Modern Machine-Shop Practice Part 220

[Ill.u.s.tration: Fig. 3200.]

[Ill.u.s.tration: Fig. 3201.]

Various forms of side heads are shown in the figures from 3200, to 3207.

Fig. 3200 is a two-sided plain head, or in other words two diametrally opposite sides of the head are provided with bolt holes, for cutter fastening bolts. Fig. 3201 represents a four-sided slotted head, each side having T grooves, so that the cutter may be adjusted endways on the head. This enables the use of four narrow cutters, thus taking the cut in detail as it were.

[Ill.u.s.tration: Fig. 3202.]

[Ill.u.s.tration: Fig. 3203.]

The two-sided head shown in Fig. 3202 is provided with a set screw, by means of which a delicate adjustment of the height of the cutter may be made. Fig. 3203 represents a three-sided slotted head, or in other words T-shaped grooves, and not bolt holes are used.

CUTTER HEADS WITH CIRCULAR CUTTERS.

[Ill.u.s.tration: Fig. 3204.]

This form of cutter head was invented by S. J. s.h.i.+mer, and are generally known as s.h.i.+mer cutter heads. The principle of construction is shown in Fig. 3204, which is for an ogee door pattern.

The cutters are circular in form and are seated at an angle to the f.l.a.n.g.e to which they are bolted, this angle giving side clearance to the cutting edges.

[Ill.u.s.tration: Fig. 3205.]

[Ill.u.s.tration: Fig. 3206.]

The full amount of cut is taken in successive stages or increments; thus in the figure, the two upper cutters would produce one half the moulding, and the two lower ones the lower half. As the cutters are sharpened by grinding the front face, therefore they will maintain correct shape until they are worn out. Fig. 3205 represents a s.h.i.+mer head for producing the tongue, and Fig. 3206 a similar head for producing the groove of matched boards.

[Ill.u.s.tration: Fig. 3207.]

Fig. 3207 shows the action of the groove head, the cutter or bit D being shown in full lines and the second cutter being shown in dotted lines.

Cutter D, it will be seen, operates on one half of the groove, and cutter C on the other half, each cutter having side clearance, because of being seated on a seat whose plane is not at a right angle to the axis of revolution of the head.

By thus taking the cut in detail, the head works steadily, while the side clearance makes the cutters cut clean and clear.

JOINTING MACHINE.

"Jointing" a piece of wood or timber, means producing a surface, so that the joint between two pieces that are to come together or be glued shall be close. In order to produce surfaces that shall be true enough for this purpose, it is necessary that the work be held in such a way that it is not sprung or deflected by the holding devices or feeding apparatus.

[Ill.u.s.tration: Fig. 3208.]

Fig. 3208, for example, represents a jointing machine, in which the work abuts against an inclined plate P at one end, while the other end is clamped down to the table, which is traversed past the revolving head H, to which are secured two gouge-shaped cutting tools, one of which is seen at T. By using tools of this cla.s.s, the amount of cutting edge in action is small, and will not therefore spring the work, and if the cutter spindle is adjusted to have no end motion, the work will be true, notwithstanding any slight vibration of the head, because its plane of revolution coincides with the plane of the surface being surfaced or jointed.

[Ill.u.s.tration: Fig. 3209.]

In some jointing machines, knives are set on the face of a revolving disc, an example of this cla.s.s of machine being shown in Fig. 3209, which is for facing the spokes of wheels and for finis.h.i.+ng the mitre joint on them.

Three cutters are used, each being set at an angle to a radial line, so that the inner edge of the knife will meet the work first. This gives the knives a shearing cut, and prevents the whole of the cutting edge from striking the work at once. The spokes are placed against a stop on the table, and brought into contact with the cutters by the foot treadle.

The table has beneath it a spiral spring at each end, which returns the table as soon as the foot pressure is released from the treadle. The cutter head or disc is 10 inches in diameter, and should make 2,000 revolutions per minute.

Stroke jointers are machines (such as shown in Fig. 3210) in which a long plane _e_ of the ordinary hand plane type is worked along a slide by a connecting rod C, operated by a crank motion. A machine of this cla.s.s will do very accurate work, but is obviously suitable for thin work only.

