dealing with small drill bits/holes

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Newz2000
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dealing with small drill bits/holes

Post by Newz2000 » Mon Jan 29, 2007 8:11 pm

I've finally accepted Eagle and started using it for my boards. I've got a complaint, and that is the pads on many through-hole parts are too small to easily drill. I have tiny drill bits - I picked them up at Radio shack, of all places. Same as the ones you get at the hobby store, but at RS you get a variety pack with a hand drill for < $10. At the hobby store you pay $25 and you get a bunch of just one size. All of these bits are < 1/16th inch.

The first problem is, these drill bits are too small for the chucks in my drill or dremel. I've been wrapping them in masking tape so that I could use them in the dremel.

Another problem is, these bits dull quickly (50 - 60 holes, which seems quick to me) and are rather expensive compared to 1/16th inch bits.

Lastly, the pads in Eagle are often so small that even if I don't ruin the pad between etching and drilling, there's not much room for the solder to stick.

Don't get me wrong, I'm getting the job done, but it just seems like things could be easier.

What would be nice is if there was a way change the pads in an Eagle board so that they had 1/16th inch holes and at least a few mils of copper, and to ensure the ground plane stayed far enough away that you didn't have to worry about bridging as much.

Has anyone already worked through this problem and come up with a good solution? In some "drawing" style programs, where you don't mess with nets but just place your pads and parts however you like, you can choose any pad size you want. I kind of wish you had that kind of control over the pads here.

Any advice is greatly appreciated.

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Lenp
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Post by Lenp » Mon Jan 29, 2007 8:50 pm

Newz2000

I do many custom and small production boards, with Easy PC. We've used this software for years and just about everything is adjustable. Pad size and drill size can both be easily changed.

As for the drilling, use carbide bits, which often yield thousands of holes, and are available from resharpeners in mixed size lots quite reasonably.

Caution though, these bits are brittle and will quickly snap if flexed so the smaller sizes should be used at high speed, with a gentle touch, in a drill press, or the Dremel with a drill presss attachment.

Since they are designed for automated board drilling, all the different sizes come on a standard 1/8 stem so they will properly fit a drill chuck or Dremel. Router bits are also available in the same form.

(Note:Broken bits make great scriber points!)

Hope this helps!

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philba
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Post by philba » Mon Jan 29, 2007 8:54 pm

you could edit the package and make the pads bigger. You should learn the library editor anyway.

From the sound of it, you've got high speed steel (HSS) bits. These just don't cut it (pun intended) for PCB drilling. FR4 is very abrasive. You should buy carbide drills. they usually come with a 1/8" shank so you can use standard chucks on them. I use HSS bits occasionally, you can get a small chuck for the HSS bits - the one I have is about 1/4 in diameter and that you can use in a regular drill chuck.

I hate drilling PCBs so I switched over to surface mount as much as possible. It's surprisingly easy to do. Some packages are hard to use on homemade boards but if you stick to SOICs and 1206s you can pretty much do it all by hand. You will still have to drill some holes for header pins and such but you can easily reduce your holes count by 50 to 75%.

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MrAl
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Post by MrAl » Tue Jan 30, 2007 2:25 am

Hi Newz,

Just to let you know, Dremel makes something like four different
inserts for their drills made for bit sizes 0.000 inches to 0.125 inches.
Yes that's right, one goes all the way down to 0.000 inches and will
even hold a straight pin (used for sewing). In fact, with the smallest
one i have even used a straight pin to drill holes through fiber boards
and it works ok although it doesnt make as clean of a hole as a bit.
A standard size straight pin makes a hole suitable for a dip ic pin.

The carbide bits are great, and cut quickly through the boards, but these
are very very very sensitive to the angle at which you drill through the
board. With a regular Dremel (no attachments) the tendency of the
human hand is to start out drilling straight through the board but once
the bit comes out the other size the hand tilts the drill slightly, and even
that very slight change of angle breaks the bit off !!
It's very hard to stop this from happening, so if you go with the carbide
bits be sure to buy at least five of the small size because they will
break.
What helps is to get the drill press for the Dremel but i dont think that
is offered for sale anymore. If you cant get that, then at least get
the 90 degree angle chuck, which gives you a 90 degree chuck so
that the bit sticks out of the tool at a 90 degree angle and this makes
it easier to keep the drill bit perpendicular to the plane of the board
at all times while boring through the board, which prevents breakage.
Once the bit breaks it's usually not useable because it breaks off
down below the last flute on the bit so it cant be sharpened.
All of the carbide bits come with an 1/8 inch shank so you dont need
any smaller size inserts.

BTW, i have one board that i drilled a few hundred holes in with
a straight pin (using the smallest insert for the Dremel).
LEDs vs Bulbs, LEDs are winning.

Robert Reed
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Post by Robert Reed » Tue Jan 30, 2007 8:12 am

Not to get off the subject too much, but in reading these replys, it got me to thinking of a tool that I need for doing freehand layout on ground plane circuit boards. What I am looking for is a tool that would cut a ring trough the copper clad only. This ring would be about ~0.3" in outside diameter and about 0.1" thick. In other words, I would end up with a 0.1" circular copper pad setting in a ~0.3" island of bare board.This tool could hve a small drill bit machined into its center or if not, the thru hole could be a separate machine operation afterwards. Any one seen anything similar to this ?

danbob
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Post by danbob » Tue Jan 30, 2007 7:26 pm

I got a nice 50 piece set of carbide drills (5 or 6 sizes) from Dan's Small Parts for $10.00 http://www.danssmallpartsandkits.net/

Newz2000
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Post by Newz2000 » Tue Jan 30, 2007 8:37 pm

SCORE! danbob, awesome link. The winter sale has them for $7.50! And, he's got surface mount component grab bags, too.

