What type of Drill Rod for Axles?

[FKreider]

Many plans call for drill rod and/or "silver steel" (in the UK) as the material of choice for axles. When going to purchase Drill Rod I am given the choices of three types; "A-2" "O-1" and "W-1" (there are other types as well however these three seem to be the most prevalent.)

I suspect that any of these materials would do the trick however I am just wondering if there is a preference among us hobby machinists? Is one type easier to machine and/or easier to get better surface finish with?

[gwrdriver]

Frank,
I think the scale of your project has some effect on what might be the best (and most convenient) material to use, however in general I don't use drill rod for axles at all, even for small (3/8", 3/4") scales. In addition to the relatively high cost, DR offers few physical advantages for driving axles. Most mild steels (1020 etc) will do the job just fine although my preference for driving axles in 7.5"ga is 4140.

What are you building?

[Greg_Lewis]

And do not buy drill rod expecting it to be round. I once spent $30 on a piece of 1-inch dia. expecting it to be within the advertised spec of a couple of tenths only to find it tri-lobed by well over three thou. Since I had already cut off a piece and started to machine it, I was stuck with it.

If you need a bearing surface, I'd use something else and put a hardened race over it.

[Builder01]

One thing drill rod usually offers, is an accurate ground finish. If the rod is not round, it was not made correctly. Generally speaking, drill rod is made with a ground finish with a very specific diameter. It is available in not only fractional sizes, but number and letter drill sizes, (hence the name "drill rod"). For a sleeve type bearing surface, even in it's unhardened state, it works quite well.

David

[Marty_Knox]

I use ground and polished stress proof for axles.

[hoppercar]

Why use drill rod at all ?....mild steel is just fine

[Steggy]

My go-to material for axles is C1144 TGP (turned, ground and polished), sometimes referred to as Stressproof®. The material is reasonably easy to machine, has good strength-hardness properties and has a bearing-quality finish. An alternative if C1144 TGP isn't available is C1045 TGP.

[Steggy]

Why use drill rod at all ?....mild steel is just fine

Not if you expect the axle to also be a bearing surface.

[tetramachine]

The name drill rod applies to a dozen types of steel. All of which can be hardened, and available in Fractional, Numeric, Metric, and Letter sizes. If you want exact sizes, you need to buy material which is TGP Type. That is Turned, Ground, Polished, and many sizes can be PH which means Pre hardened. The PH is still machinable with HSS or Carbide. The hardness is between 25-30 R-C. While fully hardened material would be over 50 +R-C, and almost unmachinable.

I suggest D-2 which can be air quenched, if you need real hard, used for needle bearings without an inner race. 4140 is cheapest, and is available TGP and PH, and can be purchased in almost any size.
My .02

[hoppercar]

True...I guess it you want your axle to be a bearing surface, you will have to use drill rod orsome other type of tool steel

[Greg_Lewis]

...
If you want exact sizes, you need to buy material which is TGP Type. That is Turned, Ground, Polished...

That's what I bought when I got the tri-lobed junk. Be sure to check the stock before you start with it. Set it on a pair of v-blocks and check it with a d.t.i. by rotating it in the blocks. A tri-lobed piece will still check OK with a mic.

[Steggy]

True...I guess it you want your axle to be a bearing surface, you will have to use drill rod orsome other type of tool steel

Not so.

There are steels that are turned, ground and polished (TGP) to within a few tenths of the nominal size and are intended for use in axles and shafting. Most of these steels are either medium carbon types, such as C1045, C1144 and StressProof® (StressProof is a variation of C1144), or alloys of the 4000-series or 8000-series. Some stainless alloys are also available in TGP, although extravagant for hobby use.

My recommendation for an axle that must have a bearing-quality surface would be C1045 TGP or C1144 TGP, both of which are readily machined and require no heat-treating. Drill rod is not a good choice for shafting and axles.