Feeds & Speeds

Formulas for Feeds and Speeds

Welcome to our comprehensive guide on calculating speeds and feeds for machining operations. As a seasoned machinist, I want to emphasize that the figures provided here serve as a foundational starting point. It’s crucial to note that these recommendations are tailored for High-Speed Steel (HSS) tools. The nature of the tool material, be it HSS or Carbide, significantly influences the optimal speeds and feeds for any given operation. This guide aims to equip you with the knowledge to make informed decisions on your machining processes, ensuring efficiency and precision in your work.

 

Taps Spindle Speed

RPM=SFPM.26 x Tap OD

SFPM=Surface Feet Per Minute

Material

SFPM

Lubricant

Aluminum

70-90

Soluble Oil

Brass

60-100

Light base Oil

Copper

60-80

Light base Oil

Grey Cast Iron

30-60

Dry or soluble oil

Alloy Cast Iron

15-30

Sulphur Based Oil

Malleable Iron

20-40

Soluble Oil

Magnesium

50-70

Soluble Oil

Plastics

50-70

Dry, Liquid Soap

Mild Steel

30-50

Sulphur Based Oil

Carbon Steel to 4%

20-40

Sulphur Based Oil

Carbon Steel to 7%

20-30

Sulphur Based Oil

Carbon Steel to 7% or more

15-25

Sulphur Based Oil

Stainless Steels

10-20

Sulphur Based Oil

Tool Steels

15-25

Sulphur Based Oil

Drilling, Reaming and Counterboring

RPM=4 x SFPM Diameter

Drilling Spindle Speeds

Material

SFPM

Aluminum-

200-300

Bakelite-

100-150

Plastics-

100-150

Brass and bronze-

200-300

Bronze, high tensile

70-100

Cast iron, chilled

30-40

Cast iron hard

70-100

Cast iron soft

100-150

Magnesium

250-400

Malleable iron

80-90

Monel, metal

40-50

Nickel

40-60

Steel annealed

60-70

Forged steel

50-60

Stainless, easy

60-70

Stainless, hard

30-40

Tool steel

50-60

Slate marble and stone

15-25

Wrought Iron

50-60

Reaming and Counterboring Spindle Speeds

Material

SFPM

REAMING

SFPM

COUNTERBORE

Steel, 1018

65

45

Steel, 4140

60

40

Steel, 4340

45

30

Stainless Steel, 303 ( Easy )

50

50

Stainless Steel, 304 ( Hard )

35

25

Aluminum

300

125

Plastic

180

150

Polycarbonate

160

120

FEEDRATES

Feed=Speed x IPR

Drilling and Reaming Feedrates

Drill Diameter

Feed (IPR)

Under .125

.001-.002

.125-.25

.002-.004

.25-.5

.004-.007

.5-1.

.007-.015

Reamer Diameter

Feed (IPR)

Under .125

.003-.006

.125-.25

.005-.009

.25-.375

.007-.012

.375-.5

.01-.015

.5-.75

.015-.031

Counterboring Feedrates

Counterbore Diameter

Feed (IPR)

.375

.004

.625

.005

.875

.006

 

Beyond the foundational data provided, successful machining requires a keen understanding of your specific machine’s capabilities, the unique properties of the material being machined, and the cutting environment. Factors such as machine rigidity, coolant use, and tool wear can all impact the optimal speeds and feeds for your projects. I encourage machinists to use this guide as a starting point and to experiment and adjust based on real-world results and experiences. Remember, the goal is not just to complete the job but to optimize for longevity, surface finish, and efficiency. Happy machining!

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