Pocket carving not flat on bottom

Hey guys.

So I carved a test piece today and noticed that the pocket carving doesn’t wind up flat. Not sure what the issue could be. Here’s a pic to show you what I’m talking about speed was 75ipm and . 06 depth per pass.

Is your base board flat? The base board (waste board, spoil board, whatever one calls it) has to be flat first.

Yes the wasteboard is flat.

I have had hold down methods cause an issue using double sided tape the initial plunge pushes it in harder then the lighter spiral out is fine leaving a bad groove also had tape come loose and one corner popped up higher than normal…

What end mill are you using?

Your Z axis is not level.
I think this link can give you some ideas how to do it

that and maybe use a shallow finishing pass.
Roughing passes tend to be like that since the machine isn’t super rigid. finishing off witha shallow pass will put very little strain on the machine and will likely yield better results.

That’s not a bad idea! I only did one pass just to test how good of resolution I got with a certain bit. Usually I think when I normally carve it’ll do a shallower finishing pass.

I’m also gonna go over my z axis and look for any deflection. I just got the suckit dust boot from kickstarter and I’m wondering if it’s adding too much weight to the front of the spindle causing it to twist forward.

If that’s in the middle of a large piece of wood and you’re using an upcut bit, the middle may be bowing up with the initial cut (bit acting like a screw). If you don’t have this problem licked, try throwing some double-sided tape under the middle of the board and see if it does it.

@anon68752607’s suggestion to have a cleanup pass is a good idea as well. I usually set my cut depth so that the final cut is .010" or so, to allow it to clean up the bottom. That’s too shallow to have the corkscrew effect with an upcut bit.