Drill bits for homemade PCBs?

[Martaine2005]

Blimey. I sounded a little like Colin there...

 

[hevans1944]

Somewhere on the web there is guidance on surface speed for carbide tools cutting various materials. However, the general rule-of-thumb is the smaller the bit diameter the higher the RPM required for cutting instead of just heating the tool. Good ol' trial-and-error will usually lead you to the "right" speed that works for you, especially since the tiny carbide drill bits that used to cost a fortune are now so inexpensive (made-in-China or Japan, which is where some of mine came from) you can afford to break a few learning how to use them. If you closely examine under magnification the holes produced by whatever drill bit you are using a dull bit, whether HSS or carbide, will be evident immediately. Sharp bits produce clean holes with square sides. Dull bits don't.

Back in the last century, when I first started making circuit boards, it didn't take five minutes to realize that ordinary HSS drills didn't cut it for drilling fiberglass boards. Later, the titanium nitride coated bits weren't much better. However, carbide drill bits back then were very expensive. Sometimes we could find used ones at Mendelson's that were acquired from the National Cash Register Company, when NCR was still in Dayton and venturing into electronics instead of manufacturing mechanical cash registers. These used bits were quite adequate and sharp enough for hand drilling at moderate RPMs, but clearly NCR discarded them for a reason. They probably weren't sharp enough for production drilling. The cost of changing out a dull drill bit, even at ten to twenty dollars a pop, was insignificant compared to the cost of down time if one broke and damaged a circuit board. However, it was the breakage problem when free-hand drilling that led my laboratory supervisor to approve the purchase of a table-top drill press with a high speed motor and an accurate spindle with precision bearings and very little runout. IIRC, back then (mid 1970s) they cost less than five hundred dollars, but not much less.

My Dremel Moto-Tool Drill Press is a Model 210. It does not work with my wife's Dremel 4000. So, unless I can find my old Dremel tool (which happens to be misplaced at the moment), I guess I will have to spend forty-six bucks and change to purchase a 220-01 Rotary Tool Work Station from Amazon...

 

[Martaine2005]

Back in the last century, when I first started making circuit boards, it didn't take five minutes to realize that ordinary HSS drills didn't cut it for drilling fiberglass board

Before I answer , ordinary HSS drill bits?
Hop you are being a little zealous

 

[Martaine2005]

Good ol' trial-and-error will usually lead you to the "right" speed that works for you

I am really glad to point this conversation back to to me.
That was a hefty read . But what happened.?

 

[BobK]

At 10000 RPM how long do you think it takes a drill bit to cut through a PCB? I don't force it and there is never any burning, it is just that it really drills that fast. Seeing as I have not broken or worn out any bits over thousands of holes, I think my method works adequately.

Bob

 

[hevans1944]

... Hop you are being a little zealous

I don't think zealous is the proper description; just practical.

The question seems to be: is a carbide drill bit necessary for drilling PCB holes, or will high speed steel (HSS) bits work just fine, cost a little, do a lot, and last a long time? It has been my experience that HSS drill bits are totally inadequate and a waste of money for drilling accurate holes in copper-clad fiberglass (FR4) printed circuit boards. Your mileage (or kilometers) may differ.

That said, I haven't actually had to make a PCB or drill holes in same since about 1978, switching to commercial products about then, although I am thinking of taking it up again in retirement for quick turnaround hobby prototyping. It is hard to beat the price and delivery of commercial PCB manufacturers though, even for onesie-twosie quantities. And double-sided boards with plated-through holes and gold-over-nickel-plated edge contacts are pretty much out of the question for the hobbyist.

Perhaps HSS drill bits, especially those with titanium nitride (TiN) or titanium aluminum nitride (TiAlN) thin-film coatings, now rival carbide bits. The lab where I worked until retirement coats aluminum die-casting mold core pins with these coatings to prevent molten aluminum from sticking to the steel core pins. If that happens, it's a real bitch kitty to get the die set open and the stuck pin removed. Our coating more than doubles the life of the core pin and saves a lot of expensive down-time if the core pins are replaced on a regular basis before the coating fails.

Applying the thin-film coating, which is only a few micrometers thick, is an expensive process involving radiant heat, a vacuum chamber, a filtered cathodic arc, and various reactive gases in a proprietary recipe. It would increase the cost of an HSS drill bit by at least a factor of ten for our TiN or TiAlN coatings, and by at least a factor of one hundred for more exotic thin films involving hafnium compounds. I don't know what process is used to produced commercial drill bits with so-called TiN coatings, but I have not found any that hold up as well as the coatings we produced on a small scale for an automobile engine manufacturer. But then, commercial TiN coated drill bits only cost about five times as much as a common HSS drill bit. You pays your money and you makes your choices. I will continue to purchase and use carbide drill bits for PCB holes.

