PCB drill bits

[SavannahLion]

So I shattered my only Dremel bit trying to drill a test hole in a piece of scrap circuit board. I wasn't happy with the holes I was turning out free hand anyways so I started to look around on a bunch of sites to figure out what drill press I can use. A bunch of great DIY stuff (anyone here weld while we're on this?) but not a whole lot about what drill bit sizes to get. Checking eBay yields a huge ---steaming pile of meadow muffin--- load of re-sharpened bits for around $10 for 24 (3 each of 8 sizes) but the sizes are all over the map and half the time they're in inches and the other half they're in mm. And of course there's a few sites (and a lot of Chinese) that sell PCB drill bit sets.

Anyone have a suggestion for selecting the most common used sizes? Anyone have a decent source?

[MonMotha]

15 or 20 (for vias, depending on your taste - you could also use 28 and may have better luck if drilling by hand), 28-30, 35-38, 42-45, 50, 55, 70, 100, and 130mils would get you a pretty decent start.  You'll often not have the exact bit you want, but you'll have something close enough for most purposes.

In mm....um, convert those   In general, a typical PCB these days will have drills in both units in order to comply with what the manufacturer of the part being put in the hole recommends.  Most PCB fabricators will stock both, but there's usually at least 2-3mil tolerance, so they may not give you exactly what you asked for to start with if they think they can still meet the tolerance spec.

Honestly, I find that you can get cheap PCBs made professionally these days at cost comparable to what I'd pay in materials (including consumables - and that includes drill bits) to make them myself, and the results are way better.  Of course, if you want to play around, it's an interesting experience.  Are you planning to etch, or do you have a milling stand?

[SavannahLion]

Etching at this point but I imagine drilling would be the next logical step. I toyed with a few methods with some being too pricey in the long run and a few others not working out. I found a really cheap Epson printer at a swap meet so I figure I'll hack that apart and give it a shot since I happen to have the appropriate inks and accessories from my other Epson.

I'm still trying to work out the drilling portion. I (my wife) has a Dremel drill press but it's not the most SOLID if you catch my drift and my own Dremel is really old (around twenty years) so it's not directly compatible and the bearings probably need a little work. My wife's is a more modern (specifically a slightly different "grip" and a shorter shaft than my own) but it has seen way more abuse getting applied to everything you can imagine including wifey's experiments with glass, clay, plastics, wood, ceramics, rare metals, etc. Mine has seen more use around plastics and common metals but, as I mentioned, it is far older than hers. I honestly can't figure if I should gamble and try for a Harbor Freight Crapper, patch up my Dremel and hobble together a drill press, or look around on eBay for the more "refined" drill presses.

I have some of the supplies already from repairing other PCB's. A kind of hodgepodge of SMT and TH parts. So I figure I can just keep going with what I have. It's just that I found there are times when the TH part is quite a bit cheaper and/or easier to obtain than the SMT equivalent.

I took a good long hard look at having someone etch and print my boards for me. I guess part of the problem is I always used pre-existing designs but never my own and it's hard to fathom spending money for a board of my own design that may... or may not work. But then, as you said, I'm spending money for my own fabrication. Can't win either way I guess.  . Most of the PCB places I looked at also have a minimum of some kind. Either a board size, monetary or both. There are a few things I'd like to build as experiments, such as using an SMT part as a "drop in" replacement for a TH part where a proto-board just isn't going to work. For that, I honestly can't see ordering twelve tiny boards when I only need one.

[MonMotha]

The best deal I've found so far is to panelize several designs up to near the maximum 60 sq in size for the Advanced Circuits $33/ea deal.  You can get 4 each of however many designs you can fit in 60 sq in (you cut apart) for ~$205 to your door.  If you can get 10 designs on the panel, that's a quite reasonable $20 each for 4 copies.  Not too shabby, and the specs are way better than you can do at home (among other things, you get a soldermask and 6/6 mil trace/space).

If you really do only want one of a single design, you'll probably have to go through the hobbyist batch/pooling services.  Be prepared to wait and still probably spend ~$50 or so.  Unfortunately, the process at those volume is basically all set-up: materials barely factor into the equation for the fabricators.

Yes, the Dremel brand drill presses apparently suck.  A pity, since the tool is pretty ideal for this application.  A full 3 axis gantry milling machine is great if you can get one.  You can get about 10/10 design rules out of a decent one, though registration between the two sides can be tricky, but that's true of most home etching processes, too.  Protomat makes some reasonably priced ones, but you can have an awful lot of professionally made PCBs done for the price of one, especially still factoring in consumables.  They're really only good for extremely rapid turn needs.