Mcfly cutter question

Hello. I’ve been using the mcfly cutter to surface my stock. Recently, I have been getting these lines on the left and right sides of the boards. Any idea what is causing this?

Have you trammed your spindle? If the spindle is not really close to perpendicular to the plane of gantry motion, then one side of the bit is always cutting slightly deeper. Wide surfacing bits like the McFly magnify tramming issues due to their cutting width vs 1/4" endmills.

But if you have trammed your spindle well, then the issue could be your material changing in shape as it is being surfaced - cupping upwards at the ends. This is ususally seen more on solid pieces wood stock vs laminated board, but it could still happen. I’ve had wood cup up drastically while doing a long carving operation on it. First time it happened I couldn’t believe that the wood changed shape so quickly upon cutting into it - and this was after I had already surfaced the other side. Proper clamping or securing to the CNC bed is the only way to prevent this. I believe I had used tape/crazy glue to hold my piece & the wood just pried itself away from the tape.

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So I am not familiar with tramming the spindle so I’m going to say no. I’ll have to watch a video on that. I secure the stock with tape but like you said, I’m sure it comes up in certain locations. Thank you for the information

In addition to tram, it can help to set up a toolpath so that it doesn’t cut cross-grain.

See:

for an example of one way to set up geometry for that.

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Thank you for again for your help