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chucketn
12-01-2012, 12:18 PM
I have finally succeeded in making a pcb for my Rotary Table indexer project. Next step is drilling the through holes for the components. The component leads range from .020 to .042 Can I use HHS drill bits or should I get carbide?
I have a HF bench model drill press and an X2 mill. Which would be better? What speeds for the dill bits? Any other suggestions/cautions?

Chuck

Mcgyver
12-01-2012, 12:48 PM
the fibre glass is tough on bits, carbide is preferred. you won't be able to spin them at their theoretical max but don't worry about it, just use the highest speed you have - use whatever is fastest and has least runout. There is no requirement to spin tiny drills and at tens of thousands of rpms, run out and lack of sensitivity are the bigger challenges

tyrone shewlaces
12-01-2012, 02:03 PM
You can use either.
Phenolic/fiberglass is kind of abrasive so it will wear down sharp edges faster, so carbide is the first choice. However, carbide is more brittle than HSS so there's an increased sensitivity to whatever might break a bit, like a wobble of your hand or whatever. HSS is a little more forgiving.

If you don't have too awful many holes to drill in any one size (like 50 or so), then I'd say just buy the less expensive of whatever you need and git -er done. Sometimes carbide bits are cheaper than HSS depending on what you can find.
Don't just get one each of the sizes you need unless you feel lucky. Personally I know if I had three of each, I'd never break a bit, but if I had only one I'd bust it on the first hole. Murphy's law.

Evan
12-01-2012, 02:18 PM
Don't try drilling tiny holes using a carbide bit in a hand drill. It will break, probably on the first hole. They do not bend.

Bob D.
12-01-2012, 06:00 PM
Horrible Fright has cheap carbide PC drills

http://www.harborfreight.com/20-piece-solid-carbide-micro-bit-grab-bag-44924.html

I use a Dremel in its own little drill press for this type of work. Run at the highest speed you can.

Like others have said, easy on the pressure, and the smaller the runout, the better. These bits break if you look at them sideways...

beanbag
12-01-2012, 06:12 PM
My local tool supplier sells carbide tipped pcb drills for $3. Buy two. They come on a 1/8 shank. Use them in a collet in the x2.

John Stevenson
12-01-2012, 06:24 PM
Chuck,
I'm more interested in what the mods are to the indexer project ?

Paul Alciatore
12-01-2012, 06:52 PM
If you are just doing one PCB, I would suggest the HSS. They will get dull fast - 8 to 20 holes. You can just sharpen them or buy in packs of 12. Not worth the sweat of carbide and breakage.

darryl
12-01-2012, 07:55 PM
The carbide ones sure do break easily, but they will drill 100 times as many holes before getting too dull. Many years ago I built myself a custom drill press with an x-y table on it just for pc boards. I used an old dremel and cobbled it up with some ball bearing slides as a 'head'. Even made my own helical rack and pinion for the downfeed. The basic structure was made from mdf, then all corners well rounded and covered the whole thing in fiberglass.

The table uses 1/4-20 threaded rod as lead screws. Therefore it moves 50 thou per revolution, so 2 full turns gives the standard .1 inch IC pin spacing. I found that the best results were had by laying out the board for the IC positions, and anything three terminal, then marking only 1 of the pins positions. I let the drill press make the proper spacing between holes, and basically finish the layout that way. I drilled all the holes for the multi-pin devices, then laid out the board pattern for the rest of the parts after that.

Because most of my pc boards were roughly 100-300 holes, I drew them by hand using a fine tipped permanent marker. I could draw the pads surrounding the holes quite easily, and drawing the traces point to point after that was just as easy- a little tedious, but for the most part only needing a steady hand. Having a lot of the holes drilled already made it fairly easy to draw the traces by hand and still get a nice looking board. The holes never interfered with etching the board. The best result is if the layout can be mapped out totally according to a .1 inch grid pattern- then all the holes drilled through using only the x and y dials to move the board. The artwork is drawn after the holes are all done.