A machine constructed by J. J. Spilker, for cutting mitre joints by hand, is shown in Fig. 3211. The frame A carries a slideway for the slide to which the mitre cutting knife K is secured. The handle G operates a pinion gearing into a rack, which gives vertical motion to the slide and knife. At _c_ is a fence or gauge against which the work is rested, and which is capable of a horizontal motion, so as to bring the work more or less under the knife. For heavy work, the fence _c_ is set back, so that the first cut of the knife will leave the moulding, as shown at H, partly severed, and a second cut is necessary to sever it; for very fine work, a fine shaving may be taken off by a cut taken on the end of each piece separately, after the piece is severed. At D is a graduated scale or rule for cutting the work to exact dimensions, and as its lines are ruled parallel to the right hand edge of the knife K, the inside measurements of a mitre joint may be taken at the outer edge, and outside measurements at the inner end of each line, a set stop at E serving to gauge the pieces for length.

[Ill.u.s.tration: Fig. 3210.]

[Ill.u.s.tration: Fig. 3211.]

MOULDING OR FRIEZING MACHINES.

These are machines that cut mouldings on the edges of the work. The term friezing is applied by some, when the machine has but one cutter spindle, while by others these machines, whether having one or two spindles, are termed edge moulding machines. Still another term applied to this cla.s.s of machine is that of variety moulders or variety moulding machines.

In machines of this cla.s.s, it is of primary importance that lost motion or play in the bearings be avoided, because the cutter end of the spindle overhangs its bearings, and any side play of the spindle in its bearings is multiplied at the cutting edges of the cutters. Perfect lubrication of the spindle bearings, and ample bearing surface on the journals and bearings, are therefore of the first importance.

The work is rested on the upper surface of the table, and is fed to the cutters by hand.

[Ill.u.s.tration: Fig. 3212.]

[Ill.u.s.tration: Fig. 3213.]

[Ill.u.s.tration: Fig. 3214.]

[Ill.u.s.tration: Fig. 3215.]

[Ill.u.s.tration: Fig. 3216.]

Figs. 3212 to 3215 represent a machine by J. S. Graham. The frame B, B, Fig. 3213, of this machine is cast in one piece cored out, and the base is wide, so as to give necessary solidity. The hollow column is fitted with a door W, and shelves V, V, forming a very complete case for the reception of tools, cutters, etc. The spindle boxes and slides C are one casting. They are planed on centres and held in the frame B', Fig. 3215, by large gibs L, and sliding surfaces shown in C', Fig. 3214. They are adjustable vertically by hand wheels K, in front of frame in connection with nut O, as shown in Fig. 3214, and require no lock to hold them at the proper height.

The cap O' (Fig. 3213) has an oil chamber J and wick which feeds the oil to the upper bearing. The lower box is fitted with a patent self-oiling and adjustable step shown at _a_, _b_, _c_. The cap _a_, upon which the spindle D rests, has a small opening in the centre. The circular block _b_, under it, also has a hole in the centre. The bolt _d_ has two holes in it, one horizontal and the other vertical.

The chamber surrounding this step and cup is filled with oil. The motion of the spindle D on the cap _a_ causes the oil to flow from the chamber through the openings to the spindle. Thus the oil is kept in constant circulation. The end of this spindle D is by this arrangement kept always lubricated.

The spindles D are of 1-7/8 hammered tool steel accurately turned and fitted in the boxes, which are of extra length, and lined with the best genuine Babbitt metal. They are 30" from centre to centre, and have independent screw tops, as shown at S, enabling the operator to use various sizes for large or small work, or clear the table of either spindle for special work.

H is the threaded part of the screw top, G is the nut, and F the fill-up collars.

The iron table A, A is 5 feet by 4 feet, planed and fitted with concentric rings E, E around the spindle, to suit the various sizes of heads and cutters. A heavy wooden table, made of narrow glued-up strips of hard wood, can be used if preferred.

This machine has been run up to 6,000 revolutions per minute, without perceptible jar, and cutter heads as large as 8" diameter may be used on it for heavy work.

Fig. 3216 represents an edge moulding machine by J. H. Blaisdell. In this machine the table is raised or lowered by the hand wheel upon the central column. The construction of the spindle and its bearings is shown in the sectional view, which also shows the square threaded screw by means of which the table is raised. The spindle has a coned hole for receiving the cutter sockets, which are therefore readily removable.

[Ill.u.s.tration: Fig. 3217.]

Figs. 3217 to 3220 represent examples of the shapes of cutters for use on edge moulding or friezing machines. Fig. 3217 represents a cutter for bevelling the edge of the work, the cutting edges being at A, B, or at C, D, according to the direction in which the cutter is revolved.

[Ill.u.s.tration: Fig. 3218.]