US2255457A - Hacksaw machine - Google Patents

Description

Sept. 9, 1941, G, swAlN ETAL 2,255,457

HACKSAW MACHINE Filed Nov; 16. 1938 4 Sheets-Sheet 1 FIG.1.

Sept.- 9, 1941. G. swAlN Erm. 2,255,457

HAcKsAw MACHINE Filed Nov. l1e, 1958 4 sheets-sheet 2 Flai 'Sept 9, 1941. G. swAlN E-rAL.

HACKSAW MACHINE 4 Sheets-Sheefc 3 Filed Noy. 16, 1938 sept. 9, 1941. G, SWMN -FAL 2,255,457

HACKSA'N MACHINE Filed Nov. 15, 1938 4 sheets-sheet 4 59% 7f- 58. 47 N; f- *6 so 54 57 [IP-IGS. 45

64 3 ,62 l /I se @y #mi cfm Patented Sept. 9, 1941 HACKSAW MACHINE George Swain and William Leslie Bower, Sheiield, England, assignors to .llames Neill & Company (Sheifield) Limited, Sheffield, England Application November 16, 1938, Serial No. 240,866 In Great Britain November 30, 1937 16 Claims.

This invention relates to hack-saw machines. The main object of the invention is to provide a hack-saw machine in which the hack-saw blade is supported approximately opposite to the work and between its anchorages so that the blade is, :T

at least in part, relieved of bending in its own plane.

A further object is the provision of a guide support against which the back of the blade slides in operation.

Another object is the Y'application of at least the main part of the force required to feed the blade to the work, not as heretofore to the ends of the blade through the blade anchorages, but to the mid part of the blade substantially opposite to the work.

A further object is the provision of lateral support for the sides of the blade whereby the blade is prevented from bending or chattering perpendicularly to its own plane.

A further object is the provision of a machine in which each successive tooth is caused to remove its own quantum of material during the working stroke, the successive teeth being constrained to follow each other during the working stroke along parallel paths successively deeper in the work.

A further object is the provision of a machine in which an effective positive feed of the successive teeth eacli through a pre-determined distance into the work takes place during each working stroke.

A further object is the provision of an irreversible feed step near the beginning of each working stroke followed by an effective positive feed of the successive teeth each through a pre-determined distance into the Work during the working stroke.

A further object is the limitation of the force applied in the irreversible feed step at the commencement of the workingstroke.

Another object is the provision of a hack-saw adapted for use in the machine and to pre-determine, in the manufacture of the hack-saw, the distance through which the successive teeth of the saw are positively fed into the Work during each working stroke.

According to the invention, the back of the hack-saw blade bears against and reciprocates relatively to a guide-support, which may be of less width than the saw set, located opposite the work and adapted, during the working stroke, to support the saw blade against any tendency to bend in its own plane. The guide-support is ,l preferably rigidly connected to freed mechanism, '5

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so that the force required to feed the blade to the work is applied, not Vas heretofore to the ends of the blade through the blade anchorages, but to the mid part of the blade substantially opposite t0 the work.

Lateral guides for the saw may also be provided, adapted to bear against the sides vof the saw blade nearer the back than, and clear of, the saw teeth, these lateral guides being situated adjacent the work and being adapted to support the saw blade against lateral vstresses in a direction at right angles to its own plane.

The guide support and saw are preferably fed or ladvanced towards the work by a substantially irreversible mechanism.

