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Drilling stainless a bunch of times.
2

Drilling stainless a bunch of times.

Drilling stainless a bunch of times.

(OP)
I have to modify an industrial humidifier, really just a electro-mechanical atomizer.

It's made of some-sort of stainless steel. I have to drill twenty 6mm holes and twenty 13mm holes.

This is 0.042in sheetmetal. I was thinking of getting a piece lasered out with all those holes then realized I'd then have to cut a long narrow slot out of the same sheetmetal, probably an even worse task!

Does anyone have a favorite SS drilling recipe they can share? Technique? Drill bits? Psychiatrist?

If this mod works I'll have to do it all a second time...

Keith Cress
kcress - http://www.flaminsystems.com

RE: Drilling stainless a bunch of times.

CNC turret press?


Politicians like to panic, they need activity. It is their substitute for achievement.

RE: Drilling stainless a bunch of times.

The challenge isn't the stainless steel, it's the thickness. Thin metals break drill bits. Use bits designed for thin materials. I use stepped drill bits with good success on SS electrical enclosures. I've never seen one in metric, though.

Also, stainless requires a lot of feed pressure to drill so you may need to support the thinner materials.

RE: Drilling stainless a bunch of times.

The major cutting by a step drill is from the tapered portion, so a similar effect, since this is so thin, can be had with a pilot hole and a countersink or a tapered reamer. The holes will need to be deburred anyway, so any sharp edge on the other side will be taken care of then.

I'd probably make the pilot hole with a punch. Basically pound a nail through backed by a block of hardwood. File the nail so it's a conical point rather than being cut. Alternatively sacrifice some smaller self-drilling/self tapping screws to do the drilling.

If going with a countersink, backing with hardwood to support the metal is a good idea.

Normally this would have been better done when the metal was flat and in a CNC punch and, of one has access to a punch and die set and an arbor press or a hydraulic press then do that.

RE: Drilling stainless a bunch of times.

(OP)
Pud; This is already totally fabbed so I can't reasonably get it into a press.

Tug; That's exactly what my local machinist guy said - "Christmas Tree Drill". Except, these holes have to be fairly close to 6 and 13mm so I can't imagine getting close with any christmas tree bits I've ever seen.

3DD; Backing! Oh yeah definitely a good idea since it's in the middle of that big span. I probably have access to a bunch of arbor presses but I'll still be in trouble over those metric hole sizes. Wish I knew a water-jetter around here.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Drilling stainless a bunch of times.

Bay Ship and Yacht in Alameda has a water jet.

RE: Drilling stainless a bunch of times.

(OP)
Tug; Indeed! If I can find them. A search turns up both in MSC but the 13mm one looks crazy different so I'm wondering if they screwed up the picture.

6mm

13mm

They both state SS too. Price is even reasonable.

Haven't figured out what centers these things yet.

+++++++++++++++++++++++++++++++++++++++++=

I also actually DID find christmas tree bits at McMaster-Carr in metric though I have to buy two to get 6mm and 13mm. The one with 13mm is also about the most expensive one they stock >$100++. TiN coated no less.

==========================================

3DDave; Nice. I'll go see if we have press-age that will run those. I have a 10 ton press out side.. Wonder what it would take to keep the dies aligned. Those aren't cheap are they!

Keith Cress
kcress - http://www.flaminsystems.com

RE: Drilling stainless a bunch of times.

In the Hougen link, the arbors are at the bottom. It looks like a spring loaded pin holds it on a center punch indentation.

RE: Drilling stainless a bunch of times.

Water jet cutting can be a good choice.

RE: Drilling stainless a bunch of times.

Part Geometry, thickness,, hardness , Machine Type ,EG CNC Mill ect

RE: Drilling stainless a bunch of times.

Using CNC drilling can do it with high accuracy.
If by electrical discharge machining, the RA of the inner side of the hold will not be as good as you wish.

David
Mechanical project manager
JLFY technology company
Https://www.customized-tech.com

RE: Drilling stainless a bunch of times.

1.0mm sheet shouldn't be too hard if you going about it the right way.
Your biggest issue is going to be preventing whatever you use from flexing then rubbing and work hardening the S/S. If you can get a block of wood or some other sacrificial block in behind the piece you're drilling so you can apply plenty of force without the sheet flexing that will really help.
I'd be just centre punching all the holes, and then using a 3mm pilot drill, and then 6mm drill (for 6mm holes), followed by 10mm then 13mm (for 13mm holes). De-burr, job done.
Use Carbide drill bits, a little cutting lube and you should get through them no worries on a single set of bits. Would use a drill press if possible, otherwise just hand drill in situ.

