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Hello, new to the forum and CNC. I've had my CNC router for about 2 weeks and working on a project where I want to get a friction fit between two pieces cut out on the router. I'm using a 1/8th bit and outside cuts on both pieces. I've tried an inside cut to outside cut, center cut to center cut and the results were worse. This is close, but not quite there.

I'm using PowerPoint to draw my initial outline, turning it into a vector graphic and then importing it to makercam.com to get my NC file for the machine. I don't have the $$ to spend on V Carve Pro or Aspire or anything that isn't cheap at the moment. If I can get this figured out, I can generate some revenue to get the software needed.

With all that in mind, do you have any ideas how I might be able to adjust something in order to get a friction fit between my pieces? I've even tried increasing the trident size by 1%, but that results int he arches increasing in size and causing larger gaps there as the tines fit better. I'm hoping there is an easy solution someone knows that I am just overlooking. Willing to share NC files or SVGs if you like.

I've made one of these on the band saw by free hand and the result was good, but this would be much much faster.

Thanks!
 

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John
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Hello welcome to the router forum.
Sorry I can not be of help but one of the members will be along to help.
 

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Hi James, and welcome to the forum.

When I need to make a friction fit joint I usually use the same vector for both sides of the joint. The vector needs to have rounded outside corners to match the inside corner where the spinning bit can't make a square corner. The radius of each round over should match or exceed the radius of the bit you are using. I'll cut outside the vector for one half of the joint, and inside the vector for the other side. Using the same vector eliminates any chance of a drafting error that could happen when drawing up separate vectors for each half.

If the joint/fit is too tight, then the bit may be smaller than you told the software it was. If you need a little room between the halves (for glue maybe?) then check your software for a way to add an allowance value to the profile cuts. If there is no allowance option, then sometimes you can lie to the software and tell it your bit is smaller than it really is. I'm talking just a few 1/1000ths here.

4D
 

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Not sure why you are using PowerPoint for drawing your design. Can you actually control the geometry with PowerPoint? I think this might be your problem.

You can actually draw in makercam.com but it is not too user friendly.

There are several good free cad/cam programs available like Fusion 360 https://www.autodesk.com/products/f...M7yqVwYzKuATuqKIDy0xen1FVEWcEHaMaAl-jEALw_wcB

You should be able to do just about any design with this program, run toolpaths and output gcode.
 

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David
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Welcome to the forum, James! Like Mike suggested I would use Fusion 360 - it's free. It's fairly straightforward to draw the first object and then select the outline and do an offset by however many thousandths you want to create the second piece.

I've done that several times and have some of them on video at my YouTube channel - David Falkner Woodworking. Go to the videos 'Splines for miters' and 'Making a B-52 tail shaped cutting board' and you'll see two examples of creating a pocket and then using offset to create the insert piece. I would link them directly but that would make the videos post here and I don't want to hijack your thread with my videos. This way you can look if you want.

David
 

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Discussion Starter #6
All,

Thank you for the welcome. Also, thank you for the advice. I will take a look at Fusion 360. The reason why I went with PowerPoint is because it is something that I know how to draw in. I've tried Sketchup and other CAD type programs and I can't wrap my head around them. I've played around with the trial version of V Carve and I get understand how it works. So far in Fusion 360 it's just as confusing for me as every other CAD I've ever tried playing with.
 
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