Divot when cutting circles

Hi all

When I cut circles on the Longmill I usually get a divot where the start point is. The router plunges into the material a bit, goes around in the circle, plunges some more etc until the circle is cut out. Where that plunge point is it leaves a small line where the router bit starts. Is there a way to stop this?

Using Vcarve Pro and gSender



OK I see what you mean, when you cut a profile there is an option for a separate last pass that will help with that. The way it works is you set a small distance in “Allowance” and it cuts that far away from the line until the last pass. On the last pass it cuts next to the line and cuts away that mark that you see. On the last pass it is cutting with the whole bit so make sure the cutting edge on the bit is longer than the material is deep.

Because it is cutting with that much of the bit is why you want to keep the “Allowance” as small as what gets rid of that line. I usually use 0.1mm - 0.2mm. Hope that helps!

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@StuartG In addition to @_Michael advice, always use ramps and use leads if you have the material to do so.


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OK. So I think I got this. If I check the ‘Do Separate Last Pass’ option and set a value say .025’ it will cut all the passes .025" outside the line and on the last pass will move the bit basically on the line and do a full depth skim pass to clean up the edge.

I’m currently just using a straight 1/4’ router bit with a single flute. Nothing special. Would using a different type bit say up or down cut also improve the cut quality and lessen the divot?


@StuartG try a 2 flute spiral end mill if you have one. One flutes are for softer stuff.
Not on the line, same line trace as your original.


I get what you mean, I just meant that the cutter would cut in the ‘correct’ place after the last cut.

I’ll have to search the catalogs and find some spiral bits. I bought a Whiteside 60 degree V bit. It was a fair amount more than other bits but the cut quality was so much better. I think I’m done buying cheap bits unless it’s for some one off simple project.

I just did a test cut using a .025 last pass and it made a huge difference. This time there was just the smallest hint of a line. Was cutting 1/2" MDF.



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@StuartG As you have resolved your initial issue, I am closing this thread. Feel free to open a new thread if you have additional questions. Have fun.