Although the'guide-support and saw may be gradually advanced throughout the working stroke lof the saw, in which case the pitch line of the saw teeth may be parallel to the direction `of reciprocation of the saw, it is preferred to feed vthe guide-support and saw irreversibly in a step at 'about the end of the idle stroke and beginning of the working stroke and to dispose the pitch line of the saw teeth at an inclination to the direction of reciprocation. Preferably means are provided for limiting the force applied to the irreversible feed mechanism which may comprise a screw and nut relatively rotated by torque applied through a friction clutch in steps each of which terminates 'after the commencement of the working stroke. Since the feed mechanism is irreversible, the amount of feed anddepth of cut during the working stroke are pre-determined by the amount of revolution of the clutch before slip takes place and, after the feed operation has been completed, the loading lof the saw or the force applied in the feed direction `is the dependent variable, instead lof being, as in prior hack-saw machines, the independent variable; the independent variable throughout the remainder of the working stroke is, in the case of the invention, the effective distance of feed due to the inclination of the pitch line ofthe saw teeth to the direction of reciprocation. Thus the saw teeth are positively fed and -are constrained to move in straight parallel lines during the working stroke so that each successive tooth may remove substantially the same depth of material and the total depth cut kby each working stroke may be pre-determined by the angle of inclination of the teeth pitch line to the reciprocationline and by the distance through which the guide-support and saw are advanced towards the work at each `feed step.' For use in this manner the hack-saw may have the pitch line of its Vteeth inclined to Figure 3 is a section on the line 3-3 of Figure 2,

Figure 4 is a vertical section in a plane at right angles to and on the line -ll of Figure 1 of part of the feed mechanism,

Figure 5 is an elevation partiy broken away to show the interior in the direction of the arrows of Figure 4,

Figure 6 is a bastard horizontal section on the line B-S of Figures 4 and 5, and

Figure '7 is a horizontal section on the line -l of Figures 4 and 5.

Like reference numerals indicate like parts, where applicable, throughout the several figures of the drawings.

Referring now particularly to Figure 1 the hacksaw machine comprises a base itl upon which is carried a main frame il supporting `a work holder in the form of a vise having jaws i2 and an actuating handle E3. The main frame i also carries rollers i4 supported by brackets l5 and adapted to support the work and enable it to be easily traversed across the main frame Il. The saw bow it is carried in guides, the construction of which is shown particularly in Figure 3 in a pivoted feed arm il so that the saw bow has freedom to move in both dimensions in a plane. The eed arm il is connected by links H8 to a feed mechanism l t9 by means of which the feed arm il, and together with it the saw bow I6, may be fed downwards towards the work. The hack-saw blade 2li is carried between anchorages located at the ends of the saw bow i6.

As best shown in Figures 2 and 3 a guide-support IS for the back of the saw blade is carried upon brackets or lugs $9 depending from a plate 2) extending over part of the length of the lower surface of the feed arm il. The guide-support i8 is located by dowels 2i and clamped by means of clamping plates EQa and bolts 22 to the brackets or lugs i9 and the plate 2i) from which these brackets or lugs extend is bolted to the feed arm il by bolts 23.

The guide-support i8 is of approximately the same width as the back of the hack-saw blade 2G which is clamped in the anchorages of the saw bow i6, this width being less than the saw set so that the guide-support i8 may follow the saw through the material being cut. The length of the guide-support I8 is approximately equal to the maximum width of material which the machine is designed to cut, the position of the guide-support on the feed arm ll being such that it is opposite, immediately above in the oonstruction illustrated, those teeth of the saw 24 which are in operative position in regard to the work.

The lower edge 28 of the guide-support 1s straight and smooth, being preferably ground and polished and the back of the saw blade 24 may be similarly nished.

The lugs l and plates |901l extend beyond the lower edge 28 of the guide support i8 to embrace the saw blade 2d to form pairs of lateral guides but do not extend to the edge of the saw blade, the set teeth of the saw blade 24 projecting beyond the ends of the lugs l and plates lSa. The lugs IS, which may be of cast iron, may be provided with replaceable bearing pieces or llets 25 as shown in Figure 3. The fillets 25 may be located by dov/els 26 and clamped by bolts 21. 'I'he replaceable llets are not required for the lower ends of the plates ld as these plates may be of suitable bearing material and, being small and detachable, may be replaced when desired.

