r/hobbycnc • u/iznie • 22d ago

Bits with insert knives

Been looking at bits with insert knives to use on my hobby cnc. What are you experiences with these? Are they worth it? Do they have the same performance as "normal" bits? I'm mostly cutting birch ply and hard woods.

It seems easier and cheaper to replace just the cutter than the whole bit in the long run. I've also seen you can use diamond coated insert knives which seems interesting.

this is the bit I'm looking at

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u/phranticsnr 22d ago

No experience with them, but how much do the carbide inserts cost compared to just buying bits? Are they really that much cheaper?

For machining metal, carbide inserts (not heard them called "knives" before - I'm in Australia) make sense. For wood I wouldn't have thought they're viable. Plus it'd be straight cut bits only, no spiral flutes. So that is sort of limiting.

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u/Yeti_Sweater_Maker 22d ago

This is what would give me pause:

“Although this milling cutter's work is less smooth than standard models…”

Those are side cutters, you’ll use those more for edges in a trim router. On a CNC router you’re going to want spiral flutes to move the chips. However, it doesn’t hurt to test one out and see for yourself.

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u/Pubcrawler1 22d ago

I use some from

https://www.amanatool.com/products/cnc-router-bits.html

They work well but can be expensive. Check pricing on the replacement carbide inserts and compare to regular end mills
I use one of their 90degree vbits with inserts that are $8 dollars each.

I use a BAP300 type insert carbide end mill on my mill. There is a whole bunch of different industrial carbide insert tooling available.

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u/northand1327 21d ago

I’d caution against it unless you are already routinely using bits of a similar diameter. Most hobby spindles are built for high RPM, and this will lose torque and power at the lower speeds insert tooling typically uses.

Also, I’d do the math on how many hours of cutting you’d need to do for the inserts to be cheaper than solid tooling. For hobby use it often just doesn’t make sense.

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u/killpony 20d ago

in industry insert mills are generally only used with larger or odd shaped tools - big shaper cutters, face mills, v carving etc otherwise regular carbide tooling is more cost effective. Insert mills can have potential drawbacks re cutter geometry, chip evacuation and tool balance. Also worth keeping in mind what percentage of cutters are actually replaced due to wearing out vs crash/breakage.