Speeds and Feeds

Spindle speeds given in RPM Revolutions Per Minute

RPM Formula:

Applies to lathe, mills, drilling, etc.

Cutting Speed normally given in tables based on Surface Feet Per Minute (SFPM) tool to work piece relationship # of feet per minute that pass formula converts to inches per minute

Cutting speed tables in text

CS D = ? Drill Press = Dia of twist drill Lathe (Drilling) = Dia of twist drill Lathe (Turning) = Dia of work piece Vertical Mill = Dia of cutter Horizontal Mill = Dia of cutter

Cutting speed constants influenced by: tool material work material rigidity of setup use of cutting fluids

Use lower cutting speeds for machining hard or tough materials if vibration or chatter

Feed the machine movement that causes the tool to cut along the surface of the work usually measured in thousandths of an inch expressed in different ways on different machines

Drilling Feed Rates feed expressed in inches per revolution (IPR) drill advances into the work a given amount for each revolution no formula - simply look up in table

Sensitive drill press no power feed operator senses or feels the correct amount of feed

Drilling feed variables drill diameter drill material work material

Lathe Feed Rates (Two)

1.) Turning expressed in IPR single point cutting tool advanced along the work a given amount for each revolution no formula - look up in table

2.) Facing Feed Rates expressed in IPR no formula - look up in table problem of uniform finish on large diameter work piece CNC lathes equipped with Constant Surface Speed

Turning & Facing variables tool material work material surface finish required depth of cut - roughing cuts should be as much as possible without undo stress

Milling Vertical and Horizontal Milling expressed in Inches Per Minute (IPM)

Milling Feed Formula: Feed (IPM) = RPM x # teeth x IPT IPT = inches per tooth taken from table Vertical Milling IPT usually between.001” and.010”

General rule for depth of cut in steel for end mills standard end mill depth is approx. 1/2 diameter of the tool roughing end mill depth is approximately 1-1/2 times the diameter of the tool

Calculating drill point angle distance.3 x Diameter of the drill example: 1/2” drill.5 x.3 =.150” drill point angle distance