American-Machinist-July-28-1892.html

A JOURNAL FOR MACHINISTS, ENGINEERS, FOUNDERS, BOILER MAKERS, PATTERN MAKERS AND BLACKSMITHS,
VOL. 15, NO. 30. WEEKLY.
NEW YORK, THURSDAY, JULY 28, 1892.
83.00 per Ann-um, ( SINGLE COPIES 6 CENTS
COPYRIGHT 1892, BY AMERICAN MACHINIST PUBLISHING COMPANY.
New Re-sawing Band-saw Machine.
We illustrate herewith a new re-sawing band-saw which will use saws as thin as 24 gauge and up to 6 inches wide, and will saw 16,000 to 20,000 feet per day, making a kerf only -jf,- of an inch, or less, instead of to 1-" more than this, as has been quite common. The feeding is effected by four strongly geared live rolls, while two smaller idle rolls guide the last end of the stock up to the finish of the cut. Strong springs hold the rolls upon one side np to their work, and enable them to yield to all inequalities of thickness or shape, while the rolls upon the other side form a guide in perfect line with the saw, thus insuring a cut parallel with one side of the stock. A friction device, controlled by a single lever, enables the feed to be instantly stopped and started, or to be run at any speed de-sired without changing belts, and thus the exact maximum feed can always be se-cured, resulting, of course, in increased out-put as compared with machines using stepped pones or gears. The saw runs between hardened rsteel plates filled with dogwood plugs, with the end grain in contact with the saw, and each plate can be accwately adjusted by a single screw. The back of the saw has a bearing inches long on the beveled edge of a conical roller of a special composition, harder than steel. What little wear does occur takes-
fi,11 thn br,Arolorl
For Sale Everywhere by Newsdealer:. ENTERED AT POST OFFICE, NEW YORK, AS SECOND CLASS MATTER.
wheel, the result being a broken saw. To provide doubly against such an accident, a wooden block is fitted in the throat between
The loose pulley is self-oiling, and one inch smaller in diameter than the tight pulley, to slacken the belt when the machine is stopped,
saw and wheel, so as to catch all chips and and it is provided with a step at the inner edge,

feed-rolls, 21 inches--12 in. on one side of the saw and 9 inches on the other; height of stock that can be sawed, 30 inches. The manufacturer is P. Pryibil, 498 to 510 West Forty-first street, New York City.

The Rivett Bench Lathe.
We publish on this and the succeeding page some illustrations of a bench lathe, which, with its attachments, possesses many points of interest to the mechanic. The en-graving on this page represents the lathe as arranged for milling, while on the next page are engravings showing it in its plainest form; with the grinding attachment ready for use, and also some of the attachments by which it is made to do a great variety of work. The lathe is intended for the finest work done by tool makers, electricians and ma-chinists, and is highly finished all over, in-cluding the bed and feet. The head-stock spindle and bushings in which it runs are of tool-steel, hardened, ground and lapped, the spindle being 2k" diameter, and the bearings 211" long. The end of the spindle is threaded for face plates or chucks, and there is a draw-bar which extends through the spindle for holding split chucks which vary in size from -8-11" to 4-", the rods extend-ing through the spindle, which has a hole through it 4" diameter. The cone has three steps for a 14" belt, the smallest step being 3" and the largest 41" diameter. The flange the rPnr And of the ormp

RIVETT BENCH LATHE.
The body is a box-shaped casting, in one piece, very strong and rigid, and it can be placed on any good floor without a special fo(lthdation.

inches; driving pulley, 22 to 30 in. d':ameter, as ordered, for an 8-in. belt; spew 450 to 525 turns per minute, accordin- and width of lumber; thielz—
or cross-slide has a move-ment of 4" and the nu, slide 5". At Fig. 5 is shown a block which clamps to the bed in the usual way, thes.,,, upper portion of this block swiveling in a horizontal plane upon a graduated base. The left-haa side of this block as shown jr the engraving is'adapted to receive th(

