Cutting Speed and Feed

Cutting speedCutting speed for drilling is the rate at which

the tool passes over the surface of the metal.

i.e how fast the cutting tool is spinning . It is

commonly expressed in metres per minute.

Cutting speeds depend on:The material being cutCondition and strength of the tool and machineDepth of cutRate of feedMaterial of which the tool is madeAvailability of cutting fluidSize of the bit being used

Cutting speed selectionThe softer the work material, the faster the

recommended cutting speed

The hardness of the cutting tool material has a great deal to do with the recommended cutting speed. The harder the cutting tool material, the faster the cutting speed. The softer the cutting tool material, the slower the recommended cutting speed

Calculating cutting speedGiven in metres per minutespindle speed of machine (N) and diameter

of work must be known

S (m/min)= πDN/1000Where π= 22/7 or 3.142 D= diameter of material N= Spindle speed(rev/min)

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Spindle SpeedThe rate at which the spindle rotates. It is

commonly expressed in revolution per minute.

Calculating Spindle speed (rev/min)

D xS1000 rev/min

S (m/min)= cutting speedWhere π= 22/7 or 3.142 D= diameter of material N= Spindle speed(rev/min

ExamplesCalculate rev/min required to drill a hole

15mm diameter in a piece of machine steel (CS 90)

Find the cutting speed of a 10mm diameter drill with a spindle of 178 rev/min.

5. Find the cutting speed for: Diameter 9mm. Spindle speed 180rev/min Diameter 6mm. spindle speed 20rev/min Diameter 5mm. spindle speed 160rev/min spindle speed 120 rev/min. Diameter 10mm.

6. Find the spindle speed for: Diameter 16mm. Surface speed 20 m/min Diameter 14mm. Surface speed 30 m/min Diameter 15mm. Surface speed 15 m/min.

FeedFeed rate is the velocity at which the drill bit

is fed, that is, advanced into the work piece.

Feed rate is dependent on the:Type /size of the tool Surface finish desiredPower available at the spindle Rigidity of the machine and tooling setup Strength of the work piece set up Characteristics of the material being cut, chip

flow depends on material type and feed rate. Depth of cut