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How to do a "reverse inlay"?

Posted: Fri Aug 25, 2023 9:56 pm
by BassCentral
Greetings Aspire pros:
I am looking for a way to do a sort of a "reverse inlay" logo on a guitar headstock veneer, but as of yet I have not come up with a good way to do it. The attached photo shows a decription of what I am trying to do. Basically, I would like to carve out the light-colored wood material around the logo leaving the fancy lettering behind. Then, out of another piece of wood, I would like to carve out the circular, dark-colored wood knockout so that it will slip down into the pocket over the logo. I can't quite wrap my head around this project. If anyone has an idea of how I could get this done, it would be greatly appreciated.


Re: How to do a "reverse inlay"?

Posted: Fri Aug 25, 2023 10:58 pm
by adze_cnc
One thing to clarify before people start throwing out suggestions is: by inlay do you intend to use:

Re: How to do a "reverse inlay"?

Posted: Sat Aug 26, 2023 6:13 pm
by litzluth
If you have some matching headstock wood, I'd do it this way, seems simpler.
1) Create an inlay in a large enough piece to create the circle part. Male inlay toolpath to mill the part for the headstock colored wood, and female toolpath to mill into the darker wood that will become the circle. I tend to cut the male part first, so I can leave the female side in the clamp until I test the fit, to make sure it doesn't need adjustment. Fit the parts together, then do a circle profile toolpath to cut the combined part into a circle for inlaying in the next step.
2) Use the circle vector to create a pocket toolpath in the headstock to inlay the part created in step 1. Again, I would leave the headstock clamped in the CNC until you test the fit.

In the inlay toolpath, you can adjust the fit with the "allowance offset" setting. In a pocket toolpath, I think the only way to adjust is to change the size of/offset the vector used for the pocket.

Re: How to do a "reverse inlay"?

Posted: Sat Aug 26, 2023 11:35 pm
by BassCentral
Thank you for the quick reply Adze and Itzluth. To address Adze's questions, this "inlay" will be straight-sided, not tapered. I have looked over the "Simple Ways" post and did not see any description of the unique application I am attempting. Itzluth, I also have thought about doing it the way you describe, but I guess I was trying to be a bit too tricky with the technique. After reading your post, I now think that the workflow you decribe has a better chance of delivering a good fit between the lettering inlay and the dark background. As you said in your reply, I can adjust the allowance offset (e.g., .004" to start) in the inlay toolpath and experiement to see what works best. Thinking ahead, this technique would also allow me to create a production run of these logos that I can assemble now and use on future guitar builds!

I always get good advice on this forum, and this post is no exception. Many thanks again for your expert advice.

Re: How to do a "reverse inlay"?

Posted: Sun Aug 27, 2023 9:57 pm
by adze_cnc
I wonder if instead of trying to match the headstock material for the lettering if you were to say: this is the material I am using for the dark and this is the material I am using for the light. The benefits would be:
  • you could batch create a number of logos by:
    • cutting out, say, a half-dozen light pieces
    • cut and fit the light pieces to a half-dozen dark circles
  • whatever light headstock you have you just pocket a circle and fit in one of the pre-made medallions
You could also create reverse medallions if you will be making dark wood headstocks.

The tapered inlay could actually be of great use in that you'd only have to mill a socket in the headstock for the dark inlay plug to fit into. In this case, the lettering would be a perfect grain match as it would be the material of the headstock showing through.

It would reduce the operations from 4:
  1. mill the lettering
  2. fit into dark circle
  3. mill pocket in headstock
  4. fit dark circle into headstock
down to two:
  1. create inlay plug (could be a batch run to keep a number on hand)
  2. mill inlay socket into headstock

Re: How to do a "reverse inlay"?

Posted: Tue Aug 29, 2023 1:13 pm
by rscrawford
Don't overthink this. That is just a normal inlay (inlaying the dark wood into your light wood). It would be easiest using the v-carve method, as you'd get the sharp corners this way. Someone else posted a link with instructions.