Oak Vcarving chip-out on letters

[banderson]

I am using a PRS standard with PC router and 60 degree Onsrud bit to make small signs in .75 thick Oak. With some fonts, I end up with sharp leftovers, for example, the material that is left after the letter K is carved. These sharp leftovers often chip off during the cut (not so much in other woods).
feed rate is 1.0i/s.

Anybody have any ideas on how to avoid this?

[adrianm]

Oak is prone to chipping like that. I switched to V-bits with three cutting surfaces and that pretty much cured it for me.

I use these which aren't available in the 'States as far as I know but CMT do something similar.

http://www.wealdentool.com/acatalog/Online_Catalogue_Engraving_60_degree_719.html

[tomwillis]

Bret - here's another option in the states.
http://www.vortextool.com/index.cfm?fuseaction=category.display&category_id=38
Tom

[srwtlc]

Like Adrian stated, oak tends to do that. CMT and Infinity have similar 3 flute 60º v-bits.

http://www.amazon.com/CMT-858-001-11-Cutting-Diameter-16-Inch/dp/B000P4NSYG/ref=sr_1_1?ie=UTF8&qid=1357674199&sr=8-1&keywords=cmt+60+degree+v+bit

http://www.infinitytools.com/1_4-Shank-Laser-Point-Bit-5_8-CD-7_16-CH-60-CA/productinfo/58-001/

For 90º v-bit work, I've had good luck with a 1/2" shank CMT 815.690.11. The latest version that I've gotten has one of the two flutes notched at the tip which makes it a one flute for a short distance and allows the tip of the other flute to be ground to a dead on point. This also allows you to run at higher RPM's without overheating the tip as it is virtually a single flute bit there. Holds good detail.

[rb99]

What is "laser point"? Do they use a laser to hone the point?

[srwtlc]

Nah, it just that it comes to a sharp point instead of being sort of blunted in the bottom of the cut (like many two flute 90º bits are/do).

[Rick W]

Brent,
Try changing direction and/or your start point depending on where it is breaking off. (depends on the letter). Hard to explain, start with the delicate parts. Hopefully this makes sence.

Rik