pg-2 AMERICAN MACHINIST  Oct-17-1892
moved from one stop to the other. The number of divisions selected must be an exact divisor of the total number into which the scale is divided. The scale is tested by adjusting the cross-hair of the microscope directly over one of the divisions, while the sliding table is against one of the stops, after which the table is moved until the second stop is reached. If the stops are set precisely in the correct position, and the scale is without error, the cross-hair of the microscope would fall directly over the mark on the scale, but, ordinarily, the cross-hair will not fall over the line, and the amount of deviation is measured by a micrometer. Each succeeding portion of the scale is gone over in this way. After the entire scale is gone over, the sum of the micrometer read-ings is taken, and that portion of the error due to setting the stops eliminated by sub-tracting the mean value of the corrections from each. This gives the relative error of each successive subdivision; to obtain the accumulated or total error reckoned from the initial point we sum the series. In the case of the meter scale, the error of the middle graduation was first determined, and the errors for the decimeters worked over until the error for the middle division came the same by the two methods. The discussion of this paper was mainly in regard to the difficulty of obtaining a perfectly true surface. Mr. J. A. Brashear stated that in special cases he had spent several weeks in making a plan surface for optical purposes two inches wSeveral other members pres-ent gave' t views in regard to the proper methods of grinding to a true surface. Prof. Rogers replied that he did not strive to obtain a mathematical true surface in his bars; his test was to move a microscope, used '"oheoglin testing the graduations and having a high magnifying power, along the face of the-bar; if this ritmained in focus, he considered the s accurate enough for his purpose.

 
-10°18 USE OF LONG STEEL TAPES IN 
so that by no means could the operators overstrain the tape. Temperature observa-tions were made in each case, three special thermometers being used w, {`h blackened bulbs, so that the surface had approximately the same radiating power as the tape. It was proved by the comparator that, with ordinarily careful handling, there was no variation in the length of the 100 meter tapes after long use. To test the efficiency of the steel tapes when used in the field,'A kilometer was measured by means of the iced bar, and this kilometer used as a stand-ard. It was found that the probable error of a single measurement of this kilometer by means of the steel tapes was about one part in 500,000, and that the probable error of the average of a number of observations was about one part in 1,500,000. So that the general conclusion arrived at is, that for measuring base lines, steel tapes, as standard-ized by the iced bar comparator, will give ample accuracy. The time required to make duplicate measures of the kilometer with the tapes is about one hour, and in spe-cial cases it was measured in one direction in twenty minutes. The method of measuring the standard kilometer by means of the iced bar apparatus, and probable error of the total length, was given in another section of the society, but as it is of interest in connec-tion with the present paper, the following table is here given, which compares the probable errors involved, with the results ob-tained by previous workers in the same line : 

bar; if this litrained in focus, he considered the Su accurate enough for his purpose. 
ON " USE OF LONG STEEL TAPES IN MEASURING BASE LINE. REPORT OF U. S. C. AND G. SURVEY. 
BY R. S. WOODWARD, WASHINGTON, D. C. 
A method of standardizing steel tapes by means of an iced bar comparator was first described, after which numerous experi-ments were presented that showed the error involved in using such tapes in measuring a base line one kilometer long. The iced bar employed in the comparator consists of a bar of steel, on which are lines five meters apart, at a temperature of 32 degrees Fahr. To preserve the bar at this temperature it is surrounded by ice. The whole is mounted on a carriage that travels on a small railway. In measuring off the length of the com-parator, which in most cases was 100 meters, the cross-hairs of two microscopes were first made to coincide with the lines on the bar. The bar was then moved forward, and the mark on the end nearest the starting point placed under one of the set microscopes. A third microscope was then set over the end away from the starting point. The micro scopes were mounted on wooden posts. At the ends of the comparator two stones arc solidly imbedded in the earth. In each of these stones a rounded brass projection is imbedded, to mark the ends of the com-parator. To place the microscopes directly over these end points a special device con-taining a level is used. Having obtained the proper setting of two microscopes that are the length of the comparator apart, the tape is held under them in a way that was found to be the most convenient and reliable in field work. Stakes are set ten meters apart along the line to be measured, and in the side of these round steel wire nails are driven. The tape is supported on these nails. The corrections necessary to apply, if the posts are set at a greater distance, as in crossing a stream, can be easily computed from data furnished by preliminary experi-ments. The tension of the tape was made the same, about 25 pounds in all measure-ments, by means of a spring balance at one of its ends, a breaking piece being inserted, 
quarter that of any other method presfiously adopted. The greatest source of error was found to be the difficulty of determining the tempera-ture of the tape correctly. It is generally supposed that a cloudy day is preferable for measuring with steel tapes, but the experi-ments indicated that such was not the case. The best time was found to be in the evening, while dew was being deposited.. Prof. Rogers stated that he agreed with Mr. Woodward that the temperature ele-ment was the greatest source of error in measurements of length. In his opinion the exact results obtained with the tapes was due to the fact that they were of a small mass, and partook readily of the same tem-perature as the air. Prof. S. W. Robinson gave a description of the method employed in measuring a base-line in the ordinary way. A clearing is pre-pared and graded as carefully as a railway bed, and the apparatus employed is very bulky. He also mentioned another methed that he had employed some years ago, of measuring with a steel piano wire having circular pieces fastened on it at the measuring points. Around the circular pieces V-shaped grooves were cut. In using the wire the circular pieces were held against ordinary surveying pins. If the operator happened to pull too hard on the wire while it was be-ing held against the pin, the form of the groove was such that the circular piece would slip by the pin without tending to displace it. This method was recommended only where moderate accuracy is required. 
 