cones or gears. The saw runs between hardened !steel plates filled with dogwood plugs, with the end grain in contact with the saw, and each plate can be accwately adjusted by a single screw. The back of the saw has a bearing 14- inches long on the beveled edge of a conical roller of a special composition, harder than steel. What little wear does occur takes place across the full width of the beveled surface, and therefore does not form grooves, as would be the case with a plain roller. The upper guide is counterbalanced, and is adjustable vertically by a hand-wheel. This hand-wheel, the lever for controlling the feed, the hand-wheel for setting the feed rolls, and the scale showing to what thick-ness they are set, are all readily accessible from the sawyer's usual working position. The upper wheel has a rim of bent ash with sted spokes, and the lower one is a heavy iron casting. The lower wheel being thus much the heavier, it acts as a by-wheel to pre-vent sudden and violent fluctuations of speed, as in starting and stopping, and thus prevents the overrun-ning of the upper wheel, which, being lighter, is capable of following the motion of the lower one without causing the saw to slip or to become slack on the working side. The rims of both wheels come upon a vertical line, which is considerably with-in the outer ends of the bearings, so that the shafts are well supported with-out the necessity for using outside bearings. T h e upper shaft can be angled while in motior. An adjust( ale spring maintains a proper tension on the saw, and renders it much more secure against breakage than the weights, commonly used for this purpose, as the inertia- of weights prevents them from yielding quickly enough when a chip gets between: the saw and tai,sawdust, rim.

'NEW RE-SAWING MACHINE.
and discharge them beyond ..thetto eauseip belt to shift easily. Height of ma-The lower wheel is kept free from chine, 10 ft. 7 in.; width of machine, 7 ft. 5 accumulations of sawdust by a scraper, and in. ; depth of machine, 6 ft. 5 in. ; weight the upper one by a brush. complete, 7,000 lbs ; diameter of wheels, 60
'the spindle being 2i" diameter, and the bearings 2#" long. The end of the spindle is threaded for face-plates or chucks, and there is a draw-bar which extends through the spindle for holding split chucks which vary in size from A-" to 4-", the rods extend-ing through the spindle, which has a hole through it diameter. The cone has three steps for a 1/.." belt, the smallest step being 3" and the largest 44-" diameter. The flange at the rear end of the cone is drilled and provided with a pin for indexing. The foot-stock spindle is also of steel, hardened and ground, 1" diameter, and with a bearing 5.' long. The lathe swings over the bed 8", and takes between centers 18". The slide rest, which is shown on .page 2, Fig. 4, fits over the sides of the block, on which the T-rest is placed in Fig. 2. It has two circular graduated bases and two slides, the lower one of these being always at right angles to the center line of the lathe, so that a squaring or facing cut can be taken at any time when boring or turn-ing taper without disturb-ing the adjustment of the rest. The various binding arrangements are efficient, operating to hold the parts very securely with very light pressures. The tool holder is an eccentric device by which the tools are readily brought to the center or otherwise adjusted, and it is especially arranged with a view to enabling the tool ,maker ty make his own tools where the services of a blacksmith or tool dresser are not at command, as is often the case where such lathes are used. The lower

RIVETT BENCH LATHE.
The body is a box-shaped casting, in one piece, very strong and rigid, and it can be placed on any good floor without a special fo(lthdation.

drillpti

RIVETT BENCH LATHE.
The body is a box-shaped casting, in one piece, very strong and rigid, and it can be placed on any good floor without a special fo(lthdation.

2 AMERICAN MACHINIST JULY 28, 1892
rest in the manner shown in Fig. 1, where the slide rest is so placed as to hold an arbor on which is placed a blank foi an angular
milling cutter to have teeth cut in various slides and graduated bases constituting a means of placing the work arbor in any possible position that maybe wanted for doing almost any kind of work. Arranged thus, the lathe is, of course, very useful for cutting gears, bevel or spur, or for doing any kind of intricate and fine milling work. Gears up to 4"' diam-eter and 12 pitch can readily be cut upon it. Index plates with 46, 56, 60, 72, 80, 84 and 100 teeth are supplied with the device. It will be perceived that this &vice can be put in place very quickly, and that no extra belt-ing is required, the machine being ready for use as soon as the rest is in place. Fig. 6 shows the quill used in milling, this being put in place of the ordinary tool holder, and clamped in place by the same means. Fig. 3 shows the lathe and counter-shaft fixed for grinding, the grinding attachment being shown at Fig. 7. This also slips in place of the tool holder, and is belted in the manner shown, the large grooved wheel and guides being preferred by the builders to the usual drum. Here again the universal adjustments of the slide rest are useful in making the grinding device applicable to almost any kind of outside or inside grinding. An automatic feeding device is sup-plied for the slide rest when desired, by which screws from 10 to 160 per inch can be ' chased by the gears regularly furnished, or gears for metric threads are supplied when desired. There is also a turret slide which goes on the bed in place of the foot-stock, the slide rest being used in con-nection with this. The turret is moved by a lever, and revolves automatic-ally. It has six holes for -WWI. An automatic wire feed is also supplied when desired, making the lathe a complete screw P
it, the Naval Constructor Pook. Their report was as follows : The Board of Examiners have, as instruct-ed by the department, examined the plans be fired under water. The lines of the for-ward part of the vessel are made to converge into and are terminated by the gun, which also may be used as a ram. lie also proposes

