Month: February 2022

“The” Hardening Process – #1 – Which Steels

In the process of learning to make chisels, I decided that I should see if my chisels could match commercial chisels. In the back of my mind, making something and having it work less well that well established tools (in this case, late 1800s English chisels, or earlier or later if the characteristics are similar) isn’t very satisfying. The why of that is because I’ve now thrown away most of the early tools that I made. They were fun to make, but you realize unless it’s going somewhere, it’s just leisure time wasting and you end up using purchased tools. What’s “going somewhere”? Well, you do almost always need to make something lacking to learn what to correct so that it’s not.

I ended up matching or bettering all of the new and old chisels that I have except for japanese types, and perhaps in some cases (For example, HSS chisels always seem to fare better if they’re introduce to trimming metal and wood junctures). But in this case, we’re just talking about normal wood and “normal” use (chisel goes straight into wood or slices it).

How? This process is what I ended up with – it’ll take more than one post, but it’s not that complicated and doesn’t require anything expensive. How good can the results be? As good as commercial heat treatment, and with some steels, maybe better. But more importantly, you’re doing the hardening, so there’s no pooling lots, finding out that someone chose a different spec for hardness because they weren’t paying attention, etc. All I can really do in the shop is snap steel samples and see how small the grain is (which is good, but not always perfect – the composition of the steel itself can make comparing two samples difficult. An example of this is 26c3 or white steel vs. O1. The two former types will have carbides in them (carbon in this case) and larger visible grain than the latter, but samples of 26c3 end up with a better hardness/tougness profile. )

To cap things off, I guess you have to have samples analyzed. I have sent samples of 26c3 and O1 in to be tested by a metallurgist who specializes in knife steels and I can match the results for ideally heat treated O1 and better them for 26c3. The fact that I can means you can, too. There are no secrets here – if I wanted to really perfect this and market it as a proprietary process, it wouldn’t be disclosed.

What Steels?

This is a process for simple steels. That means iron and carbon and a small number of additives that improve iron carbides, but that do not result in free carbides of other types. This includes:

  • 1084
  • 1095
  • O1
  • White 1 / 2
  • 26c3

This does not include 52100, A2, D2, M2, etc. Anything that involves chromium carbides or more than just a little bit of tungsten (O1 has tungsten, but not in large amounts), vanadium, etc, is not something that this perfects. I have had OK luck with 52100, but it’s a high toughness steel and it probably benefits from a long duration soak before quenching. That’s something you just won’t want to bother with long even if you had bionic eyes – I don’t think good things happen in the open atmosphere with steel held at high temps.

Before the Process – What if You just Want Simple?

Good quality O1 steel from a good name (bohler, starrett, etc), cut something with the grain oriented to the length of the item, heat it to nonmagnetic quickly, then allow it to heat a color brighter (so if red when a magnet stops stick, allow it to get to orange quickly ) and then quench in clean oil until all the heat is gone, wipe off and then temper in a kitchen oven for an hour at 400F.

That’s simple – it works, no expensive oils, no temperature holding. YOU ARE NOT A FURNACE, so you will go off the rails if you read commercial schedules and attempt to duplicate the numbers by eye. All open atmosphere heat treatment before quench involves getting to temp quickly and uniformly, overshooting a little and then quenching.

If your oil is warm when you quench, toss whatever you’re making in the freezer for half an hour when you’re done, or dip it in ice water. You’ll end up with better hardness.

What about the Knife Steels with Lower Carbon?

I don’t use them – if you’re into knives, I don’t know what optimizes them, but nothing in the process will harm them. For tools, steels that aren’t super high toughness but that attain a certain property at higher hardness are better. Toughness can lead to folding or damaged edges hanging on and that’s not great for use in working wood- we want damage that occurs to leave and be sharpened away later vs. straightening an edge and moving on like can be done with knives.

If you’re into tools, don’t allow someone to tell you that you should be using leaf springs or 5160 bar stock. It’s not the right thing for chisels and plane irons (better for a froe, hatchet, axe, machete etc).

Black and Purple Hone Slates

The title of this is a bit more general than it should be, but because I don’t think each of the separate hone slates is worth a full post. Lumping everything into one covers a lot of territory. As far as I know, the Water of Ayr is a slate, the purple hones that originated in Wales (often with little light green streaks or specks in them) are slate, and slate is found all over the world, so there are probably many many different regional slate hones and some slates that just aren’t very good at all.

Water of Ayr stones in a size useful for woodworking are probably enormously expensive now. I’ve got a couple of unlabeled small hones that are probably that, and one large hone that may be (not categorized here, because I’m not sure that it’s WoA). The suddenly valuable Eschers are hone slates (thanks to shaving forums, what was a $100 labeled collector’s stone quickly went to $600-$900 – the usefulness of those stones for razors vs. anything else is closer to the $100 range, but they are very uniform in characteristics, which makes them safe for a newbie- at least safe other than price).

For this post, I’ve chosen to show the work of two hone slates – a lower value unlabeled black slate that leaves a cloudy surface on steel, and a dandy little purple hone slate that I got from a very generous forum user and that I treasure for razors (even though razors rarely need to be sharpened).

