Cuts are different between hardwood and softwood/plywood

Why would my result look good on my practice stock (plywood) but on my final cut on hardwood (oak) look wider? I am trying to get a very fine line engraved. The tool and toolpath are the same.
The tool I am using is a 1/32" from Amazon. " CNC Router Bits 1/8" Shank CNC Bit End Mill 1/32" Cutting Dia Flat Nose Carbide Endmill Two Flute Spiral Upcut Milling Cutter Tool Set for Wood PVC MDF Hardwood (1/32 in, 5)"

See photo of resulting cuts.

Looks like your are cutting into oak which has open grain. Using an upcut bit will cause the grain to lift when cutting which is why you are not getting the clean cuts you are after. I would suggest using a down cut tool. This puts downwards pressure on the grain and you will get a much cleaner result for this application.

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Spyd, you nailed it. That makes perfect sense. I installed a 1/32" downcut and it looks great. Thanks for the help.

But I guess I should have slowed down the speed. Broke my only down cut 1/32” shortly after I started the job.

Possibly, the depth per pass should be very shallow as well since the tool is so fragile. I don’t use anything smaller than a 1/16" tool. Any smaller than that, I use a 30 degree V-Bit for my cut.

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I use my 1/32" Carbide bit a lot. However I always use the recommended F&S from C3D. Luckily I have never broken that little work horse 1/32" bit. Of course now that I have bragged on it the next cut it will likely break. I have cut a lot of hardwood with that little bit on Advanced Vcarve projects. I did buy a 1/32" down cut bit from Amazon and it broke in about 1" of cutting. The mileage varies on different vendors bits.

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You can also use a V-Bit to effectively scratch a thin line, but it requires that you be precise in your depth because the deeper you cut the wider the line. And funny note: I’ve broken every downcut 1/32 bit I have purchased.

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