Explain high-quality wire drill bits to me

[mmagliaro]

For years, I've used the typical wire drills we can buy through hobby dealers - places like Walthers
or Micro-Mark, and others.  Most are okay, and with patience, you can drill a #80 hole through brass with them.

I bought some real cheapies a few weeks ago from an eBay dealer that were so dull that it would take
forever to drill such a hole, and what's more, even with a #76 bit, which is getting a little more sturdy,
the bit would actually bend over like a soft lead pipe.  I've never seen such a thing.  Drill bits are usually
made of hardened drill rod and if you overstress them, they snap.   Bend???

So, now, I happened to buy up some new old stock wire drills made by
Precision Twist Drill and Machine Co (of Crystal Lake, IL).   They are AMAZING.  They are so much harder and sharper
than anything I've ever tried.    A #80 bit digs right into brass with NO punch mark, and makes a clean hole
without ever trying to walk off the mark, and it cuts clean and fast.

These were old little paper packages, and I wondered if the company was still in business.  Apparently, they
are, although they've been bought up by another company.

http://www.mscdirect.com/product/78521747

At $3 or so per bit, they ain't cheap (my eBay purchase of them was much cheaper than that).

So now I want to ask, what do you know about drill bits?   Why are these things so much better and sharper
than the hobby bits we all use?   I see terms like low-helix and high-helix, and the degree angle of the
tip (118 degrees).   What should I be looking for in a bit that can easily drill tiny holes through
brass and other soft metals (in addition to styrene).

Thanks.

[Chris333]

last time I bought a bunch of #80 bits on ebay they had no point at all to them, completely blunt, wouldn't call them drill bits more like fluted rods...

I've got to try out the ones you listed.

I found these on e-bay for around $30:

But you know how they snap when looked at funny.

[Chris333]

Just searching. It looks like I overpaid 
http://www.ebay.com/itm/50-Solid-Carbide-Micro-Drill-Bits-PCB-80-0135/310731178738?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D17848%26meid%3D1546475535851769491%26pid%3D100005%26prg%3D8208%26rk%3D2%26rkt%3D5%26sd%3D310754515226%26#ht_1888wt_1399

[VonRyan]

From what I know about drill bits, I'd say that the cheapie ones you bought were not good quality metal. Probably not hardened.
It sounds like you found some really good bits so treasure them with your life.
And post a picture of the package so that I know what to look for when I'm rooting through old tools at the local flea-market. 


-Cody F.

[robert3985]

I use both the "hobby" bits available at my LHS distributed by Walthers and drill bits I buy from my local machine supply shop.

I NEVER use drill bits for hobby work which I am not familiar with, which means, I buy one or two, test 'em and if I like 'em...I'll buy more.  This means that I won't buy bits from Harbor Freight tools, Walmart, Target, or from unknown sources off eBay.  You can count on those being substandard.

Another source is Drill Bit City, and I've purchased several .007" and smaller bits from them, but they supply Tungsten Carbide bits that have been resharpened, which turns out to be okay, but I discovered that I don't like TC bits, because they are very unforgiving and break easily.

My other ultra small bits, I purchase from my local machine shop and they're steel and flexible, but very sharp and cut like crazy.  They also cost me 10 bucks apiece, so I'd better know what I'm doing when I'm drilling.

Here's how to drill holes in metals.  (1) As you've discovered, buy acceptable bits (2) If you're drilling with a motorized drill motor, keep the RPM's under 300.  The smaller the bit, the slower I go, which is why I NEVER use my Dremel, but I used my Foredom tool, or my Craftsman battery powered precision screwdriver with a Micro Mark drill bit adapter on it (3) For ALL METALS lube your bit.  NEVER drill a hole in metal without lubing your bit.  I have a tube of extra good lube that my local machine supply store gifted to me, which does not have any labels on it.  It's more like a precision grease, but it makes my bits cut like crazy...including the Walthers bits.  Give yours a visit, tell them what material you're drilling and the size bits, and they'll know what lube to sell you.

Pretty simple.  If you drill your holes in metal using these principles (you can drill holes in Styrene and wood without lube, but RPM rules still apply) your expensive bits should last a long time.  Way back when, when I bought my first .007" bits at ten bucks apiece (I had to buy a dozen of 'em at one time), I was afraid they'd break like crazy as my purpose was using them to make brass masters for my little master fabrication/lost wax casting business.  I still have all 12 of 'em, and I've drilled thousands of holes with them.

As I've said already, I don't like Tungsten Carbide bits for hand-held hole drilling.  They're okay chucked up in my mill, but I much prefer high speed steel bits.

As to bit angles, the expensive bits are more precise, which means the point of the bit is centered and is more likely to not "walk".  However, for precise drilling hand-held, I always create a starter punch mark, even with bits that don't "walk".  That's because I only have one good eye and I frankly can't ensure myself that I'll put the hole where it belongs without that little dimple since my binocular vision is poor at best.

Tip angles and twist rates vary depending on materials you want to cut.  Pointy tips are usually for drilling in abrasive materials such as hard rubber or fiberglass.  These bits usually have low twists also, which is proper for evacuation of the type of chip plastics and rubber produce.

Low twist rate drills are usually for brass, which helps evacuate the type of chips brass produces.  These will work in a pinch for aluminum too, with the twist being developed specifically for production machinery and high rates of feed.

