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Thread: Speed for burrs when cutting silver?

  1. #1
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    Jul 2016
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    Default Speed for burrs when cutting silver?

    Hello all - I recently bought some Busch burrs for using with silver. I intend to use them to open out a predrilled hole into a conical shape to take faceted gemstones in my first attempt at a Gipsy setting.

    I wondered what sort of RPM these are best used at? In my head I think it should be probably as fast as possible (think my proxxon goes up to 20k rpm) since the diameter of the burr is very small, so the linear velocity of the cutting edges would be proportionally slower than those on a larger diameter cutter, but I've no idea whether this is right?

    I also wondered if I should use some sort of cutting lubricant (maybe beeswax?) to get best results?

    Any advice gratefully received!

    Andy


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  2. #2
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    There most likely is a correct speed, myself it just seems to be a skill you develop and it feels right when you have the right speed,
    there are corporate products for lubrication that many people swear by personally I use paraffin wax.
    One of the other members many of who a more knowledgeable than myself will most likely be able to give a more technical answer
    Last edited by china; 20-03-2017 at 02:16 PM.

  3. #3
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    Its actually the opposite- as slow as possible or you will burn out the burr very quickly.
    And yes you absolutely need to use a lubricant, I use cut lube but there are many others including beeswax.

  4. #4
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    They have said it all above: the slowest speed that will remove silver to your satisfaction. Small ball burrs polish to shiny spheres quite quickly if abused.

    The simplest lubricant is candle grease. Burr Life mostly ends up as a powder on the bench because it crumbles in use and it is about ten times more expensive. Dipping the burr any in light oil also works.

    However if you want to be a boy racer get tungsten carbide burrs, which have a different angle of cut and thrive on high speeds. Dennis.

  5. #5
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    Fantastic!! Thanks for the advice - I'm glad I asked since the correct method is the complete opposite to my guess!!!
    I'm looking forward to having a go now as I feel a bit more confident!!

    I also read in a book that for the gipsy setting I could cut the conical hole then cut a small groove just below the surface so that the stone's girdle would snap into place prior to pushing the metal around the stone. I can't quite envisage how I'd do this on the tiny scale of a 2mm stone? I have an engineering interest, and I could easily do this with a larger piece of metal on a milling machine with rotary table but not sure how you'd tackle such a task on such a small scale especially without things like milling machines and rotary tables?


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  6. #6
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    This idea is sometimes advocated for diamond setting, as they will withstand snapping without snapping. Most modern setters use a microscope and make the undercut with a burr.

  7. #7
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    My setting is useless without the microscope, best piece of kit ever.
    The key to flush setting is getting the hole exactly the right size really

  8. #8
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    Buy a little pot of burr save/cut lube (whatever make) & it'll last years.
    As for speed...there is no exact correct rpm.
    Different sizes/makes prefer different speeds.

    Sometimes I prefer to do some drilling holding the job by hand which reduces chatter.

  9. #9
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    I go nice and slow by using my burrs in a wooden handle and doing it by hand. This works fine when I am cutting out a V shape for a gypsy setting. However I have always just made a V shape and pushed the metal over with a burnisher. Am I missing a trick by not cutting a under-cut groove to snap the stone into? I suspect it would be hard to cut that using my hand-held approach with the burr.

  10. #10
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    If it works for you, that's just fine. I often turn burrs by hand too, to save wearing them out.

    However, Bush Setting Burrs match faceted stones better than V-shaped burrs, and minimise the amount of metal to be moved with the burnisher.
    So after drilling a hole, I continue with a round burr, which is much cheaper to replace when blunt and refine the seat with a setting burr.

    As for the undercuts, they are only appropriate for hard gemstones. For larger stones, if you don't have a motor, try a scorper. Dennis.

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