US2372722A - Apparatus for polishing - Google Patents

Description

April 3, 1945. 1.. R. HEIM APPARATUS FOR POLISHING Filed July 28, 1942 4 Sheets-Sheet l I INYENTOR Lewis R. Helm BY Q lit/1Z2 WM} r ATTORNEYS April 3, 1945. L. R. HElM APPARATUS FOR POLISHING Filed July 28, 1942 4 Sheets-Sheet 2 Heim INVENTOR Lewes B BY 1 W4;

&m ZLL ATTORNEYS L. R. HEIM APPARATUS FOR POLISHING April 3, 1945.

Filed July 28, 1942 4 Sheets-Sheet 3 HIM I20 1 H I L33 I2 IZIH'O 3 11% w INVENTOR Lewis Heim [ATTORNEYS April 3, 1945. L. R. HElM 2,372,722

I APPARATUS FOR POLISHING Filed July 28, 1942 4 Sheets-Sheet 4 VENTOR I v 17 is R. Helm ATTORNEYS Patented Apr. 3, 1945 2,372,722 APPARATUS FOR POLISHING Lewis B. Heim, Fairfield, Conn., assignor' to The Heim Company, Fairfield, 001111., a corporation I of Connecticut Application July 28, 1942, Serial No. 452,593 8 Claims, 151-145) This'invention relates to apparatus for polishing or grinding metal articles, and more particularly to a die polishing machine.

One of the objects, of this invention is to provide a machine for polishing or grinding metal articles, such as dies, which is simple and sturdy in construction and capable of efficient operation over an extended period of time. Another object is to provide a machine of the above nature characterized by inexpensiveness and readily operable by unskilled labor. Another object is to pro vide a machine of the above nature capable of treating dies, such as drawing or extrusion dies, of a wide variety of configuration. Another object is to provide a machine of the above nature capable of being operated at high speed, but

without danger to the operator. Other objects will be in part apparent and in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts as will be exemplified in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the drawings, wherein there is shown one embodiment of my invention,

Figure 1 is a side elevation of my machine, a portion thereof being broken away;

Figure 2 is a front elevation of my machine;

Figure 3 is an enlarged fragmentary view of the front central portion of the machine;

Figure 4 is a section taken along the line 4-4 of Figure 3;

Figure 5 is an enlarged fragmentary side view of the machine;

Figure 6 is an enlarged fragmentary section taken along the line 6-6 of Figure 2;

Figures 7, 8 and 9 illustrate different shapes of dies and the relationship thereto 01' complementary pressure arbors which force the polishing belt against the surfaces being treated; and,

Figure 10 is an enlarged fragmentary sectional view taken along the line Ill-40 of Figure 2.

Similar reference characters refer to similar parts throughout the various views ofthe drawings.

The grinding or polishing of drawing and extrusion dies of various sizes and shapes has given rise to a number of difiiculties, first by reason of the character of the dies, and secondly be cause of the wide variations in their size and shape. As pointed out in Patent 1,418,677 to O. W. Sadler, Jr., it is desirable in polishing a drawing die, for example, that the abrasive act on the Working face ofthe die in substantially the same directionas the flow of the work during the drawing operation so as to avoid the creation of tool marks in the die normal to the dies axis, which tool marks might well mar or scratch the work and damage the tool. However, the polishing of drawing or extrusion dies, or the like, characterized by internal shoulders, for example, or by bell mouths, or by a straight edge on the discharge side or by other peculiarities gives rise to problems and difiiculties toward the obviation of which the machine described hereinbelow is directed.

Referring now to Figure 1, my machine, in general, comprises a base ID, a column ll, and a motor support l2, on which a motor l 3 is suitably secured. Column l l is provided with spaced ways l4 and I5 (Figure 2) on which are slidably mounted, for vertical adjustment, a work support bracket IS, a pulley supporting bracket l1 and a lower bracket I8. Work support bracket 16 carries a rotatable work support generally indicated at I9 (Figure 2) adapted to support a work piece W, such as a drawing die, for example, the inner surface of which is to be treated by a belt 20 trained over an upper driving pulley 2| and a lower driven pulley 22. Thus, upon operation of the machine, motor I3 drives -pulley 2| which drives the opposite sides of belt 2 0 (Figure 2) downwardly and upwardly, respectively, through the rotating work piece, thus to abrade or polish the work piece.

