How far are you drilling the pilot. Better to just spot the start. What style of drill? For brass you need slow spiral, they have a low helix and a wider flute so they grab less and get rid of the swarf easier. Drill no more than 3 diameters at a time before withdrawing. How many rpm? Cutting speed for drilling brass is 160 fpm, which equates to 11,000 odd rpm. A soluble oil cutting fluid is best. Oils tend to clog flutes on small diameters. Really, if you haven't got a sensitive high speed drilling machine, you chances overall are fraught with failure.
HSS is OK for brass. Carbide is very sensitive, no need for that. Well, what others said. Peck-drill. 1.2mm isn't really a challenge. But also a depth of about 3 times the diameter isn't really asking for peck-drilling. Highest RPM you can get. Stable drill-press (axial play?). Don't hold the piece with you hands, but in a vice. Pay **big** attention that the drill goes into the centre. Know how to do that? DP off, lower the drill into the centre and watch wether it bends left/right or back/forth (look from different angles). Adjust. Then drill, don't break. :-)
Next time, do that with a 0.3mm drill to sweat.
And please don't tell us that you try to do it with a Dremel and a carbide drill freehand!
On or around Sat, 02 Jun 2007 15:30:04 -0700, ora enlightened us thusly:
yikes.
I'm not an expert, but from my experience...
workpiece held rigidly
drilling machine of sufficent quality and condition
correct speed
correct lubricant.
I don't know what the last 2 are, but I venture to suggest that for a 1.2mm drill, the former will be "fast".
Also, by going more than about 4mm deep you're drilling a "deep hole". The drill will not clear the swarf, you'll have to peck-drill it. It's probably not practical to arrange to drill upwards... although I've always thought that typical drilling machines are built upside-down.
Why don't you stone the helix cutting rake of the drill to zero for just a few thou. This stops the drill grabbing which is causing the breakages. Regards Alan
--What he said; this will make a big difference. One last trick: if you can get 'em try cobalt drills. What I like about these: they start to squeak just before they fail, which gives you time to back out and save the part.
Hi Alan, something must be wrong if you cannot drill 1.2mm through a 3m
brass piece, it should be easy, maybe there is an answer, its the kin of brass that is at fault, try using engraving quality brass and se the difference,,Dav
On or around Sun, 3 Jun 2007 20:08:56 -0500, DCreed enlightened us thusly:
It's not through 3mm. look back at the picture supplied, the hole is much deeper than 3mm. I suspect the brass plate is 1/8" thick, but he's not drilling it that way.
Your correct, I'm drilling into the 1/8" edge of the brass and the hole would be about 12mm to go right through and make it easy to tap.
I can get 4-5mm deep easily enough but deeper and SNAP! that's following advice and clearing the hole very frequently with the work piece in a vice on the drill table.
I've been successful drilling 1.6mm using a high Cobalt drill and have
2 X 1.2mm Cobalt on order if they fail I have another approach I can take.
Pre-drill/tap a small 4mm section of brass (easier to do) then solder it into place, my only concern about that is that I may wind up with tapped hole flooded with solder. Is there a product I could use to prevent this happening?
'Snopake' and other similar typists' correcting fluids are ideal for use in controlling the flow of either soft or silver solder. Just paint it on where you don't want the solder to go, and them remove the residue with a stiff brush when the job's done. I would strongly advise against using grease anywhere near anything you're trying to solder! --
Chris Edwards (in deepest Dorset) "....there *must* be an easier way!"
12mm, now that is much more a challenge with a 1.2mm drill!
Are you sure that the table is dead perpendicular to the spindle? The drill is not strong enough to move the work around. He will have to bend and flex and then he will break. I guess the drill starts to squiiiik and then it breaks. The side of the drill is rubbing too much, expands and then he seizes. Use coolant fluid.
I have drilled similar parts for airguns. The brass is kind of miserable stuff to work with, but not as bad as the powder metallurgy parts that Crosman uses in some of their other models.
Put a flat on the cutting edges of the bit. A diamond file works very well for this. You want a flat a couple thousandths of an inch wide, with the face parrallel to the lenght of the drill.
The object of the flat is to make the cutting edge "scrape" rather than dig in.
Use magnification to see what you are doing with the drill tip. 1.2 mm is still pretty large.
If possible, drill this job in a lathe. This will allow the chips to clear, otherwise, you will have to peck drill and blow out the chips as you go. Often. Even better would be to arrange the part to be drilled from the bottom, up, to allow gravity to clear the chips, though that may not be very practical.
I would not worry so much about the speeds that may be calculated. Worry about setting the cut up so that the drill is able to take a continuous light cut, with the chips able to clear. A lower rpm and a smooth continuous cut are better than a high rpm and a broken drill.
No step drilling. One shot to final size. Trying to step up a small hole like this is just asking for misery. Esp. in brass.
Sorry for confusing the problem, i see the picture now, i still feel i
is down to the type of brass you are using. Drilling 12mm x 1.2mm di is a challenge for anyone but using the sticky type of brass is nightmare, i would rather drill mild steel. I have to ask that if yo are having problems just drilling the hole, how do you think you wil get on with tapping. I regulary use 10ba taps but will not try and ta this type of brass with these, @20 quid per tap, its not worth th chance, if you get stuck, i have some engraving quality off cuts yo can have, Dave Whitley Ba
Your right, looking at them it hardly seems posible to make bolts that small. I've got 2 more cobalt drills, I try to fatten the cutting edge on one of them adn see it I do any better :)
I'll post the results in a few days when I have time to try again.
Have you considered that each time a bit snaps in thew hole it may leave a bit of the point embedded in the hole
LIKE I SAID EARLIER ON YOU MUST HAVE A GOOD CHUCK TO HOLD THESE DRILLS WITH NO RUN-OUT
and it must be a chuck that is capable of holding tiny drills ...many only go down to 3mm.................others 1mm..........mine does from about 0.3mm - 13mm
i bought a couple recently from chronos ...on ebay ...
these are very very good drill chucks for Chinese ...i was mightily impressed advertised as
0-13mm...well ummm...more like 0.3mm -13 ...And the price is amazing for what you get .=A320
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Here's a few holes i had to drilled the other week these holes are 1mm diameter, done with the chronos chuck
and i had to do these with a busted quill spring as well through 10mm of stainless steel
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