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IndustryArena Forum > Material Technology > Glass, Plastic and Stone > Stone and granite CNC bit recommendations?
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  1. #1
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    Stone and granite CNC bit recommendations?

    Hi, new to stone fabrication but I got a budget to build a CNC machine to mill granite and as a non-required goal to also engrave simple reliefs on leftover pieces. The build of the frame and motion system are nearing completion but I'm finding it hard to find any accredited information on how to choose abrasive finger bits. I would trial and error my way through a variety of bits if they weren't so expensive for someone starting off. I'm using a 110V 2.2kw water cooled spindle with RPM's up to 24,000 (this RPM is the limit of my spindle, I'm not looking specifically for a bit that requires this RPM). Its collets can hold a shank up to 13mm or 1/2" but I'm prepared to order an adapter from a machine shop if absolutely necessary. Any advice is greatly appreciated!

  2. #2
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    Re: Stone and granite CNC bit recommendations?

    We use diamond burrs/saws etc to cut stone, though Granite is softer than what we typically cut. I think your going to find that spindle may be lacking for stone work, high RPM is not usually your friend when doing stone. For cutting out shapes a mill/router is REALLY slow as well, this is where a Water jet excels. Stiffness is also critical in the machine design, as flex will chip the stone and wipe the diamond right out.

  3. #3
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    Re: Stone and granite CNC bit recommendations?

    Interesting, those are really good disclaimers to know about. What are the toughest stones that you might cut through? Quartzites? My machine will be pretty similar to the stone pro's stone shark cnc machine:

    https://www.youtube.com/watch?v=QrygY_0iLMM

    I'm hoping it will be strong enough, are there any burrs that you would recommend?

  4. #4
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    Re: Stone and granite CNC bit recommendations?

    I suppose I should clarify I'm not looking for a new machine, the machine is already built, I am just looking for bits to use in it because this machine will also be expected to mill wood, soft metals, and pcb's. Waterjets are nice, don't get me wrong, but they just aren't flexible enough for what I need.

    This is the bit used in the stone shark cnc is referred to as an incremental bit or incremental finger bit depending on the source:
    https://www.granquartz.com/stone-pro...l-bit-sp162-hs

    The bit is not cheap and threaded meaning I'd need a custom adapter for it to fit on my spindle. I frankly don't know how long something like this would last and in the event I order this and it flops, I'd have an expensive adapter with no other similar fittings to use it on. Not sure if any of you know of similar bits so I don't feel like this is a monopoly bit.

    This is a bit I got my hands on to test, I know it won't last long especially on hard stones like granite with only a single layer of diamonds brazed on its surface but since it is 5 times cheaper than other type, there is no harm testing it. Best thing about it is the straight shank and 1/2" diameter meaning it is compatible with my ER20 collets without any form of adapter. Not sure if any of you have or know of some videos of this bit failing, the reviews are mixed.
    https://www.amazon.com/Toolocity-FBQ...ustomerReviews

    Been looking up sintered bits and I'd never seen these before, anyone think they could be used as cnc bits or simply too fragile because of their length? I am guessing they are intended for making small holes only either for wires or bolts but I'm just not sure.
    https://www.amazon.com/WEIJ-Sintered...78&sr=8-5&th=1

    Two similar looking products to the stone shark's bit but intended for only drilling holes. The shank is compatible with my collets which is helpful.
    https://www.amazon.com/Concrete-Begi...%2C178&sr=8-11

    https://www.amazon.com/JINGLING-Diam...%2C178&sr=8-13

    This looks to be a better bit than the brazed bit but not sure, anyways, had ordered the gold one a while ago already but not sure if this is worth trying out.
    https://www.amazon.com/Diamond-Sinte...gateway&sr=8-5

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