Pulley 2| (Figures 1 and 2) is attached to or integral with a hub 01' brake drum 23 secured to one end of the armature shaft of motor 13, so as to rotate therewith at the same number of revolutions per minute as the motor. Drum 23 is preferably of substantial peripheral area to provide sufficient braking surface for cooperation with a brake, generally indicated at 24, which is manually operable to rapidly brake the rotation of the drum and pulley when the motor is turned off, and thus avoid unnecessary consumption of time in waiting for the pulleys and belt to stop. Brake 24 includes a (bracket 25 secured to a projection 26 extending forwardly from the upper front portion of column ll. Bracket 25 includes a pair of upwardly extending lugs 21 between which is pivotally mounted a link 28, the outer end 28a (Figure 2) of which is pivotally connected to a pair of bifurcations 29 formed on and extending from a brake shoe 30. Thus, when link 23 (Figure 1) is pivoted counterclockwise, brake shoe 30 is forced against drum 23 to stop the rotation thereof. To effect this movement of the shoe, I provide a cam 3! which is secured to a shaft 32 pivotally mounted in bracket 25, the cam having a lobe 3la adapted to ride under the bottom of link 28 and force the link counterclockwise, as viewed in Figure 1, when shaft 32 is rocked clockwise, by an operating arm 33 secured thereto. Preferably cam 31 and its lobe, and the bottom of link 28, against which the lobe bears, are so designed that when lever 33 is released, the several parts automatically resume their normal brake-01f position, shown in Figure 1. However, a torsion spring (not shown) may be provided to bias the brake toward its off position.

Bracket [6 (Figure 3) includes a pair of integral, forwardly extending webs 3d, which support a circular housing 35 within which is rotatably mounted, as on balls, a carrier 36 which in turn is adapted to have secured thereto a chuck or adapter plate, such as, for example, the universal chuck generally indicated at 31, within which the work piece W may be clasped. As shown in Figure 1, carrier 36 has a plurality of teeth 38 out therein, which are adapted to mesh with a bevel gear 39 secured to one end of a shaft 48 rotatably mounted in suitable antifriction bearings (not shown) disposed within a tubular housing 4! carried by a web 312 formed preferably as an integral part of bracket it. To the outer end of shaft All is secured a pair of change pulleys 43, which are electively connectable as by a belt 44 with either of a pair of lower change pulleys 45 rotatably mounted on a shaft (not sho'wn) secured in a boss 46 extending from the machine column. Also mounted o this shaft and secured to pulleys 45 is a pulley 21 connected by a belt 48 with a driving pulley 49 attached to the left-hand end, as viewed in Figure l, of the armature shaft of motor 13. Thus it will appear that upon operation of the motor, its pulley 49 drives lower pulley 4'! through belt 48 thus to drive the lower change pulleys '55. These lower change pulleys drive upper change pulleys 43 through belt 44 to elfect rotation of shaft 45 and accordingly rotation of carrier 36. It will also appear that the carrier 36 may be rotated at either of two speeds, depending upon which of the change pulleys 53 and A are connected by belt 44.

Inasmuch as the vertical position of change pulleys i3 varies upon vertical adjustment of work support I9, as will be described below, I provide a belt tightener generally indicated at El), this tightener comprising an arm 5| formed on and extending from a collar 52 mounted on shaft 40. The lower end of arm 5i carries a pair of pulleys 53 (see Figure 2) either of which may be engaged with belt 44, depending upon which set of change pulleys is being used. A suitable torsion spring (not shown) is disposed within collar 52 to bias the belt tightener clockwise, as viewed in Figure 2, thus to maintain belt M taut at all times.