.The lower edge 23 of the guide-support I8 bears against the back of the saw blade 24 and prevents any flexing of the saw blade in its own plane. The saw blade 24 is laterally guided between -the pairs of lateral guides provided by the plates la and the fillets 25 which are located on opposite sides of the work. Flexing and chattering of the saw blade 2li in a direction at right angles to its own plane are thus prevented.

The lower edge 28 of the guide support I 8 is, in the embodiment shown, parallel with the line of the guides upon which the saw bow I6 runs in the feed arm H. The pitch line 29 (Figure 2) of the teeth of the saw blade 2li is inclined to the back of the saw blade at a small angle, the apex of the angle between the line 29 and the back of the saw blade being beyond the end of the saw which leads in the cutting direction. Thus, as the saw bow It is reciprocated relative to the feed arm Il' in a straight line, the saw blade 211 is reciprocated in a straight line along one dimension in a plane with the pitch line of its cutting teeth 2Q oblique to that straight line in such a manner that the tooth leading in the cutting direction traverses a straight path at a higher level and the tooth following at a lower level throughout the stroke. The saw blade 24 follows a path in the plane which is at an inclination to the line of the cutting teeth 29, the motionof the blade having a component along the line of the cutting teeth and a component at right angles thereto. The prolongation of the path of the blade in the working direction diverges from the line of the cutting teeth 29 towards the work holder, whereby an effective positive feed of successive teeth 29 towards the work is secured. Thus each tooth follows the preceding tooth at a slightly greater depth in relation to the work and so tends to remove its own individual contribution of material.

Since the saw blade is mounted in the machine with its back parallel with the line of the guides upon which the saw bow l is reciprocated, it will be appreciated that the distance through which the successive teeth of the saw are positively fed into the work during each working stroke is pre-determined by the inclination of the line 29 of the teeth of the saw blade to its back.

In the embodiment of the vinvention shown in the drawings the feed arm il', and with it the guide-support i8, the saw bow I and saw blade 2li, are not loaded by some pre-determined force as in prior hack-saw machines but 'are together irreversibly fed 'towards the work a certain distance at the commencement of every cutting stroke. In prior hack-saws the loading or force in the feed direction applied to the saw bow is the independent variable. In contrast the hacksaw machine shown in the drawings operates with the distance of Vfeed or depth of cut as the independent variable, the feed load or force being the dependent variable. i

This is achieved by' a feed mechanism l|9 shown in detail in Figures 4, 5, 6 and '7 of the drawings.

Referring to these figures, the links ||8 are trunnioned to `the feed arm I 1 `and are connected at their other ends to a gearbox 36. A righthanded main feed screw 3| is journalled with end thrust bearings in the gear box 36 so that any thrust or tension applied to the feed screw 3| is transmitted through the gear boX 36 to the links ||8 and the feed arm |1. 'I'he gear box houses a bevel wheel 32 which is keyed to the end of the feed screw 3| and engages a bevel wheel 33 which is journalled upon a spindle 34 rigidly secured in the gear box 38. The bevel wheel 33 is splined or dogged to a handle 35 which is rotatable upon the spindle 34 and also movable axially thereon without dis-engagement from the bevel wheel 33. The handle 35 is provided with dogs 36 adapted to engage corresponding dogs on a collar 31 secured to the spindle 34. A spring 38 urges thehandle 35 to one extreme position in which its dogs 36 are engaged with those of the collar 31 so that the handle 35 is located against rotation. With the handle 35 so located the screw 3| cannot be rotated. On the other hand the handle may be moved against the spring 38 to a position in which the dogs 36 are dis-engaged from those of the collar 31, when the handle may be rotated to cause rotation of the screw 3|.

