Modern Machine-Shop Practice Part 132

[Ill.u.s.tration: Fig. 1883.]

The construction of the bearings for the cutter driving spindle of the machine is as in Figs. 1882 and 1883. A is the spindle having a double cone to fit corresponding cones in the sleeve B, the fit of one to the other being adjusted by means of the nut C, which is threaded upon A.

The mouth of A is coned to receive the arbors or mandrels for driving the mills or cutters. At the back bearing, Fig. 1883, the journal A', and bore of the sleeve B', is parallel, this sleeve being split at the top so that when it is (by means of nut D) drawn within the head E its coned exterior will cause it to close to a proper fit upon A', by which means the wear of the parts may be taken up as they become perceptible.

[Ill.u.s.tration: Fig. 1884.]

[Ill.u.s.tration: Fig. 1885.]

The head J, Fig. 1880, is used (in connection with the foot block I) to suspend or hold work by or between centres, its centre fitting into the spindle at _h_, which is capable of being revolved continuously (to enable the cutting of spirals), by means of change gears, and intermittently through a given part of a circle by means of the index wheel _i_. The block _j_ carrying the spindle is also capable of elevation for conical or taper work, two examples of such uses being shown in Figs. 1884 and 1885, in which C is the cutter and W the work.

[Ill.u.s.tration: Fig. 1886.]

[Ill.u.s.tration: Fig. 1887.]

Fig. 1886 is a sectional view in a vertical plane through the centre of the head, and showing the construction of the spindle and the means of elevating the block _j_; _h_ is the spindle having journal bearing in _j_, and secured from end motion by the cone at _a_ and the nut _b_; its bore is coned at the front end to receive the arbor C carrying the centre D, upon which is the piece E for driving the work dog, which is secured within E by the set-screw _f_. Fast upon spindle _h_ is a worm-wheel F made in two halves, which are secured together by the screws _g_. At G is the worm-wheel (for driving F) fast upon the shaft H'.

It is obvious that the block _j_ may be raised at its centre end upon H as a centre of motion, the worm F simply moving around upon G. At V is a bolt to lock _j_ to J, and thus secure it in its adjusted position. W W are lugs or blocks fitting into the slot in the work table, and serving to secure the head, being in line with the foot block (shown at 1 in Fig. 1880). A sleeve Z is used to cover the thread and protect it when a chuck is not used.

[Ill.u.s.tration: Fig. 1888.]

[Ill.u.s.tration: Fig. 1888_a_.]

Fig. 1887 is an end view partly in section to show the construction of the worm shaft and the index plate. H is a sleeve upon which _j_ pivots, and H' the worm shaft, which may be revolved by hand by the lever L, or automatically by means of the bevel-gear K, which connects with the train of change gears; these change gears being thrown out of operation when gear K (and therefore _h_) is not required to revolve automatically nor continuously. L is an arm for carrying the index pin _l_ for the index plate _i_. The pin _l_ is adjustable for radius from the centre of H (so as to come opposite to the necessary circle of holes on the plate _i_), the arm L being slotted to permit of this adjustment, and being secured in its adjusted position by the nut on the end of H'. Pin _l_ is pushed into the index holes by means of the spiral spring coiled around _l_ at _m_, which permits _l_ to be withdrawn from _i_ under an end pressure, but pushes it into _i_ when that pressure is released. To indicate the amount of rotation of _i_, without counting the number of holes, a sector N N' is employed, it having two arms adjustable for their widths apart so as to embrace any given number of holes on the required circle. At R' is a pin which is pulled forward and into holes provided in the plate _i_ to prevent its turning when using the lever L.

N and N' are held to the face of _i_ by the friction of the spring Q. A face view of index plate _i_ is shown in Fig. 1888, the lever L, Fig.

1887, being removed to expose N and N'.

The surface of the plate is provided with rings of holes marked respectively 20, 19, 18, &c., the holes in each ring or circle being equidistantly s.p.a.ced.

