Drill 1/16th inch hole through 8mm stainless steel rod?

I've done this kind of drilling before and nearly always break a bit - when breaking through the bottom side.

What did I do wrong?

Pass it on, if you wish... :)

Richard fired this volley in news:xpGdnffHJ4NDFOPMnZ2dnUVZ snipped-for-privacy@earthlink.com:

When the bit first starts to break through, and when you're applying down-pressure by hand instead of with a power down-feed, the center of the bit penetrates the work first, while two "flute sized" hunks of metal still remain to be cut down by the height of the bevel on the bit.

When the bit slips down, the flutes grab on those two 'wings' and wrench the bit off (or spin the work, if you're one of those "hold it by hand" guys).

With a hand fed drill press, there are two ways to beat it: One is to clamp the work tightly to a waste sheet of similar material, and drill through both -- not so easy with round stock.

The other is to carefully set the depth-stop on the press so that the bit cannot penetrate further than the shoulders of the bit. That way, it'll stop JUST before it grabs.

In either case, you've got to securely clamp the work to the table so it cannot climb the bit as it penetrates (and for your own safety).

LLoyd

"Stormin Mormon" fired this volley in news:xExft.245235$ snipped-for-privacy@fed11.iad:

If he's drilling #304, that's an invitation to smoke the bit -- without breaking it. As soon as it starts to "skate" under light pressure, it'll work-harden the metal, dull the cutter, and end up making lots of smoke and noise; and go nowhere.

And it likely will ruin the hole so you can't get anything else through it except carbide.

LLoyd

My practice is to keep drilling while the chips flow out freely, but stop frequently to brush them off the bit if they don't, because they can jam and break the bit.

I don't extract the bit completely so that small chips won't fall in and land under the cutting edge.

If the chips come out in continuous strings I relax most of the feed pressure briefly when they reach a couple of inches long, to break them so they don't wind into a spinning, sharp-edged blob. I used to raise the bit but found that unnecessary unless the chips aren't feeding up the spiral. jsw

Richard fired this volley in news:eZ- dnVoOoJWqKePMnZ2dnUVZ snipped-for-privacy@earthlink.com:

If they fit well enough to prevent the smaller tube from 'climbing', and if you don't drill all the way through the 4th wall.

LLoyd

To avoid some already-mentioned problems -- such as work-hardening the stainless steel due to center-punching, or work-hardening it due to the bit skating around while trying to start the hole, or breaking bits while starting, or breaking bits on punch-thru -- you could make a work-holding / drill-guiding fixture.

Start with a chunk of metal (eg a steel cube 3/4" to 1" inch on a side). Drill an 8mm hole from one face to the opposite face. Drill a 1/16" hole to meet the 8mm hole on centerline. With a rod inserted through the hole and the fixture clamped in a vise, you can apply adequate down-pressure to avoid work hardening, without needing to release pressure when the drill bit is almost through. (If you are drilling multiple holes in the rod, it only solves the problem for the first, unless you have multiple 1/16" guide holes in the fixture.)

x2 the whole post. :)

Gunner, eatch-your heart out looking at these babies... ;)

Single speed 1000 and 1200 rpm hand drills that I use a light dimmer (or ceiling fan*) speed control to set the "power" and when it goes to dempling the bottom of the material, the speed reduces and you left off downward pressure before the bit grabs. :)

I drill through all sorts of stuff using that method and it works great. :)

And don't tell me you can't drill down through the middle of a pin or something like that. You can drive a vehicle at 80mph between 2 semi's on the freeway but can't steer a drill bit? ;)

The two rings were pulled off the M42 3/32" drill bit...

...check out how crooked the nickel-silver pins were too. :)

If this dumb retired ditch digger can do it so can you.

Alvin in AZ

*Basically the same thing except the fan speed control clicks from off to full-blast then decreases speed as you turn it further.

The light dimmer clicks over to basically~off then increases as you turn it up.

Never heard that before.

I'm old, I take 81mg Aspirin, I get cut or scratched, I bleed. xD

-----------------------

Was "hand" drilling vehicle leaf springs with a ~7/16" drill bit and making up to three foot coils of -spring- steel, it was cool! :)

I deeply countersunk the holes, hammered down a steel rod peening it out until the hole and countersinks were completely filled.

Made the leaf spring clamps from 3" square tubing... :)

Double nutted the 3/8" bolt and that's 3/8" fuel hose. Wow, that was >11 years ago and they still look like new. :)

Alvin in AZ

You havent done enough of it to learn "feel". Thats all.

Indeed!!

As a rule...stainless steel chips tend to be a bit "gummy" and tend to block the clearance of the bit. Given the small diameter of the flutes...it may or may not pack the flutes. So a quick up and back tends to get rid of them. Keep in mind..that you are going nearly 5 diameters (of the bit) deep... and there is some additional cooling of the bit, however quick...when you "peck" drill.

I work in commercial machine shops..keeping machines alive and running..and "pecking" is something that is almost always programmed into the CNC program when the holes are more than 2-3 diameters deep...particularly when working with "gummy" materials.

Do as you see fit..but its a strong suggestion. That bit is afterall..only 1/16 of an inch in diameter.

Another poster also mentioned short drill bits. Yes indeed! The shorter the better. Keep in mind..that any drill can be considered a very fragile "spring"..so keep em short..keeps them stiffer and less likely to snap.

What you really need are "screw machine" drill bits. They are half the length (more or less) of standard "jobber" drill bits and as a result..are stiffer and less likely to snap. Just remember...some screw machine bits are left handed..so if you get some..examine them closely and if using a hand drill..simply run em backwards.

Gunner

Well..there is always EDM

Gunner

One can always make up a fixture using drill bushings

If one were drilling enough holes to warrant the cost of the additional materials and the extra labor

For one (1) hole....it may..may be a bit much.

I don't disagree. Any oil is better than none.

Dan

The other thing I like about oil is that it lets me know when things are getting hot by smoking. The sound will sort of tell you too, but it takes a few times of getting it wrong.

There is that too. Shrug

If you listen/feel carefuly..you will notice a change in sound/vibration just before breakthrough...99.9% of the time.

Tune yourself for that "change" and at that point...back off a smidge

Ive hand drilled so many holes over the years with a drill motor..that its become automatic for me. Tune your brain for it..and you will very seldom ever break a bit. That and keeping the drill/motor in line.

It even works in wood.

Gunner

-I don't disagree. Any oil is better than none.

Dan

Pipe threading oil from the BORG is as good as most.

You didn't "lighten up" :-)

As the drill point breaks through the bottom of the work the area of the drill point that is opposed by metal decreases, thus the pressure (in PSI) increases unless you reduce pressure on the drill press handle...