As pointed out above, work support I!) is vertically adjustable, i. e., bracket It; may be moved up and down ways M and 15. To this end, bracket web 42 has integrally formed therewith an interiorly threaded boss 54 which threadedly receives an elongated screw 55, the upper end of which is journaled in a bracket 56 secured in the upper portion of machine column ll. Screw 55 also has secured thereto 'a spiral gear 51, and

the screw is held in proper operative position and against axial movement by a pair of collars 58 and 59 secured to the screw on opposite sides of bracket 55 and gear 57, thus permitting rotation of the screw, but not axial movement thereof. Spiral gear 57 meshes with a worm (50 secured to a shaft iil, rotatably mounted in bracket 56 at right angles to screw 55 and extending outwardly through an opening in the upper part of column H and to the right thereof, as viewed in Figure 2, so as to receive a hand wheel 82. It may now be seen that upon rotation of hand wheel 62 in one direction or the other, shaft 6| (Figure l) and worm 60 are rotated in turn to rotate spiral gear 5'! and screw 55. Rotation of screw 55 in one direction or the other raises 0r lowers bracket 56, thus to adjust the vertical position of work support l9 relative to driving and driven pulleys 2i and 22. The vertical position of the work support between these two pulleys may to a certain extent be used to determine the angular relationship of the up traveling and down traveling sides of belt 20, although this angular relationship of the belt sides is preferably determined primarily by guiding devices to be described hereinbelow.

It may now be seen that an angular Work piece W, such as a drawing die, for example, may have its inner working surface ground or polished, depending on the character of the abrasive on belt 2!), by drawing the belt upwardly and downwardly through the die at a high rate of speed while at the same time the work piece is rotated at either of two speeds. By virtue of the vertical adjustment of which work support I9 is capable, the angle at which the up and down traveling sides of the belt engage the work may be controlled so that from this adjustment alone a certain amount of control may be had over the pressure with which the belt engages the work. It might be well to note at this point that it is important that the pressure of the belt against the work be uniform so as to avoid removing more material from one portion of the die than from another.

For 'properly operating on various types of drawing dies, the working surfaces of which are more or less complex in configuration, it is desirable to control the angular relationship of the up and down traveling sides of belt 2i) (Figure 3) so that all portions of the die, 1. e., Work piece W being polished, for example, are engaged by the belt at the same, or nearly the same pressure. Accordingly, to attain this precise and desired angular relationship of the belt to the work, I have provided upper and lower belt guides, generally indicated respectively at 63 and 5 3 (Figure 2). As is more clearly shown in Figure 3, upper guide 63 comprises a generally L-shaped bracket 65 having a vertical leg 66 (Figure 5) in which an elongated slot 57 is formed. As shown in Figure 6, leg 66 is channel-shaped in cross section, and accordingly embraces the right-hand vertical side of bracket !5 and along which it may be vertically adjusted and held in adjusted position by a bolt 68 which extends through slot Bl (Figure 5) and is threaded into thevertical edge of bracket I6.-

Upper guide bracket 65 also includes a horizontal arm 59 (Figure 3) in the opposite ends of which are formed elongated slots H1 and H. The reduced portions 12 and 13 (Figure 6) of a pair of studs 74 extend respectively through slots 10 and H, and the inner ends of these reduced portions 12 and 13 are threaded to receive knurled nuts I8 and 11, respectively, which may be tightened against arm 69 to lock studs," and Him any adjusted positionwithin their respective slots 18 and II along the arm. The outer ends of studs 14 and I rotatably carry pressure pulleys 18 and 19 (Figure' 3), these pulleys preferably being mounted on the studs by suitable high speed antifriction bearings 18!) and 19b. Preferably pulley I8 and 19 are provided respectively with tires 18a and 19a of suitably alloyed steel capable of resisting the abrasive action of belt 20.

It may now be seen that pressure pulleys 18 and 19 are adjustably positioned on opposite sides of belt 28 so that the angular relationship of the up and down traveling sides of the belt at the top of work piece W may be varied as desired. It will also appear that this angular relationship with respect to the top side of the work piece may be controlled by three factors, namely, the vertical position of work support I9 relative to driving pulley 2 I, the vertical position of guide pulley bracket 65 and accordingly guide pulleys I8 and 19 relative to the work piece, and the lateral position of one or both of pulleys 78 and I9 relative to the axis of the work piece. Thus, by varying the relationship of these several parts, each as to one or more of the others, practically any desired angular relationship between the belt and the work can be attained, thus to guide the belt properly, regardless of theconfiguration of the work piece surface being operated on.

