Examining a Later Stanley Iron – Rehardened – How Bad? Not as Bad as the Reputation

Yesterday, I posted about a laminated Stanley iron and my surprise at just how high carbon the iron is. It was not well behaved in rehardening, but the ultimate finding was that with routine 400F tempering and a fast oil (and good technique), the iron yielded very high hardness and it’s closer to a Japanese white steel than anything else (albeit, the carbide density looks more like a white II type steel).

So, looking for a solid iron from a “good” era of stanley tools, I found that all of the good-shape irons that I have are laminated except for a type 20 iron from a later 6. This irons are notoriously bad, but in my experience, they feel like they are slightly lower carbon and just tempered soft. I don’t know what Stanley’s market was in 1960, as in, who they were aiming for – but I can imagine that few planes were being sold for fine bench work. Regardless, I have a soft spot for types 20 and have three of them. Once they’re flattened, they work wonderfully. I’ll post a flattening process at a later date – it’s useful if you’re going to work entirely by hand as it speeds dimensioning and you can rely on the plane to communicate when something is flat.

The Conclusion for the Type 20 Iron

Since my posts go long, I’ll tell the findings first, and then the details. The type 20 iron (in this case, one with sharp corners and not rounded corners) is solid and not laminated (no surprise), it does not have surplus carbides appearing in the wear matrix (so it’s likely something around 0.9% carbon or below – I would guess a little below that based on resulting hardness), and when it’s given the standard routine and double tempered at 400F, the resulting hardness is good, but well below the old laminated iron. I would estimate it at 60 on the C scale as the india stone hones it readily but it hones finely on a washita and has excellent behavior.

It won’t be a long-wearing iron compared to anything with abrasion resistance, but it hones well, takes a fine edge, holds it and would probably be a better iron for someone working entirely by hand than something like A2 or V11 (because in heavier work, just the course of regular honing should keep the edge free of damage). In nearly all cases, a modern iron with chromium in it in significant amounts should outlast this iron all other things being equal.

Now, the Details

You may wonder why I’m rehardening these. It’s really a matter of three reasons. I use the same rehardening process for simple steels every time. The process should improve anything that doesn’t have surplus non-iron carbides, and where the iron lands in terms of hardness after a 400F temper is a good indicator of how much carbon is in it. Plan irons are thin, and with fast oil (Parks 50 in this case), it’s not hard to get good full hardness results with them.

Irons that end up with lower hardness (testing with an india and a washita stone – two stones that will give good feedback of how hard a simple steel is), generally do so due to lower carbon. There are often other things in smaller irons, but not in large amounts (perhaps a small amount of vanadium, some small amount of chromium, and in older irons, sometimes tungsten). These change the feel on a well used sharpening stone.

So, anyway – reason 1 is to see what the hardness will be after a standard process. Reason 2 is that I’ll probably like the actual iron better after rehardening (if I don’t, there’s no real hope for it). And Reason 3 is to see how practical it is to reharden.

I would estimate the hardness of the iron in this case to be around 60 on the C scale. I doubt i’m off by more than 1 in any hardness guess with plain steels. I expect off of the stone that we’re not going to see excess carbides unless they look like chromium carbides. The one plain steel that would have excess chromium is a bearing steel, but this doesn’t feel like a bearing steel. So I really don’t know.

The iron is improved for bench work – which is pleasant since it’s such a poorly regarded era – and would now make a really wonderful day-to-day iron. It’d be great if it hit high hardness like the old laminated iron to have a biting sharpness off of natural stones, but it still attains a nice edge and is practical. Why did stanley leave it softer than this? I don’t know. The demands of the market, perhaps, a nod to sharpenability (a softer iron will always sharpen faster and easier, no matter what it is), and maybe margin of error as a chippy iron will yield complaints while one that’s slightly too soft may result only in a few groans. I’m convinced the world of consumer knives is filled with underhardened knives to prevent damage that results in returns from low-experience users as it seems fairly easy to better commercial knives with shop made knives. Even marking knives.

The Initial Edge and Carbides

After rehardening, the initial edge comes off of the washita stone relatively fine. Use of this stone is a preference because it’s got such a wide range as long as steel isn’t too soft or far too hard for it (it’s a great tip finisher for japanese chisels, though). A picture of the initial edge is here (you can see a tiny burr left – that burr is probably about a thousandth of an inch long).

A fine edge off of a washita stone – with a minimal burr left. The height of this picture is 1.9 hundredths of an inch, so this burr will depart with first use, but it’s better to remove stropping.

This edge looks a little strange, but it’s safe to say it’s at least as good as an 8k waterstone. Looking at the other anomalies, I flattened this iron quickly after rehardening – the back is near polish but some of those marks are probably dirt or oil.

A comparison of washita to an 8k waterstone will be shown at the end of this as you can’t tell how fine this edge is without a reference.

The thinness of shaving possible from the edge shown above is in the next picture. I didn’t strop the edge, but it’s a good idea to – and doing it very lightly with a very fine oxide on wood or hard leather (or a buffer) is even better.

This is a reasonably fine edge and can be recreated in less than a minute once the iron is dull (which is the advantage of an iron that’s not that abrasion resistant). The steel is fine, there aren’t edge anomalies, overall very pleasant.

