# very small drills



## itowbig (Dec 28, 2009)

my ? is how do u guys "n" gals sharpen those itybity drills ive broken three so far and i really need to get them sharp again or i have to go buy some more. and its really hard for me to drill itybity holes how do u drill them with out breaking those itybity bits.
im having the darndest time with those. small things are not my thing but i do want to learn how to make small stuff too.
pics if u got them would be great. thank u


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## winklmj (Dec 28, 2009)

D-bits maybe? 

http://www.homemetalshopclub.org/news/09/newsletter0912.pdf



> "Ed Gladkowski showed his jig holder (left photo) for sharpening very small homemade drill bits. The design for a straight, V-pointed, non-spiral bit was introduced by D. G. Gordon. A detailed description of Gordons technique for producing them can be found in Live Steam Magazine for August 1998, Vol. 21. Ed indicated that they are easily sharpened using his holder-jig along with a wet stone. It is nearly impossible to re-sharpen small diameter spiral bits (#60 and smaller) in the home shop."



I have not tried finding the Live Steam article referenced above.


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## jack.39 (Dec 28, 2009)

How tiny is itty-bitty? My Dad taught me how to hand sharpen drill bits when I was a kid, and the smallest sort of fell in stepp, after becoming good at 1/4".

By "hand sharpen", I mean holding the bit and using a grinding wheel, no jig or fixture involved.

jack


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## 90LX_Notch (Dec 28, 2009)

Sid,

Here's what I have found: 

To drill very small holes everything has to be perfect. The part can't move and the drill has to be lined up perfectly over the punch mark. The drill can not be allowed to flex. Also, the drill has to be running true in the chuck and the chuck needs to run true. Peck drill and use plenty of oil to clear the chips. "Choke up" on the handle to reduce the amount of force being applied when drilling. 

Bob


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## ksouers (Dec 28, 2009)

90LX_Notch  said:
			
		

> Sid,
> 
> Here's what I have found:
> 
> ...



... And they have to spin very fast! Depending on how small, say about 1/16 inch or less, greater than 2,500 RPM for brass or aluminum. Haven't tried anything small in steel. Not looking forward to it, either.


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## hammers-n-nails (Dec 28, 2009)

drilling little holes is never fun, and its imposible to sharpen a bit by hand and get it to cut a smooth true hole thats the same size as the bit, alright for most things but nothing real precise.


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## joe d (Dec 28, 2009)

ksouers  said:
			
		

> ... And they have to spin very fast! Depending on how small, say about 1/16 inch or less, greater than 2,500 RPM for brass or aluminum. Haven't tried anything small in steel. Not looking forward to it, either.



I recently had occasion to do some holes in steel with a #59 drill (.041")... ran it at 2,100 RPM and it went OK. I hadn't been looking forward to it either, so I was pleasantly surprised with how well it went. Did this in the milling machine, as my drill press has more run-out than that size of drill has diameter :big:

My solution to sharpening drills to date is to buy another one... really got to learn how to do this before the box of "good enough for wood-working" gets too full ;D

Cheers, Joe


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## Penguingeoff (Dec 29, 2009)

To work out RPM for drilling/milling/lathe work.
Formula RPM = 300V/D where V = cutting speed of MATERIAL being machined. D= Diameter of drill/Cutter or work in the Lathe in MM.
V for Mild Steel = 30, Cast Iron = 15, Aluminium/Brass = 40.
 Example 10 mm drill in Mild Steel - 300 * 30 / 10 = 900 RPM
       10 mm drill in Cast Iron - 300 * 15 / 10 = 450 RPM
        1 mm drill in Mild steel - 300 * 30 / 1 = 9000 RPM
        1 mm drill in Aluminium - 300 * 40 / 1 = 12000 RPM 
        0.5mm drill in Brass  - 300 *40 / 0.5 = 24000RPM
  50 mm (2 inch) dia in Mild Steel - 300 * 30 / 50 = 180 RPM

