METHOD FOR MANUFACTURING AN INSERT POCKET OF A CUTTER BODY

Abstract

A method for manufacturing an insert pocket of a cutter body is disclosed. First, the insert pocket of the cutter body a rough milling process. Then, the insert pocket is forged using a forging tool having a shape that generally conforms to the shape of the insert pocket. Then, the insert pocket undergoes a finish milling process to qualify the pocket geometry without removing the majority of the forge-enhanced pocket material. The insert pocket can be optionally heated prior to the forging step. The grain orientation of the inset pocket is compressed by the forging process to increase the impact and fatigue resistance of the insert pocket.

Description

BACKGROUND OF THE INVENTION

Forging is a manufacturing process involving the shaping of metal using localized compressive forces. Forging is often classified according to the temperature at which it is performed: “cold,” “warm,” or “hot” forging. Forged parts can range in weight from less than a kilogram to 580 metric tons. Forged parts usually require further processing to achieve a finished part.

Forging is one of the oldest known metalworking processes. Traditionally, forging was performed by a smith using hammer and anvil, and though the use of water power in the production and working of iron dates to the 12th century, the hammer and anvil are not obsolete. The smithy or forge has evolved over centuries to become a facility with engineered processes, production equipment, tooling, raw materials and products to meet the demands of modern industry.

In modern times, industrial forging is done either with presses or with hammers powered by compressed air, electricity, hydraulics or steam. These hammers may have reciprocating weights in the thousands of pounds. Smaller power hammers, 500 lb (230 kg) or less reciprocating weight, and hydraulic presses are common in art smithies as well. Some steam hammers remain in use, but they became obsolete with the availability of the other, more convenient, power sources.

Forging can produce a piece that is stronger than an equivalent cast or machined part. As the metal is shaped during the forging process, its internal grain deforms to follow the general shape of the part. As a result, the grain is continuous throughout the part, giving rise to a piece with improved strength characteristics.

Some metals may be forged cold, however iron and steel are almost always hot forged. Hot forging prevents the work hardening that would result from cold forging, which would increase the difficulty of performing secondary machining operations on the piece. Also, while work hardening may be desirable in some circumstances, other methods of hardening the piece, such as heat treating, are generally more economical and more controllable. Alloys that are amenable to precipitation hardening, such as most aluminum alloys and titanium, can be hot forged, followed by hardening.

Production forging involves significant capital expenditure for machinery, tooling, facilities and personnel. In the case of hot forging, a high temperature furnace (sometimes referred to as the forge) will be required to heat ingots or billets. Owing to the massiveness of large forging hammers and presses and the parts they can produce, as well as the dangers inherent in working with hot metal, a special building is frequently required to house the operation. In the case of drop forging operations, provisions must be made to absorb the shock and vibration generated by the hammer. Most forging operations will require the use of metal-forming dies, which must be precisely machined and carefully heat treated to correctly shape the workpiece, as well as to withstand the tremendous forces involved.

There are many different kinds of forging processes available, however they can be grouped into three main classes:

1) Drawn out: length increases, cross-section decreases;
2) Upset: Length decreases, cross-section increases; and
3) Squeezed in closed compression dies: produces multidirectional flow.

Common forging processes include: roll forging, swaging, cogging, open-die forging, impression-die forging, press forging, automatic hot forging and upsetting.

Due to the interrupted-cut nature of a metalworking machining operation, the pockets of a tool holder are subjected to impact and fatigue loading. Various techniques, materials, and material properties, such as gas-nitriding, laser hardening, tool steels, increased hardness, and the like, have been used in the past to increase the stability and life of the pockets in the tool holder.

SUMMARY OF THE INVENTION

The problem of lack of stability and life of insert pockets of a cutter body has been solved by a method for manufacturing an insert pocket of a cutter body comprising:

• • a) rough milling an insert pocket of a cutter body;
  • b) forging the insert pocket using a forging tool; and
  • c) finish milling the insert pocket.

The insert pocket can be heated prior to the forging step.

BRIEF DESCRIPTION OF THE DRAWINGS

While various embodiments of the invention are illustrated, the particular embodiments shown should not be construed to limit the claims. It is anticipated that various changes and modifications may be made without departing from the scope of this invention.

FIG. 1 is a perspective view of a forging tool for manufacturing an insert pocket according to an exemplary embodiment of the invention;

FIG. 2 is a perspective view of the forging tool of FIG. 1 approaching a cutter body during a forging operation;

FIG. 3 is a partial cross-section view of the grain orientation of an insert pocket manufactured using the method of the invention; and

FIG. 4 is a partial cross-section view of the grain orientation of a conventional insert pocket.

DETAILED DESCRIPTION OF THE INVENTION

Below are illustrations and explanations for a method for manufacturing an insert pocket of a tool holder. However, it is noted that the fastener may be configured to suit the specific application and is not limited only to the example in the illustrations.

Referring to FIGS. 1 and 2, wherein like reference characters represent like elements, a forging tool 10 for forging an insert pocket 12 of a cutter body 14 is shown according to an embodiment of the invention. The tool 10 includes a head portion 16 and a body portion 18. The head portion 16 includes a forward end 20 with a front surface 22 that has a shape that generally conforms to the shape of the bottom surface 32 of the insert pocket 12. The head portion 16 also includes a plurality of side surfaces 24 that extend from the front surface 22 rearwardly toward the body portion 18 of the tool 10. The side surfaces 24 have a shape that generally conforms to the shape of side support surfaces 34 of the insert pocket 12. In the illustrated embodiment, the head portion 16 includes a total of four (4) side surfaces 24, of which at least two generally conform to two side support surfaces 34 of the insert pocket 12. However, it will be appreciated that the invention is not limited by the number of side surfaces 24, and that the invention can be practiced with any desirable number of side surfaces 24 that are required to generally conform in shape to the number of support side surfaces 34 of the insert pocket 12. The head portion 16 may also include one or more radiused corner surfaces 26 that provide clearance for the tool 10 during use.