Launch of the Cunard Twin-screw

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pg-2 AMERICAN MACHINIST  Oct-17-1892
moved from one stop to the other. The number of divisions selected must be an exact divisor of the total number into which the scale is divided. The scale is tested by adjusting the cross-hair of the microscope directly over one of the divisions, while the sliding table is against one of the stops, after which the table is moved until the second stop is reached. If the stops are set precisely in the correct position, and the scale is without error, the cross-hair of the microscope would fall directly over the mark on the scale, but, ordinarily, the cross-hair will not fall over the line, and the amount of deviation is measured by a micrometer. Each succeeding portion of the scale is gone over in this way. After the entire scale is gone over, the sum of the micrometer read-ings is taken, and that portion of the error due to setting the stops eliminated by sub-tracting the mean value of the corrections from each. This gives the relative error of each successive subdivision; to obtain the accumulated or total error reckoned from the initial point we sum the series. In the case of the meter scale, the error of the middle graduation was first determined, and the errors for the decimeters worked over until the error for the middle division came the same by the two methods. The discussion of this paper was mainly in regard to the difficulty of obtaining a perfectly true surface. Mr. J. A. Brashear stated that in special cases he had spent several weeks in making a plan surface for optical purposes two inches wSeveral other members pres-ent gave' t views in regard to the proper methods of grinding to a true surface. Prof. Rogers replied that he did not strive to obtain a mathematical true surface in his bars; his test was to move a microscope, used '"oheoglin testing the graduations and having a high magnifying power, along the face of the-bar; if this ritmained in focus, he considered the s accurate enough for his purpose.

pg-14 Ads     AMERICAN MACHINIST   Dec 17, 1887 

cam to contend with I have not, as I use flat plates; the cam curves developed upon them, and fastened to the slide C. As the worm controls the movement of both the spindle and slide, the speed is the same in both. The slide A can be fastened to any milling machine platen; a pin with a roll is driven into it, and passes through the cross-slide to the former, which drives the spindle head B B forward or back as the spindle rotates. The length of the formers is the circumfer-ence of the worm gear on the pitch line plus what is necessary for fastening. In using this. fixture you would have to keep this in mind in timing cams, as the same length of former does for all sized cams. By hinging head B, and removing slide C, and replacing by angle plate D with roll on, and placing former on spindle extension, you can cut any shape or kind of cam with the same fixt-ure. This may be an old idea, but was new with me. C. F. SMITH. 
Flies and Drawing Ink—Learning—American Boasting. Editor American Machinist : It has been my experience to find flies with a very decided penchant for Higgins drawing inks, and have found muriatic acid a good antidote to drive them back to their proper sphere. I tried hartshorn, but don't know whether the flies became accustomed to the combination or evaporation took place. I take exception to your rubbing fresh ink every morning and noon, because it takes time; time is money, and, furthermore, a draftsman cannot " think " and rub ink at the same time. W. goes at the kernel of the nut in good shape in his " Practical Talk to the Boys." The apprenticeship question is one that demagogue workmen and fool employers always try to cDmbat and surround with mystery. My advice to the young man de-termined to succeed as a mechanic, is to go on and up. Don't change from your present place for the sake of more pay, but if you are not learning now, change to the shop where you will learn, and opportunities be given for you to learn. I would just like to say one thing on the " American Boasting " discussion Mr. 
bors. Now over here in the old country I believe I should be safe in saying that nine persons out of ten, if asked the question, would say: "Americans! Why, of course, they are all boast" ; they would probably say so, whether they knew anything about Ameri-cans or not, as it is generally accepted as an axiom on this side the water. Where there is smoke one is justified in suspecting fire. Personally, however, I believe that what we so generally put down as brag on the part of our American cousins is more a matter of 
than we find their prototypes over here to be.. There are few civilized countries who do not possess some, perhaps many reasons for national pride, and which may be far from the region of boast ; but in this matter it is for we machini'ts and engineers to con-fine ourselves to our profession. Myself, as an engineer, I ignore the demarkation of territory; as an engineer I claim the world as my country, and all engineers as my countrymen. feel nearer akin to that brown-skinned fellow-creature and fellow-machinist who made 