It is of course equally important, particularly I Pulley 8| is also provided with a hardened tire Ma and pivotally mounted, as by an antifriction bearing 8Ib on an arm 98 carried by a stud 94 journaled in a boss (not shown) similar to boss 84 (Figure 1). Arm 93 (Figure 3) includes a central boss 95 drilled toreceive a stud 96 which is pivotally mounted in a nut 91. Nut 91 has interior threads which mesh with a screw 98, the threads of which are cut opposite to those on screw 98. The right-hand end of screw 98, as viewed in Figure 3, has secured thereto a knurled knob 99 bywhich both of the screws 98 and 98 when dealing with dies of complex configuration,

to control the angular relationship of the up and down traveling sides of belt 28 below the work piece. Thus, belt guide 84 comprises a pair of guide pulleys 88 and 8| equipped with hardened tires 88a and Bid and disposed on opposite sides of belt 28 and movable laterally through mechanism now to be described. -Pulley 88 is'rotatably mounted as by a suitable high speed antifriction bearing 8812 on the upper end of an arm 82 (see also Figure 1) the lower end of which is pivotably mounted on a stud 83 (Figure 3) secured in a boss 84 (Figure 1) which is preferably formed integral with and extends from the lower end of bracket I6. Formed in the mid-portion of arm 82 (Figure 3) is a boss 85 which is drilled out to receive one end of a short stud 88, the other end of which extends into and pivotally supports a nut generally indicated at 87. This nut com prises concentric sleeves 88 and 89, the former of which has interior threads, and the latter of which has both interior and exterior threads, the

interior threads of sleeve 88 meshing with the exterior threads of sleeve 89, and the interior threads of sleeve 89 meshing with a screw 98 which extends through the nut 87. Inasmuch as sleeve 88 of nut 81 is secured to the main body of the nut, and accordingly, cannot rotate about its own axis, rotation of sleeve 89 by an integral knurled ring 9| in one direction or the other moves'nut 81 and accordingly arm 82 to the right or left relative to sleeve 89. Rotation of sleeve 89 in one direction or the other also causes movement of the sleeve to the right or left relative to screw 98. Hence, it follows that the movement of the arm is the sum of the movements of sleeves 88 and 89. Preferably a lock ring 92 is threaded on sleeve 89 between ring 9| and sleeve 88 so as to lock arm 82 in its adjusted position relative to sleeve 89. It may accordingly be seen that arm 82 and pressure pulley 88 may be adjustably positioned along screw 98, without resorting to rotation of this screw.

may be rotated together, as will appear.

The adjacent or inner ends of screws 98 and 98 are respectively secured in a pair of collars I88. and I8I connected, together by a reduced portion I82 rotatably mounted in a yoke I83 (see Figure 4). Yoke I83 is formed on the end of a stud 84 which is pivotally disposed within a boss I85 preferably formed integrally with work support bracket I8 (Figure 3). It will now appear that upon rotation 01' knob 99 (Figure 3) screws 98 and 98 are rotated, but as these screws are oppositely threaded, arms 82 and 93 are moved simultaneously toward or away from one another and accordingly pressure pulleys 88 and 8| are similarly moved to control the angular relationship of the upward and downward traveling sides of belt 28 below the work piece W. Under certain circumstances it may be desirable to vary the angular position of one side of belt 28, e. g" the upward traveling side, and under such circumstances, pressure pulley 88 is adjusted independently of pulley 8| through manipulation of knurled rings 9| and 92, as heretoforedescribed. It will also appear that through the provision of the pivotable yoke I83 and connected collars I88 and IN, the axis of screws 98 and 98 may move up and down or tilt, de-

pending on whether one or both of pressure pulleys 88 and 8| are moved, without any danger of binding.