The screw 3| engages a nut 96. This nut has a collar 39 which bears against a shoulder of a screwed sleeve 48 through ball-bearings, the nut and sleeve being axially located relative to one another by an end thrust bearing 4|. The screwed sleeve 40 is located in a screw-threaded aperture of a housing 42 which is carried by trunnions in brackets 43 (Figure 1) supported upon the base l0 of the machine. The screw cf the sleeve 46 is left-handed. The screw 3| and nut 88 form an irreversible screw and nut mechanism.

j A transverse rock shaft is journalled in the housing 42 and is oscillated by means of a crank 46, connecting rod 41 and a lever 46 which is mounted upon a journal on the machine frame (see Figure 1). The other end of the lever 48 carries a roller 4Q which bears against a cam 50 carried by the main crank shaft 5| of the machine which drives the saw bow through a connecting rod 52. The lever 48 may be biased by a spring 53 to maintain the roller 43 in contact with the cam 56. The rock shaft 45 is provided with an arm 54. The arm 54 lies between a lug 55 depending from a collar 56 of the screwed sleeve 46 and a lug 51 projecting from a clutch plate 58 embracing the nut 86. The clutch plate 58 is frictionally coupled to the nut 80 by means of friction linings 59 which bear against the collar 33 and a slidable collar 65 which is splined to the nut 80 and urged to close the friction clutch by a spring 6 I.

The collar 56 has a single tooth 62 which engages a slot in a spring-loaded plunger 63. The plunger 63 is loaded by a spring 64 bearing against an internal shoulder of an adjustable nut 65. The end of the plunger 63 projects beyond the internal shoulder of the nut 65 and is provided with a head in the form of a nut 66. By adjustment of the nut 65 the movement of the plunger 63 to the left and consequently the return movement in an anticlockwise .direction in Figure 6 of the nut 4), following the movement of the arm 54, `may bevadjusted.

The clutch plate 58 is similarly equipped with a tooth 10 engaging a slot in a spring-loaded plunger 1| governed by a nut 12 in a similar manner.

Furthermore a pawl 15 loaded by a leaf spring 16 is provided in the housing 42 to engage a ratchet 18 formed upon the outer surface of the collar 68 which is splined to the nut 88. The pawl 15 and ratchet 18 thus prevent rotation of the nut in the clockwise direction in Figure 6 during the return stroke of the clutch plate 58 under the bias of the spring loaded plunger 1| and also the pawl 15 and ratchet 18 ensure the irreversibility of the screw and nut mechanism.

In operation, if it be assumed that the machine is just about to commence a cutting stroke and is in the position shown in Figure 1, the parts of the feed mechanism will be substantially in the positions shown in the drawings. As the cutting stroke commences the lever 48 is permitted by the cam 50 to rotate under the bias of the spring 53 in a clockwise direction thus rotating the rock shaft 45 in an anti-clockwise direction in Figure 1. This anti-clockwise rotation of the shaft 45 in Figure 1 causes a clockwise movement of the shaft in reference to Figure 5 and thus causes the arm 54 to rotate the clutch plate 58 by engagement with the lug 51. Rotation of the clutch plate 58 takes piace in an anti-clockwise direction referring to Figures 6 and 7. This rotation is transmitted to the nut 65 whereby the feed screw 3| is lowered until the teeth of the saw blade 24 are brought into contact with the work and forced into the Work with some force which is dependent upon the slippage of the clutch. The feedscrew 3| is then held in this position throughout the remainder of the cutting stroke of the machine by the pawl 15 and ratchet 15. The cutting stroke proceeds until, near the end of the cutting stroke, the rock shaft 45 is rotated in the reverse ydirection by the cam 5i), thus permitting the clutch plate 58 to reverse its rotation and to be restored to its normal position by the spring biased plunger 1|.

,This reverse rotation of the rock shaft causes the arm 54 to engage the lug 55 thereby to rotate the screwed sleeve 40 through some predetermined angle. Rotation of the screwed sleeve 46 within the housing 42 causes that sleeve to be raised and with it the nut 8E), feed screw 3| and feed arm l1, so that the saw blade 24 is raised out of contact with the work. During the return inoperative stroke the saw is maintained out of contact with the work. Near the end of the return stroke the cam 56 again permits the lever 48 to rotate in a clockwise direction in Figure 1, thus again rotating the rock shaft 45 and arm 54 in a clockwise direction in Figure 5. The screwed sleeve 45 is then rotated under the bias 0f the plunger 63 in an anticlockwise direction in Figure 6, its lug 55 following the arm 54. The feed arm |1 is thus lowered to or near to the position to which it had been at the end of the preceding cutting stroke. The arm 54 then contacts with the lug 51 of the clutch plate 58 again to rotate the clutch plate 58 to lower the feed screw 3| and the cycle of operations is repeated.