 

[Martaine2005]

Yes, I stand corrected!
Having read many websites, carbide bits seem to be the norm.
However, if there is any defence, I am very finicky and do not let any of my cutting tools dull.
They are all kept sharp and clean. So I probably would never have noticed.

When I was carpet fitting, even the stanley blades we used were constantly sharpened on a stone on our belt.
They lasted weeks as opposed to minutes.
They did get smaller though.!!

Martin

 

[hevans1944]

... I am very finicky and do not let any of my cutting tools dull.
They are all kept sharp and clean. So I probably would never have noticed.

If you have a technique or tool for sharpening those tiny (sub-millimeter diameter) drill bits, please share! I once worked with a machinist who could sharpen most anything by hand, aided only by his trained and experienced Mark I Eyeball, but I never master that process except maybe for wood lathe chisels.

When I was carpet fitting, even the stanley blades we used were constantly sharpened on a stone on our belt.
They lasted weeks as opposed to minutes.

Perhaps slightly off topic, but I too love those Stanley reversible blades. They do dull quickly, especially when scoring drywall board prior to snapping, but they will slice up a huge stack of cardboard for disposal (re-cycling) before getting dangerously dull. I keep a box 100 replacements on hand, and that has lasted several years now, but I also will take a few swipes over a very fine stone to touch up an edge if both ends are dull and the replacements aren't nearby. Really nice tool and available everywhere, but don't try to fly with one.

 

[Martaine2005]

but don't try to fly with one.

That made me chuckle Hop.
Are you talking US customs?
Or in the front pocket during turbulence?

I use miniature diamond files for tiny drill bits and any router bits with tight flutes. Jewellers tools.
And straight diamond stones for normal cutting edges.
Even slightly damp timber can burn, a rubber to clean the tracks of Hornby railway cleans up the residue.
I find it very therapeutic. Boring yes at times. But when you think of the people that throw away bits because they are blunt, that's what the seller wants.

Martin

 

[hevans1944]

I kept a box of dull bits at work, hoping to sharpen them eventually. Most of them were large enough to use with a Drill Doctor that has a high-speed diamond cylinder that does a decent job of producing a fine edge. A new hire spotted the box and sent the whole lot out for professional sharpening. I have no idea what that cost, but the drills came back in "like new" condition, their cutting ends protected with some sort of soft, removable, coating. Seeing that, I put the Drill Doctor away and never touched it after that. Wouldn't mind owning one for home use, but they are a bit pricey.

 

[hevans1944]

Are you talking US customs?

I am talking Transportation Safety Administration (TSA), those friendly folks who keep people from carrying on stuff that might be used as a WMD or worse... provided it isn't carried on in underwear.

I've tried to avoid flying since a few buildings came down on September 11, 2001, presumably caused by airplanes hijacked by terrorists wielding box cutters flying into them. My last flight was round trip to Albuquerque NM a couple years ago to visit some physicists at Sandia National Laboratories. Got to see a lot of new toys there, but I doubt I will fly anytime again soon since it would be on my dime instead of the taxpayer's.

TSA seems to be doing its job keeping the American sky safe for commercial air traffic, and I had no problem clearing their checkpoint in either direction. Not so sure about other countries, although Israel has an excellent reputation because they not only examine but also profile passengers. The TSA is not supposed to be allowed to profile, except if you are on their "no fly" list which will deny boarding, so high-tech fills in the blanks, hopefully!

 

[Laplace]

However, it was the breakage problem when free-hand drilling that led my laboratory supervisor to approve the purchase of a table-top drill press with a high speed motor and an accurate spindle with precision bearings and very little runout. IIRC, back then (mid 1970s) they cost less than five hundred dollars, but not much less.

I still have mine, purchased in the late 1970s ~$400. Precision machined cast iron & steel. Made in Japan. Height=16" shown next to a Dremel Tool for comparison. I added the clamp bar to the base. This stays on the shelf except for special drilling jobs. As far a I can tell nobody still makes these.

 

[CDRIVE]

Uhhh, I was going to post my two cents but when I see friends snapping at each other I think it best that I pass on this one.

I see nuuuthing! I hear nuuuth-ing! I Know nuuuu-thing!

Chris

 

[antonschutte]

Hey Everyone!

I wonder if you guys could tell me what you use to drill your homemade PCBs with (like what drill press you use/where you get your drill bits).

I started drilling a PCB I made but after a only few holes, the drill bits snapped. I think that it may be because the drill press I'm using isn't very precise and has quite a bit of play in the shaft. It may also be because I was using some $4 bits I bought off of ebay.