Phil, I so agree... I recently started soldering surface mount parts. Now that I'm confident and comfortable making my own boards, surface mount is so easy not to do it. The only problem is, I have all these TH parts, I've got to restock. That's ok, its fun looking for good deals.

What do you think, are the plcc-2 LEDs easier to solder than the 1206 style? They look bigger, but I can't tell if the pads are tucked under or if they stick out.

Also looking for 6 or 12mm smt switches, if you see any cheap, let me know, but if worse comes to worse, I'll resort to the technique Forest Mimms describes where you make your own momentary switches using aluminum foil over a spacer and a pcb. That's what my cell phone has in it.

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Lenp
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Post by Lenp » Wed Jan 31, 2007 4:50 am

Hi Robert
What I am looking for is a tool that would cut a ring trough the copper clad only
Years ago there was a breadboard kit that used ground planes and indeed it did have such a cutter. I'll wade through my 'collection' to see if it wants a new home! If not I have an associate that does 'hobby machining' and perhaps he could make one. I'll be back in touch soon, don't despair!
Len

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Post by wd5gnr » Wed Jan 31, 2007 5:38 am

I've had good luck with the Dremel with the drill press attachment. A regular drill press probably has too much run out unless you have a better press than I do.

The carbide bits are a must. I got an assortment from someone on the Web (might have been Dan's) but I also have noticed $13 for 50 assorted at Harbor Freight (http://www.harborfreight.com/cpi/ctaf/d ... mber=34640) -- I'm sure these are resharps, but that's fine.

These have 1/8" shank which should fit in the dremel with the right insert.

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dacflyer
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Post by dacflyer » Wed Jan 31, 2007 6:25 pm

i have used my dremmel a lot..and with the 4 different size collets,
i got lucky one day and aquired a bunch of dentist drill bits. they are great.
maybe you might can find some on e-bay ?

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Bob Scott
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Post by Bob Scott » Wed Jan 31, 2007 8:59 pm

Mr. Reed,
Robert Reed wrote:Not to get off the subject too much, but in reading these replys, it got me to thinking of a tool that I need for doing freehand layout on ground plane circuit boards. What I am looking for is a tool that would cut a ring trough the copper clad only. This ring would be about ~0.3" in outside diameter and about 0.1" thick. In other words, I would end up with a 0.1" circular copper pad setting in a ~0.3" island of bare board.This tool could hve a small drill bit machined into its center or if not, the thru hole could be a separate machine operation afterwards. Any one seen anything similar to this ?
Couldn't you just use standard .1" grid prototype board with ground plane on one side?

Bob

rshayes
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Post by rshayes » Thu Feb 01, 2007 3:22 am

Robert Reed:

Vector Electronics (www.vectorelect.com) sells a pad cutter that is similar to your description. It can probably be ordered through one of their distributors. It probably isn't a very common item in retail stores.

Engineer1138
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Post by Engineer1138 » Thu Feb 01, 2007 9:52 am

Talk about a topical discussion! I'm in the middle of building a more precise drill press because of the runout in my Dremel spindle (only when using the chuck; not the collet) and the lack of rigidity in the Dremel drill press. I'm thinking of using a laminate router since they're cheap on eBay and run at the right speed for carbide bits, so if anyone knows where I can get a cheap 1/4" collet for a 1/8" shaft, let me know!

Newz2000: the Dremel drill press holder is a necessity! You will break multiple carbide bits every time if you try to do it free-hand. Even if you have to rig up some kind of a sliding holder out of wood, it's better than freehand.

The PCB cutter can be built pretty easily. You can take some steel tubing and cut two teeth on one edge with a file and fill the other end of the tube with solid metal so a drill chuck can grip it and you'll be set. Then you have to drill the center hold in the PCB. A better (but harder to set up) way would be to get about a 1" length of steel rod of the right diameter and drill a 1/8" hole through it lengthwise. Again cut one or two teeth on the bottom and fit a 1/8" shank PCB drill into the hole you drilled. Voila: annular cutter with center drill.

Actuallya cutter like this would be perfect for some of the prototyping I do. I'll try making one if I have time tonight.
Robert Reed: if you want one just PM me and I'll make two if my idea pans out. If nothing else, it'll be an interesting little project :-)

Robert Reed
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Post by Robert Reed » Thu Feb 01, 2007 2:11 pm

Lenp
Hope its not buried to deep in your "junk box". Thanks for the offer.
Bob
This is for VHF work and the circuit will dictate the actual component layout(somewhat custom).
RS Hayes
I will check out that site as soon as I finish this reply.
Eng 1138
Will PM you shortly.
God! I hope I didn't miss anybody.

Dean Huster
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Post by Dean Huster » Sun Feb 04, 2007 3:41 pm

You cannot ever expect success if hand-holding the Dremel with carbide bits.

The Dremel 3-jaw chuck does not have enough concentricity and cylindricity to handle carbide bits. You MUST use a collet.

The only way that any drill press has a chance of working is if you run the table up to within about 1/8-inch of the tip of the drill bit so that a minimal length of quill needs to be extended to drill the hole. The more quill that's extended, the greater the play. I've had excellent results with both the Dremel and the Craftsman presses.

Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.

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