Drilling tiny holes.

I am faced with drilling some 1mm dia open-ended holes in mild steel and have never drilled such a small diameter before. My drill speed calc chart tells me that I need a rotational speed of 8000 rpm, but my drilling machine max speed is only a little over 4000. How critical is this drilling speed? Any hints or tips on drilling small holes would be valued.

Sharp drill, little bit of cutting oil or lard, maximum speed. Take a cut with light pressure, and back if off every 2 or 3 mm to clear away the swarf. Make sure you have a good quality drill bit and I find the TI coated bits(Gold colour) superior to ordinary HSS bits
BobH

Speed isn't critical, but you'll have to reduce feedrate accordingly. There are three main issues. One, how to hold a small drill. I use an Eclipse pin chuck in the main drill chuck. Second is how to start the drill. At these small sizes a centre drill, or even a spot drill, may leave too large a spot, without a clean centre. I usually just let the drill gently touch the work and it'll find it's own centre, especially if it's 4 facet. Third, the main killer is chips getting jammed, so peck very frequently and use a thin liquid to provide some lubrication and to wash the chips away. I use WD40, mainly because it's handy in a spray bottle. The smallest holes I've drilled were 0.7mm and 10mm deep, albeit in brass. But the drilling was done on a Bridgeport, which doesn't make it easy.

Andrew

If a very small drill does not cut easily then sharpen or replace it or it will break. Colin

As Tubal Cain observed, if small drills aren't razor sharp and fed quite firmly, they tend to 'spin' at high speeds and blunt rapidly, so as Andrew observes, lower speed and take it gently should work fine.

Neil

Drill Services have supplied me with c/drills in sizes 0,1/0, 2/0 3/0, 4/0 ,the. 4/0 has a tip size of 10 thou, that's small enough to centre a drill to tap 16 BA! If your chuck has problems gripping 1mm , a 3/32 std shank drill may be an alternative, I have obtained these from Expo Tools in sizes down to o.5 MM. They are claimed to be to aDIN spec

My experience suggests that a hole and half with a fair wind💨💨💨💨

For centre drilling for small holes liek that, I often use my regular centre drill but just use the very tip of the small extension - just enough to make a tiny dot on the job. It seems to be enough to get the main drill started on centre and does away with the risk of snapping the extension off the nose of those tiny sized centre drills -- all too easy to do if your chuck has the usual few thou of runout and the drill press spindle the usuall few thou of slop.

Albrecht sensitive drill feed with the matching chuck would do the job superbly, as that is what they are designed for. Just Google Albrecht sensitive drill feed. Also use good drill bits, and as Andrew mentioned 4 facet ones would be best .

I think also that there are plans about for a similar set up to the Albrecht.

To hold small drills (below 1/16" / 1.5 mm), I have a zero to 1/4" size Jacobs chuck with a short shaft on it(I can't get it off), that I fit in the Jacobs type chuck in the Rexon vertical mill. This set up runs true, I can't measure the run out. The mill doesn't like running much above 1200rpm, but it drills ok if I take a peck every .5 mm to 1 mm. I have not tried any thing below .4 mm.

Ian S C

,See here from Arc a sensitive drilling attachment, I have a spring loaded one made close to 50 years ago used on a jig borer drilling (a lot) 0.015" holes PM me if you want a photo etc

**LINK**

PS I think the max speed was 2500 rpm so don't worry about theoretical speed too much

Edited By JohnF on 05/03/2017 09:39:33

I do this often when making violin/cello bows and agree with the above. The tip of a centre drill and sharp drill bit in Eclipse pin chuck, withdrawing frequently. I do this in a Fobco at medium speed - I have electronic speed control. I keep a supply of new TiN bits in the smaller sizes and when they're no longer sharp I don't mess about - I throw them away

Thank you all for those useful pointers. All I need now is the nerve to tackle the job.

I used to drill thousands of .25 mm dia holes in mould tools to vent air, and used an air drill mounted in a stationary drill chuck, although they were in aluminium blocks. I would try a few test pieces before going live on a job, just to get the feel on how you need to back off and when to lubricate etc.

David

When spotting for tiny holes I use a very pointed D bit I made quite a few years ago, relieved on the back of the taper.

Drill Speeds already covered by others

If it is 1mm would recommend PCB drills. (For drilling circuit boards).

They're solid carbide, they're sharp and they're very cheap. They don't wear so they don't get blunt and break, but if you do break one at about 40p ea you don't really mind.

They normally have a large shank typically 1/8".

Just run them as fast as you can and it will be fine.

Now for very tiny holes

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