Thus it follows that through the provision of upper and lower belt guides 63 and 84, and their individually adjusted pressure pulleys, practically any angular relationship between the upward and downward traveling sides of belt 28 and the work piece may be attained within the limits of adjustment provided. For example, upper and lower pressure pulleys I8and 88 may be so adjusted toward the work piece axis as to completely disengage the upwardly traveling side of belt 28, assuming that the left-hand side of the belt, as viewed in Figure 3, is the upwardly traveling side, from engagement with the work piece. By virtue of the variations in position which may be imparted to the lower pressure pulleys 88 and 8|, the treatment of the discharge side of the 'die can be closely controlled. Thus,

:if the edge on the discharge side of the die or work piece W is not to be polished, then the two pressure pulleys 88 and BI may be moved toward one another by manipulation of the mechanism described, so that neither side of belt 28 engages this portion of the work piece. On the other hand, if it is desired to have the discharge side of the die or work piece W bell mouthed,

, then one or both of pressure pulleys and 8| As pointed out above, dies such as drawing dies are often characterized by complex configurations, and in Figures 3, 7, 8 and 9 I have illustrated several types of drawing dies the working surfaces of which although complex can readily be treated by my machine. I have found, however, that when operating on such surfaces to polish them, for example, the treatment thereof, may be substantially expedited by applying pressure to the polishing beltin addition to the pressure resulting from the adjustment of the angular relationship of the belt sides by the guides 63 and 66. To this end, I have provided a pressure device which is generally indicated at I66, adapted, as will be described in detail below, to resiliently or flexibly press an arbor, such as arbor m1, against one side, preferably the down traveling side, of belt 20 against the surface of the work piece being operated on. Thus, as shown in Figure 3, the work piece is illustratively a drawing die having a generally conical surface, the entry and discharge ends of which have radii. In this case, the pressure end III'Ia of the arbor ID'I is conical to conform to the shape of the hole in the work piece, wherein it may flexibly press one side of the belt 20 against the surface being polished.

In Figure 7, the work piece W is characterized by a working surface having large and small diameters L and S joined by a shoulder H having a radius R between the shoulder and diameter L. In this case arbor IU'I may take the form shown, so as to press the downwardly traveling side of belt 20 against the larger diameter L I and against the shoulder HI, so as to polish the radius R. The angle of the two sides of the belt at the entry and discharge ends of the work piece W is, of course, controlled as desired through the adjustment of guides 63 and 64 (Figure 3) as heretofore described.

In the case of a work piece W, having a working surface configuration such as shown in Figure 8, I have found it suitable to provide arbor I01 of generally cylindrical form, as the radii R at the entry and discharge ends of the die may be polished through the adjustment of the belt guides 63 and 64.

If the work piece W has a working surface of the configuration shown in Figure 9, i. e., a working surface characterized by a frusto-con.ical portion F and cylindrical portion C at the discharge end of the die, belt 20 may advantageously be pressed against these surfaces by a specially formed shoe attached to arbor I67 and suitably configured in conformity with sur faces F and C so as to uniformly press belt 20 against these surfaces. Thus it will appear that regardless of the configuration of the work surface of the die being polished, arbor lb'I may readily be adapted thereto so that all portions of the dies working surface may be treated whether the die is bell-mouthed at one end or both or has other complex configurations. Referring back to Figure 3, pressure device IDS includes a bracket I08 which, as may be seen in Figure 1, is generally channel-shaped so as to embrace arm 69 of bracket 65. Referring back to Figure 3, bracket I08 is slotted as at H19 and cut away as at III to provide clearance for studs I4 and I5 of the pressure pulleys I8 and IQ, respectively. Bracket I08 is so. machined as to be readily slidable along arm 69.

The upper edge of bracket I08 has a pair of spaced upstanding lugs III and II2 formed thereon, the latter of which rotatably receives the unthreaded end of a screw I I3, the threaded shank I ISa of which extends through a threaded boss H4 formed on bracket 65. The outer end of the screw has a knurled knob II5 attached thereto by which the screw can be turned. The left-hand end of screw I I3, as viewedin Figure 3, has a collar H8 secured thereto, and this collar is disposed between bosses III and H2 to hold the screw against axial movement relative to these bosses. Thus, upon rotation of screw I I3 by knob H5 in one direction or the other. bracket I08 may be moved in one direction or the other along bracket arm 69 and according ly a lateral adjustment for pressure device IDS is provided. As shown in Figure 6, a screw I24 having a knurled head I25 extends through a slot I26 (see also Figure 3) in arm 69 and is threaded into bracket H13. Thus when the screw is taken up the bracket is clamped in its adjusted position on arm 69.

