Drilling a .004" hole.

[Laverda]

Some months back I asked about drilling holes in brass with a number 78 drill which is .016"

Your advice about using a sensitive type drill chuck helped.

I have now been asked if I can drill the same holes with a .0039" drill?

I have the drill bits but they are $17 each and I am scared that even breathing on one will break it!

So I am thinking this is not a job I can do and should leave it up to the experts.

The part is a air restrictor on a vacuum line.

 

[Fasturn]

I used to do work like this. If on a BP mill. I used the thumb screw stop and peck down in tenth turning the stop on each pass. Not easy on a BP. Was on a Hauser jig bore with micrometer stop. Control.... is the game on this. A pump chuck is useless ! Good NC mill is the way to go. Peck cycle has to be modified for that small of a drill. Good luck and not fun.

 

[michiganbuck]

What is the length of the .004 hole?

Was the .016 a success? did you peck it and what were your feeds between pecks.

 

[Thunderjet]

You are going to need to turn that drill bit around 10'000 at the slowest. 25'000 would be better.

If you can find an air powered, spindle mounted grinder head, you might get close to the RPM you need. Balance and runout becomes critical at those speeds.

You may just try to mount a pin vise in your BP with a spring type dead center and try drilling those by hand.

That's the way I would go, if it's still in brass, like you said.

 

[michiganbuck]

Here is a fellow drilling what looks like a .020 or so drill on a lathe.
Micro Drilling -- Stop Breaking Small Drills !! - YouTube

If one had the likes of an acme threaded bar alongside of a drill job and fingered the next thread as the peck length stop, running through a swing-away guide bushing just for starting location...just thinking.

A weighted slide chuck stem in the drill press, going to the next peck stop.

 

[moonlight machine]

You should have bought that little CNC mill I just sold for dirt cheap, we used to drill .004 holes all the time. 40,000RPM spindle makes it easy.

 

[Joe Gwinn]

Some months back I asked about drilling holes in brass with a number 78 drill which is .016"

I have now been asked if I can drill the same holes with a .0039" drill?

I have the drill bits but they are $17 each and I am scared that even breathing on one will break it!

The part is a air restrictor on a vacuum line.

There are small specialized drill presses for such things. As well as watchmakers lathes. How often will this kind of job come up, if you have such a drill press?

 

[Milland]

If it's not already, be sure to thin the area where you're drilling to about .005" - .008". If it's for a metering orifice, a .04" drill should be fine, with the point stopping just before breakthrough. Then finish the hole to size.

Make sure to countersink the far side to at least 1/16" edge break...

 

[Laverda]

I am helping out a friend and and have never needed to drill holes this small before. So it should be a one time job, I hope. I only need to drill six holes. I am only drilling through a few thou of brass. Most of the hole is 1/8".

I do have a air spindle for the Bridgeport that will spin up to 30,000 rpm. But with a Bridgeport you have no feel at all what a drill bit this small is doing.

I am thinking it may be better to put the air spindle in the lathe tail stock and drill it that way?

Or an even crazier idea, my grinder has a air bearing spindle and uses 5C collets. If I put the air spindle in the grinder air bearing spindle and make a tool to hold the brass, I will have a good feel what is happening.

I am starting to feel like I was an idiot for even saying "sure no problem, I can do it". He is paying for tools and materials. The labor I agreed to do for free!

Here is a sample of the part. This one has a .006" hole. And the air spindle I have to use. I don't have a small drill press, just a big 1950's Rockwell floor drill.

 

[jim rozen]

You need one of these:

Or a friend with one.

 

[52 Ford]

I'd get a micro drill press. Proxxon makes one, but the spindle only goes up to 8500RPM I think, it's $250.

Cameron makes some with 30000RPM spindles and they claim their drill presses are good for drilling down to 0.002".

Equipment

 

[boslab]

Drill through some plastic rod leaving just enough to drill the hole, the plastic helps stop the drill bowing under pressure an failing, crude but it works, I had a NC drill ( punch tape!) that used to be for drilling toothbrushes originally, I think I could run at 20k rpm ( bit slow) but it drilled 1/4” steel square bar at sub second a hole, looked brutal but drills lasted a couple of thousand holes amazingly, I was too scared to touch them at the start till I got used to how tough they really are.
Mark

 

[JST]

Things like this are made to do it. For $11,500

 

[Joe Gwinn]

You need one of these:

Or a friend with one.

Yes. What kind of lathe is that?

 

[jim rozen]

What kind of lathe is that?

That's a Boley lathe, with a story behind it. I was able to purchase all the parts from Manhattan Supply (this was before they became MSC!) Also purchased a set of WW collets and the WW-mount precision albrect chuck as well. So I had the headstock, tailstock, toolmakers compound, a motor, pulleys and belts.

They would NOT sell me the bed. So I went and was grousing to one of the model makers at work, and he said "what they heck, I can make that for you easy."

And he did. So the bed is custom length, custom size part. We seldom use that machine, but when you need it, it's invaluable. It would drill 0.004 holes all day long.

 

[Screwmachine]

While having a lot or rpm helps, it's not critical. Most important is the drill runs concentrically. The biggest issue (aside from concentricity) is feeding correctly. If you calculate the chipload needed you will be surprised how fast you need to feed at 10k rpm to avoid rubbing the lips dull. Chipload for a drill this size would be about half a tenth per lip, or 0.0015mm. Even at 3k it's one second for 0.006", which I guess is around the "few thousandths" the OP needs to drill.

 

[Joe Gwinn]

That's a Boley lathe, with a story behind it. I was able to purchase all the parts from Manhattan Supply (this was before they became MSC!) Also purchased a set of WW collets and the WW-mount precision albrect chuck as well. So I had the headstock, tailstock, toolmakers compound, a motor, pulleys and belts.

They would NOT sell me the bed. So I went and was grousing to one of the model makers at work, and he said "what the heck, I can make that for you easy."

And he did. So the bed is custom length, custom size part. We seldom use that machine, but when you need it, it's invaluable. It would drill 0.004 holes all day long.

So that's why I didn't recognize it. And that bed isn't exactly hard to make, so I don't know what MSC was thinking. Maybe a contract with Boley was the issue.

How fast can it spin the bit?

 

[jim rozen]

The drill is at zero rpm. The workpiece is in the chuck and that's probably upwards of 10K.

 

[Fasturn]

While having a lot or rpm helps, it's not critical. Most important is the drill runs concentrically. The biggest issue (aside from concentricity) is feeding correctly. If you calculate the chipload needed you will be surprised how fast you need to feed at 10k rpm to avoid rubbing the lips dull. Chipload for a drill this size would be about half a tenth per lip, or 0.0015mm. Even at 3k it's one second for 0.006", which I guess is around the "few thousandths" the OP needs to drill.

I agree , was drilling @ 3000 rpm with .007 Titex drills in copper. RPM helps, but not like you have to run 20,000 to do it.

 

[MCritchley]

Have you considered buying a flow control orifice with the hole already in it?
Mc Master Carr might have something this small.

And I’ll second drilling without the hand feed sensitive drill chuck mounted on a slide. To drill in a Bridgeport- Get a good drill bit from Guhring with a 3mm shank and buy a 3 mm collet to hold it. Lube the quill, I also don’t have that heavy of a setting on my retract spring.
Advance the drill a thou or two at a time with the thumb wheel depth stop. Come down on it quick and don’t dwell. Four thou dia. sounds tough I’ve gone down to .008”in tool steel and it didn’t break.
Go for it, and let us know how it goes