I was thinking about buying a special drill press for PCBs, but before I did I though I would ask you guys what you use.

Thanks a ton for your time!!!
Dan

Hi Dan

I found a company in my local village of Auckland, who sell drill bits that are shanked up to 3.5mm. The bits themselves are from.3 to 1 mm...you choice. Local cost including freight around $NZD30 per pack of 6. They are called "test n tools", and I am sure they can advise you re your local supplier of the same goodies

 

[Old Steve]

Uhhh, I was going to post my two cents but when I see friends snapping at each other I think it best that I pass on this one.

I see nuuuthing! I hear nuuuth-ing! I Know nuuuu-thing!

Chris

Of course you're right, Chris. Sometimes I should just hold my tongue.

 

[CDRIVE]

Blimey. I sounded a little like Colin there...

Now that's scary!

Of course you're right, Chris. Sometimes I should just hold my tongue.

It's just that I've always felt very comfortable here at EP. Kinda like a big happy family. But then again families, even though they love each other, do fight now and then.

So, that said. IMHO, drilling fiberglass PCBs should be done at high rpm at ~10,000 RPM with Solid Carbide bits and ABSOLUTELY NO Freehand Drilling.... EVER! This should be SOP! If the bit it held in a Jacob's type chuck then it's best that it's shanked. Even collets at these diameters are struggling to hold the bit securely. So shanked carbides are a good choice.

Cheers,
Chris

 

[Old Steve]

Now that's scary!


It's just that I've always felt very comfortable here at EP. Kinda like a big happy family. But then again families, even though they love each other, do fight now and then.

So, that said. IMHO, drilling fiberglass PCBs should be done at high rpm at ~10,000 RPM with Solid Carbide bits and ABSOLUTELY NO Freehand Drilling.... EVER! This should be SOP! If the bit it held in a Jacob's type chuck then it's best that it's shanked. Even collets at these diameters are struggling to hold the bit securely. So shanked carbides are a good choice.

Cheers,
Chris

I promise not to snap.

I think that it's 'horses for courses' Chris, with relation to hand drilling. I've done it that way for 20 years+ without problems. When printing the PCB transparency, I set the output to "Show holes", and it leaves a nice little spot to centre the drill bit on, making it easy to drill without the bit 'skating' across the copper when starting.
And collets are fine, (which I use with my little mini-drill), and hold the bits very securely.

After all, a Dremel 4000 uses collets, and screams at speeds up to 35000rpm. When doing my woodwork, I regularly use 1/4" router bits in mine, at 20-25000 rpm. I actually often use my little screw-on Jacobs chuck when doing it too, but prefer collets because they centre better and are more stable, (less vibration). I only ever use it at less than 20000 on timbers that tend to burn a little, or for cast acrylic, (12000rpm).

 

[CDRIVE]

I promise not to snap.

I think that it's 'horses for courses' Chris, <snip> When doing my woodwork, I regularly use 1/4" router bits in mine, at 20-25000 rpm.

Ha! Mr.Ed. I love seeing him again on OTATV! He's smarter than Wilbur.

I've also noticed that there are very, very few electronics heads that are not also amateur machinists and woodworkers. Check it out. You'll see that I'm spot on! I think it translates to .. Electronics Heads are arguably the most creative, resourceful and broadly skilled demographic on this Earth,... and somewhere in between all their activities, they still manage to fit sex in there tight schedule to create what will hopefully be perfect harmonics!

Cheers,
Chris

 

[Old Steve]

Ha! Mr.Ed. I love seeing him again on OTATV! He's smarter than Wilbur.

I've also noticed that there are very, very few electronics heads that are not also amateur machinists and woodworkers. Check it out. You'll see that I'm spot on! I think it translates to .. Electronics Heads are arguably the most creative, resourceful and broadly skilled demographic on this Earth,... and somewhere in between all their activities, they still manage to fit sex in there tight schedule to create what will hopefully be perfect harmonics!

Cheers,
Chris

Sex??? What's that.

Yep, I've been surprised how many of us are also into woodworking. (chopnhack for one - the name gives him away.)
For me, mostly woodturning, but I do a bit of everything. Wooden scale model cars are one of my passions. I made a scale 1928 model A a little while ago, for a mate who was born in that year. That's where the small-scale routing comes in - right down to 0.8mm end-mill bits for grilles, bonnet (hood) vents etc.

 

[CDRIVE]

Sex??? What's that.

Yep, I've been surprised how many of us are also into woodworking. (chopnhack for one - the name gives him away.)
For me, mostly woodturning,

We'll have to talk woodturning in our own thread sometime. Yes, I love it more than any other woodworking discipline.

Cheers,
Chris