Boss III (Figure 3) has a short stud III extending therefrom, and this stud pivotally supports a downwardly depending arm II8 which carries an arbor holder H9 within which arbor It'd may be adjustably secured. Arbor IU'I is, for illustrative purposes, shown raised from its operative position. The lower end of arm I I8 lies between projecting bosses I29 and I2I formed on bracket H18, and these bosses define the limits of pivotal movement of arm H8 and accordingly arbor I61. Boss I2I is provided with one or more set screws I22 which may be adjusted as desired to determine the extent of counterclockwise movement of arbor IIII, as viewed in Figure 3. Preferably boss I20 is provided with a spring I23 which presses against the lower end of rm H8 and accordingly biases arbor I07 counterclockwise. Thus it will appear that arbor I6? is flexibly and resiliently disposed with relation to the work piece W so that the arbor end Iiila may be resiliently pressed against preferably the downwardly traveling side of belt 29 to supplement the pressure of the belt due to its angular relationship to the work piece.

In order to maintain belt 20 taut, lower pulley .22 (Figures 1 and 10) is so supported on pulley supporting bracket II as to be capable of vertical movement relative thereto, i. e., the weight of the pulley and the structure which supports it maintains the belt taut. Thus, the pulley is mounted on a stud I3Il (Figure 1) which is supported in a boss I3I integrally formed with and extending from a hollow post I32. Post I32 is slidably mounted on a vertical shaft I33 (Figure 10) the lower end of which is secured to the outer end of an arm I34 (Figure 1) which extends outwardly from bracket II. This arm rests on and accordingly is supported by the upper end of a sleeve I35 having a hand wheel I38 attached thereto, sleeve I35 being threaded to mesh with the upper threaded end of a post I 36 secured to the outer end of an arm I31 extending outwardly from lower bracket I8. Lower bracket It may be secured by suitable means (not shown) in any desired adjusted position along ways I4 and I5 (Figure 2) thus to adjust the vertical position of bracket I? and accordingly pulley 22. Further adjustment of bracket II and the pulley may be attained through the manipulation of hand wheel I28 in one direction or the other to raise and lower the bracket. This vertical adjustment of bracket I! and pulley Z2 is provided as under different conditions it is desirable to use belts, such as belt 20, of different length. Referring back to.

Figure 10, hollow post I32is provided with a boss I3Bwhich rockably receives a stud I39 the ends ofwhich extend beyond the sides of the boss and have secured thereto the bifurcations I49 and MI, respectively of a yoke generally indicated at I 42. The bifurcations of yoke I42 extend to opposite sides of post I32, sufiicient the pulley supporting bracket ll (see Figure 2).

The left-hand end of shaft I41, as viewed in Figure '2, has secured thereto an arm I49 by which the shaft, the bracket M5, and accordingly yoke I42 may be rocked in one direction or the other. Thus, as viewed in Figure 1, if arm I49 is rocked counterclockwise, yoke I42 is rocked in a similar direction to raise hollow post I 32 and accordingly pulley 22 to relieve the weight of the pulley, post, yoke and arm on belt 29, to facilitate removal of the belt from the pulley, for example. On the other hand, the combined weight of the pulley, post 132, yoke I42 and arm hi9, particularly if the arm is slightly off center clockwise, as viewed in Figure 1, is sufiicient to maintain belt in a suitably taut condition. Inasmuch as yoke I42 is slidably mounted on post I44 (Figure 10) the rocking movement of the yoke is readily accommodated.

It will thus appear that pulley 22 (Figure 1) is not only readily adjustable vertically with respect to the work piece W, but also in its adjusted position is flexibly related thereto thus being capable of absorbing vibrations ensuing from high speed operation, the pulley also being readily raisable by operation of arm I49 to permit removal of belt 29.

I have, accordingly, provided apparatus for polishing or grinding metal articles which attains the several objects set forth hereinabove in a thoroughly practical and efficient manner.

