Making segments for bowl turning

WillAdams · December 12, 2020, 2:48am

First, set up your stock size and draw a rectangle of an appropriate size:

Then draw in a rectangle of a suitable size to chop off the end if rotated:

Then work out the math to determine the angle of rotation — in this instance we want six segments, so:

 360 / 6 (number of segments) / 2 == 30 degrees

(you have to halve things because each angle is made up of 2 board ends)

duplicate the geometry and flip along the vertical axis:

Drag each copy to the appropriate corner:

Select the rectangle for the board and then shift click on a cutting rectangle so that the latter is the key object and has a dashed appearance:

and choose Boolean Subtraction:

(if using a version which doesn’t tidy up after this operation, delete the extraneous left-over geometry)

repeat for the other part:

Verify the fit by duplicating and rotating 60 degrees and repeating this until one gets all the way around:

WillAdams · December 12, 2020, 2:53am

The fact that a 60 degree endmill is available makes it possible for one to use such an endmill to cut along the edges of a board to create a set of six boards which can be combined to make a column or a post, just draw up the board, (or a suitable sheet of plywood) and draw in rounded rectangles which are board length plus board thickness long, and board thickness high which will cut board thickness deep using a V carving toolpath.

gdon_2003 · December 12, 2020, 2:59am

Will you always have creative ideas. I make segmented bowls and use the
Wedgie system on the table saw. I like to make 12 sided rings because I turn them on the lathe. Your premise is a good one but will waste a lot of wood to make the same amount of segments that can be cut more efficiently on a table saw. That said if your only tool is the Shapeoko then your instructions would work.

This is a forum dedicated to CNC machine but some jobs in the shop are simply better done the old fashioned way. I have planners, jointers, bandsaws but sometimes a good old hand plane or chisel is the best and most efficient way of doing some things. To each his own.

If a carpenter only has one tool, a hammer, then everything looks like a nail. Use your full tool kit and mix up the machines with hand work.

WillAdams · December 12, 2020, 3:03am

Excellent point. Naturally when cutting one would alternate and rotate the boards 180 degrees for the most efficient use of stock.

Mooselake · December 12, 2020, 5:20pm

This Wedgie system?

gdon_2003 · December 12, 2020, 7:25pm

Yes. I bought the system before I got the CNC. I think I could make my own wedgie templates now with the Shapeoko. I used several other sleds and the seg-way and wedgies are spot on with no adjustments.

WillAdams · January 7, 2021, 12:14pm

As noted above, it’s simply a matter of:

draw a rectangle of the correct size:

Draw a rectangle larger than needed

rotate it:

drag it into alignment

duplicate it and mirror horizontally:

drag the duplicate into position:

select the rectangle, then shift-click on one of the rotated square making the latter the key object (indicated by a dashed highlight):

Boolean subtract (and if need be, delete the extraneous geometry):

repeat for the other side:

Note that it is important that your machine be calibrated for belt stretch:

since even a tiny deviation will be magnified to a large one by the repetition.

Mooselake · January 7, 2021, 3:12pm

It’s pretty common for woodturners to glue up half the segments in each of two pieces, then use a disk sander (I have a 12" one) to flatten the two faces before gluing together to fix any accumulated error. You could do the same with a ShapeOKO, just make a straight line pass across the edge.

CrookedWoodTex · January 7, 2021, 8:13pm

Woodturners wouldn’t care about some misalignment since they’re going to cut it off anyway.

WillAdams · January 11, 2021, 3:03am

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