to advantage (of which ite board has serious doubts); the plans propbsed by, Mr. Durfee to work them are more feasible than any yet off. red for examination. There is also to be one revolving tower amidship, and one fixed tower in the forward part of the vessel, with the gun revolving upon a platfor!n. It is proposed to have the guns so mounted that they are turned, elevated or depressed in the center of the port, 'so as to make the ports as small as possible. The plans are well conceived and show much ingenuity, and Mr. Durfee de-serves great credit for his efforts to produce an efficient ship; but, after a careful examination of his plans and listening to his explanations, the board has come to the conclusion that, un-til more reliable experiments are made to test the efficiency of guns fired under water, they cannot recommend this plan for adoption. he manner of mounting the gun in the tower, the muzzle to rest in a chock upon the end of the carriage, when elevated or depressed, would be found difficult in practice and not reliable. The gun built into the bow of the vessel, with the addition of the tower, would be too much weight in that end of the vessel, and could not be supported in the manner proposed. The it n shield over the rudder is also objec-tionable, as it cannot be supporteZt and would weaken the vessel. The weights at the extremities should be avoided as much as possible. This plan is not recommended for adoption. The gun built into the bow of the vessel, mentioned in the above report, was designed to serve both as a gun and a ram (that in the "Destroyer" cannot be used as a ram, because of the presence of the muzzle shutter, which ramming would destroy), and was contrived to open at the breech without admitting water to the vessel. The design also contemplated the use of breech-loading broadside guns, which could be fired below the water line. These guns were provided with nneumatic recoil mil-

Fig. 2.
cones or gears. The saw runs between hardened !steel plates filled with dogwood plugs, with the end grain in contact with the saw, and each plate can be accwately adjusted by a single screw. The back of the saw has a bearing 14- inches long on the beveled edge of a conical roller of a special composition, harder than steel. What little wear does occur takes place across the full width of the beveled surface, and therefore does not form grooves, as would be the case with a plain roller. The upper guide is counterbalanced, and is adjustable vertically by a hand-wheel. This hand-wheel, the lever for controlling the feed, the hand-wheel for setting the feed rolls, and the scale showing to what thick-ness they are set, are all readily accessible from the sawyer's usual working position. The upper wheel has a rim of bent ash with sted spokes, and the lower one is a heavy iron casting. The lower wheel being thus much the heavier, it acts as a by-wheel to pre-vent sudden and violent fluctuations of speed, as in starting and stopping, and thus prevents the overrun-ning of the upper wheel, which, being lighter, is capable of following the motion of the lower one without causing the saw to slip or to become slack on the working side. The rims of both wheels come upon a vertical line, which is considerably with-in the outer ends of the bearings, so that the shafts are well supported with-out the necessity for using outside bearings. T h e upper shaft can be angled while in motior. An adjust( ale spring maintains a proper tension on the saw, and renders it much more secure against breakage than the weights, commonly used for this purpose, as the inertia- of weights prevents them from yielding quickly enough when a chip gets between: the saw and tai

,sawdust, rim.
' NEW RE-SAWING MACHINE.
and discharge them beyond ..thetto eauseip belt to shift easily. Height of ma-The lower wheel is kept free from chine, 10 ft. 7 in.; width of machine, 7 ft. 5 accumulations of sawdust by a scraper, and in. ; depth of machine, 6 ft. 5 in. ; weight the upper one by a brush. complete, 7,000 lbs ; diameter of wheels, 60
'the spindle being 2i" diameter, and the bearings 2#" long. The end of the spindle is threaded for face-plates or chucks, and there is a draw-bar which extends through the spindle for holding split chucks which vary in size from A-" to 4-", the rods extend-ing through the spindle, which has a hole through it diameter. The cone has three steps for a 1/.." belt, the smallest step being 3" and the largest 44-" diameter. The flange at the rear end of the cone is drilled and provided with a pin for indexing. The foot-stock spindle is also of steel, hardened and ground, 1" diameter, and with a bearing 5.' long. The lathe swings over the bed 8", and takes between centers 18". The slide rest, which is shown on .page 2, Fig. 4, fits over the sides of the block, on which the T-rest is placed in Fig. 2. It has two circular graduated bases and two slides, the lower one of these being always at right angles to the center line of the lathe, so that a squaring or facing cut can be taken at any time when boring or turn-ing taper without disturb-ing the adjustment of the rest. The various binding arrangements are efficient, operating to hold the parts very securely with very light pressures. The tool holder is an eccentric device by which the tools are readily brought to the center or otherwise adjusted, and it is especially arranged with a view to enabling the tool ,maker ty make his own tools where the services of a blacksmith or tool dresser are not at command, as is often the case where such lathes are used. The lower

