Choosing the Right End Mill: Part 2 -Getting the Most from Your Tool

In Part 1 of our end mill series, we covered how material, flute count, geometry, and coating can help determine which end mill is right for an application. 

But selecting the tool is only part of the equation. 

How you set up and run that end mill can have just as much impact on tool life, surface finish, and cost per part. 

Keep Tool Length in Check 

It can be tempting to choose a longer end mill simply because it provides more reach. But longer isn’t always better. 

As tool length and overhang increase, so does the potential for deflection and vibration. That can contribute to: 

• Chatter 

• Poor surface finish 

• Dimensional inaccuracies 

• Uneven tool wear 

• Premature tool failure 

Whenever possible, use the shortest tool and cutting length that can safely complete the application. 

Choose the Right Diameter 

Tool diameter affects rigidity as well as the features you’re able to machine. 

A larger-diameter end mill generally provides greater rigidity, while smaller tools may be necessary for tight corners and detailed features. 

When the application allows, choosing the largest practical diameter can help create a more rigid cutting setup. 

Look Beyond the End Mill 

Even the right cutting tool can struggle if the rest of the setup isn’t working with it. 

Machine rigidity, toolholder condition, runout, workholding, and tool overhang can all affect performance. 

Excessive runout, for example, can cause one cutting edge to take more of the load than the others. That creates uneven wear and can shorten tool life. 

Think of the end mill as one part of the complete machining system rather than an isolated component.

Get Your Feeds and Speeds Right 

The right end mill still needs the right cutting parameters. 

Spindle speed, feed rate, chip load, radial depth of cut, and axial depth of cut all influence tool performance. 

Running too aggressively can create excessive heat or cutting forces. But running too conservatively isn’t necessarily better. If a tool isn’t forming a proper chip, it may rub against the workpiece instead of cutting effectively, generating heat and accelerating wear. 

The manufacturer’s recommended parameters are a good starting point. From there, adjustments can be made based on the machine, setup, material, and actual cutting conditions. 

Don’t Judge an End Mill by Price Alone 

It’s easy to compare two end mills based on purchase price. But that’s only one part of the cost. 

A better comparison considers: 

• Tool life 

• Cycle time 

• Parts per tool 

• Tool change frequency 

• Machine downtime 

• Scrap and rework 

• Overall cost per part 

  
  

An end mill that costs more upfront may actually cost less to run if it lasts longer, reduces cycle time, or produces more consistent parts. 

Look at the Complete Process 

If an end mill isn’t performing as expected, the solution isn’t always switching brands or simply slowing down the machine. 

Look at the complete application. Tool selection, toolholding, rigidity, runout, feeds and speeds, and machining strategy all work together. 

Small adjustments in any one of these areas can sometimes make a significant difference in tool life and productivity. 

Butler Bros. works with manufacturers to evaluate cutting tool applications and identify opportunities to improve tool life, productivity, and cost per part. If you’re trying to solve a tooling issue or determine whether there’s a better option for an application, reach out to your Butler Bros. representative to start the conversation