Shade-Tree Metal Hardening

I'm going to make a wire-bending fixture for putting fairly small-radius bends into 1/8" music wire*. I have some 1/8" oil hardening drill rod and a slightly undersized 1/8" reamer designed for installing dowel pins in tooling. I also have some 1-1/4" round bar, made of mystery steel but there's a good chance that it'll harden at least a bit if encouraged.

So I'm planning on putting a couple of pins made out of the drill rod into the end of a bar, and bending the music wire around the pins. I'm _assuming_ that if I don't harden the drill rod that it'll bend, although I'm in a hurry so I'm going to test that assumption by trying to use the tool.

After I bend up my first attempt at a fixture I'll want to do it up right. It seems like I should just be able to heat up my whole assembly to a dull red then chuck the thing into a bucket of water -- does this sound correct? I have some pottery clay lying around so I'll probably paint the pins with clay & charcoal in an attempt to protect them from decarburization. When I fish it out of the bucket should I try tempering it? If so, how, and how much?

The heat-generating tools I have available are pretty much a propane torch and an O-A cutting torch. The temperature measurement tools I have are my own somewhat color blind eyes.

  • Music wire is moderately high carbon -- 0.7 to 0.9%, and drawn in a way that work-hardens it nicely. It's soft enough that you can cut it with diagonal cutters successfully, but hard enough that you'd better hide the cutters from their rightful owner when you're done.
Reply to
Tim Wescott
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Ideally, heat it until a magnet (or magnetized screwdriver etc.) doesn't stick to it. That ensures that you've got it hot enough to harden. as soon as possible after quenching, put it in the pre-heated kitchen oven at about

220C/430F or a bit higher for an hour. If you don't do that, there is a danger of the pins shattering :-(

Soap, mixed with water to a creamy consistency works quite well to shield parts form air. It should come off when quenching.

If you can find them, use a couple or four fire bricks or some mineral wool to contain the heat. Takes a lot less effort to heat parts up with an approximation to a forge...

Mark Rand RTFM

Reply to
Mark Rand

Yea, the best approximation I have to a forge is an old forge that needs some TLC before it can be fired up -- but I'm trying to _reduce_ my project load, not _increase_ it.

Reply to
Tim Wescott

So are fire bricks a Home Depot thing? A local welding shop thing? A "forget about it and get mailorder" thing?

(I want to make a decent forge/furnace that's at least big enough to heat treat model airplane crankshafts in, and maybe enough to melt aluminum for a model airplane crankcase, but that's a project for another year).

Reply to
Tim Wescott

I would harden the pins before pressing them in the jig.

You can probably get firebrick at Home Depot. Better places to try are places that carry pottery supplies. They will probably have insulating firebrick. You could also try places that sell woodstoves or masonry products.

For a decent forge/furnace you probably want castable refractory. You can make your own using vermiculite or Pearlite from the garden center and some fire clay.

Dan

Reply to
dcaster

They're a place that sells woodstoves thing. There's a woodstove dealer on hwy 213 near Leland Rd ( at least there used to be) that'll have them. Paul

Reply to
# 42

I'd buy the pins already hardened. Small alloy dowel pins are cheap and will be stronger and tougher than what you're likely to get with primitive methods without a fair amount of experience. Hardened drill blanks are stronger still, at the expense of toughness.

Reply to
Ned Simmons

You know of dowel pins already -- so why not get some. 1/8" dowel pins are quite inexpensive, and a *lot* harder than you could get the drill rod to be without it being too brittle.

As for the mystery steel -- I think that it is as likely as not to be low carbon enough so you won't get *any* appreciable hardening with it. But why would you need that? You want it tough, to hold the dowel pins, not hard, because it is not a wear surface in this application.

And music wire is hard enough so it will dent the drill rod, likely even if you've hardened it before use.

Water is too extreme a chill for oil-hardening drill rod. Cut the rod to length and bevel the ends (assuming that you don't get dowel pins), then wrap them and some paper in some stainless steel foil wrap, crimp it closed and pack as tight as possible around the pins to exclude as much air as possible, then heat that to your red heat. The foil keeps out any air which is not already there, and the paper burns up the oxygen which is already inside.

Once you reach the red heat, cut off the end of the stainless steel wrap and let it fall into a container of oil -- engine oil will do if you don't have anything better. This will quench it at the proper rate. You might have a flash of flame from the vapor at the top of the oil's surface, but it will go out very quickly. (Do it outside anyway to be safe.)

