High speed drilling, sensitive drills?

[goldstar31]

Hi Guys,

Tracey Tools do a very nice 1/4" inch capacity Rohm drill chuck that will hold a 1 mm drill and is very accurate and quite inexpensive. Though I do use solid carbide PCB drills in it that have 3.2 mm (1/8" inch) shanks.

I bought a couple of so called Rohm chucks from them recently ad was told that -- they are not .
I've had to overhaul my Boxford ( Tenths of a thous) and simply awaiting getting my own readings from them.

I'm getting rattling fits and I know that it isn't the tailstock.
More anon as they say!


Norman

 

[BaronJ]

Hi Norman, Guys,

I've held mine a time or two in the lathe chuck soft jaws with a 3.2 mm carbide drill and not been able to see any run out with a 1/2 thou test indicator. Certainly no more than noise from rotating the chuck.

I did make a threaded mandrel but by the time you have cut the threads and screwed it on you have at least a couple of thou there. When I get the time I will turn the mandrel down with the chuck in the soft jaws. That should get rid of the run out, at least I hope it should.

 

[BaronJ]

I bought a couple of so called Rohm chucks from them recently ad was told that -- they are not .
I've had to overhaul my Boxford ( Tenths of a thous) and simply awaiting getting my own readings from them.

I'm getting rattling fits and I know that it isn't the tailstock.
More anon as they say!


Norman

Hi Norman,

I have found, particularly with smaller drills, that the more pressure you apply with the tail stock the bigger the drilled hole. Even though the cutting faces have been ground to be identical.

It can make the difference between a press fit and a loose fit !

 

[goldstar31]

Hi Norman,

I have found, particularly with smaller drills, that the more pressure you apply with the tail stock the bigger the drilled hole. Even though the cutting faces have been ground to be identical.

It can make the difference between a press fit and a loose fit !

Thank you for invaluable advice

Norman

 

[goldstar31]

Thank you for invaluable advice

Norman

It suggests that I drill amost on size with a cleanup to take the final whisker off and see

 

[BaronJ]

It suggests that I drill almost on size with a cleanup to take the final whisker off and see

Part of the issue is that the drill bends ever so slightly under pressure. It is worse if the drill is blunt and even worse if the drill is cutting off center.

This is why if you want a dead on size, for say a dowel pin, you drill under size and then you ream the hole. Even then with a reamer you can make that cut over size.

Now we wait and see how many turn up to tell me its rubbish !

 

[goldstar31]

Hi John

No argument from me! I'm going to do a test drill as I said and if it still proves oversize, I'm , I'll drill undersize and use a micrometer boring head for the last cut to size.

So my thanks

N

 

[IanN]

Next problem - maybe with the obvious solution that I have missed?
I am OK drilling 0.25mm and 0.30mm holes as the drills have 3.2mm shanks - great for collets or the ROHM chuck (down to 0.5mm maybe?).
But today I want to make some 0.35, 0.40 and 0.45 jets - so I have an age-old problem of to to accurately hold these? The pin-chucks I own only go down to - you guessed? - 0.5mm. And anyway, they have knurled outside and are NOT precision for aligning in the lathe when I hold them in a precision tail-stock chuck. I'm calling it precision, as it hold the 0.3mm drills just fine - on centre every time. Know any good watch maker's web sites for tools? - Maybe with proper pin-chucks true to 0.3mm?
I'm going into the freezing cold garage to start with a 0.30mm drill and opening it out by holding the larger 0.35mm drill somehow... But a good tool should do the trick - it's just I don't trust all the cheap stuff called "precision" that isn't!
K2

Hi

Get a good pinvice - it will grip close to zero diameter

Then drill by hand in the lathe as I described in my previous post - no need for precision drilling machines, no need for high speeds.

Watchmakers have been using this method for over three hundred years

Ian

 

[GrahamJTaylor49]

Seeing the conversations concerning very small drills and the difficulty in using them, one of my clients manufactures
air bearing spindles. These are used for drilling holes as small as 0.005" and run at speeds as fast as 80-100,000 rpm.
I have no idea of the cost but might be worth having a look at.

 

[goldstar31]

Seeing the conversations concerning very small drills and the difficulty in using them, one of my clients manufactures
air bearing spindles. These are used for drilling holes as small as 0.005" and run at speeds as fast as 80-100,000 rpm.
I have no idea of the cost but might be worth having a look at.

Sounds very similar to dentistry- and as my late wife and my daughter folloeed this employment, I'll 'keep my mouth shut'

Mumble, mumble

Norman

 

[L98fiero]

Deleted

 

[Richard Hed]

There is always the possibility of getting a laser drill, don't know about the efficacy of this, but it WOULD be very straight. Also, EDM might be a possibility but I understand that takes quite a while to do.