ROUGHING BORE FINISHING TOOL HAVING TAPERED MANDREL COATED WITH ABRASIVE MATERIAL

Abstract: A one-step bore finishing tool including an expandable sleeve (12) mounted on a tapered mandrel (14) and with the mandrel having an abrasive coating (17) thereon for increasing the frictional engagement of the sleeve (12) with the mandrel (14).

Description: ROUGHING BORE FINISHING TOOL HAVING TAPERED MANDREL COATED WITH ABRASIVE MATERIAL DESCRIPTION Technical Field The present invention relates generally to bore finishing tools having an expandable sleeve mounted on a tapered mandrel. The mandrel is provided with an abrasiv coating to increase the frictional engagement of the sleeve and mandrel, thereby preventing relative rotation between the sleeve and the mandrel. The sleeve is formed with a lead-in taper at its lower end; a section of reduced taper; a cylindrical section; and a reverse taper at its upper end. Background Prior Art Expandable finishing tools are known in the art. For example, U. S. Patent No. 4,173,852 to Fitzpatrick discloses an expandable cutting tool for machining a bore, wherein the tool includes an expandable cutting section that is adjustable to machine the bore to the required size. Another example is U. S. Patent No. 4,253,279 to Althen, which discloses a honing device having an expandable sleeve mounted on a tapered shaft. The sleeve is mounted on a mandrel having tapered portions, and has an elongated slot extending the full length of the sleeve. The sleeve includes helical grooves which aid in removing material from the bore. Summary of the Invention The present invention discloses an adjustable bore finishing tool designed as a one—pass device, that is, it moved only once through a bore to remove a significant am of material and to accurately finish and size the surface the bore. The bore finishing tool of the invention utili particles of wear-resistant abrasive substance on the out surface of a sleeve and may be adjustable. The present invention includes an expandable sleeve mounted on a tapered mandrel for adjusting the diameter o the cutting lands. Due to the large grooves and long lea the tool can take a significantly larger cut than known types of tools. It is important that the grooves be at least as wide or wider than the cutting lands and the lea be approximately two times the length of the sleeve. Importantly, the present invention includes an abrasive coating on the tapered mandrel to provide an improved coefficient of friction between the mandrel and the sleeve. With the improved cutting tool, multiple pass finish¬ ing of bores is eliminated. For example, one pass with th tool of the present invention will remove enough material to presize the hole to a close tolerance. If required, th hole can then be honed to an even closer tolerance. This eliminates the need for reaming on soft materials such as die cast stators or frames for small motors. Brief Description of Several Views of Drawings The foregoing features and advantages of the present invention will be apparent from the following more particular description of the invention. The accompanying drawings, listed hereinbelow, are useful in explaining the invention wherein: FIGURE 1 is an isometric view of the inventive tool; FIGURE 2 is a plan view of one embodiment of the inventive tool; OMPI FIGURE 3 is a cross-sectional view taken along the line 3-3 of FIGURE 2; and, FIGURE 4 is a schematic diagram of the external sha of the cutting tool. Detailed Description An expandable cutting tool constructed in accordance with the present invention is indicated by the reference numeral 11 in the drawings. The cutting tool 11 sizes an finishes a bore upon the rotatable and axial tool movemen through the bore. The cutting tool shown generally at 11 includes a unitary tool body having a solid tapered shaft or mandrel 14, terminating at one end in a diametrically enlarged mounting portion 16. A sleeve 12 is mounted on the mandrel 14. A pilot and adjusting nut 18 is threaded on the tip 20 of the mandrel 14, as shown in FIGURE 2. The mandrel 14 includes a tapered body portion 21 extendi from adjacent the threaded tip 20 to the shoulder 22 of t mandrel 14. The length and degree of the taper will vary with each application. The cutting sleeve 12 comprises an elongated hollow member, which is slipped onto mandrel 14 with a tight fit. Cutting sleeve 12 includes helically extending cutting lands 24, plated with a suitable cutting abrasive such as fine diamond particles or grit 26. The cutting lands 24 are separated by clearance grooves 25, in left-handed helical configuration, which in operation allow the coolan to flow easily and thereby aid in chip removal and prevent clogging of the cutting lands. It also improves chip clearance and coolant circulation to prevent overheating and binding during the cutting operation. The sleeve 12 includes a slot 15 extending in a helical path, also in a left-handed helix, along the full length of the sleeve. The lead of the helical cutting lands 24 is approximately equal to twice the length of sleeve 12. The configuration of the slot is shown in the cross-sectionaliview of FIGURE 3 in which the bore hole is shown in dotted lines. This slot provides for