Failure to get sharp

I don't see any mention in your process of quenching after drawing the temper in the toaster oven. Did you quench it? Buy an oven thermometer, they are CHEAP. I use a garage sale toaster oven to draw temper on A-1, and to cure Teflon-Moly gun finishes. The oven thermostat on mine is off by about

30 degrees F compared to 2 different oven thermometers. It makes a difference.

Are you sure a toaster oven will get hot enough to draw W-1?? I thought the correct temp was on the 475-525 range to achieve Rc 60 or so?

Bill

I agree. Given what follows, the most likely suspect is honing technique. Without knowing your proficiency at honing this kind of edge, it's hard to say, but if you don't raise a wire, you're simply not going to get a very sharp edge.

Are you honing both sides of the edge? What is the shape of the blade? If it's a woodworking blade like a plane iron or chisel, are you flattening and honing the face (I.e., the back) first? What type and grit of stone(s) are you using?

So, it's safe to assume W-1.

Now it's hard. So far, so good.

Ok...

Between hardening and tempering? Or before hardening (heat/quench)?

Generally, rough shaping/grinding is done before hardening.

It's unnecessary to exercise so much caution before hardening. Finish grinding (after hardening and tempering) is a different story; overheating will ruin the blade's ability to take an edge.

If you cleaned the steel between hardening and tempering, it appears that the true tempering temperature was under 400. No matter, though, that's a good temper for edge tools.

If you don't overheat the edge while grinding, it won't affect the maximum sharpness that the edge can take. However, it's generally a good idea to temper immediately after hardening, to prevent other bad things from happening. Rough grind before heat treatment, finish grind and hone after.

It used to be hard for me to get a razor-sharp edge on my plane irons and chisels. Eventually, I just got the hang of it.

No. Even at full hardness (no temper), that could not happen with this type of steel at the grit ranges of any stone intended for honing.

Possibly, but there's not enough info here to know. You've got (or you had) the thermal processing well enough in hand to make a good edge tool. The clues to that are (1) you identified the type of steel, (2) you got it hard (file wouldn't cut it), (3) you succeeded in tempering it (pale yellow color, and the tool didn't break), and (4) you didn't destroy the temper (no temper colors while grinding). That pretty much leaves honing.

Good luck,

Jim

It could be excessive hardness (unlikely, given your tempering method) or excessive grain-coarsening. This is quite possible. More to follow.

Any water-hardening steel has enough hardening versatility that it will make no difference at all which one it is, given your crude...er, home-shop hardening methods.

Two points to consider here. Firstly, heat-hardening with a torch is very tricky business. "Red hot" means different things to different people, under different light, and in different moods and degrees of patience.

If you want to calibrate your eyeballs, take some cheap piece of plain, high-carbon steel, cut it into four or five pieces, and heat each one to a different degree of "red," immediately quenching it in water. Try your file on them. The first one up the "red" scale toward yellow that puts up real resistance to your file represents something close to 1400 deg. F. That's your starting point.

If you don't do this, the only way to learn what "red hot" is, is to keep making mistakes until you get it right. Don't rely entirely on your magnet. The actual (as opposed to the theoretical) critical temperature is slightly above the temperature at which most magnetism disappears.

It's very difficult to hold a consistent temperature that long with a torch. But you don't have to. With steel that thin, as soon as it's the right red, it's ready to quench.

Even a short period of holding it at an excessive temperature (an extremely short period, if you go more than 200 deg. F or so over critical temperature) can coarsen the grain. That will make the steel weak and brittle, and can make it difficult to sharpen. There is nothing you can do to fully correct this problem unless you anneal the steel, hot-work it, and then re-heat-treat. Even then, you'd better know what you're doing, or you won't get the grain-coarseness out.

Don't stir. Plunge. If you make a lot of blades, get a 5' piece of soft copper tube, drill it full of small holes, squash one end flat, and (using a plumbing adaptor), solder the other end to a hose fitting. Coil the copper into a coil 3" in diameter and a foot or 18" long. Attach to garden hose, or, if you're lucky, to the faucet on your laundry sink. Turn on water and you'll have a great spray inside the coil. Plunge your heated blade into that, and you'll get quick, even quenching.

I made mine in less than an hour.

A cheap oven thermometer will be worthwhile. Toaster ovens tend to run on the cool side of nominal.

You oven is cool.

As often as not. I finally bought a dozen firebricks and I set them up into a crude oven when I need to heat treat something like that. Two propane torches supply the heat. I use the same bricks laid out flat to make a take-down brazing/welding table.

If you can't get the edge to curl, it may be too hard, or the grain may be too coarse. Unfortunately, the test for either -- breaking the blade in a vise -- produces a similar result either way, except that, with experience, you'll be able to tell a blade that's grain-coarsened from one that's just too hard by the way it breaks. But the latter shouldn't be a problem anyway, because you'll see tempering colors as soon as you've reached a useful tempering temperature.

I suspect coarse grain. But that's not certain.

Soft steel often will take a very nice edge, if the grain is fine. It just won't hold it.

There's no need to. With water-hardening (or oil-hardening) steel, quenching after tempering has no effect at all.

Ed Huntress

Twenty degrees (total angle between the faces) is awfully small. Try 30. I'm a violin maker, and I care about sharp, and I use 30 as about standard.

Ah, that did not occur to me.

OTOH, W-1 ordinarily has a rather fine grain, doesn't it? And it's quite a forgiving material to work with. I've made numerous good edge tools successfully in it with methods just as crude (home-shop ) as those of the OP. I don't doubt that I have occasionally overheated the steel with no obvious ill effects.