High twist bits are for low tensile strength metals such as aluminum, copper, Zamac as well as wood and plastics like Styrene and Polypropylene.

However, since you're not drilling your holes using production machinery, I wouldn't worry about twist rates and tip angles.   If you find your bit isn't evacuating the chips fast enough, just pull it out often so it doesn't break.

That's about the extent of my drill bit use knowledge.

[mmagliaro]

Thanks for the info so far guys.
I will say this:  I have tried the bits like the ones Chris showed in his photo.  Carbide bits are very sharp
but extremely brittle.  So for us guys drilling with a pin vise, they are a very bad choice because they snap off
if you whisper at them.   I would stick with high speed steel (HSS).

Here's what the Precision Twist Drill packages look like:



You can buy these from MSC, and the bits are about $3.00 a piece.  But given how good they are, I supposed
that is far better than buying bits for $1 that aren't nearly half as good.

[peteski]

Nowadays, I am pretty use the tungsten-carbide PC-board drills for small holes. Once I tried them, I never looked back at the standard small HSS twist drills. The split-point end (even on small drill sizes) drills through just about anything just like through butter.  The 1/8" shank also makes them very easy to use and handle.  Yes, I break my share of them by being clumsy, but the cost of resharpened ones is low enough that I can replace them.  #85 is the smallest one I use often, but I also have #95 for when I need a really small hole.

[u18b]

When it comes to styrene, I often use homemade bits for less than #80.

I take hard thin wire-- like .008 guitar string and cut it at an angle.  The cutter compresses the metal so that you have a sharp point and a burr on the back side.  By spinning this on styrene it will make a small hole.

[delamaize]

When it comes to styrene, I often use homemade bits for less than #80.

I take hard thin wire-- like .008 guitar string and cut it at an angle.  The cutter compresses the metal so that you have a sharp point and a burr on the back side.  By spinning this on styrene it will make a small hole.

this is what i do for less than #80 also.....

[spr1955]

For bits that bend and don't break they would be carbon steel (cheap quality) but they have their place like bell hanger bits which are used to install wire for security systems and such, you can actually bend the drill as you drill through studs to get the hole where you want it. Most drill bits of any kind of quality for metal working are made of high speed steel. HSS. Precision Twist Drill was one of the better USA mfg's of twist drills for eons, but they sold out to the Chinese and everything comes from there. Frankly , there is almost nothing in cutting tools being mfg stateside any more. Everyone was bought. So, the quality of the steel varies and so do your drills. Generally speaking USA mfg is superior to overseas. Carbide is extremely hard but also very brittle, expensive and should only be used in a drill press or other mechanical device, no hand held stuff. It has not lateral strength and therefore snaps easily with hand held drills.

HTH

David P.

[mmagliaro]

For bits that bend and don't break they would be carbon steel (cheap quality) but they have their place like bell hanger bits which are used to install wire for security systems and such, you can actually bend the drill as you drill through studs to get the hole where you want it. Most drill bits of any kind of quality for metal working are made of high speed steel. HSS. Precision Twist Drill was one of the better USA mfg's of twist drills for eons, but they sold out to the Chinese and everything comes from there. Frankly , there is almost nothing in cutting tools being mfg stateside any more. Everyone was bought. So, the quality of the steel varies and so do your drills. Generally speaking USA mfg is superior to overseas. Carbide is extremely hard but also very brittle, expensive and should only be used in a drill press or other mechanical device, no hand held stuff. It has not lateral strength and therefore snaps easily with hand held drills.

HTH

David P.

Very interesting!
And since my bits are new-old-stock in very very old little cardboard packages, I would wager they are from the days
when Precision was still American made.    This was a fellow selling out all the parts and tools from his father's machine
shop, so the stuff could be very old.

Are you sure they sold to a Chinese company?  They are still listed as being located in Crystal Lake, IL, although
I cannot see their website (www.precisiontwistdrill.com)

[Chris333]

I saw the same guy selling his dads stash and bought a pack. Can never have too many bits and I also drill brass with them to attach details.

[mmagliaro]

I saw the same guy selling his dads stash and bought a pack. Can never have too many bits and I also drill brass with them to attach details.

Post when you get them and let us know what you think.  I was really impressed with the #80 drilling through
the side of a heavy piece of K&S brass pipe (the .029" wall stuff).  I noticed right away that it stuck, dug,
and little spiraling chips of brass came out as it went, much like you see when you drill with big heavy
bits through metal.   I don't think I've ever seen a #80 bit work that well.  They usually drill out
brass dust as they go. 

[Lemosteam]

One thing to keep in mind is that you could herden the "cheap" bits yourself with pliers, a torch and a cup of water.  There may be just enough carbon in the bit to harden the drill point without making the bit too brittle.  Just heat the bit up to glow and dip the tip in water.  Not sicentific, but it will harden the tip.  I've also been successful sharpening a bit on a dremel disc after hardening for a nice new point. 

I've also done this with low grade steel screws to make a quick tap after grinding the cutting groove into the threads.  Very handy when you have a screw but no tap!

[mark.hinds]

When hand-drilling metal with small drill bits, I lubricate with beeswax.  No idea if this is best practice, but it makes a huge difference in how the bit cuts.

MH