The sector arms N and N' may be opened apart or closed together so as to embrace any required number of holes in either of the circles. As shown in the cut they embrace one quarter of the circle of 20, there being five divisions between the holes S and _t_. The screw W secures them in their adjustment apart. Suppose that pin _l_ (Fig. 1887), is in S, and arm N' is moved up against it, the arm N leaves _t_ open, and indicates that _t_ is the next hole for pin _l_, which is withdrawn from S, and lever L (Fig. 1887) is moved around until the pin will enter _t_, and the sector is then moved into the position shown in Fig. 1888A, indicating that hole _u_ is the next one for the pin. This obviates the necessity of counting the holes, and prevents liability to error in the counting. Three of these index plates are provided, each having different numbers of holes in the circles, and in the following tables are given those specially prepared for use in cutting the teeth of gear-wheels:

------+-------+------------++------+-------+------------ No. of| Index |No. of turns||No. of| Index |No. of turns teeth.|circle.| of index. ||teeth.|circle.| of index.

------+-------+------------++------+-------+------------ 2 | ANY | 20 || 35 | 49 | 1-7/49 3 | 39 | 13-13/39 || 36 | 27 | 1-3/27 4 | ANY | 10 || 37 | 37 | 1-3/37 5 | " | 8 || 38 | 19 | 1-1/19 6 | 39 | 6-26/39 || 39 | 39 | 1-1/39 7 | 49 | 5-35/49 || 40 | ANY | 1 8 | ANY | 5 || 41 | 41 | 40/41 9 | 27 | 4-12/27 || 42 | 21 | 20/21 10 | ANY | 4 || 43 | 43 | 40/43 11 | 33 | 3-21/33 || 44 | 33 | 30/33 12 | 39 | 3-13/39 || 45 | 27 | 24/27 13 | 39 | 3-3/39 || 46 | 23 | 20/23 14 | 49 | 2-42/49 || 47 | 47 | 04/47 15 | 39 | 2-26/39 || 48 | 18 | 15/18 16 | 20 | 2-10/20 || 49 | 49 | 20/49 17 | 17 | 2-6/17 || 50 | 20 | 16/20 18 | 27 | 2-6/27 || 52 | 39 | 30/39 19 | 19 | 2-2/19 || 54 | 27 | 20/27 20 | ANY | 2 || 55 | 33 | 24/33 21 | 21 | 1-19/21 || 56 | 49 | 35/49 22 | 33 | 1-27/37 || 58 | 29 | 20/29 23 | 23 | 1-17/23 || 60 | 39 | 26/39 24 | 39 | 1-26/39 || 62 | 31 | 20/31 25 | 20 | 1-12/20 || 64 | 16 | 10/16 26 | 39 | 1-21/39 || 65 | 39 | 24/39 27 | 27 | 1-13/27 || 66 | 33 | 20/33 28 | 49 | 1-21/49 || 68 | 17 | 10/17 29 | 29 | 1-11/29 || 70 | 49 | 28/49 30 | 39 | 1-13/39 || 72 | 27 | 15/27 31 | 31 | 1-9/31 || 74 | 37 | 20/37 32 | 20 | 1-5/20 || 75 | 15 | 8/15 33 | 33 | 1-7/33 || 76 | 19 | 10/19 34 | 17 | 1-3/17 || 78 | 39 | 20/39 ------+-------+------------++------+-------+------------

------+-------+------------++------+-------+------------ No. of| Index |No. of turns||No. of| Index |No. of turns teeth.|circle.| of index. ||teeth.|circle.| of index.