Before showing the pictures, what’s the deal with the slates? They have limited cutting ability for their level of fineness, but can be very fine. It is *always* the case that a fine stone can be set up by a prior stone that’s much faster and slightly less fine, and in the world of japanese stones, the dippy fascination with a stone that’s “really fast and fine” is often bettered by getting two old used stones – a prefinisher, and a very fine and slow finisher. The latter combination may cost 1/6th as much and work twice as fast in combination, and also result in a finer edge. This is the case with hone slates, though they do vary somewhat in cutting power.

They do also like a slurry – stones that are a little slower quite often work well with a slurry and the same relationship holds with all stones – generally the slower a stone is when not slurried, the larger the disparity slurried vs. “clear water” on the surface. There are a few stones that are slow even on a slurry (chinese agate comes to mind, and reminds me that the agate may make a good base stones for loose diamonds, as it’s punchless on hard tool steel).

What am I moving toward? Like coticules, there’s no great reason to buy slates. There’s no reason at all to buy random slate stones that may look like a black arkansas stone.

Another forum user also gave me the coarse stone in the following two pictures. So, on to the pictures.

Compare these pictures to an 8000 grit Japanese Waterstone

First, a coarse black slate

Black slate, likely home/farm made for economy. Not a terrible looking edge, but not a fast stone compared to well established types and not capable of creating a “close” edge that can just be hone stropped or used straight off of the stone. This is a slurried result, but the stone itself isn’t hard and it will slurry on its own (like blue tanba aoto).

Compare that to a fine vintage purple hone slate (suitable for razors)

Fine purple slate honed edge. Also slurried. At first glance, this doesn’t look that much finer than the picture above, but look again at the crispness of the edge and lack of rounding.

I have the benefit of using these stones and learning what visual cues result in use differences. I realize looking at the picture above leads you to see mostly the bevel itself and not the edge. But just as a tip here, compare the evenness of the edge and the shadowing that occurs at the top edge. It’s not really a shadow – the coarse slurry slightly rounds the edge but without leaving it that fine – that’s an artifact of the rounding. That is, the light from the microscope isn’t reflected back. A little bit of rounding might be nice, but only when the edge is fine.

When the edge on one of these pictures looks completely visually uniform and there’s no shadowing at all, you are moving toward something that would probably win a planing competition.

If you’re out hunting flea market stones and you see older stones that are black with tiny little sparkly specks and extremely smooth, those could be Water of Ayr and are worth picking up if they are only a few dollars (you can always offload them on ebay). If you see a small very smooth purple stone (vivid purple), especially if there are little mint green bits in it, same thing – just buy it. Anything else that’s slate without a label is probably not worth your time.

A guitar…

This isn’t really a guitar blog, but one of the things that I want to do along with continuing to make tools is to get better at making instruments and then branch out beyond guitars (potentially to violins and mandolins, supposing I have the nerve, time, money and initiative to do it in the future – at 45, it’s easy to tell that I have more focus and patience as a kid, but getting turned around thinking about something is easier. Or maybe it’s just also the case that with age comes more intolerance for mistakes and desire to not abandon projects)..

At any rate, this is my first carved top guitar. Indian rosewood top, limba back (to get good low/mid density one piece honduran billets these days is tough, and limba has the nice open low note when tapped that honduran mahogany does).

The neck is hard maple. The hardware is all good stuff (nothing cheap, but nothing weird, either – just tone pros stuff, grover keystones, bourns pots, good wiring and seymour duncan antiquities, which I don’t like the look of. Duncan makes these in “not distressed” version, but a guy who buys used pickups is also a guy who will get distressed when that’s what’s available used).

If this guitar ever makes it out of my hands, the instant assumption will be that the rosewood is a veneer over who knows what under…finding an 8/4 wide board of rosewood that I could justify was a stroke of luck. The equally showy maple cost very little and the limba was a steal (a 16″ wide dead QS board for $170 that I found on ebay years ago – but the board is big enough to make three bodies like this plus some and it’s a little heavy for limba, which puts it in the range where you’d expect mahogany to be).

The result is this guitar is acoustically snappy, filled with all sorts of little unwanted evidence that it’s hand done (that’s sloppy when seen close up, with little mistakes).

It’s a guitar that was designed to be made with carving/duplicator machines, pin routers and jigs and some hand fitting and belt sanding. And there are a few doofuses like me, I’m sure, who want to do it mostly by hand with bits by eye wherever possible.

Maybe it’s OCD, but I can’t build the “keep it moving and use the patterns and power tools” way – I’d need to build 5 at a time to trust at least a couple would turn out OK.

This guitar won’t satisfy purists – especially the peghead design. I didn’t want to copy Gibson’s open book style as I don’t think I’ll ever sell this guitar, but that may change in the future if I make a whole gaggle of things. Listing a guitar with a copied peghead pattern is not a good idea – especially if it’s one of a number of companies (Gibson is definitely one of them).

Working by hand provided the freedom to do a lot of this. planing blanks precisely, match planing top wood precisely and not fearing using a top wood board that is expensive and will be hard to replace. Using incannel gouges to cut the celluloid inlay, working to a thousandth or two when needed, and just to eyeball on others.

I can’t imagine what this would be like without purposely focusing on the freedom of working unjigged elsewhere.

Oh, and the finish? Buttonlac. It’s going to shrink a little and at a later date, I’ll take the stuff that sticks up off of the body and refresh any pores that appear.