always sharpen this type of drill on the inside of the cutting edge, otherwise you will reduce the actual cutting face.

Continue boring to a point a little over half-way through the wood. Remove the work from the lathe and replace the pronged driving centre with a counter boring tool. This looks very much like a four-pronged centre but the spurs are shaped to have a cutting action, and in the centre is an interchangeable guide pin or pilot of similar diameter to the auger being used, see plate 13C. Return the wood to the lathe, but the wood is now reversed and supported on one end by the counter boring tool, using the hole you have just bored, as a centre. The tailstock end is again supported by the ring centre as previously described. The shell auger is brought into use again and boring continued until the two holes meet.

If you have paid attention to the lathe speed and the sharpness of the auger, you will have no difficulty in making the two holes meet. Although the spurs of the counter boring tool are designed as a cutter when pressure is applied from the tailstock, it can be used as a driving centre. Repeat this process for the other piece of your lamp standard. The two pieces must now be fitted together. The top portion of the lamp standard had a pin or dowel turned on one end, and this should have been made the same diameter as the overall diameter of the counter borer. The bottom portion of the standard lamp should now be mounted loosely between counter borer and tailstock. The lathe is then rotated at about 1,000 r.p.m. and the wood is held firmly with the left hand, and the right hand advances the tailstock so that the counter borer cuts into the wood. The pilot will follow the hole previously drilled, thus ensuring a parallel hole being drilled by the counter borer. Continue to advance the tailstock, until sufficient depth has been bored out to take the pin of the upper portion. It may be necessary to stop the lathe from time to time to remove the waste, in order to maintain a clean cutting action.

For shorter holes there are a number of different types of bits that can be used, the most useful being a normal twist bit, as used in metal drilling. This drill can be used in its standard form, but it will cut better and be easier to handle if a small point or spur is ground at the nose, as in plate 13G and I. In use, a speed of 1,000 r.p.m. will be ample but it may be necessary on medium length holes to withdraw the bit from the wood to clear the waste wood. Another type is the Jennings pattern, a very common type which is used with a brace and bit. When using it in a power driven machine, it is advisable to grind off the thread in the centre spur, to a diamond point, thus preventing the bit pulling itself into the work and consequently boring farther than you intended. Many cheap drills on the market sold for use with power tools are not suitable for the work intended, the most common fault being that the twist of the bit is badly designed and therefore pulls itself into the wood. At all times the operator must be able to control his drilling, and not the drill control the operator.

For holes over 3/4 in. diameter, the cheapest form of bit is the carpenter's centre bit, with the square end removed and the threaded centre spur ground to a plain diamond point, although deep holes drilled with these bits will very often wander, particularly when boring end grain. If deep holes are required, using the centre bit, it is a good idea first of all to drill a pilot hole of about 1/16 in. diameter, which will prevent the bit from wandering off course. I have used centre bits of this type for many years, as they are cheap enough to be able to throw them away when they become damaged.

If it is accuracy and perfection in drilling that you are after, then the Forstner pattern bits are the ones to go in for, although the price is a bit high for some people. This bit has two cutting edges and will definitely not wander, either with the grain or across it. I did many years of wood-turning before I treated myself to a set of these bits, but they were well worth waiting for.

For some types of work, the tailstock is used to push the wood on to the drill, and to have some blocks of wood that will fit over the barrel of the tailstock, will prevent the drills becoming damaged. For faceplate work which may require drilling in the centre, for example, a base for a small table lamp, etc., the wood can be drilled using a small 'long and strong' gouge, pushed into the centre of the rotating wood. This will cut a very clean bore, very much in the same manner as the parrot or spoon bit.

Drilling can also be done by holding the drill stationary in a chuck mounted in the tailstock, the drill being fed into the rotating work by the tailstock handle. Specific depths of drilling can be set by pencilling a mark on the drill or by wrapping a piece of adhesive tape around the drill. Quite often one is called upon to drill a very large diameter hole. In this case the end of the wood to be drilled is first rounded off, then this portion is supported either by a three-jaw steady mounted in the tool rest, or by a block of hardwood, previously bored to take the rounded portion of the work, mounted on the lathe bed and lubricated with soap or grease as shown. Drilling is carried out with the chuck moun­ted in the tailstock.

The speed for drilling, of course, varies with the size of the drill, but 1,000 r.p.m. is the fastest speed you should use, and for holes over 1 in. in diameter, 500 r.p.m. to 750 r.p.m. Keep all your drills sharp. Too much force applied to a drill to make it cut faster will only result in the drill wandering. Except in the case of centre bits, try and buy all your bits having two balanced cutters, then you will not be troubled very much with crooked drilling.

Much could be written about drills and drilling but as woodturning is our subject, let's not get too mixed up with 'bits and pieces'! However, a few words on the care of your drilling and boring tools, will help you to keep them in good order. Most amateurs sharpen their drills far more than is necessary and consequently, the life of them is very much shortened. Before sharpening any bit, carefully examine the shape of the cutting edge, and when filing, make an endeavour to retain the original shape. With bits having two cutting edges, try and keep an even balance of these edges, so that each side, when in use, does the same amount of work, both sides being filed equally, then you will keep the bit boring true. Use a very smooth file taking a light cut, the object being to remove as little metal as possible. The cutting edges should be sharpened on the underside only, never on the top side, otherwise you will spoil the cutting action. Where the bit has side spurs, these should only be sharpened on the inside. If you file on the outside of the spurs, you will reduce the outside diameter at the tip, with the result that the bit will bind and clog without boring. Never attempt to sharpen wood boring bits by grinding; the only exception being bits with a drill nose, such as twist drills used for metal.

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