AISI 1025 for Final output Transmission Shaft

[Tony Wells]

Good suggestion, xalky. Common, off the shelf bolts are available in a few grades, and anything grade 5 or higher would likely be stronger than what is there.

Let's see if this chart will paste in.

[TABLE="class: infotable, width: 650, align: center"]
[TR="class: toprow"]
[TH]Head Marking [/TH]
[TH]Grade and
Material[/TH]
[TH]Nominal Size Range
(inches)[/TH]
[TH="colspan: 3"]Mechanical Properties [/TH]
[/TR]
[TR]
[TH="class: subheading"]Proof Load
(psi)[/TH]
[TH="class: subheading"]Min. Yield Strength
(psi)[/TH]
[TH="class: subheading"]Min. Tensile Strength
(psi)[/TH]
[/TR]
[TR="class: sectionheading"]
[TD="colspan: 6"][h=2]US Bolts[/h][/TD]
[/TR]
[TR]
[TD]
No Markings[/TD]
[TD][h=3]Grade 2[/h] Low or medium carbon steel
[/TD]
[TD]1/4 thru 3/4[/TD]
[TD]55,000[/TD]
[TD]57,000[/TD]
[TD]74,000[/TD]
[/TR]
[TR]
[TD]Over 3/4 thru 1-1/2[/TD]
[TD]33,000[/TD]
[TD]36,000[/TD]
[TD]60,000[/TD]
[/TR]
[TR]
[TD]
3 Radial Lines[/TD]
[TD][h=3]Grade 5[/h] Medium Carbon Steel, Quenched and Tempered
[/TD]
[TD]1/4 thru 1[/TD]
[TD]85,000[/TD]
[TD]92,000[/TD]
[TD]120,000[/TD]
[/TR]
[TR]
[TD]Over 1 thru 1-1/2[/TD]
[TD]74,000[/TD]
[TD]81,000[/TD]
[TD]105,000[/TD]
[/TR]
[TR]
[TD]
6 Radial Lines[/TD]
[TD][h=3]Grade 8[/h] Medium Carbon Alloy Steel, Quenched and Tempered
[/TD]
[TD]1/4 thru 1-1/2[/TD]
[TD]120,000[/TD]
[TD]130,000[/TD]
[TD]150,000[/TD]
[/TR]
[TR]
[TD]Stainless markings vary. Most stainless is non-magnetic[/TD]
[TD][h=3]18-8 Stainless[/h] Steel alloy with 17-19% Chromium and 8-13% Nickel
[/TD]
[TD]1/4 thru 5/8[/TD]
[TD] [/TD]
[TD]40,000 Min. 80,000 – 90,000 Typical[/TD]
[TD]100,000 – 125,000 Typical[/TD]
[/TR]
[TR]
[TD]3/4 thru 1[/TD]
[TD] [/TD]
[TD]40,000 Min. 45,000 – 70,000 Typical[/TD]
[TD]100,000 Typical[/TD]
[/TR]
[TR]
[TD]Above 1[/TD]
[TD] [/TD]
[TD]80,000 – 90,000 Typical[/TD]
[/TR]
[/TABLE]

 

[Ray C]

Tony is 100% right here...

I've been reading a lot about metallurgy lately and wish to add that cold roll often has some internal stresses due to the forming that's done while it's just barely in the maleable state. Hot rolled on the other hand, is formed/shaped while it's still cherry red but, is allowed to cool slowly. -That's why round stock HR often has flat spots, because it drooped a little while sitting. In any event, steel that is formed while hot and allowed to naturally cool has less internal and surface tensions.

I've noticed on some long pieces of CR that it starts to warp a little when you turn/lathe off the some of the outer skin. -That's because the outer surface tension is being upset. On the upside, since CR is more dimensionally correct, you don't need to start-out with a 3.25" round if you need to make a 3" shaft, you can get away with a 3-1/8" raw stock and the outer flaws don't need as much cutting to remove.

If you are making something that's pretty critical, it should be stress relieved before machining then, stress relieved after machining and finally heat treated and annealed to proper hardness. -Don't know if I'd ever have need for such fanfare but, that's what is recommended in the heat treating books.

It might be a good time to define a couple of metal terms. "Cold roll(ed)" does not refer in any way to a specific grade or type of steel beyond the way it is processed. In fact, many of the various steels can be acquired in both "cold rolled" and "hot rolled", and for all practical purposes, they are interchangeable except for the fact that the final product can determine which can be used without further mechanical processing. Typically, material specified to be "cold rolled" has a better surface finish, is free of all mill scale, and is held to closer dimensional and straightness tolerances. "Hot rolled" on the other hand will have scale and is generally less accurately finished. Not though, that not all steel varieties are available both ways. I believe the most commonly (and erroneously) called "Cold roll(ed)" steels are the low carbon, mild steels such as AISI 1018 and 1020. They can be had, or rather a rough equivalent can be as "hot rolled". Of course, "cold rolled" starts as "hot rolled". After several stages of processing, including some heat treatment, it is drawn to a smaller size while "cold", relatively speaking. Don't think "refrigerated", just below the material's critical temperature.

One reference: http://www.engineersedge.com/materials/carbon-steel-properties.htm
Please consult the EMJ handbook whenever possible. And grab someone's blue book while they're not looking. I don't believe they are printing them any more. You can't have mine.

One other term I want to mention is the "L" included in a few alloys. In the case of 12L14, a very popular and useful metal, it signifies an addition of elemental Lead to improve machineability, though generally thought as a sacrifice in weldability. In the case of stainless alloys, the "L" means something entirely different. For example, type 316 allows up to 0.08% Carbon content in the chemical makeup, whereas type 316L allows only 0.03% max. That isn't much, but it makes it a far more weldable material. Small chemistry changes allow tremendous mechanical property differences.

As far as the current issue goes, most any steel would probably suffice. You should decide if you want to improve the strength of the factory material. That's a bit tough, not knowing for certain what it is. I think the guys have given some fine advice above. If it were me, I'd just do a commercial 4140 HT. It's almost positively stronger than what is there, and you should be prepared for something else to break should the fuse to fail in protecting the power train. Plus, it's about as easy to get online as anything, and you know what you have then.

 

[Tony Wells]

We're really drifting OT here, but it's all good information.

I'll add just a bit to Ray's comments. If the part is critical (and you oilfield types will recognize jar parts, drill motor driveshafts, many subs and adapters and such) often they are made from forgings if the material economics dictate, and are rough turned to near net, then normalized, quenched and tempered, then finish machined. This is usually the best way to achieve a high strength, stable part. Any time you have a choice in purchasing, choose normalized if it is a grade that will be used as machined. If not, you may experience more of the stress relief through mechanical work that Ray referred to. If you will be machining to net, then Q&T, choose your heat treater and method wisely. It's a delicate thing to get parts to stay put during the process. This applies moreso to thin and uneven cross-section parts.

But that's an entirely different thread.......