Removing a core from a model

Hey guys. So my father turns pens from pen blanks (+/-25x25x150mm) on his lathe. He has some ideas for new blanks, but he wants to see what they will look like before he turns them. So basically I want to remove the core from a pen blank model, but the core must have the details of the blank. I have tried the follow me tool and also push/pulling the unwanted pieces but with no luck. Any guidance, help or ideas would be greatly appreciated. Thank you, in advance.

Celtic Knot.skp (186.5 KB)

Is the thing on the right sort of what you are looking for?

The easiest way to do that would be to first make the “knot” a solid group/component and then use Trim from the BoolTools2. Trim the pen blank with the knot.

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Wow Dave, thank you for your speedy response. It unfortunately is not what I’m looking for. The “core” will be the same diameter as a finished pen (+/- 9mm) and about 100mm long, like a cylinder but with the knot details on the cylinder. like the attached image. I hope this makes sense.

Before and After

Something like this, then?

I used Trim again with the shape in the background to trim the knot and the blank. The hollow cigar shape is made to the shape of the finished pen.

Note that since you’ll be creating some small geometry in the process, scaling up or using the Dave Method will help you avoid missing faces.

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Dave you’re a genius. Thank you so much. Please explain how you did this. I have no clue. Or a screen recording would be even more helpful if you could? Do I need to download certain extentions?

I’m sorry I don’t have time to do a video right now.

I made the cigar shaped cutter by drawing a profile and using Follow Me to make that shape. Think of it as sort of the volume of stuff that will be removed from the model.

The extension BoolTools2 is available from Mindsight Studios. Although it isn’t free, it’s not a huge expense and will save you a whole lot of time.

Another way you could do this is to draw the profile of the final pen body and use Follow Me to make it 3D. Then simply intersect the knot object with the pen so you get the edges on the pen and you can apply the gold material in the right places. You wouldn’t be able to separate the knot from the pen in that case but you can’t do that with the real pen anyway.

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And the native Boolean tools would work quite well here too. Or Eneroth Solid Tools.

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Yes they would however they don’t work with SketchUp 2017 Make which the OP is using. BoolTools2 does work with it, though.


Thank you so much, Dave. I will try it without the extension first. I appreciate you taking time out to help me.

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Good luck.

FWIW I expect you would find BoolTools2 a big help in your modeling in general. I model a lot of woodworking related projects. I almost never model both halves of a joint because I can use BoolTools2 (or Eneroth Solid Tools in my case) to cut mortises from tenons, tails from pins, slots from biscuits and so on. Much faster and no screwing around.

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Here’s an animated version of what @DaveR mentioned above with a different pattern.
You can make the pen blanks and then use Intersect Faces with Model to get the edges that would form if it was made of sections.
This is an example that uses a single ‘Plank’ component to cut a design into a turned shape.

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Here’s another thread you might find useful too.

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Rich, I also use Make 2017 for woodworking and have prided myself on using native tools and all the intersect faces applications to get a good results, but on complex intersections it is hard to stay on top of what is what.

As a result I bit the bullet and bought booltolls as DaveR and others recommended and spent US $29 (UK £23.07) in March this year and now use it on almost of my projects. For my 2penny worth, it’s well worth the expense!

Hope you don’t mind me chipping in here.


Hey Guido, thanks for your input. I wish you had chipped in a lot more than 2penny worth. Maybe then I could afford that extension :wink:

Thank you to everyone who contributed to this post. I successfully managed to achieve the desired outcome. I scaled the model to 10x the actual size (the smaller geometry was not interesting correctly) then I cut and pasted the wedge in place, then intersected the geometry with the model, erased unneeded geometry and filled the material with the appropriate colour. Then I rotated the model 90 degrees and repeated the process another 4 times, and viola. Thank you again, everyone.

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