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CNC Turning
Design Guidelines
Difference in Shapes Between the 3D Model and the Finished Product

Difference in Shapes Between the 3D Model and the Finished Product

Although 3D CAD data will be used for manufacturing, the following cases may result in differences between the 3D model and the finished product.

Points to Note for the Finished Shapes of Internal and External Corners of Lathe Parts

Please check the examples and notes for differences in the finished product.

Tip

The finish conditions are as follows.

Models with external corners of less than C/R0.5 will have C/R 0.1 to 0.4 mm or edge breaking.
If the internal corners of the cylinder are less than 0.5 and there is no relief groove in the model, the tool edge will leave a corner of R0-R0.4mm.
→Click here to specify “Corner R0” without modeling a relief groove.

Caution

When modelled with C0.5 mm or more, machining will be in match the 3D data.
When modelled with R0.5 mm or more, machining will be in match the 3D data.

Caution

Specification of “no chamfering” is not supported.

Notes

- A standard retaining ring grooving tool has corner R0.2
- For retaining ring standards, click here.＞＞＞Specifications for External Thread and Internal Thread, Keyways, Holes and Pockets

Outer diameter grooving

Inner diameter grooving

Points to Note on Centering Holes

A centering hole made in the end face is used to keep the workpiece in place and to prevent core deflection when turning the product.

Caution

“Centering hole cannot be left” can be selected, but there may be restrictions on the shapes that can be machined that make the option unavailable. When this occurs, check the “Important Information” in the upper-left corner of the screen.

Notes

(1)When you select ”Remove centering hole”, an arrow will be shown on the model.

(2)When the model has an inner diameter, an arrow will not be shown on the model.

Points to Note on the Bottom of Holes (Turning/Milling)

A drill tip shape remains at the bottom of the hole (turning/milling).

Shape patterns	Inner diameter hole does not have a step	Inner diameter hole has a step
A
A	Drill tip shape remains (flat bottom will be 1mm or more)
B
B	Drill tip shape remains, no flat bottom

The type of the bottom of the hole will depend on the diameter and depth of the hole.
Example: If the inner diameter (D) is 10mm and the hole depth is 35mm, the depth of 35mm ÷ inner diameter of 10mm = 3.5D, so the bottom of the hole type will be B.

Inner diameter(D)	the hole depth
Inner diameter(D)	to 3D	3D to 5D	5D to 10D
D≦⌀6	B	B	B
⌀6 ＜D≦⌀30	A	B	B
⌀30＜D	A	A	A

If a flat bottom hole is required, please request it in “Additional Information”. We will confirm whether or not we can accommodate your request and reply.

Notes

Machining drill reference photo

Details for Internal Corners of Cylindrical Shapes

See below for details and examples of differences between the model and the finished product.

Outer diameter

①”Corner R0″ is specified

When you want to minimize the corner R or specify a relief groove
→ Select “Corner R0”
A relief groove will be machined to eliminate any radius left behind by the tool in the corner.

Tip

The width and depth of the relief added when selecting “Corner R0” can vary depending on the tools used. The exact dimensions cannot be specified.

① Relief size when machining with R0.4 tools

②Relief size when machining with R0.2 tools

③ If the length of the shaft is short, it may be machined with a tool with a 0.1mm radius on the end that contacts the shaft.

Notes

In the following cases, “Corner R0” cannot be specified.

(1) The model has Corner R0.5 or greater	(2) The model has a relief groove

②”Corner R0 to R0.4″ is specified

When the cylindrical corner can be any shape
→ Select “Corner R0 to R0.4”.

Tip

Cylindrical corners with “Corner R0 to R0.4” can have the following shapes.
① Radius from machine tool remains.
② Relief groove is machined on the diameter only to achieve minimum clearance.
Machined diameter clearance groove.

Groove Dimensions
③ Relief groove is machined on the diameter and the face to achieve minimum clearance.
Machined diameter and face clearance grooves.

Groove Dimensions

③Model has Corner R0.5 or more

If the corners are modeled with R0.5 or more, a relief groove will be machined to achieve minimum clearance.

Modeled radius exceeds R0.5
Machined diameter clearance groove.
Groove Dimensions

Inner diameter

Any of these corner conditions may be machined depending on the geometry.

Sharp Corner, R0
Undercut Groove
Undercut Groove with Lead

Notes

At the bottom left of the 3Dviewer, you can see the handling information for the cylindrical corners.

Points to Note on Incomplete Threads

The required undercut shape (length and depth) to ensure the thread length with an incomplete threaded position is shown. See the example below.
*If the model shape does not satisfy the following table (1) to (4), we will process it according to our recommended value.

[mm]

		External Thread	Internal Thread
Modelling	Without undercut
Modelling	With undercut
(1) Lower limit value of incomplete threaded portion length and undercut width		Pitch × 2.0	Pitch × 2.5 + 2
(2) Lower limit value of thread length (external thread) and thread depth (internal thread)		Pitch × 2.0	Pitch × 2.0
(3) Chamfered edge		Chamfered to prevent burrs	Chamfered to prevent burrs
(4) Minimum undercut depth value		Pitch × 0.75	Pitch × 0.75

Caution

④Models for which “pitch × 0.75” or less is set for the (4) minimum undercut depth value can be machined, but machine marks will remain.

Reference model
Actual finished shape after machining

Tip

The [Notes] shown in the red box below describe the applicable thread length/thread depth.

Example 1) Outer diameter specification: male thread thread length 36.6mm ＝ 44.6mm – 4.0(pitch) × 2.0	Example 2) Inner diameter specification: female screw thread depth 11.0mm ＝ 15.5mm – (1.0(pitch) × 2.5 + 2.0)

Caution

Modelled thread shape cannot be recognized. Specify the external thread and internal thread on the meviy screen.

Points to Note on the Finished Shape of the End Face Groove Internal Corners

Please check the examples and notes for differences in the finished product.

3D model with sharp edges in end face groove

Actual finished shape after machining
*Finished with a radius (R) ranging from 0.1 to 0.5 mm.

Notes

No R modeling is required. The shape is finished with a radius (R) ranging from 0.1 to 0.5.

Points to note regarding the finished shape of internal corners in pockets.

Please check the examples and notes for differences in the finished product.

Notch (pocket)
Desined with a radius (R) less than 0.5 mm, including sharp edges.

Actual finished shape after machining
*Finished with a radius (R) ranging from 0.1 to 0.5 mm.

Caution

The curved shape on the sides of the pocket is determined by the tool diameter, but we choose tools with the smallest possible diameter.
If there are any discrepancies between the model and the finished shape, we will contact you to discuss it after the order is placed.

Points to Note for slitting process

The slitting process may change the dimensions of the part.
The dimensions of the following shapes are guaranteed based on measurements taken prior to slitting.

Hexagonal Hole Information

Information and examples of differences between the model and the finished product.

The shape of the finished hexagonal hole will vary depending on the distance across the flats.
The modeled depth is used as a reference, and the shape of the bottom of the hole will vary.

Hexagonal Hole corresponding shapes and sizes

Distance across the flats	Metal	Resin
2	Finished Shape①	Finished Shape②
2.5
3
4
5
6
8

Caution

Specified surface roughness is not applied to the hexagonal hole.

Finished Shape①

Distance across the flats	Metal	Resin
Other	Finished Shape②

Notes

The tolerance for the distance across the flats conforms to JIS B 1176.

Finished Shape②