.;,
RIVETT BENCH LATHE.
The body is a box-shaped casting, in one piece, very strong and rigid, and it can be placed on any good floor without a special fo(lthdation.

add here

JULY 28, 1892]
tially as proposed would be very efficient as a means of harbor and coast defense. I claim to be the original inventor of a vessel having a breech-loading gun built into its bow, arranged to discharge shot or shell be-low the water, and capable of being used as a ram without destroying its use as a gun, and of being loaded and fired without letting water into the vessel. I also claim the con-struction of the turret described and the method of mounting the guns therein. W. F. DURFEE, Engineer. West New Brighton, S. I., July 4, 1892. *4111. Engines for the U. S. Battle-ship " Texas."
With this we give a longitudinal section and an end view of the engines for the U. S. Battle-ship Texas," which was successfully launched from the Norfolk Navy Yard on the 28th ult. A full description of these en-gines was given in our issue of June 30th. These illustrations will give an excellent idea of the general design, arrangement and type of valves, and link motion used. The " Texas " will be fitted as a flagship, and will carry a complement of 368 officers and men.
The Compound Engine.
BY WM. H. WEIGHTMAN.
The aim to carry out and employ higher steam pressures, and the advisability of mak-ing the best possible and most economical use of the steam after its generation, gave rise to the present development and intro-duction of the compound engine. The com-pound engine is a combination of the high and low-pressure engines, the high-pressure engine operating with the high initial boiler pressure against a varying lower pressure exhausted to be made use of in a second or -row-pressure cylinder, generally, and prefer-ably connected to exhaust into the vacuum of a condenser. The high-prgssure cylinder, therefor
AMERICAN MACHINIST
3
A standard ratio of areas or diameters of the cylinders in compound engine practice has not been and in all probability will never be settled upon, since surrounding conditions
cylinders, and space and opportunity con-trol the size of the high-pressure cylinder. Naturally, while the mean and final press-ures should be steady, for regular working

of the high-pressure must be such as to furnish an easy supply of steam for required use in the low-pressure cylinder or cylinders. The lower the boiler steam pressure, the larger the higher pressure cylinder must necessarily be. As the initial or boiler press-ure increases, the ratio between the areas of cylinders will increase. The product of the areas of the cylinders by the mean effective steam pressure acting upon the pistons should be as near alike as possible, likewise the initial loads at steam admission should be as near regular and equal as possible. For every increase in the initial pressures, the expansion ratios will increase for equal powers and mean pressures; wish increased initial pressures, however, increased initial strains will be developed upon the several parts. When the low-pressure cylinders are used, their diameters are preferably made alike, and the high-pressure cylinder is made of sufficient size to supply both. The local engine advantage gained by this division of the work of the steam con-sists in the reduced exposure of the steam to extreme temperatures at initial and exhaust ends of the stroke; and, the pressure upon and the work of the pistons is more steady and regular, bringing the work of the metal nearer to its initial rtquirements than would result were the expansion and work accom-plished within the single cylinder. In ordi-nary non compound condensing engines the steam is compelled to meet a sudden change of temperature, since it enters the cylinder almost immediately after the closing of the exhaust to the condenser. The average ex-haust and condenser temperatures is about 150° to 160° Fahr., and the exhaust ports being closed and steam admission com-menced, subjects the steam to a loss of heat in re-heating the cylinder metal to steam pressure temperature, changing some por-tion of the steam to water, effecting what is termed liquefaction. During its expansion and work the steam releases or loses some more of its heat, a portion of which is again taken up from the metal of the cylinder, causing a re-evapora-tion. Such re - heating and re-evapora-
ia use of the expansion abilities of 116

