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View Full Version : How I make my own drill bits - how do you make yours?



mars-red
11-26-2012, 10:15 PM
I posted up a shop made spade drill in the "Shop Made Tools" thread and someone expressed interest in seeing details on the process I use to make them. I went a little picture crazy so I figured I'd start a separate thread and at the same time get feedback from anyone else here who makes their own bits, I'm really curious to see how others do it.

I found myself needing to drill and tap a hole for M4x0.7 threads, so I needed a 3.3mm drill. This is the smallest I've made so far (I'm sure I'll make much smaller ones at some point), and the hole needed to be rather deep. I usually make my bits as short and stumpy as possible for the immediate need I have, to keep them as strong as possible.

I started off with some O1 drill rod, and for this sort of size it made sense to fire up the watchmaker's lathe:
https://lh5.googleusercontent.com/-tNCLgaDY-Zs/ULQl1hS2liI/AAAAAAAABAw/-MGJutCgKhI/s800/stock.jpg

I start by turning the point taper and the major diameter (3.3mm in this case). I don't get too fussy about the angle of the point - I typically go with a 60 degree included angle:
https://lh4.googleusercontent.com/-LSJMBFv3Gs4/ULQlztvZMMI/AAAAAAAABAg/oHl8XBqRtLE/s800/major%2520diameter%2520and%2520point%2520taper.jpg

This pic is really crappy but if you squint you can make out a slight taper turned up. I usually go for about 1 degree of taper up to what will be the shank. In this case, I will have a sort of double shank. The smaller shank, where the 1 degree taper ends, is smaller than the cutting diameter, so that I can drill deeper. A larger diameter shank, for chucking, will also be left.
https://lh6.googleusercontent.com/-qxVIu67S0Q4/ULQl1_fy7eI/AAAAAAAABA0/eJWF1U740eQ/s800/taper%2520turned.jpg

I extended the work through the collet a bit and left the diameter of the stock for the larger shank (so this drill bit is no more accurate than my collet, which is perfectly acceptable in this case). I love parting on this little machine:
https://lh5.googleusercontent.com/-pAQbYu1fR2Q/ULQl0EaQ7VI/AAAAAAAABAo/AVrQzAggpik/s800/parting.jpg

mars-red
11-26-2012, 10:15 PM
Let the filing begin!
https://lh5.googleusercontent.com/-EzjorOgjvF4/ULQlxWU3H3I/AAAAAAAABAI/bkk5riR3MwU/s800/let%2520the%2520filing%2520begin.jpg

I start by filing a flat up the tapered portion:
https://lh5.googleusercontent.com/-chN06gm5h0w/ULQlw89RS2I/AAAAAAAABAA/TyQu2bZGIhg/s800/first%2520side%2520filed%2520flat.jpg

Then I file a flat exactly opposite the first flat:
https://lh4.googleusercontent.com/-63TCuHQc-nA/ULQlpy4MvBI/AAAAAAAAA_Y/9WHSMlXMZJA/s1024/both%2520sides%2520filed%2520flat.jpg

Now I blue up the remainder of the outside diameter, in preparation for filing relief angles:
https://lh6.googleusercontent.com/-H3KoiLGvxLc/ULQlzBdpv3I/AAAAAAAABAY/KlNBkgTq2uk/s1024/outside%2520diameter%2520blued.jpg

mars-red
11-26-2012, 10:16 PM
The blue makes it easy to creep up on the relief without losing anything from the outside diameter. I file until there remains just the faintest trace of blue... this tiny amount allows for sharpening after the bit is hardened. Here is a pic showing the relief filing in progress:
https://lh5.googleusercontent.com/-X1TrDT_ZhWE/ULQlsUTn-fI/AAAAAAAAA_o/zpd5HQqvbU0/s912/file%2520to%2520eliminate%2520blue.jpg

Here is the bit after all filing is completed:
https://lh6.googleusercontent.com/-TJwMLnipRCU/ULQlt5PWHfI/AAAAAAAAA_w/uOwXu4p7dUc/s1024/filing%2520completed%25201.jpg
https://lh3.googleusercontent.com/-Ruja7Gacyzg/ULQlvmS0s9I/AAAAAAAAA_4/Xwmth3PgJnw/s912/filing%2520completed%25202.jpg

Heat treating O1 is pretty easy so I'll just mention that at this point I harden the bit, sharpen the cutting edges with a stone slip, then polish the remaining surfaces to observe the color change while tempering. I temper to a light straw color.

Here is the completed drill bit, ready to go to work after a pilot has been drilled:
https://lh4.googleusercontent.com/-Kg69opOuU6M/ULQlpMozXtI/AAAAAAAAA_Q/itvIx0QRLvk/s1024/about%2520to%2520drill.jpg

mars-red
11-26-2012, 10:16 PM
Part way through drilling, so far so good! I always use Tap Magic with these spade bits - they cut smooth as silk with it. I recommend using some sort of cutting fluid or oil, they don't really seem to like being used dry.
https://lh4.googleusercontent.com/-uJpQSnhoJKE/ULQlw4dMvBI/AAAAAAAABAE/AKnSoucIL24/s1024/drilling%2520started.jpg

Here we have the bit and the nice tidy hole it left in my part:
https://lh4.googleusercontent.com/-i9o8DqP0qdg/ULQlqXaKPoI/AAAAAAAAA_c/JqspMT7D5Pg/s720/drilling%2520completed.jpg

achtanelion
11-26-2012, 10:48 PM
Thank-you. This has definitely been filed away for future reference.

