Drilling stainless steel

[Bangkok Mick]

I have just finished making a pen out of 316 S/S reinforcing bar. I used HSS drill bits 2mm followed by a 3mm to drill the 6mm bar for a ballpoint refill on my 7x14 Chinese mini lathe. I plan to make a few more to give as presents, can anyone suggest a better drill bit to hollow core the bar, approx. 50mm from each side, to make the work go easer.

Cheers Mick

[Dawai]

Zen of drilling deep holes: forget where that book came from, mostly it was about sharpening a drill bit equally and applying the right forward cutting speed to the type metal, quality of bit, too much pressure and it went offcenter, drill bit not perfect and it went off center.
 I found a eye loupe with angles engraved in it to look at drill points, bought a carbine sharpener from HF, built a tool quorn according to NORM (he's here) and proceeded to mess up a few drill bits learning.  Then i graduated to a computer and camera microscrope, with a drill angle and center etched over the image coming in from the camera.. One side needs to be about half a shaving further back than the other side.
   Lemme look for that very special post on sharpening drills. Not sure where the book is, or went to. I am sure I loaned it to someone.

I HATE drilling stainless.. it is not really that tough, but curls up around the cutting edge like aluminum does, once it spins and the chips turn blue, you are done for. NO drill bit works.

Drilling electrical stainless panels.. now you are going to mock, laugh giggle till you try this.. I have taught 60 year old ironworkers, plumbers and steam fitters this trick. It was taught to me by a guy with not enough education or Iq to find his way to work some days..

center punch your hole, Stick a sharp drill bit on the punch, do not turn the drill on, just PUSH really hard and bump the trigger to like spin it a half turn.. again, again, again.. you got a curl, again.. you got a hole.. never really drills it, more like a rotary punch.. it never heats up and curls around the cutting edge.

Deep holes?? well I got this edm here I made for $10.. but it would take a month, too low of power..   

How about using SS instrument tube and rolling it onto a mandrel to shape it?? 5/16th (forget the mmee mee) is about perfect, what I used to make tattoo tubes with.. I silver soldered a animal hypodermic syringe needle into the end to hold my tattoo needle in the perfect spot..

[Bangkok Mick]

Hi Dawai,

Thanks for your comprehensive reply. I have not had problems losing the center but it takes an age and have blunted a HSS bit and broken another in my efforts on the one pen so far. I guess I need to brush up on sharpening bits. I think computer and cameras are a bit beyond me at the moment.

I am using bored out solid S/S rebar as I am a civil engineer and this is what we use at work so thinking of making up a few theme pens for work mates or otherwise use tubes as you recommend.

Cheers Mick

[David Jupp]

Cobalt HSS drills, ground with 135 degree point are sold as superior for use on stainless.  Could be worth a try.

[75Plus]

Hi Mick,

I drill a lot of 316 stainless so I understand what you are up against. I find that Cobalt drills will last up to 10 times as long as HSS. The point angle also should be considered. While 140 degrees is optimum for stainless that point is not common. The 135 degree points are widely available and make a pretty good substitute.  The link below gives a lot of good information on drills and drilling.

http://www.mmsonline.com/articles/choose-the-best-drill-point-geometry

Joe

David was posting while I was typing. 

[Lew_Merrick_PE]

Hi Mick,

The nickel in stainless steel makes it gummy.  Cobalt drill materials are a good starting point.  Short cutting edges (135° to 150° included angles) give you a (short) leg up.  You actually want a scraping edge rather than a chisel edge to help break up the swarf.  The edges should be well stoned and look crisp & clean even under a 20X loupe.  I find that Tapmatic Gold works the best as a cutting fluid.

I most normally drill much larger holes in 316/304 materials.  Insert spade carbide does the trick in those conditions -- but even then I stone all the edges dead smooth and apply Tapmatic Gold in liberal quantities.  My other trick is to mount the piece being drilled in a water jacket and pump ice water through it to draw the heat away.  I know of people who swear by using dry ice chilled alcohol instead of ice water, but I have not tried that myself.  I know that liquid nitrogen freezing of S/S parts is done in places such as Sandia Labs.