Confirmation of Carbides

The stones don’t communicate any significant abrasion resistance or slickness, and the hardness suggests we won’t see any carbides emerging in the matrix. A picture of the matrix after planing 300 feet of cherry edge follows (and shows no significant free carbides).

The matrix shows no free carbides, suggesting the carbon content isn’t well above 0.8%. We start to see free iron carbides in steel that’s got 0.9-0.95% carbon, but not below that level.

All in all, a pleasantly good iron, but safe to say, it’s not a flawless diamond just waiting to be rehardened. That said, if you look at the edge wear (the wear picture is at twice the magnification of the original edge, so the picture’s height is less than a hundredth of an inch top to bottom), you see wonderful uniform wear. This leaves little for you to do resharpening other than remove wear. Nicking in irons generally goes about .001″ to .004″ deep (any number of nicks greater than .004″ deep makes it difficult for an iron to start a cut, thus you’ll have to do something catastrophic to see that). Minerals, silica, dirt, knots, etc, can create the typical depths mentioned. It takes a while to hone them out, and in the picture above, they would pass through the wear strip in some cases. That wear strip does not need to be honed off to refresh the iron – at least not its length. Flattening the back and honing off somewhere around .001″ of length on a completely dull iron will do the job.

Overall, nothing groundbreaking – but the iron above is a good iron and holds up its end of the bargain in sharpening vs. edge life (which is to wear uniformly in proportion to sharpening time). If I have to make a guess at carbon content, I’d say 0.8%, though I don’t think it’s 1084 – it feels as though there are a few additives – probably to make it easier to harden and temper fully. Behavior in rehardening was fine and post-heat treatment re-flattening only took a couple of minutes. Less than 5 minutes total to get to the edge shown above.

I also rehardened a block plane iron (the only iron that I may have that’s solid and between the later-make stanley and earlier laminated iron) and a “Made in USA” 750 style chisel. I’ll post those in the next several days.

A Comparison of Washita to Waterstones

It’s difficult to make a blanket statement about washita stones. I love them (the real ones – and the real ones are no longer mined and won’t come with a label like “CASE” or “SMITHS”, etc, though old enough smiths may have slipped a few in, it’s not a great bet.

A washita stone can be slurried to cut fast, it can be used with heavy pressure or it can be used with light pressure and in combination with steel hardness, you can end up with an extremely fast sharpening routine that is pretty much zero maintenance. Less than a minute for chisels and about a minute for a plane iron that’s very dull. The touch sensitivity and wide range makes it an ideal stone for an experienced user.

Over the years, I’ve had several hundred sharpening stones (probably a hundred synthetic and 300 or more natural stones). At one point, I brought in and resold (generally at cost) japanese natural stones – I just like sharpening things, but not for no reason, and I don’t like jigs or finicky things – I like methods that save time and get results.

To get on with it, I never read about using washita stones other than that a lot of people like them (and then move on to something else, but these folks are always moving on to the next thing a retailer says is great – we’re not looking for that here). It didn’t take long to find the dimension of these stones and see how fine they are. A slurried waterstone has much less dimension (synthetic types) and one of the reasons beginners like really hard irons and waterstones is they have no feel, no sharpening sense.

Next is a picture of an edge gotten off of an 8k grit waterstone (one marketed as “kitayama”). Notice not so much what’s on the back of the iron, but at the very edge and how straight the edge line is, and how many scratches interrupt it. You can see from the edge wear photo above that scratches on the edge don’t matter much – on a good iron, the wood just wears them off, and you’ll never see their effect – the edge itself is leaving the finished surface.

Shapton Cream (12,000 Professional):

The shapton cream is a stone that claims to be 12k, but I think particle size variation makes it more like an 8k waterstone. A quote of 1.12 or 1.2 microns is given, but many of these scratches are much larger. The variance gives speed, though – it’s otherwise a fair trade off. Again, note the torn nature of the edge.

Washita on Stanley ‘Made in USA” chisel:

First edge on the rehardened stanley chisel on a washita. Scratches don’t look much different than the stones above (which should be a surprise based on grit charts. Finishing the edge for ten second with a light touch shows an edge even-ness little different from finish waterstones, but the scratches are shallower.

Sharpening fineness vs. claimed fineness is really interesting once you get a microscope. There are stones that are closely graded and very fine (like sigma power 13k and shapton 30k), but those stones give up speed for fineness and end up being less practical in use.

A picture of a sigma power 13k edge is below – this stone claims about 0.72 microns, and does appear to be closely graded.

Sigma Power’s 13K stone does look to be closely graded, but it pays a price – it takes a long time to get this finish to the edge of a tool replacing all prior scratches unless you come from another coarser finish stone first. It’s about 1/3rd to 1/2 as fast as the shapton 12k professional, and is a bit soft and easy to gouge, so you can’t just use a really heavy hand.

If you need a fine edge following something like the washita (finer than shown), 10 seconds on MDF or hardwood with autosol yields this:

Autosol after Washita. Inexpensive, just as effective as the very fine grit sharpening stones and at least as fast (faster in this case). The polish is so bright that I should’ve turned the exposure down when taking the picture. Black spots at the edge are dirt. It’s actually pretty difficult to get all of the oil (and then clothing fibers) off of an edge to get a good clear picture.