expansion of the sleeve 12 and compensates for abrasive coating wear. The abrasive diamond grit 26 is plated along the helical cutting lands 24 of sleeve 12. The diamond plati along the lands 24 extends approximately .060 inch over t edges of the lands toward the clearance groove 25 (see FIGURE 3) . The quantity of cutting lands can vary depending upon the outside diameter of the sleeve to achieve the proper percentage of cutting land surface relative to the total circumference surface of the sleeve. It has been found that the width of the groove 25 is alwa greater than the width of the cutting lands 24 in order t permit the increased cutting. As is well know, in operation the tool 11 is inserte into the bore and rotated while being driven axially through the rough bore. Because of the configuration of the sleeve 12, a single pass can provide a fully-finished bore. The cutting action of the diamond grit 26 gradually removes material as the taper 21 goes deeper into the bore. The cutting load is thus spread out over the gradua taper of the diamond cutting surface. The final 'size of the bore will match the major diameter of the tool's taper at the end of the pass through the hole; and the finish is related to the fineness of the selected particles. As shown in FIGURE 4, the exterior surface of the cutting sleeve 12 is slightly tapered from its lower end adjacent the nut 18. The lower end of the sleeve 12 from 30 to 31 is tapered to provide a lead-in portion. From 31 to 32, the cutting sleeve 12 is tapered slightly less with the section from 32 to 33 being cylindrical. From reference 3 to 34, the tool is tapered inwardly. The bore 35 of the cutting sleeve 12 matches the taper of the mandrel 14. To adjust the sleeve 12, the pilot and adjusting nut 18 is rotated; and, as it is moved upwardly (as oriented in FIGURES 1 and 2) , the nut 18 engages the shoulder 29 and drives the sleeve upwardly on tapered mandrel 14, thereby forcing the sleeve 12 to expand out¬ wardly a limited selected amount. The inwardly-directed shoulder 29 at the lower end of the sleeve 12 provides a bearing surface to accommodate the force of nut 18. Importantly, the tapered mandrel 14 is plated along at least a portion thereof with an abrasive gripping material in the form of grit 17 to increase the coefficie of friction between the inner diameter of the sleeve 11 and the outer diameter of the mandrel 14. Thus, the abrasive material 17 on the tapered mandrel 14 provides a gripping action against rotational, as well as axial, movement of the sleeve. The improved tool provides various advantages, in¬ cluding the feature that the sleeve 12 is securely retain in any adjusted position. Adjustment can be readily and precisely made by means of the adjusting nut 18 while not disturbing the true axial alignment of the tool 11. Further, the means of adjustment are relatively inexpensi With prior art forms of tools, multiple passe through a bore were required because of the need to remove material. The tool of the present invention enables a two or three spindle machine to cut and finish a precise bore in a one or two pass operation without sacrificing accuracy or surface finish. The present tool eliminates roll burnishi or reaming, thus reducing the cost of the finished part. While the invention has been particularly shown and described with reference to a preferred embodiment thereof it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims: CLAIMS 1. A roughing bore finishing tool, including a tapered mandrel, an expandable sleeve mounted on said mandrel, slot means extending axially on the sleeve, adjustable means on the end of the mandrel for adjusting the axial position of said sleeve whereby said sleeve may be moved axially on said mandrel and the diameter thereof expanded, and an abrasive material plated on the mandrel for increasing the coefficient of friction between the mandrel and the sleeve to securely position the sleeve on the mandrel and prevent relative rotation between the sleeve and the mandrel. 2. A tool as in Claim 1, wherein said sleeve has a interior diameter essentially open on one end and a restricted opening on the other end, a pilot and adjustin nut at the entrance end of the mandrel, and positioned to abut and drive against the restricted end of said sleeve. 3. A tool as in Claim 1, including a helical cutti land having a lead which is approximately equal to two ti the sleeve length. 4. A tool as in Claim 3, wherein the slot extends along the space between the lands in the same helical configuration as the land. 5. A tool as in Claim 1, wherein the slot extends along the full length of the sleeve. 6. A tool as in Claim 2, wherein the taper of said mandrel increases from one diameter at the pilot and adjusting nut to a larger diameter at an axially central point on the mandrel. 7. A tool as in Claim 1, including a helical cutting land and grooves on opposite sides of such cutting land, said grooves being greater in circumferential width than the adjacent cutting land.

Inventors: BOUCHARD DONALD W, DOMANSKI STANLEY K, BOUCHARD, DONALD, W., DOMANSKI, STANLEY, K.
Applicants: ENGIS CORP, ENGIS CORPORATION
Application year: 1983
Main classification: B24B33
IPC codes: B23D77, B24B33