For use with CARBIDE TOOLING, multiply V by 3-4 

The Value for V in this calculation is in M/Min. Dont worry about converting 10 mm to inches, call it 3/8ths. Machine tools do not give exact revs anyway. 
What can be seen from all this, is that a small drill needs buckets of rpm. Most drill presses only go to about 3000 revs, so be carefull out there. Light touch is needed as others have said. I have been teaching this in Fitting and Machining in NSW TAFE for the last 25 years, plus been in the trade since '65.
 As for sharpening TINY drills, I use a magnifier and an OILSTONE where I can, Mind you I usually just get a new bugger (I buy 0.5 mm drills and smaller 10 at a time and for small drilling use a Dremel in a work stand).
Dont worry about this too much, take it easy with little tools/jobs. Try boring a 1mm hole in a cylinder and you will see what I mean (1/2 size Tiny). Hope this helps, Geoff from Tassie


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## Artie (Dec 29, 2009)

This is just my opinion... so take it with a grain.. ;D  we know that drill bits have to be accurately sharpened to drill to size. If the centre is off slightly they will drill 'bigger' than their specs. Small drill bits are worse than their larger brothers.... at least in this respect. Also when drilling small (say 1mm or less for eg) holes accuracy is likely more important than a 6mm hole.

THEREFORE.... IMO..... dont even try to sharpen them, they cost stuff all so go and buy a pack of ten of the size you use the most.... probably cost less than that single 10mm drill bit on the same rack....

I know these are chinese imports but I just bought 50 bits from 1mm to 6mm in 0.1mm increments for $36 Aus, quite ok for aluminium and brass with a bit of care...

As I said...just my opinion... I sharpen down to about 3mm (1/8th?) then buy bulk from there... ;D

Artie (back from holidays damn it..)


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## tel (Dec 29, 2009)

Wot 'e said! Life's too short to be foolin' around with them little buggers, and it's pretty much a waste going for top of the line stuff - they are gonna break anyway, eventually.


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## 90LX_Notch (Dec 29, 2009)

I use to believe about spinning the little buggers at super high speeds but found it can be done at far less. I've drilled .016 through steel @ 2500 in the mini mill. One manufacture of micro drills says not to exceed 3000 rpm because all it does is wear the bit out. I just don't remember where I read that or I would post a link.


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## shred (Dec 29, 2009)

My Jenny Wren required a bit of tiny drilling. #80-type sizes. In the past I've used a 10K RPM spindle on the Taig to do it, but I thought I'd try with a 2500 RPM mill to see if it could be done. It can, but the keys are a good small chuck with no runout (or small ER collets), cutting fluid and 'pecking' at it with almost no pressure-- drill a tiny bit, back off, clear chips, drill a little more, repeat.


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## GWRdriver (Dec 29, 2009)

A few years ago, in Model Engineer magazine, a Derek A. G. Brown wrote up his design for a tool for 4-facet sharpening of very small drill bits. This kind of became the standard for small bit sharpening jigs. I don't have a Vol or issue number or a copy of the article, but it might be worth a look. A Google search for D A G Brown will bring up a number of hits.


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## itowbig (Dec 29, 2009)

ill give it a look GWR   i was afraid that it would be a pain to sharpen those the bits where a 57 53 and cant remember the other one but i think im going to buy in bulk and try it again. i drilled steel ok but it hung up in ally and snap. i was peck drilling very lightly but they still snapped.  maybe next time ill scale up to something i can see better :big:
thank u guys for the info ill take it and move on :bow: :bow: :bow: :bow: :bow: :bow:


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## Longboy (Dec 29, 2009)

......I just had an occasion of drilling # 60 thru holes in valve stems that started out 1/4 dia. CRS in the mini mill. Right down on the work with a jewelers loupe and hand on the hub drawing down the spindle at low speed and drops of cutting fluid. Lightening up the touch when I seen the bit flex, that little curly cue came spiralling up the shank ;D............so now I guess I'm ready for the needle seat in the mixer with a # 72!


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## putputman (Dec 29, 2009)

There is a small sensitive drill chuck that uses finger pressure for drilling tiny holes. It can be used in the lathe, mill, or drill press. 

I just finished drilling the orifices in a brass fuel mixer for a small engine I am building. The hole in the fuel intake is a .025 dia. .360 deep, then .018 dia for another .100 deep. This was done in the lathe at 1200 rpm. I then reversed the part in the lathe and drilled in from the other with a .040 drill to meet the .018 hole.

Next I set the part up in the mill and drilled a .020 dia cross hole at the point where the .025 and the .018 met. This was drilled at 1750 rpm.

I have drilled holes as small as .009 dia with this chuck.


