THINK MILLING, THINK KENNAMETAL - Kennametal - (Version JPG) - Page n° 489 - PDF Catalogue | Technical Documentation

KENNAMETAL

Technical Information

Cutter Pitch

Medium pitch is recommended when moderate feed per insert is required, and where it is more advantageous to have more than one insert in the cut. Medium pitch also reduces entry shock and cutting pressure while maintaining feed rates.

Ffce pitch is ideal when milling a severely interrupted surface such as a manifold block. Fine pitch cutters are capable of higher inch/mm per minute feed rates than medium or coarse pitch cutters. They also experience higher cutting forces and greater horsepower consumption than medium or coarse pitch cutters do.

Dlffeitnlial Pitch

A cutter with unequally spaced inserts is a differential-pitch milling cutter. This configuration breaks up the harmonics that result from equally spaced inserts, greatly reducing the chance of vibration. Most cutters use this design regardless of the cutter pitch.

2D 2C

Pitch, or density, refers to the number of inserts in a cutter. Cutters can be classified as having either coarse, medium, or fine pitch. When designing a cutter, the engineer must take the depth of cut and feed per tooth into consideration. He then must provide the necessary chip clearance in the body so that the chip can pass without restricting its formation. For this reason, cutters designed for heavy metal removal have maximum chip clearance. This, therefore, restricts the number of inserts in the cutter, making it a coarse pitch cutter.

In medium pitch cutters, the chip clearance area in the body is usually slightly smaller than a coarse pitch cutter. And, in fine pitch cutters, the chip clearance is considerably less.

1/J

iE _u

C/3

► PM is recommended for general purpose milling where adequate horsepower is available, and where maximum depth of cut is required.

C/3

: *

coarse pitch

medium pitch

fine pitch

differential pitch

Lead Angles/Cutting Forces on Workpiece and Fixturing

Cutting forces produced during the milling process are constantly changing as the insert moves through the cut. Understanding the relationship of these forces will help ensure safe operation by preventing workpiece movement during the cut. For example, fixture

design and clamp positioning are determined by the cutting forces produced in milling. Equally important is an understanding of the effect lead angle has on cutting force direction, actual chip thickness, and tool life.

0° lead angle

15° and §0° lead angle

45° lead angle

■jj

advantages:

When 90° shoulder is required

• Can be a problem solver on thin wall workpieces

disadvantages:

Highest radial cutting forces

• High entry shock load

• Increased chance of burr on insert exit side of part

advantages:

• For general milling applications and relatively rigid conditions

• Good relation of insert size and maximum depth of cut

• Reduced entry shock load

disadvantages:

• Higher radial forces can cause problems in weak machine/workpiece/fixture conditions

advantages:

• Well balanced axial and radial cutting forces

• Less breakout on workpiece corner

• Entry shock minimized

• Less radial forces directed into spindle bearings

• Higher feed rates possible

disadvantages:

• Reduced maximum depth of cut due to lead angle

• Larger body diameter can cause fixture clearance problems

_LJ

IO 1

z-2 < _LJ 2C

0° lead angle

lead angle

4go lead

5 <

angle

_LJ

table feed

direction of force

table feed

15° and 20° lead

45° lead

X _LJ

0° lead

To place an order, contact Kennametal or your authorized Kennametal distributor, or visit www.kennametal.com.

489

THINK MILLING, THINK KENNAMETAL - Kennametal - #489

Turning tool, Carbide milling cutter, Face milling-cutter, Grooving tool, Chamfering tool