PCB Drilling

[mike_mike]

Hello,
I am using a mini drill stand from Donau (D-0400), and I also built my own mini drill stand. I am encountering the same problem with both mini drill stands: if I use a new, non used drill bit, the holes are good, but, after a few holes drilled, the holes does look a little bit strange.
I am using this drill bits NO 28 854:
https://ibb.co/TgfM6xg

I will show you some images:
1. With the new drill bit:
https://ibb.co/t46JHJw

2. After a few holes (5 to 10 holes) drilled:
https://ibb.co/R64rbfs

I have also tried with cheap HSS drill bits, and the same thing happened again.
This problem also happened when the mini drill was almost new, before I opened the mini drill case to clean it.

Why is this happening ? It is normal ?

[ruffy91]

This is normal for HSS drill bits, the very abrasive FR4 destroys the sharp cutting edge in a few holes. Use carbide drill bits and you get good holes for hundreds to thousands of holes.

[woodchips]

The carbide drills don't have cutting edges as you would expect on a standard drill, they look like masonry drills.

Used to be able to buy these used for next to nothing, are they still available?

[CatalinaWOW]

Harbor Freight in the US sells the used (resharpened) bits at a very attractive price, though it is a pot luck assortment of 10 bits.  I assume there are similar outlets in Western Europe.  Also the various on line sources.

[Kleinstein]

One can sometimes get used carbides drill that are no longer good enough (to high a danger to break) for CNC use, but are still good enough for manual (in a good drill press) use.  I would guess the Harbor Freight one could be such a case.
It's a bit of a gamble how good they are, but these drills tend to be cheap.

The holes from the HSS drill look not that good, but this may no be a problem for a solder joint. For manual drilling and not so high demand on the quality I consider cheap HSS drills (no thicker shaft, but same as bit) a viable option. With a good source they can be down to some $2-4 for a pack of 10.

[Domagoj T]

The carbide drills don't have cutting edges as you would expect on a standard drill, they look like masonry drills.

Used to be able to buy these used for next to nothing, are they still available?

That's not the type you should look for.
Use this type:
https://www.ebay.com/itm/10-Pcs-PCB-Print-Circuit-Board-Carbide-CNC-Mini-Micro-Drill-Bits-Tool-0-3-1-2mm/401753732571?hash=item5d8a6375db:g:FWEAAOSwk1BcvTsH

They have standard shank size of 3,175 mm (1/8'') so you can easily use collets instead of standard Jacobs chuck, which will give you much lower runout and make drilling easier.

On my PCB drill I have a spidle similar to this:
https://www.ebay.com/itm/200w-air-cooled-cnc-spindle-dc-motor-CNC-Engraving-Machine-ER11-3-175mm-collets/322602189321?hash=item4b1c96c209:g:nroAAOSwvSNcj0Wm
It comes with ER11 collet chuck and is dead center as far as I can measure with my dial indicator.
It's mounted on Proxxon drillstand, and that is the weakest part of the drill.
Good lighting from both sides also helps a lot.

[Old Printer]

Turning at the proper speed will also make a difference, too fast with too much feed speed will cause overheating of the bit and premature wear.

[Domagoj T]

You'll be hard pressed to overheat a carbide drill bit with DIY equipment due to spinning too fast.
https://www.eurocircuits.com/drilling-printed-circuit-boards/

[Old Printer]

You'll be hard pressed to overheat a carbide drill bit with DIY equipment due to spinning too fast.
https://www.eurocircuits.com/drilling-printed-circuit-boards/

I didn't get the impression the OP was using carbide bits, but I could be wrong. I wanted to offer a possible solution for his current tooling. Sharping a bit that small by hand is not a trivial task, but with a fine wheel and a bit of practice, far from impossible..

[rx8pilot]

Carbide drill notes from someone that has drilled millions of holes in just about every drillable material.

Its true that you will struggle to overspeed them. I regularly run 1/2 inch drills at 12,000 RPM in aluminum. Tiny PCB drills run at 100k RPM +++. Pretty much the fastest spindle you can afford. The challenge with carbide is runout and vibration. They are very brittle and don't really wear much before they chip or shatter. Low end drill presses are extremely slow and have enormous runout, which breaks carbide quickly. The plentiful choices of  Chinese spindles are fairly fast and have usable runout for hobby usage where expectations are not terribly high.

Cobalt or other specialty drill geometry that are better than cheap HSS and less finicky than carbide might be good to research. Perhaps more forgiving in less than perfect drill presses.