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## doc1955 (Dec 30, 2009)

I agree finger chucks are the way to go for small holes. I've used one at work with great success unfortunately at home I haven't purchased one as of yet. Is it to late to put that on my Christmas list for this year I wonder. 
I also agree that for the price small drills you are better off just buying bulk unless you are set up to sharpen these they are a pain.


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## BobWarfield (Jan 16, 2010)

You almost can run those little drills too fast to burn them up, even HSS.

They want a surface speed of up to 200 SFM, which is far from burn up territory.

A #80 (0.0135") bit needs to be spun at 56,000 rpm to hit 200 SFM if you run the numbers through G-Wizard. Applications that drill a lot of tiny holes all use very high speeds to do it. Dumore and others made small "sensitive" drill presses that ran at 20-30K rpm for the purpose.

You can absolutely drill holes with a lot less speed than that, just trying to point out what the feeds and speeds look like. 

When you burn a tool, it's too much SFM. When you break a tool, it's too much chipload. That same #80 bit wants a chipload of 0.0005". You can feed a right smart 56 IPM to get that chipload at 56K rpm. However, let's return to reality here (unless you have an aux. Dremel or Proxxon spindle on your mill, which would be handy for this!), and try it at 2000 rpm. Now your maximum feedrate is 2 inches per minute. Let's take half that feed in our home shops to get a little more life. 1 inch per minute. That's 1mm per 2 seconds roughly. 

Feed these bits REAAAAAALLLLLLLLLLLL  SLLLLOOOOOOOOOOOOOOOOOWWWWWWWWWWW! And a sensitive finger touch chuck, pecking, blowing away the chips, a little lubricant, and a prayer or two wouldn't hurt either.

Cheers,

BW


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## putputman (Jan 16, 2010)

> Feed these bits REAAAAAALLLLLLLLLLLL  SLLLLOOOOOOOOOOOOOOOOOWWWWWWWWWWW! And a sensitive finger touch chuck, pecking, blowing away the chips, a little lubricant, and a prayer or two wouldn't hurt either.


Works for me.  ;D

I agree that faster spindle speeds are better, but like you say, you have to work with what you have.

I did notice that one of the flyer adds I recently got had finger chucks on sale.


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## itowbig (Jan 16, 2010)

wow a lot of info here . im studying everything ive got some more tiny bits and broken a few more.
ill have to research this finger chuck. thank u all for the great imput on this. im learning a great deal and thanks to folks like u its getting easy to not make as many boo boos ha ha


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## Blogwitch (Jan 16, 2010)

I am just going thru the learning process again with small drills (less than 0.010"). I have been involved with micro drills with my job many years ago, and industry provided the solutions then with super fast air bearing spindles and drives (over 100K RPM).

I was trying to recapture that somewhat with my small drill in my post here

http://www.homemodelenginemachinist.com/index.php?topic=7805.0

The reason I was going for speed rather than feel, because the smaller you go, the less feel you have, all because of the flexibility of the drill itself. With what I call a large drill, 1/32", you can actually 'feel' the strength and flex in the drill if you are using your fingertips and one of those finger chucks. If you try that with say a 0.010" drill or smaller, by the time you 'feel' it, it is already broken under the strain.
They reckon that if you spin a disk of normal writing paper fast enough, you can actually use it to abrade it's way thru steel, just like a grinding disk.
The same theory extends to drill bits, the faster you can spin them, due to the centifugal forces involved, the drill actually goes and stays more rigid, and thus the bending forces that leads to breakage is kept under control, even under heavy feed pressures.

I did some calculations a while back for the sizes of drills that I want to use, and the speeds involved are up in the 90K rpm range.

There is no way that I can reproduce those figures in my shop for more than a few seconds at a time, purely because of the cost of bearings to do continuous running at those high speeds becomes very prohibitive, and also the standard holding chucks might start to want to explode at constant hi revs. 50k was about my limit, but even at that low speed, I suspect that my drill bit attrition rate would fall dramatically.

With my newly donated commercial hi speed drill, I am now looking at making the cones for that to run at a constant 20K and put a super fine feed using a worm drive on the quill. A sort of compromise between reduced hi speed rigidity and keeping the feed rate down to prevent drill breakage. 

My problem now isn't the drilling unit any more, but the high cost of the micro drill bits. I now have a person scanning drill factories in China to see if I can get the costs down to a reasonable level. I bought all my micro HSS bits a few years ago, at 10 pence each, they are now well over 20 times that price.


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