The tool post or tool holder that permits of a tool being raised or lowered and turned around after the tool is set, without any sacrifice of absolute stability, will be better than one in which either one of these features is sacrificed.  Handiness becomes the more desirable as the machines are smaller, but handiness is not to be despised even in a large machine, except where solidity is sacrificed to obtain it.

The weak point in nearly all (and so nearly all that I feel pretty safe in saying all) small planing machines is their absolute weakness as regards their ability to resist torsional strain in the bed, and both torsional and bending strain in the table.  Is it an uncommon thing to see the ways of a planer that has run any length of time cut?  In fact, is it not a pretty difficult thing to find one that is not cut, and is this because they are overloaded?  Not at all.  Figure up at even fifty pounds to the square inch of wearing surface what any planer ought to carry, and you will find that it is not from overloading.  Twist the bed upon the floor (and any of them will twist as easy as two basswood boards), and your table will rest the hardest on two corners.  Strap, or bolt, or wedge a casting upon the table, or tighten up a piece between a pair of centers eight or ten inches above the table, and bend the table to an extent only equal to the thickness of the film of oil between the surface of the ways, and the large wearing surface is reduced to two wearing points.  In designing it should always be kept in mind, or, in fact, it is found many times to be the correct thing to do, to consider the piece as a stiff spring, and the stiffer the better.  The tooth of a gear wheel is a cast iron spring, and if only treated as would be a spring, many less would be broken.  A point in evidence: 

The pinions in a train of rolls, which compel the two or more rolls to travel in unison, are necessarily about as small at the pitch line as the rolls themselves; they are subject to considerable strain and a terrible hammering by back lash, and break discouragingly frequent, or do when made of cast iron, if not of very coarse pitch, that is, with very few teeth—­eleven or twelve sometimes.

In a certain case it became desirable to increase the number of teeth, when it was found that the breakages occurred about as the square root of their number.  When the form was changed by cutting out at the root in this form (Fig. 2), the breakage ceased.

a, Fig. 2, shows an ordinary gear tooth, and b the form as changed; c and d show the two forms of the same width, but increased to six times the length.  If the two are considered as springs, it will be seen that d is much less likely to be broken by a blow or strain.

The remedy for the flimsy bed is the box section; the remedy for the flimsy planer table is the deep box section, and with this advantage, that the upper edge can be made to shelve over above the reversing dogs to the full width between the housings.