Lastly, the operator skill will have a lot to do with the overall performance. Manual drilling PCB'S requires a delicate feel for success.

Typet purly on my fone.

[Domagoj T]

I didn't get the impression the OP was using carbide bits, but I could be wrong. I wanted to offer a possible solution for his current tooling. Sharping a bit that small by hand is not a trivial task, but with a fine wheel and a bit of practice, far from impossible..

HSS bits are entirely unsuitable for the task, as witnessed by OP. Even if his sharpening skills were top notch and he had the equipment to properly sharpen such small bits, it would still be of no use. The reduction in the hole size does not come from the dulling of the cutting edge, but from the bit being abraded on its sides, reducing the diameter. You would need to grind off all the affected length before sharpening, only to get another 5-10 usable holes before having to go through the whole process all over again.
Carbide is the only reasonable way to drill PCBs. Luckily the carbide bits of quality suitable for hobby use are so cheap that the cost of buying them should not be of concern.
In hobby use, they last forever (or until you break them, whichever comes first).

I can post some pictures/videos of the little drill I use (on Thursday when I get back to work) if anybody is interested. The setup is fairly cheap, but quite effective for PCB drilling (not much else).

[Gyro]

You can still get carbide drill bit sets for little money, eg: https://www.amazon.co.uk/KKmoon-Tungsten-Carbide-Engraving-Circuit/dp/B074DW29RR/

[Old Printer]

I didn't get the impression the OP was using carbide bits, but I could be wrong. I wanted to offer a possible solution for his current tooling. Sharping a bit that small by hand is not a trivial task, but with a fine wheel and a bit of practice, far from impossible..

HSS bits are entirely unsuitable for the task, as witnessed by OP. Even if his sharpening skills were top notch and he had the equipment to properly sharpen such small bits, it would still be of no use. The reduction in the hole size does not come from the dulling of the cutting edge, but from the bit being abraded on its sides, reducing the diameter. You would need to grind off all the affected length before sharpening, only to get another 5-10 usable holes before having to go through the whole process all over again.
Carbide is the only reasonable way to drill PCBs. Luckily the carbide bits of quality suitable for hobby use are so cheap that the cost of buying them should not be of concern.
In hobby use, they last forever (or until you break them, whichever comes first).

I can post some pictures/videos of the little drill I use (on Thursday when I get back to work) if anybody is interested. The setup is fairly cheap, but quite effective for PCB drilling (not much else).

That would be appreciated, I don't have a setup for doing thicker boards. I have done some thumbnail sized boards of .2mm material for a micro model airplane project and "drilled" them with a Co2 laser, but it does not work well on anything much thicker.

[CatalinaWOW]

I have now set up a CNC board mill which handles this nicely.  But a hack for manual drilling that aided me a lot was 3D printing a drill guide.  Your mileage may vary but it improved my accuracy and dropped drill breakage significantly.

My theory in trying this was that the relatively soft filament printing material would be not be as hard on the drill bit with initial offset errors and that the spindle runout could be gently reduced.  I don't know if either of the theories was valid, but it worked.

[Domagoj T]

As promised, this is a video of the upgrade I made for the  drill press.
The old version had a motor with significant runout. Additionally it was too slow for effective drilling with small diameter bits. The new motor is much faster, has much lower runout and is quieter.
The L bracket is still something that needs to be addressed as it is not as stiff as I'd like it to be.
The base contains the power supply for the motor, lights (both above the table and below, and the air pump.
It uses a small Proxxon drill press stand as the basis for the setup, the rest is custom made.

[xavier60]

I had not been able to use tungsten carbide  bits with my Dremel rotary tool due to too much runout.
The photo shows a modified collet. I use it with the cable drive adapter nut which has been bored out to 1/8"plus clearance.
The runout is very small now.

[Domagoj T]

Yeah, when using carbide, low runout is essential due to the brittleness of the bits. Also, the setup needs to be stiff enough and not flex when drilling, otherwise the bits will snap immediately. Hand drilling is not really feasible with small bits we use for PCBs.

[rx8pilot]

I had not been able to use tungsten carbide  bits with my Dremel rotary tool due to too much runout.
The photo shows a modified collet. I use it with the cable drive adapter nut which has been bored out to 1/8"plus clearance.
The runout is very small now.

That is a cool hack - the DIY market needs some low-runout Dremel hacks.