In one example of the cutter body 12, the cutting body 12 is made of AISI 4340 alloy steel. AISI 4340 is a heat treatable, low alloy steel containing nickel, chromium and molybdenum. It is known for its toughness and capability of developing high strength in the heat treated condition while retaining good fatigue strength. AISI 4340 steel, oil quenched 845 Deg C., 650 Deg C. (1200 Deg F.) temper, has the following properties (www.matweb.com):

Chemistry Data (%):

Carbon, C      0.37-0.43
Chromium, Cr   0.7-0.9
Iron, Fe       Balance
Manganese, Mn  0.6-0.8
Molybdenum, Mo 0.2-0.3
Nickel, Ni     1.65-2.00
Phosphorus, P  0.035 max
Silicon, Si    0.15-0.3
Sulphur, S     0.04 max

Physical Data:

Density (lb/in3)                 0.284
Specific Gravity                 7.8
Specific Heat (BTU/lb/Deg F. - [32-212 Deg F.]) 0.114
Melting Point (Deg F.)           2600
Thermal Conductivity (BTU-in/hr-f2-Deg F.) 309
Mean Coeff Thermal Expansion     6.6
Modulus of Elasticity Tension    33

Mechanical Properties:

Hardness, Brinell                217
Hardness, Knoop                  240
Hardness, Rockwell B             95
Hardness, Rockwell C             17
Hardness, Vickers                228
Tensile Strength, Ultimate (psi) 145800
                                 208100
Tensile Strength, Yield (psi)    136000
                                 200000
Elongation at Break (%)          22.0
                                 22.0
Reduction of Area (%)            60.0
                                 40.0
Modulus of Elasticity (ksi)      30900
                                 31800
Bulk Modulus (ksi)               20300
Poissons Ratio                   0.290
Machinability (%)                50
Shear Modulus (ksi)              11900

A method for manufacturing the insert pocket 12 using the method of the invention will now be described. First, the insert pocket 12 is rough milled using well-known techniques. Next, the insert pocket 12 is forged using the forging tool 10 exerting a pressure against the insert pocket 12 that exceeds the yield tensile strength of the material of the cutter body 12. Using AISI 4340 alloy steel described in the above example, the forging tool 10 exerts a pressure greater than 136000 psi against the insert pocket 12 for oil quenched AISI 4340 alloy steel, and greater than 200000 psi for oil quenched, tempered AISI 4340 alloy steel. Next, the insert pocket 12 is finished milled to its final shape.

The insert pocket 12 may be heated to a sufficient temperature prior to forging the insert pocket 12. In one embodiment, the insert pocket 12 is heated to about 800 Deg C. However, it will be appreciated that the invention is not limited by the temperature at which the insert pocket 12 is heated prior to forging the pocket 12, and that the invention can be practiced using any sufficient temperature that will assist in the plastic deformation of the material used for the cutter body 14 during the forging of the insert pocket 12

As shown in FIG. 3, the grain orientation (shown as solid lines) of the insert pocket 12 is much more compressed in the vicinity of bottom surface 32 and the side support surfaces 34, as compared to a conventional insert pocket 112, as shown in FIG. 4, with a bottom surface 132 and side support surfaces 134. As a result of this compressed grain structure, the density and toughness of the surfaces 32, 34 of the insert pocket 12 is much greater in the insert pocket 12 manufactured using the method of the invention, thereby increasing the impact and fatigue resistance of the insert pocket 12, as compared to the conventional insert pocket 112.

As described above, the method of the invention provides a simple solution for increasing the impact and fatigue resistance of an insert pocket of a cutter body by changing the grain structure of the surfaces 32, 34 of the insert pocket 12 using a forging process.

The patents and publications referred to herein are hereby incorporated by reference.

Having described presently preferred embodiments the invention may be otherwise embodied within the scope of the appended claims.

Claims

1. A method for manufacturing an insert pocket of a cutter body, the method comprising:

a) rough milling an insert pocket of a cutter body;

b) forging the insert pocket using a forging tool; and

c) finish milling the insert pocket.

2. The method of claim 1, further comprising the step of heat treating the insert pocket after rough milling the insert pocket and prior to forging the insert pocket.

3. The method of claim 1, wherein the forging tool has a shape that generally conforms to a bottom surface and side surfaces of the insert pocket.

4. The method of claim 1, wherein the insert pocket is made of a steel alloy, and wherein the forging tool exerts a force that exceeds a yield stress of the insert pocket.

5. The method of claim 4, wherein the tool holder is made of AISI 4340 steel, and wherein the forging tool exerts a force of at least 136000 psi against the insert pocket.

6. The method of claim 1, wherein the forging tool includes a head portion and a body portion.

7. The method of claim 5, wherein the insert pocket includes a bottom surface and a plurality of side support surfaces, and wherein the head portion has a shape that generally conforms to the shape of the insert pocket.

8. A forging tool for manufacturing the insert pocket of the cutter body according to the method of claim 1.