1. Have Conventional Shaft Keyway Machining Processes Become the Unquestioned Norm?

For shaft keyways, particularly closed-end pocket shapes, the tool cannot enter from the side.
Therefore, the method used to reach the required machining depth has a significant impact on machining time and the number of tools required.
The following three methods are commonly used.

Method 1: Ramping with an End Mill

The end mill enters the workpiece at an angle and gradually cuts down to the specified depth.
It then moves laterally to machine the inside of the slot, followed by shoulder milling around the periphery for finishing.
Although this method limits the number of tool changes, it requires sufficient entry distance to reach the machining depth.
For deep slots, the ramping path becomes longer and may prevent reductions in machining time.

Method 2: Repeated Shallow Cuts and Lateral Feed Movements

The axial depth of cut is set to a small value, and the inside of the slot is machined through repeated Z-axis cuts and lateral feed movements.
Although this makes it easier to reduce the load on the tool, it increases the number of passes.
When peripheral finishing is also included, the machining time required for each keyway tends to become longer.

Method 3: Drilling a Pilot Hole and Machining the Slot with an End Mill

A drill is used to create a pilot hole to the required machining depth.
The tool is then changed to an end mill, which machines the inside of the slot and performs shoulder milling around the periphery for finishing.
This method reduces both the ramping distance and the entry load on the end mill, but it creates the following challenges.

• Both a pilot-hole drill and an end mill are required
• Tool changes are required
• More tool pockets and driven-tool units are required
• Tool offset and tool-life management are required for each tool
• Tool inventory and setup work increase

2. VVFH Connects Drilling to Peripheral Finishing

VVFH is a three-flute square end mill with center-cutting edges that enable drilling.
It can drill directly in the Z direction at the machining start position.
After reaching the specified depth, it can move laterally to machine the inside of the slot.
It can then proceed directly to shoulder milling around the keyway periphery for finishing.

Comparison of Machining Methods

Conventional Ramping Method

Conventional Drill-and-End-Mill Method

Machining with VVFH

3. Three Technologies Supporting Stable VVFH Machining

Drilling and slot machining differ in both the direction of the load applied to the tool and the conditions under which chips are evacuated.
VVFH incorporates technologies that enable these different machining operations to be performed with a single tool.

Feature 1: Three Center-Cutting Edges for Drilling

VVFH features three center-cutting edges.
During drilling, all three cutting edges engage in the cut, distributing the load across the cutting edges.
Because the cutting edges remain functional at the center of the tool, VVFH can enter directly in the Z direction from the machining start position and then transition to lateral feed.

Feature 2: 150% Flute Volume Compared with the Conventional Design

During drilling, the tool is surrounded by the workpiece, making the space available for evacuating generated chips particularly important.
VVFH uses large chip pockets and provides
150% of the flute volume of the conventional design
(source: internal product documentation).
This structure reduces chip accumulation during drilling and facilitates a smooth transition to subsequent lateral feed machining.

This large flute volume not only benefits drilling but also
contributes significantly to improved chip evacuation during full-slot machining.
In full-slot operations such as keyway machining, the entire tool diameter is engaged in the cut, producing a large volume of chips simultaneously.
Greater flute volume makes it more difficult for chips to accumulate inside the pockets and prevents increases in cutting load caused by chip recutting.
This enables
consistently stable machining from drilling through slot machining.

Feature 3: Chatter Resistance with Variable Lead Geometry

During lateral slot machining, the entire tool diameter is engaged in the cut, resulting in high cutting loads and a greater tendency for vibration to occur.
VVFH employs a variable-lead design.
Its chip-evacuation performance and chatter resistance support toolpaths that transition from drilling to lateral feed in keyway and pocket machining.

4. Selecting the Right Shank to Maximize VVFH Performance

In shaft keyway machining, it is important not only to select the appropriate VVFH head but also to ensure sufficient rigidity throughout the entire tool assembly, including the shank.
During full-slot machining and peripheral shoulder milling, radial loads are applied to the tool.
As a basic principle, the tool assembly should be
as short and as thick as possible.

VSSD High-Rigidity Shank

VSSD uses a straight shank that is larger in diameter than the head connection thread, increasing the rigidity of the entire tool assembly.
It reduces tool deflection in applications subject to high radial loads, such as full-slot keyway machining and machining long slots.
In an internal slot-machining test, it demonstrated
chatter-free machining at up to three times the depth of cut of the solid end mill used for comparison.

Applications where VSSD is effective:

• Full-slot keyway machining
• Machining long slots
• High-load machining of materials such as SCM steel
• Applications experiencing chatter or tool deflection
• Applications with unstable dimensions during peripheral shoulder finishing

VER Integrated ER Collet Shank

This shank is effective in environments that use machine-side ER collets, including lathes, multitasking machines, and Swiss-type automatic lathes.
Its integrated ER-collet-compatible design shortens the tool overhang.
It helps suppress deflection and chatter in environments where rigidity is difficult to maintain, such as driven-tool units and compact machines.
Compatible with ER11, ER16, ER20, and ER25.

Shank Selection Guidelines

5. Customer Application Examples

The following customer application examples demonstrate the capabilities of VVFH.
See how VVFH delivered improvements in
process integration, tool life, and machining stability.

6. Use Different Conditions for Drilling, Slot Machining, and Peripheral Finishing

VVFH can perform multiple machining operations with a single tool, but this does not mean that every operation should use the same cutting conditions.
It is important to set suitable conditions for each machining operation.

Drilling

• Cutting speed during drilling
• Z-axis feed
• Drilling depth
• Whether peck feeding is required
• Coolant supply
• Chip-evacuation conditions

Slot Machining

• Feed per tooth
• Axial depth of cut
• Slot width
• Machining length
• Chip-evacuation conditions
• Chatter or abnormal noise
• Tool damage condition

Peripheral Shoulder Finishing

• Peripheral finishing allowance
• Radial depth of cut
• Feed per tooth
• Keyway width
• Shoulder dimensions
• Required corner radius
• Condition of the machined surface

Summary: VVFH Changes the Conventional Approach to Shaft Keyway Machining

This article introduced the challenges of shaft keyway machining and the solutions provided by TungMeister VVFH.
The key points are summarized below.

1. Shaft keyway machining presents a “number of tools versus toolpath length” dilemma:
   ramping, drill-and-end-mill machining, and repeated shallow cutting each have advantages and disadvantages.
2. VVFH connects drilling, slot machining, and peripheral finishing with a single tool:
   three center-cutting edges enable direct Z-axis entry followed by lateral feed.
3. Three technologies enable stable machining:
   three center-cutting edges, 150% flute volume, and variable lead geometry.
4. Shank selection directly affects performance:
   choose between the VSSD high-rigidity shank and the VER integrated collet shank according to the application.
5. Optimize cutting conditions for each machining operation:
   set individual conditions for drilling, slot machining, and peripheral finishing.
6. Proven in customer applications:
   results include a 69% reduction in machining time, reduced chatter, fewer tools, and fewer tool changes.
7. Replaceable-head design reduces running costs:
   the shank can be reused.

If you are looking to improve your shaft keyway machining process, we invite you to try VVFH.