This section is from the book "Woodworking For Beginners: A Manual for Amateurs", by Charles G. Wheeler. Also available from Amazon: Woodworking For Beginners.
Dowels are merely round sticks of different diameters and usually of hard wood. They can be bought ready made and can be used instead of nails or screws, or instead of mortising, dovetailing, etc. They can be used simply as pins or in many cases can be split and wedged, though the holes must be tapered with a gouge if wedges of much thickness are to be used (Fig. 516).
A common use of dowels is to fasten the frames of tables, chairs, bedsteads, and various domestic articles.
The use of dowels for such purposes is not to be recommended, however, although very common in cheap work and in much work which is not cheap in price. The mortise and tenon is usually much to be preferred. Dowelling, to be really good, has to be skilfully done, while it is a very common way to stick the work together in any manner that will look right on the outside. A dowelled joint is not, as a rule, as scientific a form of construction as a well-planned mortise and tenon, - a statement which you can easily prove for yourself by comparing some article of your grandmother's or great-grandmother's time, and which is still strong, with some modern dowelled chair, which is in so many cases all to pieces and thrown on the woodpile after a short term of service. The gaping joints and dropping apart of modern dowelled work can be seen on every hand. There are some cases, however, where the use of dowels is scientific and just what is required. For example, split dowels, wedged dovetail fashion like wedged tenons, are often very useful (see Mortising).
To find the centres for boring, so that the holes bored in the two pieces shall be in line, you can cut off the heads of some small wire brads so that they will be pointed at both ends. Stick the brads into one piece where the centres of the holes should be Then press this piece against the other in the position it is to take when the work is done and the brads will of course prick holes in the second piece exactly corresponding to those in the first piece (Fig. 517). Instead of brads, small shot can be used in a similar manner. It is well to take a round-pointed awl, or some such tool, and carefully prick a small hole with it at each of the points marked. This is to start the spur of the bit exactly at the point, as the spur sometimes has a way of working off to one side, so that the hole may not be in exactly the right place. The hardest part, however, is to bore the holes exactly at right angles to the surface, as a slight deviation in either or both may make a bad angle where the two holes meet. You can sometimes lay the pieces fiat on the bench and arrange boards or blocks so as to guide the bit straight. The dowels must be thoroughly dry. It is better to have them a trifle too large, rather than too small, for you can easily trim them down to a snug fit. Scratch them lengthways with the toothed-plane, or with the edge of a file. Countersink a little hollow around the opening of each hole (see Countersink), to catch the surplus glue which would otherwise form a rim around the dowel (Fig. 517). Before gluing you should fit the work together once, as it is very awkward to make changes after the gluing is begun. When the parts fit accurately, take the joint apart for gluing. Brush a little glue around the inside of one of the holes, dip one end of a dowel in the glue and drive into place. Wipe off the superfluous glue and repeat the process with each of the dowels in that half of the joint. Leave this to dry a day, or more if you can. Then clean any hardened glue from the dowels and glue them, as before, into the other piece, this time putting glue on the flat surfaces which are to come together. The whole should be firmly clamped and left to dry (see Gluing and Clamps). Dowels are sometimes used in joining the edges of pieces, as in Fig. 518, and in many other joints too numerous to be specified (see Joints and Jointing).

Fig. 516.

Fig. 517.

Fig. 518.
Dowelling looks very easy, but it is usually hard for the beginner to bore the holes straight and to make the pieces fit accurately.
A steel plate with various holes of such sizes that pins made by driving blocks of wood through them will drive snugly into the holes made by the corresponding bits. This is useful in fitting dowels.
 
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