CNC Turning
CNCturning
Drawing-based process planning for rotational parts, with live tooling, the C-axis and a measurement approach. One of Eclipse's target capability areas.
- Focus
- Rotational parts
- Technology
- Live tooling · C-axis
- Files
- PDF · STEP · DXF
- Status
- Capability under development
01Fundamentals
The workpiece rotates, the tool advances
In turning the geometry is built around the axis of rotation, so relationships such as concentricity come from a single reference.
In turning the workpiece rotates while the cutting tool advances in X (radial) and Z (axial) to remove material. For symmetrical geometries this is the most direct and often the most economical route.
Because outside diameter, bore, thread, groove and face operations can be done in the same chucking, related features come from the same reference, which reduces alignment errors caused by re-clamping.
- Facing
- Flattens the end face for reference and length.
- Outside diameter turning
- Creates cylindrical and stepped diameters.
- Taper turning
- Produces surfaces whose diameter changes along the axis.
- Grooving
- Cuts grooves such as seal or retaining-element seats.
- Parting
- Separates the part from the bar or blank.
- Threading
- Cuts internal and external threads to the specified standard.
- Drilling
- Makes centre and through holes along the axis.
- Boring
- Enlarges holes to the size and surface requirement.
- Knurling
- Forms a pattern on grip surfaces.
02Feature explorer
The features of a turned part
Pick a feature from the list: it is highlighted in the drawing and what to watch for is summarised.
- 01Outside diameter
- 02Shoulder
- 03Groove
- 04Thread
- 05Bore
- 06Chamfer
- 07Centreline
Part features
These are the reference surfaces for concentricity and surface quality about the axis of rotation. Specify tight tolerance only on functional diameters; economical values are enough elsewhere.
A change of diameter and a seating face. Specifying a radius or chamfer at shoulder corners gives a transition that matches the tool radius and resists damage.
Groove width and depth decide tool selection. Narrow, deep grooves raise the risk of tool breakage and the machining time; avoid them unless needed.
The thread standard, pitch and tolerance must be written clearly on the drawing. If the thread runs up to a shoulder, clearance must be left for the tool to run out.
The ratio of bore depth to diameter affects tool deflection and chip evacuation. For deep bores, discuss size and surface expectations beforehand.
Edge breaks reduce burrs and ease assembly. State them with their size on the surfaces that need them.
All concentricity and rotational relationships are defined about this axis. It matters to state on the drawing which diameter is chosen as the datum.
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03Live tooling and C-axis
The technology behind completion in one setup
This section explains the technology; it does not state equipment owned.
- 01
C-axis
The ability to position the spindle as a rotary axis. It allows flats, keyways and hole patterns to be placed at defined angles.
- 02
Live tools
Milling and drilling tools on the turret with their own drive. Off-axis features can be machined in the same setup.
- 03
Y-axis
Lets the live tool move off the centreline; used for features that are offset from the centre.
- 04
Sub-spindle and bar feeder
Options used to machine the back face in the same setup and to feed bar stock automatically.
Completion in one setup reduces alignment errors from re-clamping and lets related features be produced from the same reference.
Which configuration is applied depends on the part and on the equipment status confirmed per project.
04Typical part families
Parts for which turning is the natural route
These families show part types for which turning is commonly used in this field. This list does not imply completed Eclipse references.
Shaft
Rotating elements that transmit power or motion; may include stepped diameters, keyways and threads.
Pin
Locating and connecting elements; diameter and surface quality are functional.
Bushing
Cylindrical parts with precise inside and outside diameters for bearing or guiding.
Flange
Disc-shaped parts with a mounting face and a hole pattern.
Fitting
Connecting parts with threads and sealing surfaces.
Pulley
Grooved rotating parts for belt or chain drives.
05Process plan
The turning process from drawing to shipment
The method followed for each turning job. Steps are detailed according to the part and the requirement.
01
Drawing and requirement review
Tolerances, material, quantity and documentation requirements are read together.
02
Workholding and tooling plan
How the part is clamped and which tools machine it in what order are decided.
03
Program and proving
The CNC program is prepared; the toolpath and collision risk are reviewed before the first cut.
04
First article
The first part is measured against the drawing; work continues after approval.
05
In-process checks
Critical dimensions are checked at intervals set in the plan.
06
Final measurement
Parts are assessed against the inspection plan; required documents are prepared.
07
Packing and shipping
Shipped under the agreed terms with packaging that protects the surface.
06Design for turning
Eight practical tips
Principles that reduce cost and risk and do not depend on a particular machine.
- 01
Put tight tolerance only on functional dimensions
Putting a tight tolerance on every diameter raises time and cost. Highlight bearing, fit and sealing dimensions.
- 02
Mind the length-to-diameter ratio
Long, slender parts flex under cutting force; the need for support and dimensional stability should be discussed beforehand.
- 03
Choose inside corner radii by the insert radius
Inside radii larger than the cutting-insert nose radius, and consistent, make the process easier.
- 04
Avoid narrow, deep grooves
Narrow, deep grooves raise the risk of tool breakage and machining time; widen them where possible.
- 05
Write the thread standard and run-out clearance
State the standard, pitch, depth and whether clearance is left for the tool to run out.
- 06
Choose a consistent datum at both ends
If the part is machined from both ends, stating a common datum diameter preserves concentricity.
- 07
Add edge breaks and chamfers
Sharp edges leave burrs and complicate assembly; state a chamfer or radius on the surfaces that need it.
- 08
Think about the blank form
The form of the blank (bar, forging, casting) and its size affect the stock to remove and the process; state it on the drawing if possible.
07Quotation preparation
What to send for a turned part
The following makes it easier to prepare a quotation quickly and correctly.
Missing information is not a barrier: what is missing is completed together during the review.
PDF technical drawing
With tolerances, surface expectations, thread standard and notes.
STEP geometry
The body geometry; used as a reference alongside the drawing.
DXF profile
A 2D profile or groove geometry, if any.
Material and grade
Type, grade and required material certificate.
Quantity and call-off plan
Total quantity; state a staged delivery plan if there is one.
Heat treatment and surface treatment
Requirements such as hardening or coating, and their sequence.
Inspection and document requirements
Inspection report, first-article document, traceability expectations.
Confidentiality
State it if you would like a non-disclosure agreement (NDA).
08FAQ
Questions about turning
What are the C-axis and live tooling for?
The C-axis provides angular positioning of the spindle and live tools provide rotating milling and drilling tools. Together they allow off-axis features such as flats, keyways and cross holes to be machined in the same setup.
Can long, slender parts be machined?
For parts with a high length-to-diameter ratio, support and cutting conditions are assessed separately; suitability is confirmed after the drawing has been reviewed.
What should I give for a thread?
The thread standard and pitch, depth, tolerance class and, if the thread runs to a shoulder, run-out clearance are enough.
Is the work done from bar stock or from a blank?
The blank form (bar, forging, casting) is discussed at the request stage; the choice depends on part size, quantity and the process plan.
Is a second operation needed?
It depends on the part geometry. If there are off-axis features or back-face machining to do, completion in one setup or separate operations are assessed together.
Related pages
Capability status
Eclipse Engineering is building its precision-manufacturing capabilities step by step. The manufacturing areas described on this page are target capability areas within the company's investment programme; equipment, capacity, material scope, tolerance class and lead time are confirmed separately for each project once the technical drawing has been reviewed.
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