This document provides an overview of manual machining capabilities and processes. It discusses tools and tool selection factors like number of cutting edges and materials. It also covers spindle speeds, feed rates, conventional versus climb milling, material removal guidelines, locating geometric references, achievable tolerances, and a hands-on project. The goal is to explain the basics of performing manual machining.

1. Intro to Manual Machining
FEB 2016

2. Contents
Machining capabilities
Tools and Tool selection
Spindle speeds and feedrates
Conventional vs. climb milling
Material removal – depth of cut guidelines
Locating a geometric reference
Tolerance capabilities
Hands-on practice!
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3. Manual vs. CNC Machining
What can be machined?
What materials can you machine?
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4. Tools
Endmills
◦ # of cutting edges (flutes)  2 vs. 4
◦ Material  High-speed-steel (HSS) vs. Carbide
◦ Center cutting vs. non-center cutting
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5. Tools
Surface cutters
Side cutters
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Fly cutter Face mill
Slit cutter Slot cutters

6. Tools
Edge profile tools
◦ Chamfer
◦ Countersink
◦ Round-over tools
Other Tools
◦ Drills, Taps, Reamers, Engraving tools, etc
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Round-over
Countersink / Chamfer

7. Tool Selection Process
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1. Select Cutter Type  What feature do you need to cut?
2. Select Cutter Flutes What material are you cutting?
3. Select Cutter Size  How big of a cutter can you use?

8. Spindle Speed
Spindle Speed Guidelines (RPM)
Examples:
◦ Cutting aluminum with ¼” endmill
◦ RPM = 250ft/min * 4 / 0.25” = 4000 RPM
◦ Cutting plastic with 10mm endmill
◦ RPM = 75m/min * 318 / 10mm = 2380 RPM
◦ Drilling a 12mm hole in mild steel
◦ RPM = 30m/min * 318 / 12mm = 795 RPM
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Tool Diameter [in]
Material Cutting speed
[meters/minute]
Cutting speed
[Feet/minute]
Aluminum 75-105 250-350
Plastics 75-110 250-400
Mild steel 30-40 100-125
Hard steel 15-18 50-60
RPM = Cutting Speed [ft/min] * 4
Tool Diameter [mm]
RPM = Cutting Speed [m/min] * 318

9. Feedrate
Guideline:
Practical aspect when milling manually;
◦ Often no way to quantify feedrate on manual mills
◦ If in doubt; Start slow and adjust as you go
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Feedrate = # of cutting edges * tool chip load * RPM
Material Chip load
[in/rev]
Aluminum 1.5-2.5% of tool
diameter
Plastics 2.5% of tool
diameter
Mild steel 0.5% of tool
diameter

10. Conventional vs. Climb Milling
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Conventional Milling Climb Milling

11. Material Removal
Depth-of-Cut (DoC) guidelines
◦ If radial depth of cut > 50% of endmill diameter;
◦ Max recommended axial depth of cut: 25% of diameter
◦ If radial depth of cut is < 50% of endmill diameter;
◦ Axial depth of cut * radial depth of cut < 20% of diameter
◦ Max axial depth of cut < 2-4x endmill diameter
◦ Beware of tool deflection and/or vibrations!
Note: For smaller milling machines, power may be a
limiting factor for material removal
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12. Finding a reference
Locating an edge, line or center point (X/Y)
Locating a surface (Z) by touching
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13. Tolerances
Achievable tolerances
◦ Easy: +/- 0.25mm (+/- .010”)
◦ Common: +/- 0.15mm (+/- .006”)
◦ Doable: +/- 0.05mm (+/- .002”)
Key factors to consider;
◦ Fixture and tool rigidity
◦ Feeds and speeds
◦ Workpiece material
◦ Temperature while machining
◦ Machine rigidity setup and calibration
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14. Advanced Machining Topics
Advanced tooling geometry for a optimized cut
Advanced fixturing considerations
◦ Non-flat parts, vacuum, magnetics, etc
Squaring up the vise and mill (tramming)
CNC machining…
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15. Process Overview
1. Decide on fixturing scheme
2. Select appropriate cutter
◦ Type  Flute count  Diameter
3. Determine speed (RPM) based on tool diameter and material
4. Setup and locate physical reference features (edges/surfaces)
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16. Hands-on Project
Read and understand design drawing
Position part in vise
Locate edges with edge finder
Install tool, set RPM, and machine features
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Morten Steen – Founder
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