stainless steel for enclosure

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi

I like designing my own enclosures for the amplifiers I build.

So far i have stuck to natural anodized alu which gives a nice offset to the standard black anodized heatsinks.

obviously getting one or two units cut , bent and anodized is costly. and by FAR the most expensive part is the anodizing.

I suppose bare brushed alu is an option but my feeling is that it will scratch too easy.
Not a Huge fan of powdercoating though you do get a clear powdercoating that will look good on brushed aluminium.

So here is my question.

I am currently designing two new enclosures. One for a big class A amp and one for a tube preamplifier.

and want to try and cheap out and not go the anodizing route and try bare brushed Stainless steel. The place that cut the metal and bend says they have a 200 per cm brush which is nice and fine.

MY Question is.

For a brushed Stainless steel enclosure is 430 steel fine or should I opt for the 304 grade?
 

Attachments

  • IMG_7074 [1024x768].JPG
    IMG_7074 [1024x768].JPG
    122.7 KB · Views: 559
IN the end i gave brushed 430 a bash to see how it came out. I sent my drawings through and picked up the bent and punched metal yesterday.

And I am very happy.
It seems like the metal place mostly only stock 1.6mm and not 2 or 3 mm so it won't work if i need stronger enclosure but it looks GREAT!
 

Attachments

  • IMG_7081 [640x480].JPG
    IMG_7081 [640x480].JPG
    59.5 KB · Views: 471
  • IMG_7085 [640x480].JPG
    IMG_7085 [640x480].JPG
    66.1 KB · Views: 449
  • IMG_7084 [640x480].JPG
    IMG_7084 [640x480].JPG
    58.8 KB · Views: 232
Looks very good. Yet I have never used stainless steel for home builds. It too hard for me to cut, drill, or punch; by hand.

I have a very good sheet metal machine; 3 in 1 unit. But cutting stainless on it, is asking a bit much. Alu, is no problem. I do brushed or polish Alu., or I will paint it.

But your items look very good.

Take Care


Ivey
 
working stainless

I've worked a lot of stainless NEMA 12 chassis in a food plant. You don't cut it with any normal shear, nor does plasma cutter make any kind of straight edge. You cut it oversize with a 4.5" angle grinder, then smooth the edge with the worn down 1/4" thick wheel. (Made some safety sign backings out of SS sheet, aluminum backing will dissolve in the caustic washdown process). You drill Stainless with cobalt coated drills. These are more expensive than HighSpeedSteel drills, but he toughness of HS drills has dropped so low at my local discount stores and hardware, that I buy cobalt anyway, or mail order HS from Cleveland. You punch Stainless with Greenlee punches- wears out punch very fast. Hydraulic punch driver is very useful.
 
Kilns:

My spouse was really into ceramics. She wanted a Kiln and I wanted a new Collins Radio. So I built a kiln. It cost me $300.00 verses $1,230.00 in 1976 dollars.

I used stainless steel, boiler bricks, boiler backing, home made steel clamps, Tappen Over heater elements and monel 1/4" rods.

I had the stainless cut into strips wide enough to where, when bended into a U shape. The Boiler bricks would fit inside. Once I got it high enough (about) 28", 30" over all in height. It was 18" square inside. Just perfect for a Tappen Oven heater loop element. I had obtain 9 of these. 8 from the junk and one that I had to purchase new.

I space them out evenly inside the kiln, and attached them on hangers to the stainless steel. Then I used 1/2" stainless steel strips to form buss bars for the ends of the heater elements. I bent the end tips of the heater elements in an L shape, drilled holes in the stainless steel and inserted and tied the element to the buss strips, using stainless steel wire. I used the monel rods to connect to the stainless steel buss strips and connected a stove cable to the rods.

You have to heat and hammer the rods ends flat first, drill a hole through them to attach them to the buss strips.

I wrap the boiler backing board completely around the outside of the kiln, then bend and wrap stainless steel around the boiler backing board. Lock it in place with "bandit steel", then use the 8 home made clamps to hold it all together.

The kiln was 18" square inside and 28" of useful height. So that my spouse could do medium size pieces.

My spouse became the pride of the ceramic class and we became the electric company's best customer.

The kiln was good for 2,330 degrees f. The stainless steel was good up to 3,370 degrees f. It turned a beautiful gun barrel blue, the stainless steel that was inside the kiln.

