Hardening drill rod at home?

My polite suggestion is just to use the drill rod as is. It will be just as stiff but more prone to wear. (You said "get it working .. before spending ").

And you won't run the risk of warping it, probably a bigger factor than wear.

Don't harden it! I have had drill rod rails in service for many years and they are fine. If you must have hardened rods, get Thompson "Quick Shafts" they are cheap and readily available on the web. What bearings are you using? I use a lot of Thompson "Nyliners" they are cheap and won't wear your soft rods.

Hi Jerry,

I'd use water hardening drill rod left unhardened. The water hardening type is a bit more wear resistant in its soft state than the oil hardening style. As you are building a prototype and intend to use real linear shafts in the final version the material will probably last at least long enough to verify your design. I would guard it against abrasive grit in the same way you need to guard linear shafting, but would not expect any problems. In shafting applications such as lathe countershafts I've used water hardening drill rod unhardened many times with good results.

If you really want to harden the material, drill a cross hole to take a piece of iron wire. Build a temporary box of firebrick and using several propane torches, a weed burner, or a fairly large rosebud tip on an OA rig heat until a magnet tapped on the work no longer sticks to the material. This ensures you are above the transformation temperature. Keep the heat source moving at all times, avoiding direct hard flame contact on the workpiece. Once the magnet stops sticking when tapped on the work, heat an additional minute or so just to soak in the heat, then plunge vertically into warm (120 F or so) water or quenching oil. Keep the work moving up and down without doing figure eights or sloshing side to side. With some luck the drill rod will not warp significantly in the quench.

For one inch material you will need a fairly large quench tank, at least one gallon or larger. If using an oil quench, do it outside and DON'T have your body over the tank. The oil may well flare up and will spit a bit. A water quench will flash off a good bit of steam, so be ready and take precautions to avoid getting scalded. There is a lot of heat in a couple of cubic inches of steel at the transformation temperature.

You may need to grind the OD of the final piece after this, drill rod tends to go slightly oversize after hardening. Some folks coat the work with soap or borax powder before heating to minimize scaling.

After hardening, temper at around 425 to 450 degrees F in an oven for an hour or two.

Cheers, Stan

jerry wrote:

Stan Stocker wrote in news:u95Ab.3116$ snipped-for-privacy@news1.news.adelphia.net:

Thanks to all who replied, real useful and as suggested I'll used it unhardened. Hadn't thought about warping the rod through heating either.

Tom; I have a bunch of 'Nyliner' brand bearings with a steel outer casing. No manufacturer on the packaging but I think their thompson as they are similar to their type 2's - so it looks like I'm good to go.

Thanks all again.

Oh, yeah this is for a pair of machines to load, locate, drill and unload PCB's for custom short runs so the material waste is very abrasive. I'm planning on protection for the bearings.

jerry snipped-for-privacy@nospam.com

Just 'cause it's bothering me. "Oil hardening," "air hardening" or "water hardening" (though I'm not familiar with that term for the W series of steel) are terms that refer to tempering--there's two processes involved for hardenable steel, (1) hardening at high heat, and then (2) tempering, and differing techinques for each.

I think O-1 (drill rod) is a good general choice for machining something that needs to be more critical than mild steel. It turns/drills well enough, in any case. Frank Morrison.

The terms "oil hardening," "air hardening," and "water hardening" refer to the hardening step (specifically, to the different quench rates each grade requires/tolerates). The tempering technique for all three types is the same.

Drill rod advertised as "oil hardening" is usually O-1; "water hardening" is usually W-1, and "air hardening" is usually A-2.

Jim

Heat to yellow heat in the forge, then plunge into the cooling medium. Draw the temper back to straw. (The latter can be done in a toaster oven, about 450 F).

Realize that without a controlled atmosphere furnace you're going to get scale on the surface, and that the part is going to warp when it is quenched. You'll need to allow enough excess material to grind to final size after hardening.

Unless you have the proper grinder, you'll probably do better to just bite the bullet and buy Thomson linear bearing shafting in the first place. It isn't *that* expensive.

Gary

Orange. Yellow is more where copper melts at, you want brass temps. In fact, you could put a spot of brass braze on the piece, when it's melted, you're at the right temp; file or grind off the brass later.

Tim

-- "That's for the courts to decide." - Homer Simpson Website @

What exactly are you trying to accomplish? I peeked in McMaster out of curiosity. Precision-ground chromed steel shafting for linear slides is $15 per foot in 1" dia. Plain O-1 drill rod is $13 per foot.

Which just goes to prove that with a little knowledge, you can complicate what the old blacksmith used to do on his break into something that is now impossible. Heat it, quench it, polish it. It'll probably be ok. Don't worry about getting it through hardened, the outside is what you want hard. You're looking for a wear surface, not something you're going to grind a tool out of. Having the inside softer but less brittle isn't a bad thing.

Other option, simply run it in the annealed condition.

For a prototype test it should work fine.

Jim

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