The aim to carry out and employ higher steam pressures, and the advisability of mak-ing the best possible and most economical use of the steam after its generation, gave rise to the present development and intro-duction of the compound engine. The com-pound engine is a combination of the high and low-pressure engines, the high-pressure engine operating with the high initial boiler pressure against a varying lower' pressure exhausted to be made use of in a second or low-pressure cylinder, generally, and prefer-ably connected to exhaust into the vacuum of a condenser.
there f org,
kbett-1; partial use of the expansion abilities of the steam, reserving the balance for the low-pr essure cylinder. The steam is generally exhaust from, '11 high- pres- urecv1 into at, id termediate chamber or chest,where it is held ready for use and ad-mission in-to the low-pressure cylinder. At times there a r c two such low - press-ure cylin-ders, mak-in sr thernm-
The high-pressure cylinder, steam is compelled to meet a sudden change of temperature, since it enters the cylinder almost immediately after the closing of the exhaust to the condenser. The average ex-haust and condenser temperatures is about 150° to 160° Fahr., and the exhaust ports being closed and steam admission com-menced, subjects the steam to a loss of heat in re-heating the cylinder metal to steam pressure temperature, changing some por-tion of the steam to water, effecting what is termed liquefaction. During its expansion and work the steam releases or loses some more of its heat, a portion of which is again taken up from the metal
of the cylinder, causing a re- evapora-tion. Such re - heating and re-evapora-tion, how-ever, 0/lie place too late for en-gine useful-ness, t h e condenser receiving it with the exhaust steam. A portion of this heat trouble is overcome in the com-pound en-gine, since, the varia-tion in tempera-ture occurr-ing only in proportion to the vari-a ti o n in pressures, the cylinder metal takes up and gives out less. This is effected 4he in-piete com-b in at ion that is call-ed a three-cylinder compound engine.

noticed in the present article, but will be SOM.
Cogging Wheels—VII.
BY JOSEPH HORNER.
MARKING OUT AND WORKING.
The cogs having been all driven in and properly secured, they have to be turned, and pitched out, and worked. These mat-ters will occupy the present paper. The turning is done in a metal-turning lathe, and the wheel is revolved on an iron mandrel just as though it were running upon its own shaft. The slide rest roughing and knife tools are used for roughing down and finishing. The turning can be done also with wood turner's gouges, and with scraping chisels, but the slide rest work is to be pre-ferred. Light cuts only should be taken, be-cause heavy cutting will split out the wood, the grain of which outside the shoulders of the tenons is necessarily rather weak. Dur-ing the driving in of the cogs it is very prob-able that incipient fractures of the wood will have occurred, without becoming visible. At such spots the turning' will probably split off pieces of the wood. If so much is broken off a tooth as to leave insufficient for shaping the tooth, then at this stage the broken tooth should be driven out and another substi-tuted, and the turning afterwards proceeded with. In any case there will be a little burr-ing over of the wood during turning, but not sufficient in amount to damage the cog, provided the feed is not heavy and the wood is sound and free from shakes. The turn-ing, to be accurate, should be done with a template like Fig. 47 A if a spur wheel, and like 48 A if a bevel. The pitch diameter should be marked upon the templates a a, and transferred thence to the wheels, and the pitch circles struck round on the faces of the teeth with a diamond point. If striking lines are required for the centers of the faces and flanks of the teeth (see Fig. 52), those also must be struck round while the wheel is in the lathe. It is then ready for marking out. I think now I had better say nothing for the present about the pitching out of a bevel

