Bit question

[garylyb]

Onsrud has a chipbreaker design bit here

Onsrud chipbreaker bit


I'm just wondering if it would leave a cleaner edge on hardwood and plywood than the spiral bits that I'm currently using.

Does anyone have any experience with these bits?

Thanks,
Gary

[Deleted]

Typically the purpose of a chip breaker is to force smaller chips instead of strings so a heavier cut can be made at the expense of lower quality cut. Thus you can rough cut faster with higher DOC and feed rate but then you'll do a finish pass with a normal bit and overall saving time. But you'll have to do a tool change and your finish bit will last longer and so does the roughing bit.

[closstudio]

We did our first piece using Corian and the ridges the bit left are not what I expected. Are pieces typically finished with another bit?

[Deleted]

Sept 25, 2018 13:12:37 GMT -5 closstudio said:

We did our first piece using Corian and the ridges the bit left are not what I expected. Are pieces typically finished with another bit?

As I wrote above, these are for removing a large amount of stock quickly with less chatter and load before using another bit for a finishing pass.

[grg]

You can also just use a standard solid flute end mill, which will need to cut a little slower than a chip breaker, and avoid the tool change steps as a previous poster mentioned.  However, I found that once calculating the feed/speeds based on the ideal chip loading for most end mills, the Axiom generally won't quite go as fast as possible for some of the tool setups - especially for woods.  In other words, I don't see a need to go with a chip breaker in most cases. 

A good fresh/sharp upcut end mill leaves a razor sharp edge both sides of decent plywood but starts to frizzle when it gets dull.  Use a compression bit (has both an upcut and downcut portions) if you want a super clean edge on each side and let it go a little longer as it dulls.

Next point, for plastics, a single flute end mill is advisable.  Be sure to calculate feeds and speeds to get the most out of your machine, tooling, and material.  A good place to start is here.  Their free online tool doesn't have all of the available variables but it will get you started.
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