Over-loading of the saw 'is prevented by slipping of the clutch which may be adjusted by adjusting the spring 6| rand the adjustment of the maximum permitted feed per stroke is effected by the adjustment of the nut 12 which varies the position, in relation to the housing 42,

of its internal shoulder with which the head on the plunger 'Il makes contact to limit the clockwise rotation of the clutch plate 58 (in Figure 7) when the lug 5l is following the return movement of the arm 5A. Hence the position of the clutch plate 58 at the beginning of its feed movement and consequently the maximum permitted feed per stroke may be adjusted.

The feed arm may be moved towards and away from the work by pushing in the handle 35 to dis-engage its dogs 35 from those of the collar 3l and rotating the handle to cause rotation of the screw 3|. Rotation of the screw 3l, causes it to be raised or lowered relative to the nut Si).

It will be appreciated that one particular construction of hack-saw machine in accordance with the invention has been described and shown in the accompanying drawings and that many modifications may be made without departing from the scope of the invention. l

What we claim is:

l. A hack-saw machine comprising saw anchorages free to move in two dimensions in a plane, a hack-saw blade mounted between said anchorages and having set teeth and a back, a work holder, means for reciprocating the anchorages together in one dimension in the plane relatively to the work-holder, a guide support of less width than the overall set of the saw teeth constrained against movement relative to the work-holder in that one dimension but movable relatively to the work-holder in the other dimension in the plane and rigidly supported to bear against the back of the hack-saw blade, and means for feeding the guide support in that other dimension towards the work-holder.

2. A hack-saw machine comprising saw anchorages free to move in two dimensions in a plane, va hack-saw blade mounted between said anchorages and having set teeth and a back, a work-holder, means for reciprocating the anchorages together in one dimension in the plane relatively to the work-holder, a guide support of less width than the overall set of the saw teeth constrained against movement relative to the work-holder in that one dimension but movable relatively to the work-holder in the other dimension in the plane and rigidly supported to bear against the back of the hack-saw blade, pairs of lateral guides, rigidly secured to the guide support, the guides of each pair being located on and bearing against opposite sides of the hacksaw blade clear of the set teeth thereof, the pairs being spaced apart longitudinally of the blade, and means for feeding the guide support in that other dimension towards the work-holder.

3. A hack-saw machine comprising saw anchorages free to move in two dimensions in a plane, a tapered hack-saw blade mounted thereon and having set teeth and a smooth back, the distance between the line of the teeth and the smooth back being less at the leading end of the blade in the cutting direction than at the trailing end of the blade, a work-holder, means for reciprocating the anchorages in one dimension in the plane relatively to the work holder, a guide support of less width than the set of the saw teeth constrained against movement relative to the work-holder in that one dimension but movable relative to the work-holder in the other dimension in the plane and rigidly supported to bear against the smooth back of the hack-saw blade, and means operable near the commencement of a Working stroke in the reciprocation of the anchorages `for irreversibly feeding the guide support in that other dimensionV towards the work-holder.

4. A hack-saw machine comprising saw anchorages free to move in two dimensions in a plane, a hack-saw blade mounted between said anchorages and having set teeth and a back, a work-holder, means for reciprocating the anchorages together in one dimension in the plane relatively to the work-holder, a guide support of less width than the overall set of the saw teeth constrained against movement relative to the work-holder in that one dimension but movable relatively to the work-holder in the other dimension in the plane and rigidly supported to bear against the back of the hack-saw blade, an irreversible screw and nut mechanism effectively connected between the guide support and the work-holder, 4and means for relatively rotating the components of said mechanism.

