How to make a Turner's Cube? New Techniques and Tips...

A Turner's Cube is one of the first workshop exercises when a machinist learns to mill with a CNC machine - although it's origins date from way before computers and much of the boring is produced on a Lathe whose operators are called 'Turners'. Although clearly not round unlike most 'turned' parts, the Turners Cube thus needed special Lathe tooling ( workholding fixture ) and required careful skill in manufacture to make an accurate part due to the part fragility and the intermittent cuts causing vibration with a reduction in surface finish.

Image- derived from 'https://www.cnccookbook.com/how-to-make-cnc-turners-cube'

Let's go through the steps on creating the 3D object in DesignSpark Mechanical:

1. First, design a cube with a side of 24mm. You can change the dimension to your needs.

2. Draw 3 concentric circles on each face. In this example, the radii are 5mm, 8mm and 11mm (going outwards).

Redo this step for the other 5 faces or draw on 3 faces and use the project tool to produce identical curves on the opposite remaining faces.

Note: The Sketch plane XY 0,0 datum is usually automatically centred on the selected face. The datum position may be altered to any other location.

Below Gif shows the project tool being used to duplicate the circles which divide up the face.

3. Depth of the circular pockets: Depending on whether you'd like the nested inner cubes to free-float or remain fixed, the depth will vary but there is a mathematical relation to help you out.

Enter the highlighted dimensions (x - side of cube, r - radius of the circular pocket) to get the depth value (d) at which the nested cube will free-float but can also be taken out of the assembly.

 As you keep going inwards, x and r will change to match the side of the cube that encloses the new concentric circular pocket. So, you would to recalculate the incremental reference depth for the next pocket (this needs to be added to the first value of d that you calculated). It's up to you if want certain cubes to remain fused or free to move.

To get you going with this example, we use 3mm and 5.25mm Pull cut depths with the innermost circle ( for fastest creation ) being Pulled completely through in three directions.

Pull the next larger face to cut the holes in the solid - Pull 5.25 - drag face into the solid. 'Pull' default behaviour is set in options to 'Auto'

Note:  The ' - ' symbol next to the curser for a cutting / removal operation and a ' + ' symbol to additional / add material operation.

4: IMPORTANT NOTE: You may note that during some of the PULL operations the result is unexpected ! This is because Faces when pulled by just themselves, if also belonging to the part, may by default, increase / decrease their area due to other local face geometry or an intermittent  stop / start drag action. In this case of the Turners Cube, to prevent this, by selecting a bounding curve or curves ( external in this example, and / or internal curves depending upon the problem) this confines / enforces a full face area Pull. The 'loop' around the face should be continuous.

A FOOLPROOF alternative method to cut a precisely, no matter the part geometry or assembly complexity is to have the part in a Component and 'Active' ( Not the Document/File) , then copy the cutting face ( Ctrl C, Ctrl V) making an independent fixed size face ( child of the active part) which does not dynamically adjust and Pull cut to depth. This cuts away only the 'Active part' or any part within the Active part chain ( parent / child ) hierarchy  - which is geometry bright in colour and not 'greyed out'.

Also ,ONLY DISPLAYED PARTS / COMPONENTS CAN BE ALTERED BY PULL OPERATIONS

5. Once you finish 3 pockets all 6 sides, your final result will look similar to:

Try 3D printing this or send to a CAM software to prep for CNC milling.