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Thread: Which bits to use for PCB milling?

  1. #49
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    Default Re: Which bits to use for PCB milling?

    Hi,
    Harvey Tools have endmills down to that size but they are expensive.

    Rogers Precise Bits link shows 0.2mm endmills for $27US each and 0.25mm for $21US each. You are going to break those tools like they are
    going out of fashion so be prepared to spend lots of money.

    I got 30 0.5mm Kyocera Tycom two flute endmills for $80US and am still using them. I know where I'm going to spend my money!

    Craig



  2. #50
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    Default Re: Which bits to use for PCB milling?

    Hi,
    we have a broadly similar tax regime in New Zealand.

    All goods coming into New Zealand are subject to G(oods) and S(ervices) T(ax) of 15% There are a few specific items which also have a sales tax, but vey few and no more than an
    additional 10%. New Zealand Customs don't bother to collect duty/tax of less than $50. Thus if your overseas purchase including shipping is less than $333NZD then no tax is collected
    and they let the item in.

    If its more than $333NZD then you have to pay. In addition to the tax they tack on an extra $25 for the paperwork and another $12.50 for an inspection (border security) fee.

    Like Jesper I don't mind paying the taxes but don't much like the additional fees. At least the fees kick in at a much higher level.

    The Government is quite keen to see all imports get taxed in which case we could end up like Denmark where a $20US item may suddenly become $50US because of fees.
    Interestingly the New Zealand Customs Department are reluctant to do it. They claim that all the small importations would cause a major increase in their workload and cost
    and yet deliver little more revenue to the Government. They have been talking about it for some while without a clear result. If they could do something that could rake in
    more tax then any Government would have done it already. The fact that they haven't suggests that a more reasonable attitude is likely. There would be a political backlash
    if they introduced GST on everything AND the fees and yet without the fees to defray all the extra work it would cost Customs overall.

    Craig



  3. #51
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    Default Re: Which bits to use for PCB milling?



  4. #52
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    Default Re: Which bits to use for PCB milling?

    Better note that the target market for Precise Bits was originally people doing marquetry inlays in hard wood. The idea of trying to use a 0.2 mm end mill on steel makes me shake.

    Cheers
    Roger



  5. #53
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    Default Re: Which bits to use for PCB milling?

    Hi Roger,
    I have some 0.2mm PCB drills and they are so tender I cant really use them, there is about a 50/50 chance of getting them into the machine
    without breakage let alone drilling anything with them.

    0.2mm endmills in any substance let alone steel is going to end in disaster. I think Jesper's requirement of 0.2mm to 0.25mm between traces in heavy copper is unrealistic
    but you can't tell until you have tried it.

    Craig



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    Default Re: Which bits to use for PCB milling?

    Hi Craig

    Yeah, just handling them can be 'interesting'. Dropping one is usually unfortunate.
    Mind you, I don't think trying to use such end mills on steel will end in 'disaster' - just a few broken cutters is all. Well - all cutters broken maybe. It's just $$.

    I have used (Chinese!) carbide V-cutters with a 10 degree taper (really pointy) on copper to get such narrow gaps. Standard weight clad laminate, so the copper is only ?35um? thick. Given the cross-section of the carbide at the tip, I was really reduced to making 20 micron steps on the Z axis. I did not break too many tips, but it was SLOW. And you do need a desperately low TIR as well, and a dead flat vacuum table.

    Cheers
    Roger



  7. #55
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    Default Re: Which bits to use for PCB milling?

    Hi Roger,
    to call trying to cut steel with 0.2mm a 'disaster' is of course mistaken. The worst that will happen is breakage of tools.
    The cheapest I have found a known brand (Kyocera Tycom) is $3.80US each, plus shipping and import taxes.

    My experience with small diameter endmills started when I bought some 0.4mm (1/64 inch) tools from drillman1 for about $4.50US each.
    Over a period of a few weeks I broke all 10, with encouraging results but no real success stories. I bought another 10 and by now had the three
    major innovations/techniques in hand and results were much improved.

    Once I had used those I bought the 0.5mm endmills because they were on special. I realized once I got them that despite being only 25% greater in diameter
    over the previous 0.4mm tools they are much tougher. The cross sectional area makes them stronger. 0.2mm endmills I suspect will be very weak, not just the
    reduction of cross sectional area but the area consumed by the two flutes will inevitably consume area which would otherwise form the core and therefore the strength
    of the tool.

    I would recommend that Jesper start with tools somewhat larger, maybe 1/32 inch or 0.8mm. They are cheaper and more readily available. Thus he will be able to experiment
    with cheaper tools those techniques he will have to perfect before he starts on the real challenge of 0.2mm tools and the increased money and much increased sensitivity
    to failure/breakage.

    Craig



  8. #56
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    Default Re: Which bits to use for PCB milling?

    very weak, not just the reduction of cross sectional area but the area consumed by the two flutes will inevitably consume area which would otherwise form the core and therefore the strength of the tool.
    Totally agree with this argument.
    Ideally one would reduce the size of the flutes, but then the flutes would choke on the swarf.

