Machining Formulas

(Check out our Feeds and Speeds page fore milling and turning formulas)

Welcome to our ultimate guide on essential machining formulas, a foundational toolset for anyone in the field of precision machining. These formulas are pivotal for executing CNC machining operations with accuracy and efficiency, serving as your go-to resource for daily machining tasks. While this collection covers the most commonly used calculations in CNC machining and manual machining alike, it’s just the beginning of what’s available in the expansive realm of machining knowledge.

Whether you’re a seasoned machinist looking to refine your machining techniques or a newcomer eager to establish a strong footing in CNC machining, these machining formulas are designed to ensure excellence in every project. Remember, the world of machining operations is vast, with advanced formulas and sophisticated machining techniques extending far beyond this guide. However, integrating these essential calculations into your daily machining efficiency practices will significantly impact your work’s quality and precision. Let’s embark on this journey through the detailed landscape of machining, making these indispensable formulas a part of your everyday machining toolkit.

Inch to Metric


# * .03937

Drill Size for Metric Tap

Diameter-Pitch= Drill Size

Example: m8x1.25

8-1.25= 6.75mm= drill size for M8x1.25 tap

Drill Size for Inch Tap

Diameter- Pitch= Drill Size

Example: 1/2-13

13 threads per inch….1/13= .0769

.0769= Pitch

.5-.0769=.4231= Drill size

Distance from Drill shoulder to tip

(Basic rule can be specific per angle of drill)

Diameter of drill * .3 (This is what I personally use for all drills)

OR more specifically

Drill Point Angle:

60 Degree = 0.866 X Drill Diameter = Drill Point Length

82 Degree = 0.575 X Drill Diameter = Drill Point Length

90 Degree = 0.500 X Drill Diameter = Drill Point Length

118 Degree = 0.300 X Drill Diameter = Drill Point Length

120 Degree = 0.288 X Drill Diameter = Drill Point Length

135 Degree = 0.207 X Drill Diameter = Drill Point Length

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