Drilling 304 Stainless

I've drilled lots of 304 sheet using cobalt HSS drill bits (gotta be new and SHARP) in a drill press, or better a mill used to drill, lubricated with black sulfur oil.

The trick is to set the drill press or mill to turn slow and powerful, be very heavy handed while drilling, and be liberal with the black sulfur oil.

Some drill presses cannot turn slow enough for the larger drill bits, like Unibits to cut a 1/2" hole.

Joe Gwinn

Greetings Tim, In your situation I would use stub length cobalt split point drills. The split point is important. Use a high sulfur cutting oil. Your local hardware store probably sells some type of cutting oil made for threading. The dark stuff is usually a high sulfur cutting oil. You need to make sure there is constant pressure on the drill and that it is always cutting. If you start the drill gingerly there is a good chance that the 304 will work harden and then the pressure it takes to get the drill to cut goes way up. So start drilling like you mean it. Also, back up the sheet with another piece of metal. Aluminum is fine, mild steel too. Even hard maple might be OK. You don't want the sheet flexing away from the drill. This lowers the cutting pressure which leads to work hardening. Drilling into mild steel might be the best because it is close to 304 in hardness(but not nearly as tough!) and this will help prevent a burr being pushed out of the 304 and into the back up material. So you end up with cleaner holes and the dril is not as likely to break as it exits the 304. Ideally the drill should be spinning at about 2400 rpm. But this means you would need to feed the drill fast through the part to make sure it is cutting the whole time. Less than a second to go through 1/16 material. So maybe slower speed with constant pressure right from the start will be best for your situation with the drill press. Eric

Suggest maybe a carbide spade drill--although he''ll get a tubular exit burr, the sheet won't lift up due to flute helix causing slippage etc as it breaks through.

The holes need to be spaced 100 mils apart, and the hole in the grommet couldn't be less than 50 mil, and 1/16 is better. So it'd need to be a pretty teeny grommet.

Any suggestions where to find such?

Stainless POP rivets? Install rivet, pop, hit the back side with a grinder to smooth them off. If you want the back to look pretty use a cupped grinding point to dress them.

Or use the rivet heads and a press to form the back. Could even spin the back side down.

With a 1/16" shank, and a head (and hole size) smaller than 1/10"?

Try some split-point cobalt drill bits. They are literally only a few cents more when you buy them from MSC, KBC, etc. than the plain HSS bits. They are much more capable of handling harder materials.

Jon

Tim Wescott fired this volley in news:vt2dnVdzqLn5cd3NnZ2dnUVZ snipped-for-privacy@web-ster.com:

You can purchase all variety of gauges of stainless hypodermic tubing (McMaster-Carr), and spin-rivet it.

LLoyd

What's a spin rivet?

Tim Wescott fired this volley in news:DYydnRd2roxFrtzNnZ2dnUVZ snipped-for-privacy@web-ster.com:

It's a technique. Using a former with a conical nose and an annular groove around the nose, the nose is inserted in the bore, and the former is spun, forming the tubing into a flanged head.

LLoyd

This would increase the number of operations per hole, but anyway you might consider getting a small-diameter, say 1/8", spotting drill or countersink with a 120-degree point. Set you depth stop carefully and spot it, then switch to a 1/16" screw machine drill (shorter fluting and longer solid shank) to complete the hole.

Tom

I may have asked this before, but I'm slow:

I have some 304 sheet. I use it to make control-line model airplane handles. Each handle needs to have about 20 1/16" or .050" holes drilled in it, in a pair of tidy lines.

This stuff breaks my regular old HSS drill bits, and my drill hand- sharpening mojo is pretty spotty at 1/16".

I'm using them in a drill press. The whole process feels weird -- it feels like there's a skin on the metal which prevents the drill from starting to cut unless I feed it fairly hard, but once broken through doesn't cause much problem. Most of the time that I break a drill bit it's because I'm feeding it "just a bit harder", then SPING -- I've broken another bit.

Is there a better drill bit to use, or have I just doomed myself to trouble? Is there a better flavor of _stainless_ to use? I understand that 304 is difficult to work with, but it's what McMaster had in the thickness I wanted; having experienced its joys, however, I'm ready to consider something else.

I think my next step is to get a dozen 1/16" drill bits, but if there's some magic material that'll help here, I'm listening.

I've seen them used on R/C stuff before. Not sure where they get them though. I don't use them since I have a press and just make my own from tubing like Lloyd mentions. Actually real easy to do.

Make 6 in less time than it takes to make 1 in stainless, and throw them away when they wear. 6061T6 is pretty darn tough stuff too.

Can you get the use of a turret punch???

And, to prevent it walking, best is to get split-point drill bits. (I might get by preference cobalt steel split point bits in screw machine length, since you don't need the longer flute length of jobber's length bits.

An alternative to the split points (or perhaps just something to use in *addition* to the above) would be to put down a layer of masking tape, which makes it easier to keep a bit from walking when it starts.

Good luck, DoN.

Make them from 6061-T6 aluminum, then have them *hard anodized*. Much better at wear resistance than stainless.

Harold

The web of the point of typical twist drills doesn't cut.. instead, it rubs under pressure to displace the metal (all the way through the workpiece or to the bottom of a blind hole). That's exactly what needs to be avoided with work-hardening materials.

Split-point drills begin cutting as soon as contact is made, and continue cutting until the drill is stopped/withdrawn.

Aside from carbide drills, I believe the best approach would be to use quality split-point drills, as Phil recommended trying, with a good cutting lubricant.. while following the "uninterrupted feed" method which is critical when cutting work-hardening materials, IME.

If the holes need deburred after drilling, a small mounted stone in a Dremel/rotary tool will be quick, although a larger drill or countersink will also do the trick (even if just turned with fingers), just so the turning stops when the pressure is released.

Let's all give Wild Bill a round of applause, eih? ;>)} My filters left me 56 posts to look at and only TWO were on topic metalworking! Thanks Bill ! Good advice too..... I wonder how Tim worked it out? I've been playing around making a couple of eulers disks for the heck of it with various radius'. Got one at 14.5 " 16" and 20" radius so far. Made disks with various edges too to play with. Fun..... philk

"Wild_Bill" wrote in message news:Rfs1s.399007$ snipped-for-privacy@en-nntp-11.dc.easynews.com...

So, I haven't tried this yet (I'm getting close).

But -- there don't seem to be many 1/16" split-point drill bits in the world. Suggestions?