Shoulder milling generates two faces simultaneously, which requires peripheral milling in combination with face milling.
Achieving a true, ninety degree shoulder, is one of the most important requirements.
Shoulder milling can be performed by traditional square shoulder cutters, and also by using end milling cutters, long edge cutters and side and face milling cutters. Due to these numerous options, it is essential to consider the operational requirements carefully to make an optimal choice.
Choice of tools
Shoulder milling cutters
Shoulder face mills of conventional designs are often capable of milling “true”,
90 degree shallow shoulders.
- First choice cutter is the accurate and light cutting CoroMill 490. This cutter provides the precision for milling deeper shoulders by using repeated passes with very limited cusps.
- CoroMill 390 cutter product range offers a wide range of inserts, in particular a complete series of inserts with corner radii, which contribute to its success as a general purpose cutter. It is also the first choice cutter for shallow, heavy duty shoulder milling.
- CoroMill Century is the first choice cutter for high speed finishing of aluminum, but is also suitable for milling other materials.
- Many shoulder face mills are universal cutters, and can be used advantageously for making holes. They offer a good alternative to face milling cutters when milling axially deflecting surfaces or for milling close to vertical faces.
- The side and face milling cutter, CoroMill 331, is a slot milling cutter that can also be used advantageously for milling wide, shallow shoulders. It can also be employed for some special purpose milling operations, such as back-face milling.
Shoulder milling – end milling cutters
End milling cutters
The indexable insert and solid carbide end mills offer good solutions for shoulders requiring accessibility.
- First choice for universal milling is the CoroMill 390. A vibration dampening version allows for effective machining of deep located surfaces.
- CoroMill 790 is the first choice cutter for milling non-ferrous materials.
- CoroMill Plura solid carbide end mills are available in a huge number of versions for most milling conditions.
Shoulder milling – long edge cutters
Long edge milling cutters
Long edge cutters are generally used for milling deeper shoulders.
- First choice for general roughing is CoroMill 390; under stable conditions, it is capable of heavy metal removal.
- CoroMill 690 is the first choice cutter for milling of titanium.
- Among cutters of this type, the light cutting Sandvik Coromant finishing long edge cutter produces a superior surface finish.
Note: All the above cutters can perform edging operations and milling of ledge type shoulders.
Application checklist and hints
- Down-milling (also called climb milling) is always the first choice, and is especially important for shoulder milling due to the 0° lead angle.
- Machining should be performed in a manner that directs the cutting forces
towards the support points of the fixture insofar as this is possible. Up-milling (also known as conventional milling) can, therefore, be a favorable alternative in some cases.
- Selection of cutter pitch is dependent on the stability of the entire system, including: the machine tool, workpiece and its clamping, as well as the workpiece material.
- In ISO 40 machines and smaller, coarse-pitch cutters are recommended, due to limited stability.
- Coarse-pitch cutters are also recommended for machining components mounted high up on a cube fixture.
- The positioning of the cutter on the workpiece is extremely important and should receive extra attention. Avoid positioning directly on the centerline or at 50% of the diameter.
- It is good practice to apply radial chip compensation to create a thick enough chip to maintain proper heat levels in the cutting zone and avoid edge breakdown, especially when your width of cut is less than 40% of the tool diameter.
- If the shoulder depth is smaller than 75% of the cutting edge length, the quality of the vertical surface does not normally require extra finishing.
- Shoulder milling requires a tough grade of carbide.
- If CoroMill long edge cutters are used, the conditions are demanding, therefore, an even tougher grade may be required.
- The deeper the cut, the more important it is to choose a lower cutting speed in order to avoid vibrations.
- When vibrations occur, decrease vc and increase f z, check against the recommended hex value!
- Ensure that enough machine power is available for the chosen cutting data.
- Pay special attention to power requirements when taking large cuts, particularly with long edge cutters.
- Tool mounting has the greatest influence on the milling result for cutters smaller than 1.969 inch (50 mm).
- The larger the cutting depth, the more important the size and stability of the coupling become: since the radial forces are considerable when using shoulder face mills, particularly long edge milling cutters.
- Coromant Capto couplings provide optimum stability and the smallest deflection for all types of cutters – particularly important with long or extended tooling.
Rolling into cut
- Smooth entrances into the cut are essential for avoiding vibrations and extending tool life, particularly when milling shoulders.
- Program the cutter to roll into cut; always generate a chip thickness on exit that is zero: together this will ensure both higher feed and longer tool life.
- This method is most suitable for applications in which you are milling around external corners, as it avoids sharp changes in the cut.
- Keep the cutter engaged in a continuous cut. Running the tool on and off the workpiece can prematurely wear out the cutting edge.
How to apply
Milling of shallow shoulders
This frequently used operation is generally performed by shoulder face mills and end mills. A shallow cut allows for a larger radial cut.
Often these cutters can replace face mills, in particular when the axial pressure on the component is a limitation, and when there is a demand for accessibility close to vertical faces or fixture sections.
- Oversized diameter options or shoulder cutters provide for optimal accessibility when milling shallow shoulders located deep.
- An extra robust version of the CoroMill 390 shoulder cutter is, under stable condition, capable of heavy removal rates. It also functions reliably under demanding conditions, like milling through interruptions.
Milling of deep shoulders
Use repeated passes with shoulder face mills and end mills
To minimize surface errors, such as scallops and transition-edges between the
passes, a high precision cutter that is able to produce true 90º shoulders is an
If shoulder depth is smaller than 75% of the cutting edge length, the quality of the vertical surface does not normally require extra finishing.
Long reaches or deep shoulders could result in deflection and create a tapered wall.
Use a single pass with a long edge milling cutter
The long edge cutter is a good solution for deeper, larger and usually heavier shoulder milling applications:
- High metal removal capacity.
- Generally used for rough milling, as the resulting surface texture is characterized by side milling at high feed rates.
These cutters make demands on:
- Spindle condition
- Chip evacuation
- Tool holding
Radial forces are considerable making this a tough side milling application.
Shorter long edge cutters are suitable for:
- Radially large but shallow shoulders.
- Full slotting at a depth equal to the diameter, which can make up for machine limitations.
Longer versions are intended for:
- Milling of shoulders with moderate radial depth.
- Edging in powerful, stable machines.
Milling of shoulders located deep
- Oversized diameter options or shoulder cutters provide for optimal accessibility in milling shallow shoulders located deep. For those shoulders that are located at even larger depths, use extensions with the Coromant Capto coupling.
- Long edge cutters are also available in oversized versions to be used for deeper shoulders located deep. However, the radial depths of cut are more limited.
Milling of shoulders using side and face milling cutters
Side and face milling cutters are also used for milling shoulders, particularly if the configuration is narrow yet radially wide.
These cutters are often the only possible solution for back-facing of hidden shoulders and faces.
The right choice of a CoroMill 331 cutter for facing and back-facing in right and left-hand spindles.