Modern Machine-Shop Practice Part 217

The knives require to be as accurately balanced as it is possible to make them, for otherwise they will cause the head to jar and vibrate violently, thus producing rough work. The knives weighed individually may be of the same weight, and yet the head may run out of balance by reason of one end of a knife being heavier than the other end.

[Ill.u.s.tration: Fig. 3173.]

Fig. 3173 represents a machine constructed by J. A. Graham & Co., for balancing planer knives, moulding knives, cap screws, and knives in rotary cutter heads of all kinds.

Let it be supposed that the knives are the same specific weight, but that there is an excess of weight at one end; when revolving on the head, a violent jarring or throwing will be caused by reason of the excess. The knives could be reduced to the same specific weight by the aid of common grocers' scales, but the ends could not be made the same proportional weight as on such balance.

In the cut S S is the base of the scale; L, M the standards for the support of the scale beams B B and K K.

_d_, _d'_ are two pivots of the scale beams.

D is the loop on which the pivot _d_ works.

E is a joint in the loop.

D', E', and F show the loop and connection.

_c_ is the sliding table which has the stop _c'_, and is adjustable for different lengths of knives.

_a_ _a_ is a knife in position for balancing endwise.

G is a slotted piece, and is held to the scale beam by the screw _v_.

The slot in G is shown at G', and limits the travel of the scale beams.

H is an angular piece fastened to the lower scale beam, and receives the screw J.

I is a small weight used for fine adjustment.

O, O are weights which slide along the scale beam K K, and are held in place by the thumb screws P, P.

N shows side view of weight, which is so constructed as to allow it to be easily removed. In using the machine the lightest cutter or knife of the set is first found and its two ends balanced, by turning it end for end on the scales, and reducing the weight of the heavier end. The other knife or knives are then balanced without disturbing the adjustment of the machine as made for the first knife.

ENDLESS BED OR "FARRAR" WOOD SURFACING MACHINE.

This cla.s.s of machine has a bed composed of slats which are connected together and driven by a chain.

Fig. 3174 represents an endless bed double surfacer constructed by the Egan Company. The upper cylinder may be raised or lowered to suit the thickness of the work. The front feed roll is in two sections, enabling two boards of unequal thickness to be planed simultaneously to an equal thickness. These rolls are held to the work by a leaf spring, as shown in the cut, the tension on the spring being adjusted by the screw at D, _d_ serving as a check-nut.

A longitudinal section through the centre of the machine is shown in Fig. 3175. The spring S bears at each end on a block T, which carries the bearings for the feed roll. Feed roll M is held down by the screws E, E, acting on a rubber cushion or spring, and is provided with a sc.r.a.per to clean it from dirt, etc.

The travelling bed is composed of slats S connected together by the chain shown, and resting upon slides A, A, supported by the girts B, B.

The chain is operated by the spur or sprocket wheel W, and is therefore pulled and not pushed, which tends to keep it under tension, and therefore rigid upon the top side.

The ends of the slide A, A are depressed so that the slats shall not tilt up at one corner above the level of the slide when in the positions denoted by S'.

The lower cutter head is carried in a sliding head or frame J, adjusted for height by the gears at H, which operate screw _h_, while the bed above it is adjusted by the gears at F. It is obvious that the bottom surface of this bed is set at the same height as the lowest point in the path of revolution of the cutting edges of the knives of the front cutter head or cylinder. The upper delivery roll N is provided with a sc.r.a.per.

PLANING AND MATCHING MACHINE.

Planing and matching machines that are made narrow to suit the planing and matching of boards for flooring are sometimes called _flooring_ machines, the distinctive feature of a flooring machine being that it is (unless in the case of a double machine) made narrow (because flooring boards are narrow), and this makes the machine very stiff and capable therefore of a high rate of feed and speed.

[Ill.u.s.tration: Fig. 3174.]

[Ill.u.s.tration: Fig. 3175.]

[Ill.u.s.tration: Fig. 3176.]

[Ill.u.s.tration: Fig. 3177.]

