US62546A - Improved method of tempering circular saws - Google Patents

Description

'1. 4UPPmCOTt. A Method of Tempering Circular Saws.

Patented March 5, 1867.

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IMPROVED METHOD 0I' TEMPERING GIRGULAR SAWS.

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TO ALLWHOM -IT MAY GONCERN.:

Be it known that I, JOHN LIPPINCOTLO the city of Pittsburg, in the county of Allegheny, and State of Pennsylvania, have invented a new and useful improvement in Mode of Drawing the' Temperof Saws; and I dol hereby declare thefollowing to be a. full, clear, and exact description thereof, reference being had to the accompanying drawing, forming part of this speciiication, in which- Figure I is a representation of a circular s aw placed upon the carriage used in my mode of drawing the temper of saws, the saw and carriage being viewed from the under side.

Figure 2 is a vertical section through the centre of the saw andcarriage.

Like letters designate similar parts in both iigures.

It is a matter -of the utmost importance in the manufacture of saws that all parts of the saw-plate should be of uniform temper; this is especially the case in large circular saws, which are dillicult and expensive to malte, because if the saw-plate is of uneven temper, being hard in some places vand soft Ain others, itis very diiiicult to set the teeth which are too hard, and they frequently break in the operation or crumble atthe points, while the teeth in the soft portion ofthe plate will not carry an edge or hold the set given to them. This want of uniformity in the temper of saws is a very common occurrence, and larises from the practical difficulty of drawing the temper of a steel plate of large diameter by the methods heretofore employed for that purpose.

The mode of hardening and tempering saws in general use is to heat them in a furnace and then plunge them in a bath of oil, by which the steel is hardened. -This process has the effect of warping and lrinking the steel plate to such a degree that its surface becomes very uneven. The hardened plate is then removed to a furnace .having a level bed, on which the saw-plate is laid. It is then exposed to suificien heat to draw the temper down to the proper point.' As it is impossible to have the furnace'of exactly uniform heat all points, the saw-plate is turned round and round more or less rapidly by means of long hooked rods, operated by workmen from the open mouth of the furnace, so that no portion of the saw-plate, excepting its centre, continues for any considerable length of" time in the same part of the furnace. This mode of operation would answer the purpose very well if the saw-plate touched the bed of the furnace at all points on its surface. This', however, is not the case, owing to the warped and uneven surface of the saw-plate and as those parte of the plate which are in contact with the bed of the furnace become more rapidly heated, the temper of those parts is drawn down to the proper point before the other parts of the saw-plate, which do not bench the furnace hed, are suiiiciently heated, and thus of 'necessity the saw-plate will be harder at seme points than at others.

To remedy this defect is the object of my invention, which consists in elevating the saw-plate above the level of the bed of the furnace in such a manner that it can be rotated on its axis freely and without coming in contact, at any point at or near its circumference, either' with the furnace or with the device 'used for sup portingfthe saw. l

Another object of my invention is to support the saw-plate intne furnace in such a manner that it can be more easily and rapidly `rotated on its axis, and also' be readily inserted into or drawn out of the furnace or brought to the mouth of. the furnace to enableA the workman to inspect its condition from time to time.

To enable others skilled in the art to use my invention, I will proceed to explainthe manner in which I carry it into practical operation.

In the accompanying drawing, a represents a small carriage, made of iron, about three inches in height' and about ten or twelve inches square, or of such diameter as to Vafford sniiicient support to the saw-plate without extending too near its periphery. This carriage may be furnished with four wheels, fixed on' axles c, having their bearing in the sides of the carriage or attached to the under side of the top plate ai of the carriage. The top plate d should be a level'snrface. A long rod, e, attached to one end of the carriage, enables it to be convenientlyoperated in introducing it into the furnace and removing it therefrom, and. moving yit about fromY place to place within the furnace. In the centre of the bed-plate is a low vertical spindle,f, which projects upwards from the top' of the carriage and serves as a mandrel to receive the saw, the eye of the. saw, which is in the centre of the saw-plate g, receiving the mandrel or spindle f, and the sawplate resting on the top or bed-plate d of the carriage, as shown in fig. 2. The spindle f may be made a separate piece from the carriage and inserted in a suitable hole in the top or bed-plate d.

The mode of operation is es follows: The earriegqfbefore receiving the saw-pla-te, is placed inside ot' the heated furnace, so as to he as nenrly as possible of the sume temperature as the furnace. It is then drawn out, and -tlic hardened mwplete is-pla-ced upon it with thcmandrel f inserted through its eye. The carriage is thon wheeled bock into the furnace, und the workman, oy means-of a hooked rod, turns the scwplute round end round on its mandi-ei more 'or less rapidly, according to the heat of the furnace. During the process he occasionally 'draws the carriage to the mouth of the furnace, in order to ascertain hy the appearance ofthe sow when it hee renc-hed the required temper. Circular saws ore frequently inode six feet in diameter, and by' the old method of operation it was hard work. for two men to turn the saw on the bed of the furnace. By the use of the carriage employed by me for this purpose, owing to the small diameter of the-carriage in comu parison with that of the saw, there is but n small port of itssurfnceiin contact with its support; one man can manogeit with ease, und the rotation of the saw can be more constantly maintained, and thereby a much more uniform result attained. It is` importent to make the surface ofthe carriage on which the saw rests as small as is consistent withn suicient support, so cs to leave as large o. portion as possible of the sew-plate towards its circumference free from contact either with theoarriage or with the bottom of the furnace, because the contact of the Saw-plate with either would tend to withdrew the heut freni that portion of the saw more rapidly, ond thus produce an uneven-'temper'.

I om awarel that steel tools, such as axes, dsc., have been tempered by being placed upon. a revolving' metallic wheel, caused to revolve within u heated furnace, but this would not answer for circular saws, as in that cese the steel tools ure placed entirely within the circumference of the revolving wheel', while my object is t`o place the son as for ns possible outside of the carriage which supports it, and to cause the sew to revolve on and not with its support, so as to obvinte the injurious efect of contact with another metnllic surface of that portion of the saw-plate `which necessarily touches the carriage' in which it is supported.

I do not desire to limit myself to the precise vInode of suspending or supporting the saw within the fur nace hereinbefoie described, os other devices might he used; but that which I hnvedeecrihed I have found on trial to be very successful and convenient, as it not only secures the main object, e uniform temper in the vsaw-plete, but enables the saw to be more easily handled.

What I claim as my invention, and desire to secure by Letters Potent, is- I 1. A platform for sustaining circular' saws above theloor of the temperiugd'urnuce, constructed to support by conteo*l the central portion of the saw only, thus leaving the marginal portion of the saw free from contact with the platform or with the floor of the furnace, substantially as described.

2. The iron carriage, constructed substantially as herenbefore described, for introducing the saw-plate into the furnace, supporting and adjusting the sume during the process of drawing the temper, und for withdrawing it from the furnace when the tempering process is completed.

In testimony-whereof, I, the said-JOHN LIP'PlNCOrT, have hereunto set my hand in presence of- JOHN LIPPINOOTT.

Witnesses:

W. D. LEWIS, ALLAN C. Biurnwnnne

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