RE: Drilling stainless a bunch of times.

Carbide is totally the wrong answer here. Carbide requires rigid fixturing and parts. Breaking through the sheet metal will chip carbide bits every time. Stainless steel isn't particularly difficult to drill so long as you can give sufficient feed pressure. Using a soft backing like hardwood is a good idea. Don't use a hard (metal) backing with hole saws or annnular cutters.

RE: Drilling stainless a bunch of times.

Just going off my personal experience, we seem to have very few issues drilling thin sheet with carbide drills.
To be fair though, you do need to be careful when punching through.

RE: Drilling stainless a bunch of times.

As an in the field guy I understand we may have very different experiences vs a new production or in the shop situation. I don't know that the OP has decided between a field modification or a shop modification. It's good to share both sides.

RE: Drilling stainless a bunch of times.

generally sheet metal components are punched, laser, or water jet in the flat pattern, once it is formed it gets flimsy or awkward.
the OP never said the thickness, or the geometry. in the old days using mild steel backing was required to minimize the burrs.
drilling sheet metal once formed for production is not easy, and expensive. If accessible I would suggest laser.

RE: Drilling stainless a bunch of times.

Thickness is 0.042"

RE: Drilling stainless a bunch of times.

thanks tugboat I missed that, to flimsy unless supported. unsupported will be like wet noodle

RE: Drilling stainless a bunch of times.

If the holes aren't in the middle of a very large sheet, I try to use a sheet metal hand punch:



The distortion you see in the photo is from using it on paper-thin aluminum. IME this tool won't distort your 0.04" sheet of Cres.

Drilling CRES by hand isn't that bad. Mind a few additional rules: The Cres will work-harden if you allow it to. Support the sheet as already mentioned, and while drilling DON'T STOP. The work-hardening happens as the cutting force is released (so I was told) so keep the bit cutting and feeding at a constant rate. Fluid won't help on thin sheet.

Since it sounds like you're modifying the humidifier, account for the time wasted to disassemble everything to make it suitable for the laser, water, CNC, whatever fancy process, and then put it back together again. I would rather find a convenient way to drill the holes in-situ, provided I can do it cleanly.

For accuracy, yet allowing for hand-drilling, consider a CNC/Laser drill-guide template. Cut pilot holes in a piece of steel plate first, with whatever accurate process is cheap and handy. Clamp that in place on the humidifier enclosure, thus guiding your drill bit. The rest is elbow-grease.

You didn't specify if these holes are close-tolerance safety-critical structural holes (on a humidifier, yeah right) or bracket mounting holes that can have 3mm slop (on a humidifier, more likely). Or the positional tolerance... suggesting completely different approaches. Best odds are that hand-drilling will be fine.

RE: Drilling stainless a bunch of times.

drilled holes is done a lot on sheet metals parts on aircraft structures. but with it it's all about edge distance and match drilling multiple components. and is not close true position.
the question also is what true position is required. if more 1/8 tolerance than hand drilling is an option.

RE: Drilling stainless a bunch of times.

It smoked
If you have the capacity to cut holes with a laser then you can cut the slot in the same way.

You are judged not by what you know, but by what you can do.

RE: Drilling stainless a bunch of times.

(OP)
Here's a shot of the problem child:



The holes will run along the bottom edge about 1/2" from the bottom. Sooo no cool hand punches WindWright.

You guys have given me a ton of possibilities that now are swamping me with selection.

It's been suggested:

Drilling - but using the sandwich method top and bottom to prevent horrid burrs and a triangular hole.
Stepped drills - "The Best!"
Punch die sets - Then need the appropriate press to put them in.
Lasering - None around here and tends to need flat sheet starting point.
Water Jetting - Several around here and purportedly they don't care about the preexisting shape. Next town over.
Rotary Sheet Metal Cutters - Seems excellent but needs a buying cycle.
Two point endmills - Had them handed to me.


I have a mill/drill press. I have a fist full of TiN drill bits in 6 and 13mm I can walk out back and try these. I think I will.

Depending on how hard this is I may forgo 13mm holes for 20 fuse holders and just drop them in the bottom of the pan. Then do only the 6mm holes for the blown fuse indicator lights. I'll start with those easier 6mm holes and see how things might feel for the 13mm.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Drilling stainless a bunch of times.

The main problem with drills isn't just triangular holes and burrs but the when one flute catches and either tries to jerk the drill on the steep spiral out of the drill, the drill out of the user's hands, or - on small pieces - to both wind it up the drill and then whip it like a razor blade right where the hand that was holding still is. I've got at least one small scar from not using a block on top and a clamp to prevent that climb "to save some time." On a bigger piece the scarring won't happen, but I can see it making a dent on a drill press or mill.

