Modern Machine-Shop Practice Part 221

Fig. 3218 represents an ogee cutter, in position on the cutter spindle.

As these cutters are made solid and accurately turned in the lathe, they are balanced so long as the cutting edges are kept diametrally opposite.

The front faces only being ground to sharpen the cutting edges, the cutter always produces work of the same shape.

[Ill.u.s.tration: Fig. 3219.]

[Ill.u.s.tration: Fig. 3220.]

Fig. 3219 represents a cutter (in a chuck) for cutting a dove-tailed groove, and Fig. 3220 one for rounding an edge, it being obvious that a wide range of shapes may be given to such cutters, and that, as they may be sharpened on an emery wheel, they may be left comparatively hard, thus enhancing their durability.

To regulate the depth to which a cutter such as shown in Fig. 3220 will cut, a collar or washer is placed beneath it to act as a guide to the edge of the work.

[Ill.u.s.tration: Fig. 3221.]

Fig. 3221 represents a machine in which rotary cutters are used to produce all kinds of panel work, as well as edge moulding or friezing.

In this case the cutter is above the table, the latter being adjustable for height to suit the thickness of the work. Examples of some of the work are shown at the foot of the machine.

WOOD BORING MACHINES.

The rapidity with which holes may be bored in wood enables the feed to be most expeditiously performed by hand or by foot motion. A foot motion leaves both the workman's hands free to adjust and change the work, and is therefore suitable for light work or work having holes of a moderate depth.

The work tables of wood boring machines are provided with suitable fences for adjusting the work in position, and in some cases with stops to adjust the depth of hole.

Any of the augers or bits that are used in boring by hand may be used in a boring machine, but it is obvious that, as the bit or auger is forced to its feed by hand or foot, and as its revolution is very rapid, the screw point, which is intended as an aid in feeding when the bit is used by hand, is not necessary. On this account most augers for use in machines are provided with triangular points instead of screw points.

[Ill.u.s.tration: Fig. 3222.]

In Fig. 3222 is shown a wood boring machine by J. A. Fay & Co. The table is gibbed to a vertical slide on the face of the column, and is adjustable for height by the hand wheel A, which, through the medium of its shaft and a pair of bevel gears, operates the elevating screw B. The spindle C feeds through its bearings, the supporting rod D being pivoted at its lower end to permit C to feed in a straight line vertically. The feeding is done by the treadle F, which operates the rod E.

The table may be set at an angle of 30 degrees from the horizontal position.

The weight W counterbalances the treadle and brings it to its highest position when the workman's foot pressure is removed.

The holes may all be gauged to an equal depth (when they are not to pa.s.s through the work) by so adjusting the height of the table that the hole is of the required depth when the treadle is depressed to its lowest point, or limit.

[Ill.u.s.tration: Fig. 3223.]

Fig. 3223 represents a horizontal boring machine such as used in furniture and piano factories. The spindle feeds through the driving cone, being operated by the treadle shown. The work table is adjustable for height by the hand wheel and elevating screw. The usual fences, stops, and clamping devices may be applied to the table, which is on compound slides to facilitate the adjustment of the work.

Fig. 3223_a_ shows a double spindle horizontal boring machine, in which the table and work are fed up to the boring tools by hand. The spindles are adjustable in their widths apart, and may also be set at an angle.

The work table is adjustable for height, and the spindle carrying head is adjustable across the machine.

[Ill.u.s.tration: Fig. 3223_a_.]

[Ill.u.s.tration: Fig. 3224.]

Fig. 3224 represents a machine by J. A. Fay & Co., for heavy work, rollers taking the place of the work table. The drill spindles are fed by hand from the stirrup handles shown, which are weighted to raise up the spindles as soon as they are released.

MORTISING MACHINES.

The mortising machine for wood work consists essentially of an ordinary auger, which bores the holes, and a chisel for cutting the corners so as to produce the square or rectangular mortise that is usually employed in wood work.

The chisel is reciprocated and its driving spindle is provided with means whereby the chisel may be reversed so as to cut on either the sides or the ends of the mortise. The chisel is fed gradually to its cut.

[Ill.u.s.tration: Fig. 3225.]

Fig. 3225 represents a mortising machine for the hubs of wheels.

The auger spindle is here fed vertically by a hand lever, the depth bored being regulated by a rod against which the hand lever comes when the hole is bored to the required depth.

Fig. 3226 represents a mortising machine in which the mortising tool consists of a hollow square chisel containing an auger, and having at its sides openings through which the cuttings escape.

The chisel is rectangular in cross section, but its cutting edges are highest at the corners, as may be clearly seen in the figure.

The work is firmly clamped to the work table and simultaneously to the fence, the upper hand wheel being operated to bring the work-holding clamp down to the work, and the lower one to clamp it so as to press it to both the table and the fence at the same time.

The chisel bar is mounted horizontally in a slide way on a substantial bed that is mounted on a vertical slideway, which enables the chisel bar to be set for height from the work table. It has a horizontal traverse motion or feed, the amount of this motion being governed by the horizontal rod with its nuts and check nuts as shown.

The auger runs continuously, and works slightly in advance of the cutting edge of the chisel, which is pa.s.sive except when making the mortise.

The chisel bar and auger have a slow, reciprocating motion, and will complete a hole the size of the chisel used. An inch chisel will cut an inch-square hole, consequently a mortise 1" 4" would only require four strokes forward to complete it. It has a capacity to work mortises from 3/4" to 3" square, and 5" in depth, and any length desired. The boring spindle is driven by an idler pulley, direct from the countershaft.

The bed upon which the timber is placed to be mortised is gibbed to a sliding frame, which allows it to be set to any position, with the chisel straight or at an angle. It is adjustable to and from the chisel bar, to suit the size of material, the under side of which always remains at one height. Adjustments are provided for moving the carriage forward, for regulating the depth of the mortise, the position of the chisel from the face of the material, and the adjustment of the chisel bar, controlling the mortises to be made in the timber.

Two treadles are used upon the side of the machine; the pressure upon one carrying the chisel bar attachment forward, completing the mortise, while the other will instantly force it back when it is desired to withdraw it from the wood, without allowing it to cut its full depth.

Provision is made by stops for regulating the length of the stroke as well as the depth of the mortise.

TENONING MACHINES.

In tenoning machines, the lengths of the pieces usually operated upon render it necessary that the work should lie horizontally upon the table, while the shortness of the tenon makes an automatic feed unnecessary.

The revolving heads carrying the cutters in tenoning machines are so constructed that the cutting edges of the cutters are askew to the sides of the heads, but so set as to produce work parallel to the axis of the cutter shaft.

This causes the cutting action to begin at one end of the cutter edge, and pa.s.s along it to the other, which enables a steady hand feed, and reduces the amount of power required to feed the work.

Fig. 3227 represents a cutter head for a tenoning machine, _a_, _a_ and _b_, _b_ being the cutters and _c_, _c_, _d_, _d_ spurs which stand a little farther out than the cutter edges, so as to sever the fibre of the wood in advance of the cutter edges coming into action, and thus preserve a sharp shoulder to the tenon, and prevent the splitting out at the shoulder that would otherwise occur.

To bring the outer edge of the shoulder in very close contact with the mortised timber, the cutters are for some work followed by what is termed a cope head, which is a head carrying two cutters bent forward as in Fig. 3228, to make them cut very keenly, as is necessary in cutting the end grain of wood.

The cope head undercuts the shoulder, as shown at _a_, _a_, in Fig.

3229, which is a sectional view of a mortise and tenon.

[Ill.u.s.tration: Fig. 3226.]

[Ill.u.s.tration: Fig. 3227.]