Benefits of Using Double Chamfer End Mills for Machining Operations

Introduction to Double Chamfer End Mills

Double chamfer end mills are a specialized type of milling cutter used in metalworking. As the name suggests, these end mills feature two chamfered corners on the end cutting edges. This design provides specific benefits that make double chamfer end mills useful for certain milling operations.

What is a Double Chamfer End Mill?

A standard end mill has a flat bottom and square corners at the cutting end. In contrast, a double chamfer end mill has angled corners on both sides of the cutting end, essentially forming two chamfers. This creates a rounded bottom edge and two sharp corners on either side.

Double chamfer end mills are still capable of performing end milling, slotting, and pocketing operations like regular end mills. However, the unique shape of the cutting end allows them to excel in specific scenarios related to materials, cut types, and finishing requirements.

Key Features and Benefits

There are several notable features and advantages provided by double chamfer end mill designs:

• The rounded bottom edge improves strength and shock resistance.
• The sharp corners allow for precision machining into corners.
• The chamfers enhance chip evacuation over standard end mills.
• They require lower cutting forces than standard end mills.
• The design enables improved finishes and reduced deflection.

The combination of these characteristics makes double chamfer mills well-suited for sheet metals, aluminum, and weak materials requiring low cutting forces. They also perform well for finishing passes and machining precise corners.

Typical Applications and Uses

Double chamfer end mills provide unique performance advantages for the following types of applications:

• Sheet Metal and Light Alloys - Excellent for aluminum, brass, copper and various steels thanks to lower cutting forces.
• Precise Corner Machining - The sharp corners allow accurate 90-degree shoulder milling.
• Finishing Passes - Produce fine surface finishes while avoiding deflection issues.
• Low Rigidity Setups - Reduced cutting forces prevent deflection on weak/small machines.

These specialized end mills are common in the aerospace industry for thin sheets. They also assist hobbyists using benchtop CNC mills that have limited rigidity for finishing difficult materials.

Differences from Standard End Mills

While capable of general-purpose milling, there are some key differences to consider when comparing double chamfer mills to standard square end mills:

• Lower material removal rates due to smaller core diameter.
• Not suitable for heavy slotting/pocketing in steels and cast iron.
• Require lighter depth of cuts and feeds to benefit from design.
• More limited options for corner radii size.
• Higher cost due to specialized grinding process.

The tradeoffs show that these end mills excel at specific jobs, while standard square mills are better suited for heavy stock removal and slotting with their larger cores and lower cost.

Optimal Cutting Speeds and Feeds

The feed rates for double chamfer mills should be lower than standard end mills to gain the most advantage from their design. Typical feed rates per tooth for various materials are:

• Aluminum Alloys - 0.001" – 0.004" (0.025mm – 0.1mm)
• Mild Steels - 0.0006" - 0.002" (0.015mm – 0.051mm)
• Stainless Steels - 0.0004" – 0.001" (0.01mm – 0.025mm)

Recommended cutting speeds also depend on workpiece hardness and range between 100 – 400 SFM (30 – 120 M/min) for common materials. Both parameters should be reduced for light finishing passes.

Insert vs Solid Carbide Double Chamfer End Mills

Double chamfer mills are available both as solid carbide and with indexable carbide inserts. In general:

• Solid carbide provides higher precision, strength, and speeds.
• Inserted carbide allows for larger diameters at lower cost.
• Inserted tools use replaceable inserts to refresh cutting edges.

Both types take advantage of the double chamfer design for its unique benefits. The choice depends mainly on cost limitations, cutter sizes needed, and precision requirements.

Selecting the Best Double Chamfer End Mill

When selecting a double chamfer end mill for your operation, key factors to consider include:

Diameter and Length of Cut

Available diameters range from very small 1mm (0.039") end mills up to 25mm (1") as replaceable insert options. Choose larger diameters when possible for added tool rigidity.

Corner Radius Size

Typical corner radius options include 0.2mm (0.008”), 0.4mm (0.016”) or 0.8mm (0.031”). Smaller radii allow finer detail while larger assist chip evacuation.

Number of Flutes

2-3 flutes are most common, with 3 flutes generally preferred for fine finishing cuts and weak setups. 2 flutes are still useful for light slotting operations if needed.

Coatings

PVD AlTiN and TiAlN coatings enhance tool life and heat resistance when doing repeated cuts in abrasive materials. Uncoated tools still work but require more maintenance.

Brand and Cost

Reputable manufacturers will ensure high precision grinding and overall reliability. However, cost is also a factor since solid carbide and inserted types have a wide range of prices.

Evaluating all these aspects will lead you to the optimal double chamfer end mill style for your own milling needs.

Techniques for Using Double Chamfer Mills

These tips will help you make effective use of double chamfer end mills on your jobs:

Reduce Depths of Cut

Take light axial depths under 0.25xD cutter diameter and 0.5mm radial cuts to gain benefits of low cutting forces and fine finish capability.

Use Lower Feed Rates

Reduce feed per tooth down to 30% of standard end mill rates. This enhances edge life and reduces deflection issues.

Apply High Spindle Speeds

Run near top rpm rating of machine for best surface feet per minute based on diameter. This improves finish and avoids rubbing.

Use Climb Milling Techniques

Climb milling is preferred to reduce rubbing issues when possible. It also allows taking slight back cuts to clean up edges.

Take Multiple Finishing Passes

Use progressively lighter axial depths of cut on finishing pass iterations. This significantly enhances workpiece surface finish.

Implementing these best practices during your operations will deliver the full potential from your double chamfer end mills for precision jobs.

FAQs

What materials can I machine with a double chamfer end mill?

Double chamfer mills work well for light alloys like aluminum, brass, and copper. They also perform well in mild and stainless steels thanks to low cutting forces. Avoid cast iron and hardened steels over 45 HRC.

When should I choose a double chamfer over a standard end mill?

Consider a double chamfer mill if you need to machine precise corners, require fine surface finishes, work with thin sheets and plates, or have limited machine rigidity. They excel at finishing passes.

What size corner radius should I choose?

Typical options include 0.2mm, 0.4mm, or 0.8mm corner radii. Choose smaller radii for detailed corners down to 0.1mm, or larger radii if prioritizing chip clearance and tool life over precision.

Can I do slotting and pocketing operations?

Light slotting is possible but avoid deep pocketing compared to standard end mills. Take light 0.5mm radial passes at reduced feed rates instead. Side step-over passes allow clearing pockets.