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PCB Drilling
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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.
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