Drilling stainless a bunch of times. 2

[itsmoked]

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

 

[Pud]

CNC turret press?


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

 

[TugboatEng]

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.

 

[3DDave]

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.

 

[itsmoked]

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

 

[TugboatEng]

Bay Ship and Yacht in Alameda has a water jet.

 

[TugboatEng]

Aha!

https://www.hougen.com/cutters/sheet-metal-hole-cutters/Rotacut-sheet-metal-hole-cutters.html

Available in metric sizes, too.

 

[3DDave]

http://www.edwardsironworkers.com/c-15-metric.aspx

Not cheap, but you get to keep them or put them on e-bay.
Individual:

https://www.trick-tools.com/Piranha-DH-Round-Metric-Punches-Dies-998

 

[itsmoked]

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.

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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.

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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

 

[TugboatEng]

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

 

[arunmrao]

Water jet cutting can be a good choice.

 

[mfgenggear]

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

 

[FacEngrPE]

For the slot, try a nibbler

https://duckduckgo.com/?t=ffab&q=sheet+metal+nibbler&iax=images&ia=images.

If you only have one job like this there are some hand nibblers in the link.

 

[David-T]

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

 

[Tuckabag]

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.

 

[TugboatEng]

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.

 

[Tuckabag]

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.

 

[TugboatEng]

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.

 

[mfgenggear]

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.

 

[TugboatEng]

Thickness is 0.042"