J

oil mac
11-27-2012, 05:02 AM
Excellent post Mars, your description of this most useful item of tooling, I have noted as well Thanks for posting. your little watchmakers lathe is like my Boley always a treat to use

Mtw fdu
11-27-2012, 07:52 AM
Wow, wow, and more wow!!!

Mtw fdu.

sasquatch
11-27-2012, 09:21 AM
Excellent posting and pics!! Thanks for this.

Forestgnome
11-27-2012, 10:35 AM
That's pretty much how I make mine except for the taper. I just make them straight. I cut the relief angles on the mill in an indexer, harden, then lightly touch up on a grinder. Mostly i make them to drill brass.

TheAndroid
11-27-2012, 10:45 AM
Thanks for that! I do have a question. Is the bit triangular (or tri-lobal) after the relief is filed?

mars-red
11-27-2012, 10:51 AM
Thanks for that! I do have a question. Is the bit triangular (or tri-lobal) after the relief is filed?

Nope, it only has 2 cutting lobes - it is typically referred to as a spade drill. If you are familiar with pivot drills used in watchmaking, or with those small circuit board drills, they are the same shape.

Triangular drills are a neat idea though, if anyone here has tried it I'd love to hear about it.

fixerup
11-27-2012, 12:19 PM
Thanks for the picture and details, I now have a copy in my tricks box.
Cheers!
Phil

rklopp
11-27-2012, 12:56 PM
I can understand why you need relief on the end cutting edges, but why bother with filing relief on the sides? The sides don't cut, much less rub, because you already have some back taper from the turning operation. (That happens automatically as a result of turning a relatively long unsupported length - the outermost end deflects away from the tool the most, and therefore ends up the fattest. This happens all the time in turning.)

mars-red
11-27-2012, 01:22 PM
I can understand why you need relief on the end cutting edges, but why bother with filing relief on the sides? The sides don't cut, much less rub

I like having a cutting relief just above the point taper, I believe it gives a little nicer finish just based on my own experimentation. Given that, it's a lot easier (for me, at least) to just file relief along the entire taper than try to get the relief just above the point taper where I want it. It's only a few extra strokes of the file in an operation that only takes a few minutes once you've done it a couple times. I'd wager that anyone omitting the relief along that taper would still be perfectly happy with the results, for sure.

On a related note, if you care to form the angle where the point taper meets the shallow taper going up to the shank, into a slight polished radius, you'll find the finish comes out super nice.


because you already have some back taper from the turning operation. (That happens automatically as a result of turning a relatively long unsupported length - the outermost end deflects away from the tool the most, and therefore ends up the fattest. This happens all the time in turning.)

For my purposes, I want more of a taper than the barely perceptible amount left from turning (for what it's worth, I measured less than 0.001" difference from the unsupported end up to where the chucking shank started, after turning the major diameter) as I find it makes quite a difference for clearing chips. In my experience these spade drills will clear chips pretty nice with about a degree of taper. If you don't mind withdrawing it to clear chips more often, then a nigh imperceptible taper would suffice. The chips produced by the bits I've made are always really long, thin, and stringy and just the clearance provided by the flats doesn't seem to be sufficient to keep the bit from wanting to bind up without more frequent withdrawal of the drill.

I'm not one for discouraging anyone from experimentation - that's how I've learned most everything... I would encourage anyone interested to experiment with making some of these on their own. You may be surprised how quickly you can knock them out, and how well they work.

For an alternative to these spade bits, there are also "D" bits. I haven't made any because they're basically the same as the set of jewelling reamers I already own. They're stronger than spade bits, and I think most of us would prefer to call them reamers than drill bits. You'd follow the same steps for turning the blank, then file away half of the tapered portion (so looking at it dead-on from the end, the cutting portion would be a D shape). I've come across some detailed info on making these online - I reckon a Google search would turn it up, for anyone interested.

jhe.1973
11-28-2012, 12:39 AM
Hi Max,

Just thought I'd pass on a tip for anyone who might not be aware if it. Not a drill but this will work just as well on drills.

If you need to keep scale from forming during your heat treating, you can use silver solder flux. You just have to be careful not to overheat it.

Here is how I use it to heat treat O1 steel that I cut a clock pinion from. I set it up in the drill press at slow speed w/stop set to just plunge the pinion into the oil when it is glowing bright red.

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=1901&d=1509502100

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=1902&d=1509502128

In this case, I had to heat the teeth hotter than I would have liked to get the heat past them & into the arbor. It just made the flux a bit harder to scrape off. Normally it will just fall off.