The nice thing about the step drill is it doesn't have a helix, so it cannot spiral into the sheet metal.

RE: Drilling stainless a bunch of times.

Someone commented on using a Step-Drill if you could find one in Metric. Well, they're readily available, just not 13mm. The ones I found has steps for 12mm and 14mm but not 13mm:

https://www.amazon.com/High-Speed-LepoHome-Titaniu...

But 13mm is close to 1/2 inch so you might be able to use an Imperial Step-Drill.

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Drilling stainless a bunch of times.

Go half a step?

RE: Drilling stainless a bunch of times.

Then you end up with a hole with a very sharp inside edge on one side.

A word of warning about step drills, they do leave a nasty bur on the opposite edge. I usually flip the part over and kiss the back side with the same drill if I can.

Sorry, I have been holding out on simply linking a vendor. Your local welding supply has the rotary broaches. Don't forget the arbor.

https://www.airgas.com/product/Tools-and-Hardware/...

RE: Drilling stainless a bunch of times.

The metal is thin - most everything leaves a sharp edge. Half-was was half-joking, but if one can reach the other side then the sharp edge can be right in the middle, the location where someone might say, is that sharp? And then mumble a lot with a bleeding finger in their mouth on the way to a bandaid box.

RE: Drilling stainless a bunch of times.

(OP)
Yeah, yeah, Microstepping! No, wait, wrong field.

John;

Quote:

McMaster-Carr:
High-Speed Steel Multidiameter Drill Bits

Titanium-Nitride (TiN) Coated High-Speed Steel

5.0 mm, 7.5 mm, 10.0 mm, 13.0 mm, 16.0 mm, 19.0 mm, 21.0 mm, 23.0 mm, 26.0 mm, 29.0 mm, 31.0 mm, 33.0 mm, 35.0 mm 0.1968", 0.2953", 0.3937", 0.5118", 0.6299", 0.748", 0.8268", 0.9055", 1.0236", 1.1417", 1.2205", 1.2992", 1.378"

No of sizes: 13
Length: 79mm
Max material thickness: 4mm
Shank: Hex 11.1mm Standard
Materials: Steel, Hardened Steel, Tool Steel, Iron, Stainless Steel, Nickel, Aluminum, Brass, Bronze, Plastic

89275A35
$117.42

Keith Cress
kcress - http://www.flaminsystems.com

RE: Drilling stainless a bunch of times.

(OP)
Well, out into the rainy dark I stalked with my cache of drills and the stainless pile seen above.

Opening one of the big 13mm Cobalts I love the jewelry like look and finish and the dangerous potential it implies.



I planned to use my little mill but quickly discovered this box on it's side used up all but about 3" of my Z travel leaving nothing for a collet mounted drill chuck or the drill bit.

So I chucked up the 6mm TiN coated "sheetmetal drill" in my Milwaukee Brushless drill with a fully charged 5Ahr battery.



I was able to blast out 40 holes. It took a while since I used three clamps for my 3 inch wide aluminum backing plate I had to move numerous times. That picture is after the 40 holes. I pushed HARD and each hole took about 5 seconds.



Then I chucked up the 13mm and tried the first hole. ARGH!!!!!



No dice! It left that nasty result.

I'll use my buddy's offered step-bit tomorrow and see if that's any better.

I still had some burrs on the 6mm holes so I used the 13mm to deburr them on both sides and it worked a charm on those. Took maybe 2 seconds a hole side. Used one bar of the battery.

Stay tuned for the saga of the 13!



Keith Cress
kcress - http://www.flaminsystems.com

RE: Drilling stainless a bunch of times.

Looks good thumbsup2 A job well done is the best reward.

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Drilling stainless a bunch of times.

It smoked,
Very good Keith, now what about the slot?
B.E.

You are judged not by what you know, but by what you can do.

RE: Drilling stainless a bunch of times.

No sweat - they make a stepped slotting tool. Look between the hole shrinker shelf and the hole-repositioner shelf.

RE: Drilling stainless a bunch of times.

(OP)
LOL

Berky; The slot was a contemplation of having all the above holes laser'd out of some flat-stock that then was screwed onto this box instead of trying to drill the holes in the box manually. The slot presented an even worse problem so I gave drills and stepped drills a shot. And it worked. (Drilled 40 6mm holes with a Titainium Nitrided "sheet metal" drill then chased 20 of them with a stepped drill that maxed out at 1/2" which was apparently enough to fix 20 "13mm" fuseholders.)

Keith Cress
kcress - http://www.flaminsystems.com

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