------+-------+------------++------+-------+------------ 80 | 20 | 10/20 || 164 | 41 | 10/41 82 | 41 | 20/41 || 165 | 33 | 8/33 84 | 21 | 10/21 || 168 | 21 | 5/21 85 | 17 | 8/17 || 170 | 17 | 4/17 86 | 43 | 20/43 || 172 | 43 | 10/43 88 | 33 | 15/33 || 180 | 27 | 6/27 90 | 27 | 12/27 || 184 | 23 | 5/23 92 | 23 | 10/23 || 185 | 37 | 8/37 94 | 47 | 20/47 || 188 | 47 | 10/47 95 | 19 | 8/19 || 190 | 19 | 4/19 98 | 49 | 20/49 || 195 | 39 | 8/39 100 | 20 | 8/20 || 196 | 49 | 10/49 104 | 39 | 15/39 || 200 | 20 | 4/20 108 | 27 | 10/27 || 205 | 41 | 8/41 110 | 33 | 12/33 || 210 | 21 | 4/21 115 | 23 | 8/23 || 215 | 43 | 8/43 116 | 29 | 10/29 || 216 | 27 | 6/27 120 | 39 | 13/39 || 220 | 33 | 6/33 124 | 31 | 10/31 || 230 | 23 | 4/23 128 | 16 | 6/16 || 232 | 29 | 5/29 130 | 39 | 12/39 || 235 | 47 | 8/47 132 | 33 | 10/33 || 240 | 18 | 3/18 135 | 27 | 8/27 || 245 | 49 | 8/49 136 | 17 | 5/17 || 248 | 31 | 5/31 140 | 49 | 14/49 || 260 | 39 | 6/39 144 | 18 | 5/18 || 264 | 33 | 5/33 145 | 29 | 8/29 || 270 | 27 | 4/27 148 | 37 | 10/37 || 280 | 49 | 7/49 150 | 15 | 4/15 || 290 | 29 | 4/29 152 | 19 | 5/19 || 296 | 37 | 5/37 155 | 31 | 8/31 || 300 | 15 | 2/15 156 | 39 | 10/39 || 310 | 31 | 4/31 160 | 20 | 5/20 || 312 | 39 | 5/39 ------+-------+------------++------+-------+------------

[Ill.u.s.tration: Fig. 1889.]

A plan view of one-half of the head is shown in Fig. 1889, the edge of J being graduated for a guide in elevating the head at an angle, at V is the bevel-gear for driving K, and at S is a pinion receiving motion from the change gears.

The feed motions for the traversing table (F, Fig. 1880) is shown in Figs. 1889, 1890, and 1891, _g_ represents the universal joint rotating continuously the spindle _a_, which provides journal bearing to bevel pinion _b_ and the clutch _c_, these two being fixed together; _d_ is a clutch which rotates with _a_, but is capable of a certain amount of end motion on or along _a_ to enable it to engage or disengage with its mate _c_. When _d_ engages with _c_ the rotary motion of _a_ is transmitted through _d_, _c_, _b_, to _f_, which actuates the feed screw A, while when _d_ is disengaged from _c_, it rotates, leaving _c_ _b_ _f_ idle.

_d_ is operated to engage with or disengage from _c_, its hub is enveloped by the fork _e_, which is attached to rod _h_, which is provided with a recess to receive one end of the bell crank _l_, the other end of which lies in a recess in the rod _m_, to the end of which is connected the lever handle _n_, which is pivoted at O; hence operating _n_ laterally as denoted by the arrows, throws _d_ in or out of gear with _c_, according to the direction of motion, direction _p_ being that to throw it out of, and _q_ to throw it into gear or engagement. At _r_ is a stop that can be fixed at any adjusted position or desired location along the bed upon which the feed table or carriage (F, Fig. 1880) slides, so that when that carriage is being self-actuated it will traverse until the inner end of _n_ meets the stop, whereupon the stop will move _n_ and thereby disengage _d_ from _c_, causing the automatic feed to cease. All that is necessary, therefore, is to set _r_ in such a position along the bed that it will operate _n_ when the milling cutter has operated to the required distance along or over the work; _s_ is the stud arm that carries wheel _t_ to engage with and drive the pinions shown in Fig. 1889, and _u_ is the stud for carrying the wheels for giving the required changes of rotation to K, Fig. 1889, the wheels on _u_ receiving motion from a gear placed at the seat V on the feed screw A. The stud arm _s_ being slotted, can be moved forward, transmitting motion from the change wheels on _u_ to wheel S, Fig. 1890, causing the automatic spiral feed to actuate; or by moving _s_ outwards, this feed is thrown out of action, and either the hand feed of handle W or the self-acting feed traverse may be employed.

Thus the hand, and all the automatic feed motions are driven from the feed screw A, and each of the automatic feed motions may be started or stopped by operating the lever _n_, while the stop _r_ causes each of them to cease when the work has traversed to the required distance beneath the milling cutter.