As many possible embodiments may be made of the above invention, and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a die polishing machine, in combination, a vertical column, a bracket slidably mounted on one side of said column for vertical adjustment relative thereto, a work suppport rotatably mounted on said bracket, said work support having an opening therethrough and adapted to support an annular work piece the interior surface of which is to be treated, means for driving said work support, a, driving pulley mounted on said column above said work support, a driven pulley mounted on said column below said work support, means forming a driving connection between said driving means and said driving pulley, a flexible belt trained over said pulleys and adapted to be passed through said work piece and driven by said driving pulley to treat the surface of said opening, a pair of belt guiding pulleys disposed between said driving pulleyand said work supto said bracket whereby the vertical position of said guide pulleys can be varied as desired relative to said work support to control the angle at which said belt engages the work piece, means mounting said guide pulleys for lateral movement relative to said work piece further to control the angle of engagement between the belt and work piece, a second pair of guide pulleys secured to said bracket and disposed between said work support and said driven pulley, and means for moving said second guide pulleys laterally relative to the work piece, whereby the angle of engagement between the belt and work piece at the lower side of the work piece may be controlled,

2. Apparatus according to claim 1 wherein a second bracket is mounted on said column below the first bracket, and means for mounting said driven pulley on said second bracket for movement vertically relative thereto.

3. Apparatus according to claim 1 wherein a second bracket is mounted on said column below the first bracket, means for mounting said driven pulley on said second bracket for movement vertically relative thereto, and manually operable means for raising said driven pulley without affecting the position of said second bracket to permit removal or installation of said belt on the driven pulley. i

4. Apparatus according to claim 1 wherein a second bracket is mounted on said column below the first bracket, means for mounting said driven pulley on said second bracket for movement vertically relative thereto, manually operable means for raising said driven pulley without affecting the position of said second bracket to permit removal or installation of said belt on the driven pulley, and a third bracket mounted on said column below said second bracket and having manually operable means thereon for controlling the vertical position of said second bracket.

5. In a die polishing machine, in combination, means for supporting a work piece having an opening therethrough the surface of which opening is to be treated, a flexible member adapted to be passed through the opening in said work piece and adapted to engage said surface of the work piece and be driven back and forth therethrough to treat said surface, means for driving said flexible member, a pressure device adapted to be inserted in the opening of said work piece to press said flexible member into engagement with said surface, means flexibly mounting said pressure device adjacent said supporting means, means for biasing said pressure device in one direction only transverse of the axis of the work piece into engagement with the work piece, and means for rotating said supporting means.

6. In apparatus for polishing a drawing'die characterized by an operating surface having a radius at its entrance end, in combination, a column, means on said column for supporting the die, a driving pulley mounted on said column on one side of said work supporting means, the diameter of said pulley being in excess of the diameter of the opening extending through the die, a driven pulley mounted on said column on the opposite side of said work supporting means, a flexible belt trained over said pulleys and adapted to be passed through the work piece opening and driven by said driving pulley to treat the surface of said opening, means disposed between said driving pulley and said work supporting means for affecting the operative angle of said belt relative to said die between the die and the driving pulley, means for varying the position of said 7, In apparatus for polishing a drawing die characterized by an operating surface having a radius at its entrance end, in combination, a column, means on said column for supporting the die, a driving pulley mounted on said column on one side of said work supporting means, the diameter of said pulley being in excess of the diameter of the opening extending through the die,

a driven pulley mounted on said column on the oposite side of said work supporting means, a flexible belt trained over said pulleys and adapted to be passed through the work piece opening and driven by said driving pulley to treat the surface of said opening, means disposed between said driving pulley and said work supporting means for affecting the operative angle of said belt relative to said die between the die and the driving pulley, means for varying the position of said belt angle affecting means relative to said driving .pulley and said die and transversely of the axis of the die whereby the angle of the belt can be substantially conformed to the radius at the entrance end of the die and accordingly be maintained in proper treating engagement therewith, and means mounting said work support means on the column for vertical movement toward and away from the driving pulley, whereby the angle of the belt runs relative to the die may be varied by such movement of the work support.

8. In -a machine for polishing a die having an interior opening characterized by a plurality of different diameters, in combination, means for supporting the die, a flexible member adapted to be passed through the opening in the die and adapted to engage the surface thereof and be driven back and forth therethrough to treat said surface, means for driving said flexible member, a pressure device having a portion adapted to be inserted in the die opening to press said flexible member into engagement with said surface, said surface of the pressure device including a portion of different radii and thus having a conformation similar to the die surface being polished, means for rotating said work piece, means for flexibly mounting said pressure device, and means for urging said pressure device in one di rection only transverse to the axis of the die.

LEWIS R. HEIM.

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