Hopefully this helps you out...

[Dawai]

Friend, if you have younger eyes.. you can get away with a loupe. (hand held magnifier). print out them pictures in the post offered above, look at the end of the drill.  I don't have a microscope - camera hooked up at the moment either.

I used to lightly turn it on my thumb, if you can feel it digging in, it will cut.
Stoning the edge to make it perfect and remove the false ragged edge is great too.

It is amazing looking at things in a loupe in bright light.. I could see.. (SEE) lil balls of flesh in curled tips on the old tattoo needles.. New needles were blunt, old used needles sharper, but the tips rolled over into fish hooks.. when I had younger eyes.

I'd get so angry to resharpen a drill and it be throwing a great curl from the hole, only to find out one side took it off on a tangent off center..  You have to look at them real good to see the differences.

[krv3000]

hi well ther is drill bits out ther made for stanles steel mine are made by dormer

[Bangkok Mick]

Thanks for all the feed back guys, armed with this information I may be producing nice S/S pens yet.

Cheers Mick

[evildrome]

I spent some years drilling & boring 316 stainless. I once bought a Titex 7mm solid carbide drill with thru coolant.
A thing of true beauty. It lasted about 2 seconds. The front edges disintegrated immediately.

What worked best for me in the end was Dormer HSCO drills and lots of neat cutting oil.

Cheers,

 Wilson.

[mhh]

Drilling stainless is not always easy!

Cheap carbide tools have a tendency to workharden the material, some years ago before carbide became as fine grained as it is today the best way to drill stainless was hss.
When drilling stainless you want to avoid the drill rubbing.

My suggestion is OSG HSS drillbit. They have a series of drills called RDS and they are just amazing, the way they grind the tip really does wonders with stainless.

Like everyone else said it should be cobalt HSS

[TLGriff]

Are these through holes or blind holes you are drilling? If they are through, you may want to consider using tubing instead of round stock.

Tom

[Francalves]

Hello
  When I need to use a drill boring stainless drilling stone (those used for drilling wall) as a sharp HSS is cheap and results but do not have much precision, bat bore any very hard steel

[Gayate]

I sorry for bump...just my two cents for this old thread..
The key to drilling stainless is to use a drill bit which digs below the surface of the material so that it always cuts new ss, instead of slowly eating away at the surface, causing heat, which will work harden the stainless. It makes sense, but I don't think I have drilled stainless with these, yet. A HSS drill or bits https://mechanicguides.com/best-cobalt-drill-bit-sets/ with a less than perfect design, for stainless, may give poor results on stainless, where a HSS drill with a better design could cut just fine. If you are just buying a couple drill bits, go with the cobalt HSS if you think they will be better.

Carbide is a no go for hand drilling. It is too brittle, and I have learned that the hard way. Another reason I was willing to try noresman  HSS, is that they claim their bits are a bit, no pun intended, tougher than common HSS but also flexible enough to hold up to hand drilling under less than ideal conditions. I prefer to drill items on the mill/drill and use an air mister to keep the cutters cool, but there are plenty of times I have to drill by hand with my V28 cordless. On thin stainless, the right bit shouldn't heat up much. I thought about using some of the mist coolant in a spray bottle, since it is much cleaner than using oil, and it keeps the bit much cooler.

Welding those joints wouldn't be much fun, even if you did have the equipment and some experience. That is some thin tube and even though I have tig and mig welded for years (very little stainless), I would expect to have a learning curve. Also, Twist drills in sheet metal tend to make out of round holes. If you must use a twist drill, use Norseman/CTD drills. Their high molybdenum content makes them well suited for SS. Otherwise a good cobalt drill. Lots of feed pressure, low SFM. Use machinery's handbook for the formula for RPM to get the right SFM for your size.

However, if you need a nice round hole, Hougen makes a set of mini rotobroaches. They work excellent, just center punch and drill.

Best lube I've found is Union Butterfield, followed by Tap Magic. Avoid the dark sulphur oil on SS.