Fig. 60. ,Eig .63. COGGING
say briefly that in almost all work of this class the cycloidal form is used, and that the only differences between the teeth in ordi-nary iron and iron-toothed wheels and wooden mortise wheels are these: The teeth on the latter are shorter, thicker, and have no flank clearance. First, they are shorter. If in iron and iron-toothed wheels, the pro-portions of length to' pitch are 35-2- pitch above and below pitch line; in mortise wheels they are i of the pitch above and -A below pitch line. Second, they are thicker, and have no flank clearance. In iron and
Fig. WHEELS.
the dividers to the pitch and mark the cen-ters round, it is in large wheels a tedious process, usually requiring several slight re adjustments of the dividers before the last pitch falls into the one from which the divid-ers started. In large wheels, therefore, the task is facilitated by first dividing the pitch circle into six or eight or a dozen large sub-divisions with large compasses or trammels, and then subdividing these sections with dividers for the pitch. The usual method of obtaining tooth curves is by means of one of the odontograph
Then a thin template of zinc, Fig. 55 A, is made and moved round as required, and the dividers set upon that. Some, to save labor, make a template tooth, Fig. 56 A, after the centers and thick-ness lines have been obtained, and placing that upon the ends of the teeth, in its proper position, scribe round its edges. I do not think this method so accurate as the method of scribing lines with compasses before men-tioned. When the tooth centers and tooth forms have been marked out upon one face of the cogs, or when the pitching out only of the tooth centers has been done, the correspond-ing centers have to be marked upon the op-posite face at precise right angles with them. The centers are squared over in several ways, but the following is an accurate and gener-ally followed method. The lines are first scribed perfectly radial across the ends of several of the teeth at roughly equi-distant positions, say at every 10 or 12 teeth. The lines are scribed either by means of a notched strip, Fig. 57, notched to go down over the rim to rest upon the tooth ends, as in Fig. 58, the lines being scribed along the edge a, or radial lines are marked by the simple geometrical meth-od of intersections from equi-distant points, as in Fig. 59, a a representing the points for the tooth thickness, b b intersections of radii, and e the radial center line drawn through those intersections. These lines are carried over the faces either with a tee square, Fig. 60 A, or by the method of intersection, Fig. 61, taking a base line a across three teeth, to insure greater accuracy. The radii b-b give by their intersections the vertical line c. The squared lines c are then carried over the other ends of the teeth, either with the strip, Fig. 57, or by means of intersections, as in Fig. 59, after which the pitching out of the tooth centers and tooth form is done on the second face. Lastly, lines are scribed over with tee square from end to end of the teeth where the face curves come on the outer diameter. These afford a guide during-the working out. The cogs are cut out mostly with gouge and chisel, the rebate plane being only of service for finishing off the termination of the faces. At tile beginning, the paring

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gouge, chisel and mallet are used to remove the bulk of the wood. As there is risk of the concussion of the blows splitting out the short grain, their direction should be rather diago-nally, and away from the rim outwards in the direction of the line A A, Fig. 62, and as more and more is removed, inclining to parallel. When the bulk of the stuff has been removed the curves of faces and flanks are set in a lit-tle way with paring gouge and chisel, and the edges whitened with chalk or reddened with red lead in oil. The flanks and faces are now worked straight across from one side to the other with paring gouge and chisel, and the setting in and coloring of the curves at the ends prevents risk of the lines being cut un der with the gouge and chisel. A small, thin, narrow straight-edge is used with coloring matter, to test the straightness of the flanks as the work proceeds—a quite essential pre-caution when the cutting is done with gouge and chisel, tools 'which do not possess the initial faculty of guidance possess( d by the plane. The plane, as we see, can only be used for the extreme faces, Fig. 63 A. When the teeth are worked accurately nothing more is done to them except to give them a good oiling with linseed oil with a brush or rag. This imparts a slight hard-ness and a good appearance to the surface. The marking out of bevel wheel cogs necessarily proceeds on different methods. Still there is no more actual difficulty, but only more time required with the latter. Since a bevel wheel is a frustum of a cone the tooth centers, roots, points, flanks, and faces all run in exact planes to the apex A of the cone, Fig. 64. The shapes of the teeth are marked out accordingly on the drawing from which the wheel is Made, and are transferred to the ends of the cogs. I need not go into the details of the operation, but the drawing, Fig. 64, will convey the whole , meaning of the process to the mind of a pat-tern maker. At B there is the sectional form of the tooth, and at C D the forms and di-mensions of their outlines on the large and small diameters respectively are seen pro-jected. The radii are not taken along the semi diameters a b c d, but along the project-ed radii e b, f 4, on lines at right angles with A e. These are then drawn at C D. The thickness of the cogs on the-small diameter is
The small grooved pulley on the arm over which the slack side of the rope passes holds the rope up and causes it to encircle nearly the whole of the driving pulley, making it next to impossible for the rope to slip. It is manufactured by Albert L. Colburn, New Haven, Conn.
Two-spindle Boring and Mortising Machine.

This machine will bore two holes at once,
between centers. Weight, abo-ut 500 pounds. Either of these machines can be furnished with hand-lever and a treadle. The manu-facturer is P. Pryibil, 498-510 W. 41st street, New York City.
Two firemen who were on the steamer "Alice Blanchard " on a trip to the Yukon River brought back two novel Aleut canoes. The boats are made of rawhide supported by horizontal ribs The only opening is a circular hole in the center large enough for
LETTERS FROM PRACTICAL MEN.
Fly-wheels. Editor American Machinist : In the matter of fly-wheel diameter and weight, I like to apply Matthew Baldwin's old rule in locomotive construction : " Make it about right, and then throw in another ton of iron." With this it is suitable to remember J. A. Fay & Co.'s rule for horse-power to drive wood-working machinery: " A little too much belt power is about enough." ROBERT GRIMSHAW.