The pins are what you need *hard*, and by protecting them from the oil you will not get nearly as much hardening as you want.

Forget about hardening the body of the fixture, and get dowel pins which are already very hard and you won't have to worry about this.

But if you harden the drill rod -- read up on the tempering temperatures of the rod which you have and aim for just a little less hard than full hard. At a guess, something like 150 F to 200 F for perhaps a half hour (these are quite small, so the hour per inch of thickness need not apply).

But I would go for the dowel pins, not the drill rod. (I've got both on hand.)

Do the heating in the shade so you have a better chance of seeing the red. Or -- you could test them with a magnet. When they are no longer attracted to the magnet, they are ready to quench.

I'm not sure that 1/8" music wire will take the kind of bends which you would get from 1/8" drill rod or dowel pins. Normally for cutting music wire I would suggest the Starrett carbide faced compound leverage nippers -- but I think that 1/8" music wire may be a bit too much for them.

Good Luck, DoN.

Reply to
DoN. Nichols

Home heat treating a large lump of mystery metal with some very thin high carbon drill rod seems like a recipe for odd results.

I don't think I'd bother heat treating the assembly. Instead of using drill rod, use some straight or tapered dowel pins. These are already hardened. You mystery metal round bar is likely to be plenty strong to hold the pins.

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Tim Wescott wrote:

Reply to
RoyJ

Thanks Paul -- I've been in there drooling on their stoves, so I know how to find it.

Reply to
Tim Wescott

I bought a pile of ordinary firebricks, used to line fireplaces, at the local brickyard, for something like $1 per brick and no shipping.

When I need to do some hot work, I pile the bricks on top of my wooden workbench and have at it. The wood does not scorch or even get that warm.

I use a layer of full bricks on the wood, and half-bricks on top of the full bricks if I'm making a little forge, usually heated by a big propane-air torch fed from a 10# picnic bottle.

For quick work with the acyetlene-air plumbers torch, a single half-brick on the bench works well.

The common 20# picnic bottles are a bit too heavy for portability with a torch, so I got a half-size bottle for the torch. But I can always borrow the bottle from the gas grill.

Joe Gwinn

Reply to
Joseph Gwinn

As someone that has bent a lot of music wire springs (I'm a locksmith) I don't think you need to worry about heat treating the rod. My bending fixtures were aluminum with dowel pins and the aluminum did just fine.

The trick to bending springs is to figure out how much to bend. If you want a ninety degree bend you have to bend it further so it stays at 90 when you relax the spring. Trial and error seems to work here so if you have a bunch of identical pieces to make, mark your fixture so you know how much to bend.

Reply to
Roger Shoaf

Mark - what do you use for soap? Most of what is called soap is actually a detergent of some type.

Hul

Mark Rand wrote:

Reply to
dbr

What consensus there is seems to be to use dowel pins. Initially I'm going to use 3/16" drill rod ('cause that's what I have on hand, and I have a 3/16" reamer).

But when I do this "for permanent" I'll use dowel pins (why oh _why_ didn't I think of that?).

Reply to
Tim Wescott

Hey, you may know two things that have been bugging me, then:

1: I usually get music wire from the hobby shop; it's K&S brand which is pretty good, but the better sort of kit has harder wire that's less likely to permanently deform on a hard landing. D'ya know where to get a better grade? Or better yet, a nice selection of grades?

2: Any guidance on minimum bend radii? Someone mentioned that a 1/8 pin for 1/8 wire is probably too tight, and I'm just not sure if he isn't right.

Reply to
Tim Wescott

Common or garden unscented vegetable oil based bar soap. Made into a sloppy consistency with water.

Any cheap bar soap that doesn't claim to be good for your complexion will probably do.

Mark Rand RTFM

Reply to
Mark Rand

Just get one of these:

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Cheers! Rich

Reply to
Rich Grise

I have a similar project in my long term list of things to do. I spotted a few cheapo wire benders for sale on the net, but would have liked to have seen drawings or better pictures of what other people have made. Did you find any places on the net with good photos or blueprints?

RWL

Reply to
GeoLane at PTD dot NET

A couple of months ago I wasn't very successful at finding pix of that sort of thing. Can you point me toward a useful URL. I'm considering a similar project to Wes's.

RWL

Reply to
GeoLane at PTD dot NET

This is a bender I made for a job that required a lot of accurate bends in 1/8" Inconel wire.

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Reply to
Ned Simmons

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