I’m using a Longmill mk1 and I noticed a strange triangular pattern on my clipart project. I’m using and IDC .045 10 degree taper bullnose bit. The strange thing is the lines only showed up on a triangle on the left and right side of the piece. I hope this picture clarifies it. The tool path was set to offset. I’m curious if it is step over, but then why wouldn’t the same thing show up on x travel?
The way that offset spirals out from the center will sometimes leave tool marks for me as well. Sometimes I just see an X across the whole piece from where the bit changes direction on rectangular tool paths. Other times I can see tool marks in both directions.
My suspicion in your case is that it was the difference between the X going with the grain not leaving marks but Y going across the grain and leaving marks. I still get the marks so I’m not sure how to eliminate them. 
Maybe someone else knows how to not get this and it will help us both.
Thanks for sharing your experience. There is definitely an X with the lines only at the 3 and 9 oclock positions. The lines are definitely against the grain.
This has got me thinking and I’m not sure what software you design in but I use Vectric and in Vectric you can select Raster instead of Offset and you can change the Raster Angle. So I’m wondering if using Raster and setting the angle so it goes with the grain would give a better result because it would only go against the grain at the ends of the project and not near the center.
Food for thought.
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I use Vectric too. I will give that a try.
Thanks.
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