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IndustryArena Forum > Other Machines > PCB milling > Determine Vee Bit diamtre
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  1. #1
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    Determine Vee Bit diamtre

    I bought my 6040 a few years ago and also bought various Vee bits that I have not used yet.
    I want to try engraving some pcb's, but the labels on the bits have fallen off, so I don't know the angles or width of the tips....grrrr

    I've worked out how to determine the angles (put 3 or 4 together on the bench. If 3 makes a 90 deg angle they are 30 deg, etc, but I don't know how to determine the tip diameters.

    I put the tips against a steel rule and zoomed in with my phone to take photos, but that was inconclusive.
    I assumed they would be multiples of 0.5mm but since googling, it appears they will be multiples of 0.1mm. I can't determine that from my photos.

    This MIGHT be 0.3mm?

    Steve

    Attachment 471370

  2. #2
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    Re: Determine Vee Bit diamtre

    Short of a shadowgraph,and few of us have one in a home workshop,the only thing I can suggest is getting hold of some radius gauges for a visual comparison.I have several but they only go down to 0.75mm smaller examples may be out there.Maybe some tiny holes drilled in a piece of plastic would be a substitute.

  3. #3
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    Re: Determine Vee Bit diamtre

    a question: for PCB engraving, why do you want to know the tip radius?
    I would say you care about depth enough to remove all the copper ( plus a little deeper for reliability ) and that's it ...

  4. #4
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    Re: Determine Vee Bit diamtre

    Quote Originally Posted by Algirdas View Post
    a question: for PCB engraving, why do you want to know the tip radius?
    I would say you care about depth enough to remove all the copper ( plus a little deeper for reliability ) and that's it ...
    The software uses the angle and tip diameter to determine where the tool needs to be so you get the track widths and spacings you design.
    I originally thought my tools were 0.5mm, but if I did use that figure and it actually is 0.3mm, that represents a significant error.

    Sent from my SM-G970F using Tapatalk

  5. #5
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    Re: Determine Vee Bit diamtre

    Quote Originally Posted by routalot View Post
    Short of a shadowgraph,and few of us have one in a home workshop,the only thing I can suggest is getting hold of some radius gauges for a visual comparison.I have several but they only go down to 0.75mm smaller examples may be out there.Maybe some tiny holes drilled in a piece of plastic would be a substitute.
    Holes might work...thanks.

    Sent from my SM-G970F using Tapatalk

  6. #6
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    Re: Determine Vee Bit diamtre

    First, make sure you can maintain a constant depth of cut. It is not enough to level the table and mount the PCB flat. Commercial PCB prototyping machines have a depth limiter ring; hobbyists often use surface probing.

    Then make a test PCB, measure the actual trace widths and adjust the tool diameter accordingly.

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  8. #8
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    Re: Determine Vee Bit diamtre

    Quote Originally Posted by CitizenOfDreams View Post
    First, make sure you can maintain a constant depth of cut. It is not enough to level the table and mount the PCB flat. Commercial PCB prototyping machines have a depth limiter ring; hobbyists often use surface probing.

    Then make a test PCB, measure the actual trace widths and adjust the tool diameter accordingly.
    Thanks. I assume I can use Autoleveller software to do this. I'll give it a shot.

  9. #9
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    Re: Determine Vee Bit diamtre

    Thanks hfbuis, I'll have a look at these.

  10. #10
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    Re: Determine Vee Bit diamtre

    I reckon it's probably a 0.2, but frankly that's irrelevant. While DIY PCB milling IS a precision process, it's not actually possible to engineer that precision into it by design - you just pick values reasonably close enough to reality then tweak them based on practically produced results and go with what works. Don't for a second think that you can produce a 0.52342365mm wide trace simply by starting with the right numbers.

  11. #11
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    Re: Determine Vee Bit diamtre

    Quote Originally Posted by Sterob View Post
    Thanks. I assume I can use Autoleveller software to do this. I'll give it a shot.
    Autoleveller is what I use. Works like magic.

  12. #12
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    Re: Determine Vee Bit diamtre

    Hi,
    I use Autoleveller also, and have done for six years, would be lost without it.

    In the pcb-gcode user language program that converts my Eagle files to Gcode I nominate a 0.18mm diameter and a step over of 0.08mm
    pretty much irrespective of the engraving bit in use.

    The width of the cut will in large measure the determined by the depth cut and that in turn will depend on how you level your PCB. It needs to be flat and level
    to better than 0.03mm OR use Autoleveller.

    Craig

  13. #13
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    Re: Determine Vee Bit diamtre

    Yes, I'll just have to it and see how it goes.
    I am leaning towards the bits bring 0.1mm but as you say, it matters not too much.
    I want to clear all the copper around the tracks, so I will buy some bits around 0.5 to 0.8mm so it doesn't take an age.

    Sent from my SM-G970F using Tapatalk

  14. #14
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    Re: Determine Vee Bit diamtre

    Clearing all the copper is not always necessary, especially if your board will have a solder mask. I usually make the cuts just wide enough to clear the space between adjacent SMD pads.

    I do have a set of 1mm, 2mm and 3mm "rubout" endmills by PreciseBits, but I rarely use them.

  15. #15
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    Re: Determine Vee Bit diamtre

    Hi,
    I want to clear all the copper around the tracks, so I will buy some bits around 0.5 to 0.8mm so it doesn't take an age.
    My standard is 0.8mm isolation, and with 0.08mm step over is about 6 passes, but no rub-out. The only time I increase the isolation is for boards
    with high voltages, then I allow 3mm isolation for 230VAC.

    There is value in nominating a small step over, it eliminates little islands of copper and pesky shorts between adjacent traces, even if it does take longer.
    I don't see any value in rub out though.

    Craig

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