What's the trick to carving off an inlay plug?

How To Machining
1

So I just made my first inlay, and I had a gut feeling that when the tooling was making the final clearing cut it may tear out part of the inlay, well that’s exactly what happened. I’m not sure what the best and easiest way to prevent this from happening. The tear out was very small (1/8"x1/8") which I am trying to fill in with glue and sawdust right now, so I don’t have a picture to add to this post.

Things I thought I could try:
My first thought was to slow the feed rate for the final pass, it was 100 IPM on a .25 clearing bit.
Reduce the last pass to .125 vs .22" depth, maybe less?
Cut the plug out with much less excess material, it was only ~1/2".

Thoughts?

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What kind of bit are you using? I have had good success using a downcut endmill, like the C3D #251.

Tennis
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Project was 250mm x 250mm (~10"x10")

#251
Last pass DOC - 0.95mm
Feed - 1500mm, 18k RPM
Stepover - 2.5mm

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Golden Boy - 1/4" x 1" Upcut Rougher

also the stepover was only .1

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I would not use that rougher once you get close to the surface.

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5

I’d go with a Downcut bit at 40 ipm. The CIC workshop has some good bits, but a rough-cut bit is not the choice for a close-tolerance inlay.

If you are still having trouble with the tear-out, try a wood hardener. Wood Hardener Varathane

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I have a Jet drum sander. That makes short work for cleaning up an inlay. Not everyone has a drum sander. I have tried a planner but that is way too violent and will definitely cause tearout. Depending on how high your plug is I would use a random orbit sander to take things down to the final finish. Even on my drum sander I get it down to just a glaze and finish with a random orbit sander. Some people use a bandsaw to get the bulk of the plug off and then finish with a random orbit sander. If you have a well tuned bandsaw you can do that but if you have a lot of drift you can ruin your project. So a random orbit sander is the safest way to get your plug down to the surface. You have to sand it anyway.

Let us know how you solve your problem.

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I do have the Jet 16/32" drum sander. The project carved, plugged perfectly. The plug removal looked great until the very last pass on the final vector. I think what happened is the force of the bit cutting .22" deep caused the remaining 1/2" plug waste to tear the last 1/8" x 1/8" of the plug vice shear it off. I think I’ll try and reduce speed and depth for the final pass, then leave ~.01-.02" of material then use the drum sander next time. The sawdust and glue trick filled in the gap however due to the mix of oak, maple and black walnut the fill is a bit off color.

Thanks for all of the sugestions, when I get around to another inlay I’ll post the results.

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While this was with the older inlay mode, I just use a pocket toolpath to cut away what is not wanted:

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@WillAdams That’s exactly what I did (pocketing tool path), however I did not leave material behind that could be held in place by clamps. The plugs were cut out with a .25 offset and clamped into the center of the board to dry then I drew a square around the plug area and used a pocket tool path to clear it all out. The plugs were basically free floating after the majority of the glued areas were removed.