Why does this happen?

[jdwykrent]

Pocketing some letters that are 12" tall. What would cause what you see in the picture? bit is .25 up. step over is 40%.

I know I should use a larger DIA bit... but I have other profile cuts being made i to save time I don't want to change bits and re-zero.

[Brady Watson]

Assuming that your bit is not slipping in the collet and that the Z is not losing steps - the most obvious thing is that the material is moving while it is being cut. An upcut will pull the material up and make it cut deeper as a result. You need to use vacuum, tape or adhesive to hold down the center to resist distortion under the force of cutting.

-B

[scottp55]

Jeff, that looks suspiciously like THIS thread. Look at Ken Z's reply. Possible something similar?
http://www.talkshopbot.com/forum/showthread.php?t=20079

[zeykr]

I think Brady is on the right track on this one.

[jdwykrent]

This was .76 MDF cut depth was .125 Could it really have lifted that much? I'm going to try a straight flute on the next set.

[scottp55]

Jeff, Had very good luck with LH bits for both pocket finish and cutouts.
Ken, Ain't Brady ALWAYS on the right track?:)
No offense Obiwan:)