US73082A - Improvement in straight-edges - Google Patents

Description

@uiten glatte geg-stent @frn sAMUEL DARLING, `o F BANGOR, MAINE.-

4Leim-s Patent No.' 73,082, @faz Tammy 7, 186s.

IMPROVEMENT IN STRAIGHT-EDGES.

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TO 'ALL WHOM IT MAY CONCERN:

Be it known that I, SAMUEL DARLING, of Bangor, inthe county vof Penobscot, and State ofMaine, have invented certain Improvements in Straight-Edges; and I do hereby declare that the following, taken `in connection with the drawings which accompany and form part of this specification, is a description of my invention suicicnt to enable those skilled in the art topractise it.

The object of my invention is the production of a tool or implement,'usually designated by machinists and artisans, a straight-edge, which shall have greater durability and toughness, less liability to be fractured or bruised, andgreatcr hardness at its edges than any heretofore known or used, and which shall, also, when made with a graduated scale thereon, to serve as a rule or measure, insure great accuracy and reliability in' such scale, as well throughout its lentire length, as also for each of its aliquot parts into which it may be divided and subdivided. l l' Straight-edges, as heretofore made, have been usually formed from steel or other metal which is of homogeneous 'character and hardness throughout. If this be a soft metal, the implement, from its frequent handling and being left about, and thrown down upon the' benches amongst other metal articles or tools, is constantly liable to 'become indented or nicked at it edges and corners, until soon it becomes Aso injured and untrue as to be valueless.

If, in order to avoid these liabilities'todamage, it be made of harder material, such as hardened 'plate-steel,I and of homogeneous character and texture throughout, it is in such case, by reason of its brittle nature, in

constant'danger ot' being fractured or broken, and inleither case rendered useless.

Such tools being frequently broken, and even from slight blows and shocks, torwhich, in a machine-shop, they are constantly subject, it is, even as a mere matter of economy only, highly important to provide 'a straighti edge, which, whilst possessing at its edges the requisite degree of hardness for all purposes for'which it may'be used, shall at the same 'time have its mass or body, except at or near the edges, of such character or texture as to be but little, if any, liable to fracture, indentation, cr abrasion, and thus serve'to preserve the entire instrument for along period in eliicient working condition. Such a straight-edge forms thesubject of my presentinvention.

Figure 1, ofthe accompanying sheet of drawings, represents my improved straight-edge, with a scale graduated thereon in the manner hereinafter described, and after the same has been polished, ready fo'ruse; and

Figure Zreprcsents the same, after the edges thereof have been hardened, but before the surface has been ground or polished.

Figures 3, 4, and 5, represent modiclations and cross-sections ofthe saine.

In making my improved straight-edge, I take a pieee of steel plate, of the length, breadth, a'nd thickness desired, and heat it to a proper temperature and dip it into water; but before so heating anda dipping it, I confine the plate between two bl'ocks of iron, and-in order to limit the eifects'of the hardening-processtothe edges only, I allow the edges so to be hardened, to project beyond the said conining-blocks. The two blocks and the interposed plate are then heated together, and while the blocks serve to prevent the contact of the water with the heated plate, except at its projecting edges, they also serve t0 keep up'the temperature of the centre of'the plate, so that it does not cool so rapidly as to become brittle. Thesame result may be attained by tempering or hardening the edges by pressure between surfaces of cold iron, leaving the centre unchanged. After being thustempered, thc plate, it warped, as it is apt to be by the tempering-process, isA rendered true by hammering,`

and its edges ground straight and smooth, the opposite onesbeing made parallel.

A straight-edge cannot long remain accurate when its edges are soft, and easily worn or indented; but if the whole plate be hardened alike, besides being in such case brittle, it becomes very much warped and twisted, and being in this state very refractory, these warps and twists do not admit of being hammered out. By my improvement, however, the edges alone being hardened, the whole plate admits of being hammered on the sides to remove the warps and twists incident to the hardening-process.

My manner of obtaining the correct graduation of the hardened straighteedge is as follows: I find by experiment that the edges will, in the hardening-process, expand about one twenty-fifth (315) afan inch to the foot. I therefore eut and graduate them, before hardening the edges accurately, to one twenty-fifth of an inch to the foot short ofthe standard measure.

In preparing and hardening the edges of a number of plates, it is found, however, that they will not all expand alike. I, however, make them all alike at first, and afterwards bring or reduce each one to the exact standard, by drawing the temper. In'order to do this, theymust all be made long enough to permit this reducv Vtio/n or shortening. To effect this, I use a hot bath of oil or tallow, and the more the straight-edge needs to be shortened, the hotter the bath must be. The degree of"l heat necessary for this purpose must be learned by,4

practice. If one edge be longer than the other, then that edge alonemust be p'ut into the bath, until it be brought. down tothe true standard of the other; andthe edge not so being heated may be clamped with metal when necessary to kleep it from heating.

