We have the potential for doing some stainless stuff at work soon, we routinely do steel and aluminum, but the few times I've tried to cut stainless I've dulled tooling and hated every minute. Obviously, people use this stuff all the time, so what is the best tool/approach for precisely cutting this stuff?
We have a good Scotchman cold saw for steel, and we do the Aluminum on a quality compound miter saw with the appropriate blade...We do also have a decent abrasive saw buried somewhere under a table. My hope would be a blade/coolant change for the scotchman... but looking for all advice.
There will be more complete answers by others, but the very basics are not to go at it daintily. Stainless work hardens easily. If you drill or cut too slowly (inadequate feed speed or small depth of cut) you can easily work-harden the part you are trying to drill or cut to the point that you can't cut it, dull tooling, etc. You want to take a healthy chip.
Plenty of oil (I'm old-school enough that I'm thinking stinky sulfer cutting oil - there might be better things out there now, or not).
You didn't provide enough information to receive a worthwhile reply. Stainless comes in a wide variety of alloy types---some heat treatable, others not (all 300 series stainless can not be heat treated).
If you have options, and the material is to be machined, inquire if 303 S 0r
303 Se is acceptable. While you're at it, ask about 416. All of these materials are free machining and are a pleasure to machine. The 416 can be heat treated. All can be machined nearly as fast as mild steel, with far superior finishes.
We will need more information. What are you cutting, 14ga. Sheet or 3" diameter round? Are you machining it or just cutting shapes? If it were sheet you would use plasma and if it is round or square stock, a band saw will work, you just have to slow down the blade speed. For machining, pay attention to the cutting speeds and you'll be fine. Most people cut stainless way too fast, which work hardens it, then the fun begins. I use 40 ft / min as a starting point for machining stainless.
This is for framing for theatrical scenery to be used in a water based environment. Probably be square and round tube simply cut to length and butt welded, maybe coped to fit tube to tube, the only other "machining" will just be drilling holes to bolt things together. The major problem will be cutting tube to length.
I am getting the suggestion of using the cold saw, running the speed low, and the feed pressure high, Suggestions of favorite coolants?
We usually do Aluminum, but we think the stainless is heavier and easier to keep in a "brushed" condition than aluminum in our water environment.
We've done plenty of regular theatre, and a bunch of Ice shows, but never built scenery for immersion before... Just seeking input.
Welding will discolor the material. You can investigate electropolishing, which will restore the color, but may brighten the finish more than it was originally. I'm hardly a weldor, but I can tell you that stainless is very nice to weld. You will likely end up with 304 alloy. Avoid any of the free machining materials (303, 416) if you find them available, they are not recommended for welding.
Considering you're likely to be working with hand tools, you can use sulfur based cutting oil, applied with an acid brush, or small paint brush. That's common practice for guys on lathes and mills without flood coolant. You should be able to buy the cutting oil at any of the box stores (Home Depot). It's the dark brown stinky stuff they use when cutting threads on pipe. Keep your drills sharp. If one starts to scream, change to a sharp one. Once you dull it in a hole, the hole will ruin a new drill. Work hardening of stainless is very real, and very hard.
Harold, sounds like you have allot of SS experience. I have been CNC & manual machining SS for a long time. In Molds I have used 420 for heat teat & some pre-hard type (forgot the number 411?-418??). In assembly fixtures/nests I have been using 303. Machining is not a problem for me, but part warp is. Seems like you have to rough everything out, leaving how much stock??, depending on part shape - re-square the block & then finish. Man that's allot of work. I choose 303 for free machining & corrosion resistance, as some SS can discolor & seem to rust in very humid factory environments, Our medical customers cant have that. Is there any SS you know of that would fit my needs? I've thought of just using 420 & leave it soft?, but its an expensive quality tool steel.
\|||/ (o o) ______.oOO-(_)-OOo.____________________ ~ Gil ~ the HOLDZEM=A9=AE king
leaving how much stock??, depending on part shape - re-square the block & then finish. Man that's allot of work.
It's a little work, but part of the process, and very acceptable shop practice. Besides, you can take the roughing cuts with reckless abandon, with no concern for surface finish. Just stay away from the finish dimensions, leaving no more than is necessary to do the finish machining. The more you remove, the better the chance the material will be stable in the finishing stages. I generally allow anywhere from .03/.06", depending on several factors, as you noted.
machining & corrosion resistance, as some SS can discolor & seem to rust in very humid factory environments, Our medical customers cant have that. Is there any SS you know of that would fit my needs?
Yep! 303, either S or Se. Just passivate it after final machining and polishing. That removes the free iron that causes stainless to rust superficially. Passivation is very much a part of finishing all of the 300 series stainless alloys.
I don't have the exact proportions or the procedure, but it involves dilute nitric acid and potassium dichromate, heated, but below boiling by a considerable margin. Most plating houses that deal with MIL spec processes can passivate for you if you'd rather not get involved personally. Besides, it's very difficult to buy nitric acid these days, and it's killer expensive when you do. I used to buy it for just over $4/gallon (55 gallon stainless steel drum) when I refined precious metals. Those days, it appears, are gone!
There is also a process using citric acid and electricity (or something that is largely citric acid [CitriSurf?], and electricity). Much less nasty than having anything to to with Nitric. No personal experiece with it, but Ernie L. recommends it (s.e.j.w.) which is pretty solid - Ernie knows his stuff, and he uses it.
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