"Pull out" when machining baltic birch

[Plan_B]

Hi folks,
I make parts out of baltic birch and some areas of those parts can be relatively thin (like 1/4"). In those areas, a common problem I have is that the upper or lower layer chips away. I've tried down cut and up cut bits and have found that the problem is less overall with non-spiral, straight bits, but still too common. I generally use 3/16" to 3/8" bits. I've tried faster feed rates, slower feed rates and haven't found that there is much difference. For you more experienced people, my question is, Is my goal to completely or nearly eliminate those pull outs unrealistic? Or is there a sweet spot I might find with the bit type/size, feed rate, etc.?

Sorry if this topic is covered well somewhere else - I searched and didn't find much. Would love to peruse other existing threads if you know of any.

Cheers!

[routalot]

Part of it is the nature of wood as most types will have slightly fuzzy edges when cutting across the grain.When you are dealing with material as thin as 1/4" you don't really have the option of resorting to a compression cutter as the upcut portion is normally verging on that size,but with thicker material it might be an option.

[peteeng]

Hi PB - The straight flute will be best. What depth of cut are you using? To minimise fuzz at the bottom you need to cut down rough then use a finishing cut maybe two thin bottom cuts (0.5mm deep or less). ramp down don't plunge and the tools need to be sharp. Plus if possible the bottom cut should be in the middle of a ply not at the bondline... Peter

[boydage]

Mr B I have been machining timber for years. All the way from a cnc router with a floppy timber frame up to version 5 many years later I think with a 2000kg frame and much much heavier gantry. The last machine is good for machining alloy.

But the direction I am going is with the rigidity of the machine so is the quality of cross cutting timber. All sorts from western red cedar to age old Jarrah. I use 2 or 3 flute endmills that normally cut alloy. Almost Zero breakout. I will ramp down. But take .8mm off as a finishing run at 44mm deep max.

So a bit of food for thought its not only the endmill. I reckon the machine needs to be rigid too. But in occasions where I really really need to avoid that bit popping out on a edge, I will program a small nudge. But tell you what, there is also advantage of a good new sharp endmill on timber.

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