Fig. 3176 is a general view, and 3177 a longitudinal section through a standard planing and matching machine of recent design, constructed by Messrs. J. S. Graham & Company. The plank pa.s.ses through two pairs of rollers before meeting the front cutter head. The side heads then come into operation cutting (in the case of flooring) the tongue on one side of the plank and the groove on the other, the under side of the plank being dressed last.

The machine is built in three widths viz., 8", 14" and 26", each planing to 6" thick and matching as wide as it planes.

In place of matching heads, heads for beading, rabbeting, or fancy siding may then be used.

The board R (Fig. 3177) is fed in over the grate _m'_ until it reaches the rolls E and F', which are held in place by the boxes fitted to the roll stand _n'_, and brought to bear on the lumber by means of the screw _a'_, equalizing bar _m_ and nuts _p_, _p_, together with the lever Y Y and the weight _x_.

[Ill.u.s.tration: Fig. 3178.]

After the lumber leaves the second pair of rolls, it runs over the bed plate W (Fig. 3178) and under the shoe L, the duty of which is to hold the board firmly against the bed plate, and also to break the chips on a heavy cut. After leaving the shoe it is operated on by the upper cutter head H, then it pa.s.ses beneath the pressure bar _g_, which holds the lumber firmly while it is acted on by the matcher _c_.

[Ill.u.s.tration: Fig. 3179.]

It then pa.s.ses beneath the cleaner E" (Fig. 3177) and under the delivering roll, which is held down by the weight U in connection with the lever V and screw _a'_, the top which is shown at C (Fig. 3179). The board then pa.s.ses underneath the pressure bar Q (Figs. 3177, 3180) and over the under cutter S, from which it pa.s.ses finished.

The pressure bar Q is moved up and down by turning the shaft _a"_, the motion of which is given to the screw _h'_ by means of a pair of bevel gears. _k'_ is also a sc.r.a.per that cleans the board before it pa.s.ses under the pressure bar Q. The under cutter is adjusted for depth of cut by turning hand wheel A', which moves the screw U'. The rolls are raised and lowered by turning the shaft at P (Fig. 3176).

In feeding two boards through the machine, one thicker than the other, that end of the roll that pa.s.ses over the thick board can raise up without taking the pressure off the thin one at the other end of the roll. This raising mechanism is shown in Fig. 3179. The bevel gear C works over a ball joint Q'. The shoulder B' on the screw _a'_ works on the under side of the ball Q'. The shaft _a_ pa.s.ses through the tubular sh.e.l.l B to the opposite end of the roll. The cross tie J is bolted to the roll box K".

C, Fig. 3178, shows matcher hanger in position. It is gibbed to the bed plate Z by the gib _f_, which is so constructed as to be free from dirt.

The sliding gib _f_ is adjustable for wear. One matcher hanger is moved by the screw _e_, the other by _e'_. The left hand matcher hanger is moved by the shaft _l'_ (Fig. 3177), which pa.s.ses along the side of the machine until it reaches the shaft _e_, where its motion is imparted to the screw by means of a pair of spiral gears. An index at the rear of the machine enables the operator to set the matcher heads to any desired width. The right hand matcher hanger, together with the guide, can be moved across the machine by turning the screw _e'_ at the side of the machine (Fig. 3176).

The upright D which carries the pulley which drives the top cutter head, or cylinder as it is sometimes termed, is set at an angle so that the cylinder belt will always be of the same tension.

The top cylinder is raised by the shaft _d_ (Fig. 3176) and screw _b_.

It is held in place by the nut M (Fig. 3177). The bar I ties the cylinder boxes together. K is held down by the weight I, and yields with the pressure bar L.

The spindle of the matcher _c'_ (Fig. 3177) is driven by a belt which comes from the pulley _h_ and pa.s.ses over the guide pulley _k_, and then to the pulley _b'_.

The lower end of the matcher is held in place by being gibbed to the cross tie _p'_, Fig. 3177, which is adjusted and kept in position by the screw _o'_.

S' sustains the matcher spindle by means of an adjustable step.

Y', Fig. 3176, is the feed shaft which drives the gearing that operates the rolls. The pulley that drives the feed shaft is shown at L' (Fig.

3176). The belt pa.s.ses over this pulley and under and over the tightener pulleys _w'_, _w'_, then to the pulley U' which is on the feed shaft Y'.