It is apparent from the above that either or both edges, as the case 4may require, and to a greater or less extent, may be contracted, until the precise desired standard be obtained.

It is oi'ten necessary or desirable to have a straight-edge of great length, even to the extent of twenty feet or thereabouts. To make such a one in a single piece would be verydiiiicult and inconvenient, if not impracticable, I therefore make it'in sections, of, say, four straight-edges, each five feet long, andeach with ',hardcned edges, made as above described; 'and after iii-st making in each two or more slots, in a direction transverse of their lengths, for the reception of screws, I aiiix these sections, placed end to end, by meanspf screws, to a wide, well-seasoned board, and secure them in position, so that their hardened edges shall be in a-continuous straight line and in order to true these edges before finally -securing them in position, I make use of another straight-edge to true them by. The screws and slots admit also ot' readjustment of the whole at any time, if by accident or otherwise the parts get displaced or out of true, or if the wooden base should spring by seasoning, tc. Instead oi' a board as such foundation or support for the several section of hardened straight-edges, a sheetef metal may be used.

'i'o make a hardened straight-edge of six feet in length, I would aiiix two pieces, three feet each in length, to a six-feet soft metal-plate, and then true them by a four-feet straight-edge. An edge nearer straight and more reliable-for one of this length,-could bc obtained in this way than by making it in a single piece; whilst it also, as in the still longer ones above' mentioned, would have the additional advantage of being readily adjustable when out of true. This modeof construction is illustrated in iig. 3.

It is also important for some purposes to have thicker straight-edges than can be conveniently hardened in the manner above described. Such straight-edges are generally made from' one-quarter to one-half inch in thickness, and are called by machinists winders, which name will indicate one of the uses to which they are applied. |Ihey must be thick enough to stand irinly upon their edges.

To make a thick straight-edge, therefore, which `shall'enabodyV the distinguishing characteristic feature of extreme hardness ofthe edges, in excess of that between the edges, I put two or more hardened straight-edges,

of medium thickness, say from an eighth to thrce-sixteenths of an inch thick, together, by riveting, or any of 1 the known methods of doing such work, and then finish it as one piece, or I attach a thin hardened straightedge to a thick, unhardened one, or upon any suitable foundation.

It is desirable that thick straight-edges should have one thin edge, and they are generally so constructed so that they can be applied' with greater accuracy to the'work. 'lo accomplish this in making thick straightedges, as ab'ove described, where two or more pieces are pnt together, one of the pieces may be wider, and thinner if desirable, than the other or others. In attaching a thin vstraight-edgeto any foundation, as above described, the hardened edge may project beyond the piece to which it is attached, to serve as a thin edge, While,the opposite edge of bot'il pieces may be used when it is applied as a Winder.

' These graduated and hardened straight-edges, as above described, are of great advantage 'and utility when clamped together and used as a. gauge for gauging wire, Ste., or instead of graduating the hardened edges, an unhardened bevelled or plain pi-ece may be graduated and attached to the hardened piece. Such a formed gauge is much used by watchmakers and othermechanics, but they have not heretofore been hardened as above described, and consequently they soon wear out of true. Both plans of constructing this gauge are represented in iig. 5. The'side or part A represents it as constructed witha graduatediunhardened piece, attached to an ungraduated hardened piece; and the side or part B represents it as constructed with the graduated hardened straight-edge only. i

1. I claim a straight-edge, hardened at its edge or edges, and not at its centre, substantially as described.

2. I claim a straight-edge, having a hardened edge or edges, and admitting, when warped by hardening, of being brought into true, substantially as described.

3. I claim a straight-edge, made of two or more thin pieces, having one or both edges hardened, for the purpose of making it thicker,substantially as described.

4. I claim a straightedge,composcd of a thin plate, with hardened edge or edges, and a supporting-bed or plate, substantially as described. l

5. I claim a straight-edge, composed of two or more hardened straighbedgcs, secured end to end, upon a supporting bed-plate.

6. I claim a straight-cdge, when constructed as herein set forth, whether the same be used as a single -edge or 'with two opposing edges, as in a gauge, substantially as described. l

7. Iclaim the mode herein described of under-graduating the straight-edges, to compensate for the stretch in hardening.

8. I claim the process herein described of reducing the graduated edges to the proper Standard by tempering.

SAMUEL DARLING.

Witnesses:

JOHN E. HALL, ALBERT W. PAINE.

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