Best Bit?

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Retired 1st Sgt
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Best Bit?

Post by Retired 1st Sgt »

While doing 3D, I typically use a 1/4 ball nose for roughing and finishing. I have my feed rate at 60 and plunge rate at 40. My step over is 10%. Is there a better bit or way to make my final cut show more detail?

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Rcnewcomb
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Re: Best Bit?

Post by Rcnewcomb »

Is there a better bit or way to make my final cut show more detail?
For finishing preview it with a 1/8" or a 1/16" ballnose. If it is noticeably better then you may need to use a smaller bit for the finish toolpath.

The nice thing about the preview is you can try it with various bits and then decide which bit is best for your project.
- Randall Newcomb
10 fingers in, 10 fingers out, another good day in the shop

martindg
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Re: Best Bit?

Post by martindg »

I typically use a 1/4" ball nose for roughing with the feed set to around 120-150 and haf that for plunge rate and a stepover of 40-60%. For the finish path I will typically use a 1/8" tapered ball nose adjusting the feed rate to get a good chip load (again around 120 - 150 ipm) and, more critically, reduce the stepover to 8-10%.. If I need better detail I will go to a 1/16" tapered ballnose

Retired 1st Sgt
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Re: Best Bit?

Post by Retired 1st Sgt »

Thanks for the tips.

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ohiolyons
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Re: Best Bit?

Post by ohiolyons »

It also depends on the size of your carving.

1/4" EM and BN will not yield a good looking results on a 3"x3" carving, but could deliver excellent results on a 24"x24" carving.

Design and Make use to have guidance on bit sizing for their files, but has sense been taken it down.
Their models were optimized around 1/8" BN for finishing.
If you enlarged the model you might (depending on the level of detail) get away with a larger finishing bit.
If you reduced the model you might (depending on the level of detail) you might need a smaller finishing bit.

It mostly depends on how intricate your model is and how big of cusps are you willing to put up with.
Don't forget you love of sanding too.
John Lyons
CNC in Kettering, Ohio

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adze_cnc
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Re: Best Bit?

Post by adze_cnc »

"Best bit” and “how long is a piece of string” are pretty comparable.

A 1/4” ball nose cutter on a very samil project (say 3” x 3”) might be acceptable if that proejct is just a simple dome or dish shape. It would be less than useful if that project was an elaborate Chinese dragon and flower model. Then a tapered ball nose with a small (0.25mm R ?) tip might be more appropriate.

Whenever I hear the term “best practices” used I like to say “there are no best practices only alternatives”. We could extend that to choosing the cutters we use for projects.

My one suggestion though is to consider, as ohiolyons alluded to, using an end mill as a roughing tool rather than a ball nose bit.

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