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=1903&d=1509502143

The right side of the arbor shows how clean it will stay after hardening.

sasquatch
11-28-2012, 08:24 AM
jhe.1973, wondering, what brand of drill press is that you show?

mars-red
11-28-2012, 08:43 AM
Thanks Jim, that is an awesome tip... and a great looking pinion!

jhe.1973
11-28-2012, 11:33 AM
jhe.1973, wondering, what brand of drill press is that you show?

The drill press is a 1950s 17 inch Delta w/tilting table. A really great machine that hasn't been made for years. You could get all sorts of attachments & accessories for them such as foot feed, slow speed attachment, mortising attachment etc.

Sigh, those were the days..................:)


Thanks Jim, that is an awesome tip... and a great looking pinion!

Seeing as how I am bringing back a few photos from the Photobucket fiasco, I decided to add a view of the finished pinion above the one w/broken tooth:

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=1904&d=1509502696

Toolguy
11-28-2012, 11:36 AM
Jim-

If you soak the part with brazing flux in water (especially hot water) for a while, you can clean off the flux with a wire brush and a rinse. No scraping or chipping needed.

jhe.1973
11-28-2012, 11:53 AM
Jim-

If you soak the part with brazing flux in water (especially hot water) for a while, you can clean off the flux with a wire brush and a rinse. No scraping or chipping needed.

Toolguy: Are you referring to the borax powder type of brazing flux?

Toolguy
11-28-2012, 12:03 PM
The kind I have is Brazo Flux made by Union Carbide. Mine is white and looks like the picture when you heat the brazing rod and dip it in the flux. I don't know for sure about borax powder. Maybe you could try it and let us know?

jhe.1973
11-28-2012, 12:34 PM
The kind I have is Brazo Flux made by Union Carbide. Mine is white and looks like the picture when you heat the brazing rod and dip it in the flux. I don't know for sure about borax powder. Maybe you could try it and let us know?

I'm pretty sure that Brazo Flux is, or primarily is Borax. The silver solder flux I use for this purpose is Sil-flux or Ultra Flux. My container of Ultra Flux says it is potassium salts of fluorine and boron.

My experience has been that once the silver solder - geez, I guess I'm getting old - they now call it silver brazing, flux is heated past clear & turns black, it seems to bond to the steel making scraping necessary.

The hot water helps even then, but if you can keep the flux from turning black it just falls away w/a rinse of water.

jhe.1973
10-31-2017, 10:21 PM
Hi Everyone,

Basically a bump 'cuz I brought back a few photos from the dead!

Mcgyver
11-01-2017, 07:57 AM
great thread and nice result Jim.

I thought the traditional watchmakers protection for heat treat was Borax? Silver solder flux does dissolve in hot water, but as you say this op might be getting it hotter and really sticking it on. If it needs scraping afterward, it sort of cuts into the benefit of coating a bit

3 Phase Lightbulb
11-01-2017, 10:33 AM
I make drill bits by doing some of this which brings in some $$$ and then I buy them. That's the only way I know how to make drill bits appear in front of me :)

http://www.bitrebels.com/wp-content/uploads/2011/04/How-To-Be-Computer-Hacker.jpg

bobm4360
11-01-2017, 02:45 PM
The watchmaker's heat protection is boric acid. Expensive at the drugstore, not so much as roach poison from the hardware store. Boric acid is applied the same as fluxing a rod (heat and dip), and is more soluble in alcohol than water.

JRouche
11-01-2017, 03:48 PM
The watchmaker's heat protection is boric acid. Expensive at the drugstore, not so much as roach poison from the hardware store. Boric acid is applied the same as fluxing a rod (heat and dip), and is more soluble in alcohol than water.

Make yer own.. JR

https://science.wonderhowto.com/how-to/make-boric-acid-from-borax-302525/

garyhlucas
11-01-2017, 09:09 PM
Was wondering why you didn't make a D bit for drilling metal? It is a single flute drill with one side ground away for the chips and makes a nice round hole because it cuts like a gun drill. I made one when I was about 10 or 12 and was surprised how well it worked.

mars-red
11-02-2017, 02:07 PM
Was wondering why you didn't make a D bit for drilling metal? It is a single flute drill with one side ground away for the chips and makes a nice round hole because it cuts like a gun drill. I made one when I was about 10 or 12 and was surprised how well it worked.

Wow, can't believe this old thread got revived! LOL

Yeah, D bits work pretty well, and make nice holes, but the spade type bits definitely cut a lot easier. I'll typically use D bits for reaming, and spade bits for drilling.

Can't remember if I mentioned it previously, but a variation of the spade bit, with a rounded chisel-shaped tip, works excellent for drilling steel that has been hardened. They also are the best spade bit for center cutting, from what I've found.

Since it's on-topic, I did a video a while back about making cutters in the shop, generally, and at the beginning I yakked about, and showed, some of the custom cutters/drills I've made over the years: https://www.youtube.com/watch?v=7uJ82KqqM54