Fig. 1892 represents an attachment to this machine to facilitate cutting the teeth of gears, which it does because its index plate operates the work-holding mandrel direct, and may, therefore, be set quicker. The base bolts to the machine table and the index head and tailblock are traversed in the base by means of the four-levered handle shown.

[Ill.u.s.tration: Fig. 1890.]

Figs. from 1893 to 1899 represent a universal milling machine. This machine is so constructed that all the features essential to a universal milling machine are obtained by means of attachments (each complete in itself) which may be removed, leaving the work table clear, and, therefore, serviceable for large work, or work which may be more conveniently held without the use of attachments.

The [T]-slots in the table are furnished to standard size, and are at right angles, so that the attachments will be held exactly parallel with, or at a right angle, as the case may be, to the live spindle of the machine; hence the machine will accomplish all the varied results required in the tool room or for machine work generally.

Thus for the cutting of spirals, a fixture capable of originating any spiral right or left hand, from 2 inches to 6 feet pitch, is provided.

Two bolts secure it to the machine table, and when the job is finished it is removed. Similarly for the cutting of cams, an attachment fastened to the work table by three bolts is used, which cuts either cylinder or face cams of considerable size, and as conveniently as a machine built solely for cam cutting. A gear-cutting device is also applied in the same manner, as well as plain or universal work-holding centres.

The essential features of the machine are a standard A, Fig. 1894, with spreading base, carrying upon its top a driving cone B, which is fully back-geared like an engine lathe. The driving cone operates also the feed mechanism. Above the driving cone is an arch C, in which is inserted an arm D for supporting the outer end of the mill arbor when used for heavy work. Upon the face or front of the standard slides a knee E, which in its turn supports a carriage F, which traverses crosswise upon it and carries above it the work table, which is provided with an automatic feed at right angles with the movement of the carriage. These three movements, vertical, cross, and longitudinal, cover all that is usually required in a universal milling machine.

[Ill.u.s.tration: Fig. 1891.]

[Ill.u.s.tration: Fig. 1892.]

Coming to details we start with the spindle or arbor, the front end of which runs in bearings of bronze. These are made in two parts, tapering upon the outside and straight upon the inside, a corresponding taper hole to receive the spindle bearings being bored in the solid iron of the standard. A check nut upon each end of the bushing or bearing abuts against the end faces of the standard bearing, and by drawing the bushing or bearing through the taper hole in the standard, produces the exact required closeness of fit between the spindle journal and its bearing bore, and thus compensates for the wear of either the spindle journal or its bearing or bushing bore, the front check nut also providing a dust cap.

The back journal of the spindle runs in a bushing of considerable length. Upon the back end of the spindle is secured a train of feed gears G, the lower of which is upon a shaft that on its other end carries the first feed cone H. The corresponding feed cone I is fixed to the longer shaft J, carrying a worm (or tangent screw) K, which engages with the worm-gear L connected directly with the feed screw, for the longitudinal motion of the work table.

This whole feed work is shown fully in outline in Fig. 1894. The arm M that supports the two lower feed gears pivots upon the outboard end of the back bushing, hence its centre coincides with that of the spindle.

At its lower end a projection inwards forms a hub upon which a second lug or arm N is pivoted. The lower end of this arm is bored out to receive the threaded end of a lug O with the bearing of the second feed cone I. This threaded end carries a milled or hand nut P, so that to tighten or loosen the feed belt a turn of the nut is sufficient, the effect being to increase or diminish the distance between the feed cones H and I. The front end of the feed rod is supported in a drop box Q, and is splined to allow the worm K to travel upon it. It will be seen, therefore, that the feed mechanism is undisturbed either by the vertical movement of the knee, or the cross motion of the carriage, or the longitudinal feed of the table. The feed gears are covered with a shield R, a part of which is shown broken away. The knee with its appendages is actuated vertically by means of a crank connected with bevel gearing at S, which moves a perpendicular screw T under the centre of the knee.