Take Care


Ivey
 
Stainless steel makes a nice enclosure.
As noted by other members, of course it's a bit more difficult to work with compared to aluminium alloys.
For this application, as corrosion isn't an issue, either grade would be acceptable, although the 430 grade does fold and fabricate a little easier that the 304, no need to go to a higher chromium content 316 grade
 
IN the end i gave brushed 430 a bash to see how it came out. I sent my drawings through and picked up the bent and punched metal yesterday.

And I am very happy.
It seems like the metal place mostly only stock 1.6mm and not 2 or 3 mm so it won't work if i need stronger enclosure but it looks GREAT!
Hello,
I have worked with SS for many years in industrial and food processing applications. The saying that something is easy if you know how only applies to a limited degree to working SS. SS will eat your tools for breakfast.
300 series SS is 18% chrome and 8% nickel plus and minus a little other stuff like molybdenum. The other 70 or so % is iron.
An interesting thing between the 300 and 400 series SS is that the 300 series does not have a ferromagnetic grain structure. A magnet will not attract 300 series SS.
I have been puzzled about the magnetic shielding ability of aluminum vs. steel chassis and Mu metal. Not enough to study it. SS may have some differing shielding properties. Anybody Know?
DT
All just for fun!
 
The thing when working with stainless steel is that, like titanium, it work hardens.
That is the more you are trying to bend, shear, grind or drill it, the harder it gets and the more it will resist whatever you are doing to it.
Which is why nobody makes stainless steel cars: The press tools wear out ten times faster than when using mild steel. And the press tools are some of the costliest aspects of manufacture.
Doesn't weld that easily either although no worse than aluminium…
 
Shielding? As to what.

Radiation, will go through SS, like butter to a hot knife. Magnet Radiation is even worse. Just increase the flux. The lack of dense iron element atoms is the reason. Nothing there to keep it busy.

300 lacks iron, so when it is heated, there is no scaling. 400 is something I have to look into. To if it is do able for me. But sometimes I just can not get my hands on things unless I purchase it over the internet. I hate purchasing things sight unseen or just by a picture over the internet. I fear that they are only showing me the good side of things.

Take Care


Ivey
 
Playing with google a bit shows that stainless steel is as good as commercial iron when it comes to magnetic shielding ie a permeability of 200 for both.
Aluminium, copper, tin and lead enclosures have a permeability of 1, the same as air (or no enclosure at all). Special magnetic shielding alloys can reach 20 000+.

But it is not true shielding, these materials attract magnetic fields by giving them a path of less resistance and so divert the magnetic field from what you want to protect.
 
Radiation, will go through SS, like butter to a hot knife. Magnet Radiation is even worse. Just increase the flux. The lack of dense iron element atoms is the reason. Nothing there to keep it busy.

300 lacks iron, so when it is heated, there is no scaling. 400 is something I have to look into. To if it is do able for me. But sometimes I just can not get my hands on things unless I purchase it over the internet. I hate purchasing things sight unseen or just by a picture over the internet. I fear that they are only showing me the good side of things.

Take Care


Ivey
Hello,
“Shielding? As to what.”
The question is about electromagnetic shielding.
“I have been puzzled about the magnetic shielding ability of aluminum vs. steel chassis and Mu metal.”
“300 lacks iron, so when it is heated, there is no scaling.”
300 series is ~ 70% iron, it will not hold a magnet because of its austenitic grain structure. It most definitely will scale when heated. That is why a shielding gas is used when it is welded.
Back to EMI shielding.
I thought that 300 series SS may have similar EMI shielding properties to Mu metal because of its non-ferromagnetic nature and nickel, iron, molybdenum content.
DT
All just for fun!
 
Last edited:
Playing with google a bit shows that stainless steel is as good as commercial iron when it comes to magnetic shielding ie a permeability of 200 for both.
Aluminium, copper, tin and lead enclosures have a permeability of 1, the same as air (or no enclosure at all). Special magnetic shielding alloys can reach 20 000+.

But it is not true shielding, these materials attract magnetic fields by giving them a path of less resistance and so divert the magnetic field from what you want to protect.

