Pocketing Resin - bottom tool marks

[bob_lofthouse]

Hi folks,

I've been searching the forum for a couple of hours and only found two relavant posts (imho)

link1 (http://www.talkshopbot.com/forum/messages/29/13993.html#POST37710)

link2 (http://www.talkshopbot.com/forum/messages/26/9355.html#POST27761)

I've been asked to look into cutting and pocketing some vaneered resin (almost like bakerlite).

I'm only cutting 1mm into the stuff just enough to clear the vaneer and bite into the resin.

The sides of the cut are fine (ie. no chatter) but the bottom of the cut (ie. new exposed surface) has tool marks in the shape of a half moon all the way along the bottom of the cut.

I've tried two different bits - a 1/4inch downcut spiral and a 1/2inch straight cutter both leaving half moon tool marks. I've also tried different feed speeds all at 18500rpm.

Has anyone else any advice having cut other materials and experienced the same problem or is it a case of just knocking the rpm upto 24k

the reason this is important is that I might have to pocket a 2ft sq area!

I will try and post picks tomorrow

cheers robert

[supertigre]

Check very carefully that your spindle is vertical to your table.

[beacon14]

You can get surfacing bits with slightly rounded corners which might help minimize the problem.

[gerald_d]

Pour fresh resin into the pocket?

[bob_lofthouse]

Sussed it.... Too much play in Z... Many thanks all....

[mziegler]

Robert, I agree with Guy, your z-axis is not perpendicular to the table. Mark