PDA

View Full Version : help I.D. a stainless



rmcphearson
10-22-2009, 06:59 PM
I have been buying a 5/8" x 25" stainless shaft that is drilled and tapped on each end for some of my equipment. It rotates inside a delrin (teflon?) bushing at each end. I am paying $50 each shaft. It is magnetic and I can cut it fairly easily with a file.

My question is: Is this a hardened stainless? Should I be able to cut a hard stainless with a file?

I will be buying a bunch of these soon and may consider making them instead.

Roland

MTNGUN
10-22-2009, 07:21 PM
I'm rusty on stainless -- pardon the pun -- but doesn't magnetic suggest a 400 series ?

A hardened, tempered shaft could be cut with a file. Think 400 series gun barrels, which are hardened and tempered, yet machine easily enough.

I dunno if 400 series stainiess is available in a pre-hard version, but it probably is.

The real question is what does your application require with regards to corrosion resistance, hardness, and toughness ? Would 304 or 303 do the job, or do you require the strength and hardness of a treated 400 series ?

Fasttrack
10-22-2009, 07:45 PM
Yes, sounds like it is most likely 400 series.

Ries
10-22-2009, 08:36 PM
Even lowly 304 will get slightly magnetic from work hardening. Forging, rolling, and even some machining can cause it be somewhat magnetic.

Will a magnet stick to it as strongly as it does to mild steel?

If it is entirely non-magnetic, its probably mill finished 304.

But being slightly magnetic doesnt really tell you much.

And most stainless alloys are not really hard, the way a really high carbon steel is hard- they are, instead, tough, and have pretty high tensile strengths- so many are approachable with a file.

What are your mechanical needs for this, and why is it stainless?
Is it for chemical resistance? Salt water? tensile strength and resistance to bending?

I would agree that, unless there are really high bending forces, or a really nasty environment, 304 would probably work, but we would have to know more about the application.

bobw53
10-22-2009, 08:52 PM
Take a dig around McMaster Carr, they've got tight tolerance ground rods in several different stainless's.

Looking at a bit of an old catalog,

303, 6ft of 5/8" $49.00 88915k23 strength unrated.
304 6 ft, $39.56 9210k13 25ksi,
316 6 ft $44.28 89325k83 25ksi
416 6 ft $59.70 88955k71 40-65 ksi magnetic, likes to rust not heat treated.
440C annealed 6 ft 81.18 9094k19 60 ksi magnetic and rusts
440C hardened 6 INCHES $35.56 hard as hell, 292-338ksi
17-4 solution treated/annealed (my favorite) 6 ft $68.68 9095k19 160ksi(<-- I question that) magnetic, decent corrosion resistance.
17-4 H900 6ft $70.26 1141t27 170ksi

Those are all +.0000 -.0005.

I didn't look in the shafting section.

I'd personally go with 17-4, which you may have, very strong, really good corrosion resistance, cuts really nice, no standard work hardening pucker factor. You can get it already heat treated and then it cuts even easier.

One other thing, I bought a chunk of 17-4, solution treated/annealed, 1" diameter, 48 feet of it, it is dead on 1"(it wasn't bought as ground). Been using it for tractor pins, reaming the bushings to 1.002. It was like $45 a 12ft stick, so we stocked up.

Evan
10-23-2009, 01:07 AM
This may be useful.

http://ixian.ca/pics6/ssident.gif

rmcphearson
10-23-2009, 10:04 PM
Thanks for the responses! You guys are awesome!

The application is for a roller that supports a grass clipping basket exposed to water, sand, fertilizer, ect. The original design is carbon steel shaft with ball bearing on each end. It's a poor design and the aftermarket rebuild kit consists of the stainless shaft with teflon bushings.

Having an accout with MSC, I am looking at their 440C "heat treatable to the highest hardness of any stainless" for $67/72". I can make 2 shafts out of that for $35 each. Then I guess I could have them hardened? Maybe the final cost will be similar to what I'm paying now ($50 each). Bobw53 chart shows 440C hardened to be 300ksi, "hard as hell". If that means a file won't cut it then it's better than what I'm buying now, eh?

I have a feeling the heat treating will be cost more than I am guessing? I've never had it done before.

Roland

MTNGUN
10-23-2009, 10:51 PM
Fertilizer can be very corrosive. It may contain or become phos acid, sulfuric acid, nitric acid, etc.. Not all stainless steels will resist these acids.

I don't know what kind of mechanical stresses are on this shaft, but if corrosion resistance is important and mechanical stresses are moderate, I'd lean toward a 300 series. 304 would be the likely choice. You might even want to go with 316 for better corrosion resistance -- your call.

As another poster mentioned, 304 and 316 are available in round rods that are ground to precise tolerances -- you would merely cut to length and D&T the ends. Even non-ground round bar might have acceptable tolerances for use with teflon bushings. I use quite a bit of non-ground round 304 and find the tolerances quite satisfactory.

Heat treating and tempering would likely need to be done before any critical machining, because heat treating will warp a long shaft and maybe change the diameter by a thou or two. Unless you can find shaft material that is already heat treated and tempered -- and I suspect you can if you look hard enough -- I'd forget about heat treating and stick with 304 or 316.