5. A hack-saw machine comprising saw anchorages free to move in two dimensions in a plane, a hack-saw blade mounted between said anchorages and having set teeth and a back, a work-holder, means for reciprocating the anchorages together in one dimension in the plane relatively to the work-holder, a guide support of less width than the overall set of the saw teeth constrained against movement relative tothe work-holder in that one dimension but movable relatively to the work-holder in the other dimension in the plane and rigidly supported to bear against the back of the hack-saw blade, an irreversible screw and nut mechanism effectively connected between the guide support and the work-holder, and frictional means governed by the means for reciprocating the anchorages for applying a limited turning moment to one of the components of said mechanism.

6. A hack-saw machine comprising saw anchorages free to move in two dimensions in a plane, a hack-saw blade mounted between said anchorages and having set teeth and a back, a work-holder, means for reciprocating the anchorages together in one dimension in the plane relatively to the work-holder, a guide support of less width than the overall set of the saw teeth constrained against movement relative to the work-holder in that one dimension but movable relatively to the work-holder in the other dimension in the plane and rigidly supported to bear against the back of the hack-saw blade, an irreversible screw and nut mechanism eifectively connected between the guide support and the work-holder, and a friction clutch having one component connected with one of the components of the screw and nut mechanism and adapted to apply a turning moment thereto, and means governed by the means for reciprocating the anchorages for rotating the other component of the friction clutch.

7. A hack saw machine comprising saw anchorages free to move in two dimensions in a plane, a hack saw blade mounted between said anchorages and having teeth and a back, a work holder, means for reciprocating the anchorages together in one dimension of the plane relatively to the work holder, a guide support situated between the locuses of the blade ends, constrained against movement relatively to the work holder in that one dimension but movable relatively to the work holder in the other dimension and rigidly supported to bear against the back of the hack saw blade, and means for feeding the guide support in that other dimension.

8. A hack saw machine comprising saw anchorages free to move in two dimensions in a plane, a hack saw blade mounted between said anchorages and having teeth and a back, a work holder, means for reciprocating the anchorages together in one dimension of the plane relatively to the work holder, a guide support situated between the locuses of the blade ends, constrained against movement relatively to the work holder in that one dimension but movable relatively to the work holder in the other dimension and rigidly supported to bear against the back of the hack saw blade, pairs of lateral guides rigidly secured to the guide support, the guides of each pair being located on and bearing against opposite sides of the hack saw blade between the locuses of the ends thereof, the pairs being spaced apart longitudinally of the blade, and means for feeding the guide support in that other dimension towards the work holder.

9. A hack saw machine comprising a work holder and a relatively movable straight guide adapted to be moved to or from the work holder in a direction substantially perpendicular to its length, saw anchorages reciprocable only parallel with said straight guide and, a tapered hack saw blade mounted on said saw anchorages with its back parallel to said straight guide, reciproeating means for reciprocating saidsaw anchorages, a guide support between the locuses of said saw anchorages rigidly connected to said straight guide and bearing against the back of the saw blade, an irreversible feed mechanism interconnecting the straight guide and the work holder and operating means for the irreversible feed mechanism interconnected with said reciprccating means and adapted to maintain said irreversible feed mechanism stationary during the cutting stroke oi the machine and to operate it in a step during every cycle so as to advance the straight guide in a step.

1G. A hack saw machine comprising saw anchorages free to move in two dimensions of a plane, a tapered hack saw blade mounted thereon and having teeth and a smooth back, the distance between the line of the teeth and the smooth back being less at the leading end of the blade in the cutting direction than at the trailing end of the blade, a work holder, means for reciprocating the anchorages in one dimension in the plane relatively to the work holder, a guide support situated between the locuses of the blade ends, constrained against movement relatively to the work holder in that one dimension but movable relatively to the work holder in the other dimension in the plane and rigidly supported to bear against the smooth back of the hack saw lade, and means operable near the commencement of a working stroke in the reciprocation of the anchorages for irreversibly feeding the guide support in that other dimension.

