# Chinese Checkers - can someone help me?



## Wildwood (Aug 14, 2010)

I need to make a Chinese Checker board with 121 cove depressions for marbles.
I have a dxf file of the array, but the positions are marked as very small circles, and not points. For some reason this is leading to oval depressions instead of round ones. I do not have my own CNC machine, but a friend who has one is running tests for me using a cove bit.
Can any one point me to a dxf file where the positions are marked as points, not circles, or perhaps suggest other solutions. 
Help on this would be greatly appreciated. Rob.


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## kp91 (Sep 10, 2004)

Make a Chinese Checkerboard | CNC Router | Woodworking Project Plans


CNC Shark Forum ? View topic - chinese checkers

Share Your Files Part or Art - Page 224

Are all the ovals aligned the same way? backlash in the machine?

Maybe try with a straight cutter on a piece of scrap and see if you get round holes


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## Wildwood (Aug 14, 2010)

Thanks Doug - I got my original dxf file from the Shark Forum link.
The ovals are all aligned the same, so I will investigate the backlash suggestion. Won't get another stab at it until the weekend.


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## 4DThinker (Feb 16, 2014)

Cove bits don't plunge well as the center only spins in place. If the cove bit following a true circle is producing ovals then there must be play in the machine that lets the bit deflect while going around the circle. 

Depending on which software is being used, some prefer and can use small circles rather than points (easier to see) as centers for a drilling toolpath. I use VCarve Pro/Aspire and it has that feature (drilling toolpath). In fact I'm not even sure the software can make just a point.

4D


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## Wildwood (Aug 14, 2010)

Thanks 4D - you're helping me to understand things a bit better.


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## gtsharp (Mar 10, 2014)

Depending on the size of the cove bit, I wonder if a 'pocket' wouldn't achieve what you desire.


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## Wildwood (Aug 14, 2010)

Just to close this matter, the culprit was my dxf file. 
Magnification revealed that the small circles were anything but round.
I re-created the array in Sketchup using the smallest circles possible in the program, then exported to a dxf file via a plug-in. 
I will finish off this thread with a pic of the final board in a few days time.
Thanks once more for helping me to grow my understanding.
Rob


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## SteveMI (May 29, 2011)

Wildwood said:


> I re-created the array in Sketchup using the smallest circles possible in the program, then exported to a dxf file via a plug-in.


Sketchup exports from an angle view. I have never got one to export from a true down or side view. That is why the ovals.

Steve.


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## SteveMI (May 29, 2011)

I added points at center of the circles, but could not upload the dxf. Is that not allowed or how do I do that?

Steve.


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## SteveMI (May 29, 2011)

Ok, attached is a zip file with dxf file. It has points at center of the circles.
Steve.


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## Wildwood (Aug 14, 2010)

Steve - my original file was not produced in Sketchup, but was created from a bitmap file converted to dxf by Inkscape. Pixelation on the small circles caused Inkscape to draw very rough slightly oviate circles, creating a "wobly" path for the CNC.

The file I created in Sketchup gave absolutely perfect circles. You don't have to export from an angled view, just go to top view and change camera to parallel projection. The circles are the smallest diam. that Sketchup can produce (1/2 mm), and should serve the purpose just fine, as the next best thing to a point for the cove bit.

Thank you for the dxf file, but I do not require the large circles and lines, just the points, as if a hole will be drilled at each point. I suppose what I really need is a program that defines precise location of holes. The points you have added would serve that purpose, but not with the lines.

But my Sketchup originated file looks like it will do the job just fine.

Thanks again for your input.


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