Tool/Bit marks/ridges

I’ve tried to search for a solution but have come up empty. Anytime I do a 3D project I get tool marks that are difficult if not impossible to sand down properly. I have utilized a 40% step over in order to try to minimize the marks with little success. I have seen some projects that look almost smooth without sanding and when I do a regular pocket carve, it is 95% smooth.

To recap, I have a 40% step over while utilizing a 1/8 in round nose bit.

Any suggestions on how to minimize these ridges?

Have you tried going with a smaller step over? Have any pictures of the result with the 40% step?

40 is way too much. 40% is good for a roughing pass to hog out material fast.

For no-sanding finish I usually go 5% Up until 10% would be good finish without too much manual cleanup.

Obviously better finish means much longer cutting time… Going from 40 to 5% will be 8x cutting time. It’s a tradeoff you need to decide on.


The smaller step, you could increase your feed to compensate for some of the added time.

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Look up “ball end mill scallop” for some good explanations. Here’s a no frills calculator:

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I was having the same problem on the project below. 40% was too big I switched it to 5% and a 1/4” ball endmill. You might also try a 1/4” ball end mill.



@Zach_Kaplan, is that Corian? Do you do anything with the milled surface to “finish” it?

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Yes that was Corian.

I did one where I sanded it and one where I didn’t. They also make some solvent for Corian that congeals the surface a bit. It’s an industrial chemical so I didn’t try it.