11. A hack saw machine comprising saw anchorages free to move in two dimensions in a plane, a hack saw blade mounted between said anchorages and having teeth and a back, a work holder, means for reciprocating the anchorages together in one dimension in the plane relatively to the work holder, a guide support constrained against movement relative to the work holder in that one dimension but movable relatively to the work holder in the other dimension in the plane and rigidly supported to bear against the back of the hack saw blade, an irreversible screw and nut mechanism effectively connected between the guide support and the work holder and means for relatively rotating the components of said mechanism.

12. A hack saw machine comprising saw anchorages free to move in two dimensions in a plane, a hack saw blade mounted between said anchorages and having teeth and a smooth back, a work holder, means for reciprocating the anchorages and blade together in one dimension in the pla-ne relatively to the work holder, a guide support situated between the locuses of the blade ends, constrained against movement relative to the work holder in that one dimension but movable relatively to the work holder in the other dimension in the plane and rigidly supported to bear against the back of the hack saw blade, an irreversible screw and nut mechanism eiiectively connected between the guide support and the work holder, and means for relatively rotating the components of said mechanism.

13, A hack saw machine comprising saw anchorages free to move in two dimensions in a plane, a tapered hack saw blade mounted between said anchorages and having teeth and a smooth back, the distance between the line of the teeth and the smooth back being less at the leading end of the blade in the cutting direction than at the trailing end of the blade, a work holder, means for reciprocating the anchorages together with the blade in one dimension in the plane relatively to the work holder, a guide support situated between the locuses of the blade ends, constrained against movement relatively to the work holder in that one dimension but movable relatively to the work holder in the other dimension in the plane and rigidly supported to bear against the smooth back of the hack saw blade, an irreversible screw and nut mechanism effectively connected between the guide support and the work holder and means for relatively rotating the components of said mechanism in a step at each cycle of operation.

14. A hack saw machine comprising a work holder and a relatively movable feed arm having a straight guide adapted to be moved to or from the work holder in a direction substantially perpendicular to its length, saw anchorages reciprocable only parallel with said straight guide and adapted to receive a hack saw blade, reciprocating means for reciprocating said saw anchorages, rigid brackets depending from said feed arm between the locuses of the saw anchorages, a guide support parallel to said Straight guide rigidly clamped to said brackets and adapted to bear against the back of a saw blade held by said saw anchorages and means for applying a substantial load to the feed arm.

l5. A hack saw machine comprising a work holder and a relatively movable feed arm having a straight guide adapted to be moved to or from the work holder in a direction substantially perpendicular to its length, saw anchorages reciprocable only parallel with said straight guide, a tapered hack saw blade mounted on said saw anchorages with its back parallel to said straight guide such that, as the blade is traversed in the cutting direction successive teeth move in paths which are successively nearer to the work holder, reciprocating means for reciprocating said saw anchorages, rigid brackets depending from said -feed arm between the locuses of the saw anchorages, a guide support parallel to said straight guide rigidly clamped to said brackets and bearing against the back of the saw blade, means for maintaining said feed arm stationary in relation to the Work holder during the cutting stroke of the machine and means for advancing the feed arm in a step during every cycle.

16. A hack saw blade comprising an elongated tapered strip of metal, adapted to be secured under tension at its ends in a hack saw machine, narrower at one end than at the other and having a straight smooth surface along one of its longer mutually inclined sides adapted to be reciprocated in Contact with and in relation to a.

fixed guide support and a single series of cutting saw teeth extending substantially along the Whole length of the other of said sides, the tips of said saw teeth lying in a line which is inclined to said straight smooth surface, said saw teeth each presenting a cutting face towards the narrower end of the blade and a sloping relief, oblique to the length of the blade, towards the broader end of the blade.

GEORGE SWAIN.

WILLIAM LESLIE BOWER.

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