Cutting a cannel with a rounded bottom

hey there, very new to all this and having a great time so far. but im having an issue figuring out how to cut something concave. im trying to cut a channel for a 1" diameter metal bar to fit in.
after aboput 8 different attempts i gave up and made it a pocket path. but ive got orders for these tables and id like them to be a little nicer than this prototype.
i know thios probably isnt a difficult thing. if i had more time i would keep trying to find out how another way but im reaching out to the community for help. please dont be rude and tell me to “try and do some research before posting on here” like every other forum out there. i have spent a considerable amount of time searching for answers on this. i just need some help. thanks in advance.

Shane Doyle

If you have Pro, you can model this.

In the base version of Carbide Create you have a couple of options:

  • source a “bowl” bit of the correct diameter/rounding, clear the bulk of the material, then make a final pass w/ the tool
  • approximate it using a series of cuts w/ a ball-nosed endmill

thanks for the reply. i do have pro, but it seems like i can only model covex shapes. not concave.

Model the outside shape of the tray. I’ll guess at dimensions… Flat, Height: 0.75, Add
Now model the slot, Round, 90°, scale height: 0.5", Subtract

If you want the ends flat/vertical, make the slot 1" longer than you need & fill in the spherical ends.

Use the Equal merge type. Flat, 0.75, Equal


Use Subtract to make convex shapes:

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Thank you, subtract made sense byt for some reason every time i try the preview model screen is completely blank. I need to model the tray, and then model the channel?

You have to have something to subtract from.

well now im
just getting this scalloped shape.
this is extremely frustrating.
should i uninstall the software? i dont understand what the difference is between what im reading, and what im doing.

What settings did you use to to make the model?

Could you post the file?

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Will / Tod try this.

U 12 x 1.1 widget

Ramp 3 x .5 widget

Option two

Save widget file(PNG picture) to your PC.

You can use widgets for many projects and make you own. Made youtube video on making widgets. SEE Stephen K Cox channel

Just draw a rectangle the size you need, Highlight the rectangle and import this PNG file. Rotate and size as needed. May need to invent, equal, bump bad height to level out.

You can see numbers for each component, and it works.

All from the same two Widgets above but I stacked them.

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I see widgets can be very useful, especially for shapes that are difficult to make with the current modeling options.
Looks like the import uses a “Fill Page” scaling for the selected shape. i.e. it scales the image to the larger of the vertical or horizontal dimension, so the shape is filled, but the image can be larger than the shape in the other direction. Would be handy to have an option to scale in both directions to fit.
I made my rectangle horizontal, so it worked better if I rotated your image first before importing.
One nice thing is since my rectangle was shorter horizontally, it left the ends of the slot flat/vertical, with the rounded portion on the ends of your image being outside my vector.

I also needed to trim your image to the extents of the shaded black rectangle.


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As in the example above when your ex-wife scale it it does increase the size of the widget in both X and why direction of the direction is controlled by the height

It reduces the number of components required to build an object down to one doesn’t interfere with anything beside it. imported image stays within the shape here define. Add Max equal or all good merge types to try

Thanks for trying it it has been very useful for me building complicated models of course it’s best to know how to do it the other way as well but sometimes widgets are the only way

well it turns out im wayyyyy in over my head here. i appreciate all the input. but i just flat out dont understand any of what was just explained. im a woodworker who just aquired this machine a month ago. before this i may have spent 8 hours on a laptop in my last 10 years.

thanks again. ill just cut a flat bottom pocket.

Shane Doyle

It’s really quite simple:

Model the stock (or a region of it):

Draw the geometry for the rounded channel (and a bit extra if you want it to have square ends) and model it using Subtraction:

Sorry for the overload. Tod and I are just geeks. Will is just way too smart.

Here is a start on some training videos I made. 9 videos and more to come soon.

Here is Carbides training videos.

Your project looks good and the main point is to (make sawdust i mean to) have fun.

tray attempt 10.c2d (164 KB)
okay. i think im getting there. but for some reason everything is still scalloped. heres the file so far.

Call me lazy, but I had a similar problem.
So I just bought a large Bowling Bit.
Astra Coated Whiteside Bowl CNC Router Bits -


When you run your 3D Finish pass reduce your stepover. I typically reduce mine to .008" when I use a 1/8" ball nose.

tray attempt 10B.c2d (240 KB)


Ed.E has you headed in the right direction. Finishing pass stepover should be 10% to 15% of you ball nose bit size. Smaller step over is better. Smaller Bit is Better. Depends on detailed you want.
Smaller does take more time. If you going to do two finishing passes you could cut one at 45degree.

Here is a similar project. WillAdams is showing how to square up the ends. All good stuff.

Your project looks good. Well done be safe

okay so ive gotten a few decent products but im wasting material at this point. can anyone tell me why i have jagged edges on the 3d model and my workpiece is coming out like this?