SMALL PORTABLE DRILLING MACHINE.
and the line joining the center of the two holes may be at any desired angle to the table, from horizontal, which is the position shown in the engraving, to the vertical, or where one spindle would be vertically over the other. The table can be set 10" below the centers of spindles. It slides .forward and back
a man's body so that he can sit down. A flap of rawhide surrounds the hole, and when the occupant plants himself in the bot-tom of the craft he draws this flap up, fas-tening it tightly around his body under the arms. This makes the boat practically water-tight, and he can paddle along in the rough-est kind of weather without danger of drown-
Why Are Gears Noisy ? Editor American Machinist : In reading " Gascon's Discourses Upon Some Shortcomings in Text-books," by Jarno, I am led to attempt to put a few thoughts of my own on the same subject be-fore the readers of the AMERICAN MACHINIST.

Take any of the text-books that are now published treating upon " Involute Gear-ing "—all give a theory of constructing the gear 8ooth, and gears so constructed fail to give good practical results. In fact, some will not mesh at all. What the average ma-chinist wants is this gear question discussed in plain, every-day talk. Most writers, in explaining the theory of gearing, use technical terms, which, while probably correct, are understood by but few of the mechanics having, anything to do with gearing. The writer is one of that class who repre-sent the practical side of gearing, and what I shall say will be the result of a long and varied practice. First, I will ask the professors a few ques-tions. Can they tell us what amount of interfer-ence there is in the true involute in a pair of gears, say 3 P 19 and 69 T, and can they tell how to draw the form of teeth for these gears so they will run smoothly and quietly?. Why do gears make a noise ? How should the teeth bear upon each other to prevent a noise ? Which gear is the best and smoothest run-ning—the 144-°, 18°, 20°, or 24° pressure angle, and why ? T
wil t.ry to SITICITX7.r rviinc

start add 8-12-24

test 8-12-24

Take any of the text-books that are now published treating upon " Involute Gearing "—all give a theory of constructing the gear 8ooth, and gears so constructed fail to give good practical results. In fact, some will not mesh at all. What the average ma-chinist wants is this gear question discussed in plain, every-day talk. Most writers, in explaining the theory of gearing, use technical terms, which, while probably correct, are understood by but few of the mechanics having, anything to do with gearing. The writer is one of that class who repre-sent the practical side of gearing, and what I shall say will be the result of a long and varied practice. First, I will ask the professors a few ques-tions. Can they tell us what amount of interfer-ence there is in the true involute in a pair of gears, say 3 P 19 and 69 T, and can they tell how to draw the form of teeth for these gears so they will run smoothly and quietly?. Why do gears make a noise ? How should the teeth bear upon each other to prevent a noise ? Which gear is the best and smoothest running—the 144-°, 18°, 20°, or 24° pressure angle, and why ?

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the action being too near the line of centers. Another bad feature is that as you approach tho rack it makes the teeth too pointed. With 14i° we do not hear that thumping, because the action is nearer the line of cen-ters. There is a quick, inward motion toward the center. As the teeth meet each other with less ob-liquity they have less tendency to push the gears apart, and more of a direct push, and consequently less power is needed to run Clem, and there is less strain. The life of such gears will be much longer, and the original shape will be retained to a greater extent. Some makers of gear cutters use a large pressure angle, and make the addendum short. This is objectionable, because it makes a stubby tooth, especially so in wheels with large numbers of teeth. In my opinion; this is not the proper way. I say make the addendum longer rather than shorter for the best results in nice running gears. Now I would not object to 20° for 3 P and coarser, but in these pitches I would suggest that the tooth in pinion be made thicker than the regular one, rid the wheel tooth correspondingly thinner, so as to equal-ize the strength. For example, 1 P t = 1.0472 for gear for pinion t = 1.0872. This would make pinion of 12-tooth as strong as teeth in wheel. But only in cases where strength is abso-lutely necessary would I suggest the 20° angle, for it is a noisy gear at best, and in case of a small pinion running into a large wheel, it has but one tooth in contact most of the time, which makes it noisy. A PALE-FACE WORKMAN AT THE BENCH.
Emery Wheels. Editor American Machinist: Mr. George B. Grant, in the last number of the AMERICAN MACHINIST, has a correct and very forcible protest against the use of emery wheels of the shape which he illus-trates. As his criticism might lead many to condemn the use of any annular surface for grinding purposes, and as this use is often
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suppose that I am in any way responsible for the fact that 13 threads per inch is stand-ard for half inch bolts, though the tone of his letter would seem to indicate that. Wil-liam Sellers, the Franklyn Institute, the U. S. Navy, the Master Car Builders Associa-tion, Master Mechanics Association, and many of the leading shops of the country, are responsible for this, and the movement in

