# Best way to cut 20mm holes in FR4/G10?



## balou (Dec 16, 2009)

Hi,
for my current project (https://www.candlepowerforums.com/threads/218611) I need to drill a lot of 20mm holes into 1.6mm thick PCBs made out of G10.

Currently, I use a small milling bit with a Proxxon drill to cut out those 20mm by hand. As you might have guessed, this is an enormously tedious process.

So, anybody got an idea how to make that more efficient? I've seen round, adjustable saw-like bits... but as far as I knew those were for wood only. Would I need something like that?

Btw, I have access to a drill press.

On a side note, I also need to cut G10 sheets. I currently use a 20mm cutting disk on my Proxxon. Any other improvements to that step except using a bigger cutting disk?


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## precisionworks (Dec 16, 2009)

That is smelly, nasty, abrasive material to work with ... you should consider a dual element full face respirator combined with suction through a HEPA or Gore-Tex vacuum filter. Once those micro fibers of glass get lodged way down in the lungs (alveoli) they become permanent residents :shakehead

Back to the OP ... the most efficient way to machine glass woven fabric, impregnated with an epoxy resin binder, is to use a diamond tipped carbide insert called a PCD (_polycrystalline diamond_). Those inserts are around $100 USD each, which is a fraction of the cost of diamond coated end mills. Both need to be used on a milling machine, and either would have short life on a drill press.

Diamonds aren't the only option ... if there is a nearby shop with an abrasive waterjet, it can easily cut the 20 mm holes to within .001", and it can also cut your sheets to size. I'd look first at waterjet, as the cost per hole should be less.


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## balou (Dec 16, 2009)

precisionworks said:


> That is smelly, nasty, abrasive material to work with ... you should consider a dual element full face respirator combined with suction through a HEPA or Gore-Tex vacuum filter. Once those micro fibers of glass get lodged way down in the lungs (alveoli) they become permanent residents :shakehead


At the moment I'm using a household vacuum cleaner duct-taped to the top of my working plate and a simple cotton facemask. So I'm not entirely unprotected, and I've never seen visible dust flying around, but I think a separate thread on that would be in order...



> Back to the OP ... the most efficient way to machine glass woven fabric, impregnated with an epoxy resin binder, is to use a diamond tipped carbide insert called a PCD (_polycrystalline diamond_). Those inserts are around $100 USD each, which is a fraction of the cost of diamond coated end mills. Both need to be used on a milling machine, and either would have short life on a drill press.
> 
> Diamonds aren't the only option ... if there is a nearby shop with an abrasive waterjet, it can easily cut the 20 mm holes to within .001", and it can also cut your sheets to size. I'd look first at waterjet, as the cost per hole should be less.


So basically... no can do at home? My whole Proxxon drill cost only $100, and I don't even know what a milling machine looks like ... 

About that waterjet: I'll look around for shops. But I'd also have to look directly at what PCB fabs offer - they could probably drill those holes directly, etch the PCB, add soldermask and silkscreen, all for probably the same cost a local shop would charge.

Hm.. really no other options for doing this stuff at home besides a $100 Proxxon drill and a $5 milling bit?


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## precisionworks (Dec 16, 2009)

> I'd also have to look directly at what PCB fabs offer - they could probably drill those holes directly, etch the PCB, add soldermask and silkscreen, all for probably the same cost a local shop would charge.



That's your best bet.



> really no other options for doing this stuff at home


These materials resist heat, cold, acids, bases, and machining. They eat carbide inserts like the carbide was butter, which is the reason for PCD inserts. You can still do this at home, at a slow pace, and with frequent tool changes.



> I've never seen visible dust flying around


The worst particles, called nano particulates, are so tiny that they stay suspended in the air for half an hour or more & are practically invisible. In this case, what you cannot see is what will hurt your lungs.


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## gadget_lover (Dec 17, 2009)

Don't those materials punch out cleanly with an appropriate cutter and die? I seem to remember seeing a lot of circuit boards with what looked like punched cutouts.

If that's the case, there might be a 20mm punch set available.

Daniel


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## 65535 (Dec 17, 2009)

gadget_lover said:


> Don't those materials punch out cleanly with an appropriate cutter and die? I seem to remember seeing a lot of circuit boards with what looked like punched cutouts.
> 
> If that's the case, there might be a 20mm punch set available.
> 
> Daniel




Does not punch well.

Best bet is a very sharp cutter and high speeds. The stuff is not fun to machine. At least G11 gave me hell just drilling 17/32 holes. Bleh, was easier to drill through steel.


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## balou (Dec 17, 2009)

*Best way to cut 20mm holes in phenolic paper?*

Ok... so it really is hard to machine.

What just came to my mind - how about phenolic paper?
Could I somehow work on it on a drill press? As far as I can see, the glass in G10 is what makes it so hard to machine.


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## 65535 (Dec 17, 2009)

*Re: Best way to cut 20mm holes in phenolic paper?*

Anything with fibers in a resin or epoxy will not machine easily, the paper might machine more easily. It's not to say it can't be machined, but to drill the hole you'll need a lot of edge cleanup.


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## balou (Dec 17, 2009)

Yes, but paper surely is quite some way down from glass in the Mohs 
scale.
I have to acquire a sample of it, and see how well it can be machined.

And I do expect to do a lot of edge cleanup - I already had to do it with my manual method.
Corundum bits actually work pretty good for this job.


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## kromeke (Dec 17, 2009)

Best way is to sub it out to a PCB house. I'm in USA, so I'm not familiar with any European PCB houses. They can also make your PCB's for your project. The more you order, the cheaper they are per unit. 

If you want to do it yourself, I'd recommend a diamond core drill or a carbide grit hole saw. I'm in the land of inches, so metric bits are a little hard to find here (speaking of grit saws and diamond core bits).


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## balou (Dec 18, 2009)

kromeke said:


> Best way is to sub it out to a PCB house. I'm in USA, so I'm not familiar with any European PCB houses. They can also make your PCB's for your project. The more you order, the cheaper they are per unit.


Yes I think going the PCB route is the only viable option. Making it at home is just to time consuming and on top of that a health risk.
I thought more of fabbing it in China or another low-wage country.
Gold Phoenix PCB could be an option, I'd have to ask them if they can do 20mm holes resp. how much that would be, plus if they can make rounded edges (http://www.goldphoenixpcb.biz/). I've already ordered some prototypes once from Olimex.com, but they seem to be a bit unflexible - and also more a single-prototype kind of business than small run to big series like Gold Phoenix.



> If you want to do it yourself, I'd recommend a diamond core drill or a carbide grit hole saw. I'm in the land of inches, so metric bits are a little hard to find here (speaking of grit saws and diamond core bits).


Seems like to much hassle. One or two prototype with a standard milling bit, then either order some PCBs from China or shelve the whole project.


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## kromeke (Dec 18, 2009)

If your going the foreign route, try Alberta Printed Circuits, http://www.apcircuits.com/ They are in Canada. My company has used them in the past. 

Another is http://www.4pcb.com/ They are in the US. 

For prototyping, I'd avoid starting off with a Chinese vendor. Too many variables. 

Any vendor should have no troubles with shapes. They will most likely route (as in router) the large holes anyway. Curves, shapes, it is just numbers to the machine.


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