pleasure, not the boast, is ours, we machinist's and engineers. As .hinists we are working in differ count la,' different conditio may learn from each other and adm. other's good work. Our endeavor she by our works to show the best that can done under the conditions we are placed in. It is our destiny, more than that of any other profession, to alter the face of the world, to open up and utilize her resources for the benefit of mankind. You of us in America are showing us how to make machine tools, Corliss engines, etc., and how to illustrate them and print their description, and you have shown us the way in systematic production, which is the best thing, perhaps, you ever have shown us. We others in the rest of the world are also doing something; let us waste no time in boasting of what we have done, but show the world how much better we can do. FRANK LESTER, M. Inst., M. E. England. 

New MILLING MACHINE. 
The accompanying illustrations show a new milling machine, and a patented circular milling attachment recently put on the mar-ket by the States Machine Co., of Hartford, Conn. Fig. 1 shows the milling machine, and, as will be seen, its construction possesses stabil-ity, compactness and simplicity ; it also em-braces some new and advantageous features. The frame, including the arm supports, is one solid casting, and designed to resist with safety all strains to which it may be sub-jected. The cylindrical arm is placed 12 inches above the spindle center ; for large machines it is 54 inches diameter. Its bear-ing extends throughout the whole width of frame, and the arm has a large range of adjustment. The pendant is loose, and is also adjustable, so that it may be dropped inside of the work, where it cannot be swung in. The back gears lie entirely inside of the frame, and are out of the way. The main spindle is large in proportion it runs in double-tapered steel bushings, hardened and ground to fit, and provided with means for taking up at both ends of the bearings. The end of the main spindle is not only bored out tapered, but it is, throw- 

place for the sake of more pay, but if you are not learning now, change to the shop where you will learn, and opportunities be given for you to learn. I would just like to say one thing on the " American Boasting " discussion Mr. Sweet has not said one word about any other nation's boasters. I have put a Yankee and an English engineer together, and two greater braggarts I never listened to; they had performed wonderful things, but not half so great as they imagined. The Scotch-man does not brag much; he is after pelf. The German is a combination of the Eng-lishman and Yankee in boasting, and excels his English brother in copying and purloin-ing the products of others' brains. But the nervy Frenchman, with his electric waltzing from alpha to omega in mechanics, and back again, searching for ways and means to ac-complish desired results, without ever telling us who he was or where he came from, and his more slow-going, colder blooded brother mechanics from Norway and Sweden have always been my ideals. Being a student of human nature, as well as a mechanic, I have long noted these things, and feel that my friend Sweet is perfectly justified, so far. There is an old and true proverb, thusly, " He that htimbleth himself shall be ex-alted." This has been Professor Sweet's maxim throughout his mechanical life, and unconsciously too, I think. How many of us who stand ready to score and criticise his honesty in " giving the devil his due " can say the proverb fits us ? THE OLD MAN. 
American Boasting. Editor American Machinist : " Spare the rod and spoil the child" is perhaps one of the most practical proverbs in the language; at all events it is so, without doubt, in the opinion of the child. American machinists are favored in hav-ing so judicious a wielder of the rod as they possess in the person of Prof. Sweet. To be brought to task for one's shortcomings is a most salutary exercise, and cannot fail to benefit. As a rule, if you want to know your failings, and have them shown up full size, it is only necessary to apply to one's neigh-

    habit, a national habit, than a real intention to boast. If we get down to the bed rock of the thing, the real intentional boast, I believe we should find as great a proportion, especi-ally of mechanical boasters, in Great Britain as in the United States; at all events, if not boasters, individuals who possess a most gi-gantic opinion of themselves, which amounts to the same thing, and unfortunately we generally find that this class of people base their pretensions on a most quicksandy foundation, and that real merit loves seclu sion. It is to be hoped that those Americans who do boast are more justified in doing so 
the curious ball, or to that African smith who forged those curious chains, or to that American who made that highly-finished automatic screw machine, than I do to my lawyer neighbor next door, and wherever my profession achieves a triumph of ingenu-ity, of skill, of accuracy and finish of work-manship, I share in the pride of it—it may be in my own little works, it may be in India, Japan, Germany, America, I care not where; I do not quarrel as to what particular country belongs the honor of the steam engine, the electric dynamo, or any other mechanical triumph over nature; the honor is ours, the 
frame, and are out of the way.

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