Rotating with this crank-shaft is a finger U held by friction. This finger is in close proximity to a dial V graduated to thousandths of an inch, and as one revolution of the finger indicates 1/8 of an inch of elevation to the knee E, the ordinary subdivisions of an inch are obtained either with or without an inner circle of graduations on the dial. A similar dial upon the cross feed motion (not shown in the engraving) is also put on, which likewise reads to thousandths of an inch.

The feed of the work table is accomplished by means of a screw whose thread is in shape a half [V] and does not bear upon the bottom of the thread in the feed nut, which is in halves, with provision for closing up to compensate for wear, while check nuts on one end of the feed screw take up all end play.

The automatic feed is self-stopping (so as to enable one attendant to operate several machines) by means of the following construction:--

In the general view, Fig. 1893, there is seen a stop that is secured in the required position in the [T]-groove shown at X in the outline view, Fig. 1894, and when this stop meets the bell crank Y it unlatches it from a lug which is on the drop box Q, Fig. 1893, hence this box falls and with it that end of the worm shaft J, throwing it out of gear with the worm-wheel L, and therefore stopping the feed.

The attachments giving to this machine its universal qualifications are as follows:--

The rotary vice is shown on the work table in the general view, Fig.

1893; and requires but little description. Upon the underside of the base is a circular projection having beneath it a projection fitting into the [T]-slots in the work table. Two segmental slots in the base admit of a rotary movement of the vice within a range of 90, and it is held to the table by two bolts. The crank or handle of the vice is made more convenient by means of two square holes that fit the end of the screw that actuates the movable jaw. Using the central hole allows the handle to clear the work table, but when the vice jaws need to be closed with considerable force the handle is shifted to the end or outer hole, thus doubling the leverage.

[Ill.u.s.tration: _VOL. II._ =EXAMPLE OF MILLING MACHINE.= _PLATE I._

Fig. 1893.

Fig. 1894.]

THE UNIVERSAL HEAD AND BACK CENTRE.--This tool is used for making milling cutters either straight or angular, cutting small gears either spur or bevel, fluting taps or reamers, finishing nuts or bolt-heads, and a mult.i.tude of other jobs too numerous to particularise. The head consists, as seen in Fig. 1895, of a swinging block mounted centrally between the two upright sides or jaws of a base, and is clamped in any position by a set-screw on either side. The face of one side or jaw is laid out in degrees, and a finger or pointer on the block indicates its angle of elevation. On the front end of the spindle is secured a worm-wheel divided longitudinally, each half being used as a corrector (in the making) for the other half till all errors are eliminated. A dial is fixed upon the bushing through which pa.s.ses the shaft that actuates the worm, and consequently revolves the worm-gear and the spindle. A pointer arm carrying a handle with a pointer and appendages is secured to the end of this shaft. Under it are the usual s.p.a.ces for laying off or indicating the proper number of index holes for the required fraction of a circle the spindle is to be moved through. The spindle is hollow and has a screw on the outer end for taking a chuck or face plate. It has a taper hole for receiving the proper centre, which carries a lug for holding the dog used when the work to be finished is held between centres. Three index dials, which are made interchangeable, provide for most divisions except a few prime numbers to 360.

[Ill.u.s.tration: Fig. 1895.]

[Ill.u.s.tration: Fig. 1896.]

To prevent or take up lost motion between the worm and the worm-gear the entire bracket carrying the worm and indexing mechanism is made adjustable as follows:--

Through the base of the bracket thread two sleeves whose ends abut against the top of the block, and therefore determine the engagement of the worm with the worm-wheel. Through these sleeves pa.s.s the bolts which thread into the block and lock the bracket in its adjusted position. A simple screw bolts the back end of the bracket. The degree of fit between the worm and the wheel may be very sensitively made by revolving the worm spindle by hand.

The block carrying the back centre has some peculiar features, which enable it to be set in line with the axis of the work, whether the latter be parallel or taper, so as to suit the elevation or depression of the head, and enable the centre to fill the countersink of work held on centres, keeping it central and avoiding wear to one side. It consists of a block held between two uprights or jaws, and clamped thereto by two screw bolts. The block is slotted entirely through from side to side, the front slot being only wide enough to receive the bolt and making a changeable centre for the block to partially rotate upon.