    Cheers
    Roger



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    Default Re: Which bits to use for PCB milling?

    Hi Craig & Roger,

    I can see that you continued the thread after I left for my weekend Friday ...

    I have thought about things over the weekend and I honestly don't think that my current CNC will be capable of milling PCBs the way I would like to. 0.5 mm deep tracks with 0.2mm spacing between tracks - from what you have written - hardly will work in practice. And I have now succedeed in etching 140 um copper PCB with the 0.2mm spacing that I would like.

    So I have decided to let go of milling PCBs with my current CNC and instead try to find some PCB laminate with a 6 oz or 7 oz copper layer (0.2-0.3mm thickness base layer, single or double sided) and then refine my PCB etching process. Maybe I can make these 0.2 mm spacings with such a PCB. Some compromise but still acceptable and not least do-able within a reasonable time & cost frame. And when I need a thicker copper layer I will have to do with a larger track-to-track spacing - which also means that I can use e.g. 0.8 mm diameter end mills.

    In have also decided to buy a HQ & costly end mill (3.5 mm) from a Danish tool manufacturer - just for having a good tool reference - delivered in a short time - so as to try out my CNC before deciding how to proceed. This should tell me whether the rigidity is far off what is required - or I may get it to be as I need/wish with a sensible amount of improvements. When I know more about this I may buy from Drillman1 (which I consider a very good reference) & otherwise decide what to do with the CNC machine.

    @Craig: Any chance I can ask you to link me to a couple of end mills (face milling & ball nose) from Drillman's selection that is especially suitable for copper, brass, bronze & aluminum milling? This way I can see what is the optimum material for this and subsequently choose sizes etc ...

    Regarding cooling I have read a bit into the MQL concept, however, I still would like to keep things as simple as possible so still considering here.

    Thanks again for your considering & replying here - I realize I have met with some very qualified people here

    Cheers,

    Jesper



  10. #58
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    Default Re: Which bits to use for PCB milling?

    Hi Jesper,
    I'm going to assume you are using a router as a spindle.

    What collets do you have?. If its a European router then it will most likely have a 6mm collet. It may have a 1/4 as well. Having the right collet is essential.
    drillman1 is in the US and most of the tools he sells are US made. If you wish to take advantage of the prices he offers for tools then having 1/8 and 1/4 collets
    for your router is going to be important.

    Second issue is what speed control you have over your spindle. The universal motors used in routers tend to be fairly low torque and high speed.
    You can reduce speed but the torque does not improve, with a universal motor torque is proportional to current. Up the current at your peril.
    Also the fan built in to the armature will spin that much slower and at slow to middle speeds the router may overheat. Keep a real close eye on it
    until you are familiar with its cooling properties at slower speeds.

    Just about any endmill will work OK for materials you've mentioned. The real drama starts when you start talking steels, stainless steels, titanium and super alloys like discalloy.
    Do yourself a favour....to start with don't bother trying to mill steel, you'll smoke up and break tools and wonder what the hell is going on!

    Brass is fun to cut, it cuts well and is not inclined to form BUE. Sticky aluminum like 1000, 3000 series and to a slightly lesser extent 5000 series and pure annealed copper
    are more troublesome and BUE is likely. You may get away without cooling/lubrication but then again you may not. BUE is no respecter of whether you want to keep it
    simple or not!

    Bronzes can be fun. Silicon bronze has hard bits in it and blunt tools pretty dams quick. Phosphor bronze is used for making springs and can be quite hard but suitably
    annealed machines like a dream. Nickel bronze is tough and molybdenum bronze is tougher again.

    The bottom line is that you have to get some tools and some materials and try it out. There are certain rules of thumb and they will make sense to you once you've
    done some milling. It might be worthwhile to get some HSS tools, they are cheaper than carbide and tough as old boots, if you don't overheat them!

    Tell me what collets you have or can get and what speed control you have and maybe we can find some cheap tools to experiment with.

    Craig



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    Default Re: Which bits to use for PCB milling?

    Hi Jesper

    Etching thick copper: agree.
    Craig's comments: +1

    Look for end mills which are specified for aluminium. They will be good for plastics as well. Never try to use them on steel etc though. 'Honed' cutters are very good but dearer.
    Suppliers: I have had good stuff from CarbideChiu on eBay as well.

    Cheers
    Roger



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    Default Re: Which bits to use for PCB milling?

    I have been etching my own PCBs for some time and I use single flute ("D") cutters in a 1/8" collet. Carbide or tool steel will work fine for etching copper. I use solid carbide, but tool steel isn't as brittle. Single flute cutters, possibly referred to as V-bits, come in several long tapers to various tip widths. I've never broken one but I generally use .3-.4mm tip for more separation. The shape of the "D" cutter makes it quite strong (because of the taper). I pilot all hole locations with the "D" cutter and later drill them to .03" ( generally the size of most discrete electronic component pins - ICs, transistors, pots etc.)

    Skip

    PS: I use carpet tape to hold my stock in place and flat.

    Last edited by zqrslm; 09-10-2018 at 06:31 PM. Reason: post script


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Which bits to use for PCB milling?

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Which bits to use for PCB milling?