Hello,
Interesting insights. There is more to keeping EMI out of your circuits than shielding. I will check it out. It seems to be OT here.
DT
All just for fun!
 
stainless steel ...
Doesn't weld that easily either although no worse than aluminium…
I beg to differ on the welding of stainless. It is pretty easy. SS mig rod, tri-mix gas, or tig either one, I've done it with ease. The two difference with mild steel are that 1.If you get the MIG copper tip too hot, it will stick to the SS wire and kink it up, requiring replacement. Carbon steel doesn't do that, I've still got the same copper tip on my home MIG welder as when I bought it 8 years ago. 2. You have to move consistently on SS or it will separate the metals and rust at the weld under food plant caustic & acid baths.
Aluminum, at the food plant had a TIG welder with Helium available and a hi-frequency unit, and only one guy of the 18 of us at the factory could weld it. (He soon found a better job). The foreman always hired a contractor for aluminum jobs, who used our equipment when the job couldn't be moved. We tried for training to weld the aluminum sheet top of a garbage cart to the cast aluminum frame once. I got puddles going on both sides of the line, but no amount of poking would make them mix. ??
Resharpening cobalt drills on SS useless, because it removes the coating and they wear out quickly and work harden the SS. I brought home a lot of discarded cobalt drills which work fine on carbon steel, although a little soft behind the original tip.
400 series SS has more iron then 300 series SS, and will rust and pick up with a magnet. I never saw any, as it is useless for a food plant.
 
I am an aluminium pipe welder by trade. We used to tig weld it using argoshield.
The welder needs to be set to ac current so that it constantly 'rips' up the thin oxide layer otherwise it will never mix. The problem being that aluminium liquifies at 700-800C while aluminium oxide melts at 1100C or so.
For 2" pipe with 3/8th thickness 220amps is about right, going up to 350-400 amps when welding 1/2 plate to the pipe.
The other thing is that aluminium transfers heat exceedingly well and one has to constantly accelerate while welding.
Consequently there is a maximum length to the seam one can produce depending on the thickness. Thin sheet is very annoying in that respect especially if you try to weld it to something much thicker.
Aluminium castings are a pain as well since all but the highest quality ones contain contaminants like little gas bubbles.
So inadvertently you picked the most annoying things to weld together one could imagine.

May be stainless bugged me because I was very much used to speeding up evenly rather than go steady but I never got the welds as even as on aluminium. ;-)
 
Thanks

Thanks for the theory on the oxygen shell of aluminum metal puddles. Sure was what it looked like: two bags of melted aluminum that wouldn't break.The one successful guy told us to set the welder to reverse polarity with the hi-frequency unit (AC bias) on. I never did figure out which was was "on" for the high freq unit, either. No oscilloscope at that shop.
My standards , as a 3rd shift gnome, for welding stainless were obviously lower than a certified pro. No holes in the weld, no spatter to grab food particles and cause bacteria growth. I would never said I made any "pretty" welds. I ground off a lot of spatter. But they held up. Never heard the word "acceleration" used, but if you are running a puddle 400 degrees hotter than melting point of the metal itself, something has to be done to prevent it dripping away. Interesting.
 
Last edited:
The hf unit is always on during welding, basically the button switch on the tig torch switches both on simultaneously. If the hf unit does not work no arc will form and while on steel you could scratch start if you really must that doesn't work on aluminium.
The welder should use an ac welding current rather than dc as you would use for steel.
I think it is the change from negative half wave to positive half wave which helps to disperse the inevitable oxide layer. The only tell-tale sign that you got it right is that the puddle gets really shiny, mirror like. You've got to keep the puddle at the right size for the thickness which means constantly accelerating.
Btw I looked it up again and it's worse than I made out: Aluminium melts at 1200F, boils at 2880F and aluminium oxide melts at 3200F.

(Sorry to all others for being off topic!)
 
I did not write my post clear enough. And I am sorry. BUT

As more and more iron is removed a better grade of SS it becomes. Magnetic Flux will go right through it. Because the magnesium is not transferred. Lesser grades of SS steel is affected by magnetism. And if the Flux is strong enough, can transfer that magnetism to it.

But we discovered that magnetic flux can be disrupted if a metal is perforated. Regardless of it make up.

That was my point.

Plus, as the SS grade gets better, one gets little to no scaling when heat to high temps..

Take Care

Ivey
 
Hi guys , thanks for all the interesting posts.

one thing i possibly did not make clear. I have 0 tools to work with metal , except a hand drill to drill the odd few holes. So all my projects i send autocad drawings of my ideas of to a metal workshop and a week or 3 later (depending if it's anodized alu or plain brushed stainless) i get what i drew back.

:)

I am very happy with the 1.6mm 430 SS.

And the odd hole I had to drill was not very hard at all. not as easy as alu but that's a given.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.