Of course, I must say that overheating during hardening definitely does something, and I believe it is what you are talking about. I think I have witnessed grain growth in particular (ahem), by intentionally breaking pieces just hardened at various temperatures. The grain pattern at the fracture looks distinctly coarser or finer, depending on the sample. Am I really seeing variations in the molecular grain structure, or is that something that requires magnification or sample preparation techniques. If that's not what I'm seeing, then what might it be?

Jim

The woodworking edge tools I make range from 11 to 35 degrees included angle, with most in the 25-degree range. Just for reference.

Jim

Alternatively, if you're in the market for a multimeter, you might buy a Fluke 16, which comes with a thermocouple. Fluke specs are: Range 15 to 750 °F, Resolution: 0.1 °F, Accuracy: 1% + 1.5 °F typical.

It's a fun toy to boot. There are lots of things you'll find to measure. Did you know that there's a significant temperature gradient in a cup of boiling water (as heated in a microwave oven)?

R, Tom Q.

Yes to both. But you can coarsen the grain by overheating, and it doesn't take a lot of overheating to do it, if you soak it for more than a few seconds. Water-hardening (essentially plain, high-carbon) steel is forgiving, tolerating some mistreatment, but it's also quick to go to hell if you mistreat it beyond its limits.

I switched to oil-hardening for small tools years ago, mostly because quenching is less critical.

You're seeing grain. I don't know if the actual texture reflects individual grains, but there is a direct correspondance between grain size and the visible coarseness of grain at a break.

Ed Huntress

Yeah, a good fine grain won't be visible, it'll be an even gray; coarse grains might tend towards a sparkley or salt-and-pepper(!) texture.

Tim

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

I hear that. I can't get anything sharp unless I have sharpening jig attached to it and the angle ground is very consistent.

A society that teaches evolution as fact will breed a generation of atheists that will destroy the society. It is Darwinian.

Ummm. I was supposed to quench it in water again after annealing rather than letting it cool in air like I did?

The annealing temp looks about right. I was planning on 500º. The only reason I was going to use a toaster oven is that I saw it used in this fashion on another web page - Alden Hackman's Hurdy Gurdy building web site.

I have an oven thermometer on my shopping list. I won't have any time to play in the shop again till next weekend though.

This afternoon I got an inspiration. I grabbed my Lee lead melting furnace and lead thermometer. I managed to get the lead down to about

550 at which point it solidified. I set one of the blanks on the hot solidified lead and watched it change colors. I drew it to dark straw and then quenched in water - not because I knew to quench it again - I just assumed it wouldn't hurt anything. The color change occurred over several minutes - probably 15 or so. I was able to get the edge a little bit sharper, but not like the commercial one.

RWL

******* Remove _NOSPAM_ to reply via email *******

The blade is flat on one side and bevelled on the other to a 20º angle. Once I got it semi-sharp on the 3650 RPM grinder, I switched to emery cloth glued to heavy glass plates - ala Scary Sharp system. I must be doing something wrong, because it's not working for me.

I draw the blade away from the pointed edge over the emery cloth under pressure and gently slide it forward for the next stroke maintaining the angle the whole time - it's a broad enough bevel that it can be felt and held on the plate. After a few minutes of this stroking, I flip it onto its back / flat side and draw it away from the cutting edge.

One thing I've noticed is that the emery paper gets dull pretty quickly. I'm only using strips about 3" wide and 6-7" long. I'm using 100, 180 400 and 600 grits.

Hmmm. That would be a lot more convenient because I wouldn't have to worry about drawing the temper while grinding if I did the lions share before hardening and tempering. I was afraid to do that because I worried that I'd burn the edge / burn the carbon out of the steel at the edge when heating it to red hot on the initial hardening.

Thanks Jim. I'm strongly beginning to think I must be doing the honing wrong.

RWL

******* Remove _NOSPAM_ to reply via email *******

No you misunderstand. Process should go: Shaping, Anneal, Harden, Temper, Honing. Annealing works best in a medium like sand, ash, or virmiculite (though it depends on the steel). For W-1 Harden in Water. Temper to strawish colour and then quench in water for W-1. Then Honing using stones or sandpaper.

There should be no need to anneal water-hardening steel before heat-treating it, Ken. For high-alloy steels, yes, particularly for high-speed steel. But, unless the steel is really screwed up to begin with, water-hardening doesn't need an initial anneal.

Also, quenching in water at the end of the tempering step does nothing at all. You may have seen it recommended to terminate the transfer of heat when you're using the selective-tempering method. In that case, you need a quench to keep too much heat from reaching the edge, or whatever part you're trying to leave the hardest. But it's completely unnecessary, and completely ineffective, when you're tempering the piece to a uniform temperature, whether you temper for a short or a long time.

Ed Huntress

Tempering is *not* annealing. It doesn't matter whether you quench or not after tempering. It is a convenient way to stop the colors running if you're differential tempering, but otherwise you can just let the piece air cool.

Gary

Ah but he was doing differential tempering before hand, using a torch, and that needs to be quenched to stop the heat from the back of the blade travelling to the edge.

as to the Anealing, tempering ... he's been told a few times :-[ he'll get it soon ;-)

heat-treating

Depending on the tool size, I think I might at least normalise prior to hardening it, to be sure of a consistant grain size.

Oh Lordy I hope so. I can't believe I used the wrong term in the post. I meant tempering. Red faced and crawling under lathe bench.

RWL

******* Remove _NOSPAM_ to reply via email *******