EMERY WHEELS.
this direction has gone far enough to show that standard threads are of great advantage to all who have anything to do with ma-chinery. Of course, I do not expect that Mr. Shel-lenback's or any other 24" lathe will be used for manufacturing half-inch bolts, and I know that no lathe of any make or of any swing should be used for such a purpose; but I take it that Mr. Shellenback's lathe is especially well adapted to jobbing work where changes are frequent, and where the work may be anything whatever that comes within its capacity. For instance, it often happens that shafts of considerable length that must be, perhaps, turned in the only 24" lathe in the jobbing shop, require to be threaded at the end for a nut. This nut should be standard; and suppose it happens to be half-inch, and the lathe won't cut 13 threads ? Why, then something else is sub-
struction, and in a country like this, some-times called the Switzerland of America, the case was made worse by the locomotives be-ing cut off by slides, etc., from any work-shop for months at a time. One English engine worked nine months without going near the shops, or washing out, and the only repairs during that time were done by the engineer who was driving it, so that when the company took possession the amount of mud-burnt fire boxes and repairs necessary to motion, etc., was appalling. To bring things into anything like a satisfactory state with the small staff of mechanics and work-shops at the company's disposal was neces-sarily a work of time, but at the present mo-ment a good on-time passenger and freight service is maintained by the English engines, and there is nothing to complain about their steaming qualities, now that they have been re-tubed and tons of mud removed from their boilers. We all know the desirability of having as much weight upon the drivers as possible, but on a line like that of Costa Rica, cut on the side of a range of mountains, and running for miles with a sheer descent on the other side of 1,500 feet, and with an almost constant succession of 20' curves, it is also a desirable thing to have a good guide in the shape of a heavily-weighted bogie, even if it has to be done at the expense of hauling power. The dump and shaker grates are not con-sidered a necessity in England with its su-perior coal, and where the fires are drawn every night, not by dropping the bars, as your correspondent says, but with a long shovel through the fire doors. At the same time 1 admit that they will be an advantage here, and will no doubt be fitted on the mountain engines now in construction. There are two distinct climates in this country, and up here we suffer from neither heat nor cold, and the old bands on the Cen-tral Division would be sorry to change their lot, although they may give a passing sigh for the succulent oy.ster or the juicy mutton of the North. Below, near the coast, is sim ply life in the tropics, and of a rough order. FAIR PLAY.
" A Rolling Stone" and W. both end up by giving some advice to the boys ; the former writer says : " Let no one take the foregoing as a recommendation to tramp unless compelled to. Still, if forced to it, do not despair of success." The latter writer says : " Do not leave one shop for another till you see some bene-fit for a change." Under these circumstances I would tramp some myself. A PRACTICAL MACHINIST.
Tempering Steel—That Chinese Bell. Editor American Machinist : I have noticed, from time to time, articles in the AMERICAN MACHINIST on the treat-ment of steel. These articles are very interesting to me, and, when possible, I always give any method of treating steel new to me a I have the greatest trouble in getting two orders of the same kind of steel alikL, method of tempering milling cutters is to heat them in a charcoal fire to a low red, then dust them with powdered prussiate of potash, return to the fire, and heat up to a dull red and dip in strong brine. I take care to take the chill off the brine in cold weather, and think I can harden a cutter by this method at a lower heat than any other I have tried. 1 want to say a word in regard to Prof. Sweet's article on boasting. I think the Pro-fessor would have done a great deal more good if he had taken the trouble to find out how that little bell was made. From his de-scription he must have seen the blacksmith, as he minutely describes his kit. I am very sure that there are a great many Yankees that would sit up nights to see the job done, and never leave China until they
saw it.
JEWITT. A New Pipe Wrench.
We give with this an illustration of a new pipe and nut wrench invented by Mr. J..L. Taylor. Parts of the sliding jaw are repre-sented as broken away, to show the construc-tion of the wrench. As will be seen, the wrench consists essen-

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RIVETT BENCH LATHE. The body is a box-shaped casting, in one piece, very strong and rigid, and it can be placed on any good floor without a special fo(lthdation.

RIVETT BENCH LATHE.
The body is a box-shaped casting, in one piece, very strong and rigid, and it can be placed on any good floor without a special fo(lthdation.