Tear out in Ultraboard Foam Core

[John Murray]

I am having problems with tear out of the core of 1" Ultra Board. (Foam Core with PVC Skins). The manufacture recommends a spiral bit cutting at 2in per second at 18000 RMP. We still get tear out. We are using a onsrud 52-564 1/4" spiral bit. Any recommendations? Thank you in advance.

[Brady Watson]

I don't know if you need a 1/4" tool or if you can go larger. It looks like the right tool for the job is either a 2 or 3 flute spiral-O, but it doesn't look like Onsrud offers it in a length of cut (in 1/4" dia) long enough to get all the way through your material. Those grinds would be 52-624 or 60-241, respectively.

Harvey (http://www.harveytool.com/AdvancedSearch.aspx?Search=1&Keywords=plastic), who makes premium tools, has a similar grind in 1.25 or 2.00 length of cut, in 1/4" dia, part numbers, respectively: 986516 or 992416

I get mine from Mike @ LibertyTool.com