Another method I used, and still do now, is to use a spot cutter to mark the hole locations without drilling right through at this point. With the multi-pin part locations mapped out, I use the drill press to make a tiny divot at each hole location. I can then draw and etch the board, then finish the holes later. The only problem with that is that I can't use the table to crank the pc board to all the hole positions. If the location is off just slightly, the carbide bit will snap off and be gone before you know what happened. With a careful hand, you can position the pc board to put each hole under the bit, then let the bit center the board, then drill through. It works out faster for me that way, but you still risk breaking the tiny bits. The spot cutter is just a piece of music wire that's ground like a straight screwdriver bit, but with a sharp edge, then ground much like a drill bit after that. No flutes- it just becomes a spade bit with a 45 on the end and back relief on the lips- same as a drill bit. It ends up with a slight negative rake angle, but it works.

The key to using a carbide bit is, as others have mentioned, to have no mechanism whereby the tip of the bit moves sideways relative to the hole location. If the downfeed action is well constrained, the pc board is at a perfect right angle to the drill bit, and the bit is allowed to make its own location on the board, you can get thousands of holes from one bit.

lwalker
12-02-2012, 08:42 PM
Others have answered the carbide vs HSS angle very well. I just want to point out that OSH Park http://www.oshpark.com/ will make excellent PC boards at $5/sq inch total for 3 boards if you don't mind waiting 2 weeks or so. Not affiliated, just a happy customer: just had three small boards made and it cost $5.15 including shipping. I've pretty much given up on ever making another PC board at home ever again :-)

chucketn
12-03-2012, 08:23 AM
Lwalker, OSH wants Gerber and drill files. I have no way of producing gerber and drill files. They would be great for a professional developer wanting prototype boards, but not for a one off tinkerer like me. Thanks for the info though.

Chuck

Mcgyver
12-03-2012, 10:46 AM
some of these circuit board service co's provide the circuit board design software; board guys i know say some of the software is excellent. Personally I would want to use software for a board with 300 holes

outlawspeeder
12-03-2012, 10:56 AM
The big thing I found doing this is the past is strat the hole very slow! If the bit is dull it will rip the copper off the board.
The trick I used was with out the drill running press lightly to the spot. spin the bite backward to create a small dent. Then drill strating the hole slow.

chucketn
12-03-2012, 11:49 AM
Thanks for the tip outlawspeeder. Might get to try drilling today.

Chuck

lwalker
12-03-2012, 07:04 PM
What did you use to create the artwork? I use Cadsoft Eagle. The free version will do small boards (up to about 3.2x3.9").

-Lyndon

chucketn
12-03-2012, 08:52 PM
Artwork was a pdf developed by a fella named Lucas. It was a redesign of the origional artwork by kwackers. Thread for the build is on CNC Zone forum. Search for kwackers.

Chuck

jnissen
12-04-2012, 12:17 AM
As an alternative you could send the gerber files off for some really low cost boards. I helped my son with an amplifier project last summer. I was surprised to find out we could get 10 boards for less than $30. Only took a couple weeks as well. I was very impressed with the quality and service.

http://store.iteadstudio.com/index.php?main_page=product_info&cPath=19_20&products_id=495&zenid=h07il49uim93q83sp0s7u55174 as an example.

outlawspeeder
12-04-2012, 02:39 PM
If you used the etching stuff to make your own broads, be careful were you are storing the left over. I thought it was seal well and it was not. The fumes rusted every piece of metal in a 1 and a half foot circle. I was on a trip for four months and came back to rust growing like a fungus. It’s funny looking back on it.

lwalker
12-04-2012, 04:30 PM
OK, I see.

Reminds me of the "old days." At my first job, we printed everything out 2x or 4x on a dot matrix printer on "dark" setting then I had to run down to the basement to do a reduction to 8.5x11" film on our old Agfa camera, wet chemistry to develop and then voila: a nice dark plot on film.

Next step was to expose photosensitive PC board (pain in the butt if it was double-sided) and then develop that, etch it, fix any broken traces, and tediously drill hundreds of holes. Almost went crazy the first time I had to do a 44-PLCC socket. And if the prototype board worked, then we could send off the artwork to a PC board house to get a few 100 made. Otherwise, lather, rinse, repeat.

I don't miss that at all.


Artwork was a pdf developed by a fella named Lucas. It was a redesign of the origional artwork by kwackers. Thread for the build is on CNC Zone forum. Search for kwackers.

Chuck