Cast steel chisels

[John Holland]

Technical question from new member, any information gratyefully received.

In a number of threads about chisels some contributors suggest vintage cast steel chisels instead of new western chisels. I have happily used a set of Robert Sorby Gilt Edge bench chisels for some years, the steel takes and keeps a keen edge. Even better from my amateurs point of view they have exceedingly comfortable London type handles.

I have also inherited tools from my Grandfather who apprenticed as a railway coach (passenger car in US?) builder when they were made of wood in the 30's. I have his tool box, plain on the outside, fancy mahogany inside, and a number of tools including chisels, some he had new, some second hand so maybe pre great war. They are Sorbys and Wards, marked cast steel.

What is the difference/advantage of these over modern forged O1 or A2 steels, is there a difference in grain sizes? how do they compare in hardness and toughness? I don't use the chisels at the moment but I do find cast steel tenon saws better to use. I cannot even imagine how they cast such thin sections as the saw blades, maybe thats why no-one makes them anymore.

Anyone any information, or experience of how the steels compare?

[harry strasil]

You have to understand the terminology of the time. They didn't have the ability to make high carbon steel as we know it, so they put wrought iron into a sealed box with charcoal(pure carbon) and left in the forge till it blistered, (the carbon adhered to the wrought iron) till it looked like blisters. This Blister steel was then forged under hammers till it blended with the Wrought. Often times it was drawn out, cut almost through and faggot welded back to itself to amalgamate the carbon better throughout the Wrought, This was called improved blister steel. To further amalgamate the carbon throughout the Iron it was often remelted and poured into ingots, That is where the term Cast Steel comes from. It was then forged into different tools and or Rolled out into thin sheets for making saws. The Cast Steel Varies greatly depending on where it was made. Generally it made for excellent tools that would last a long time and hold an edge well.

Before Cast Steel, chisels and plane blades had a Laid On cutting edge, this was a thin layer of improved blister steel forge welded or (laid on) to the Soft Wrought Iron (which has almost 0% carbon content). Thats why older plane blades were thicker at the cutting edge. I prefer the laid on plane blades and chisels as they seem to hold an edge longer than most cutting tools.

[Cliff Rohrabacher]

Today a common term for encasing the metal in carbon is "Diamond Block" The process is used for High Speed Steel in small shops.

In high end or production processes they use reducing atmosphere and molten salt baths in stages.

[Mike Henderson]

To expand a bit on Harry's post, "cast steel" is also known as "crucible steel". The basic process was invented by Benjamin Huntsman, an Englishman, in about 1740.

Iron ore is smelted in a blast furnace which produces a material which is iron with a fairly high carbon content, and a variety of other elements which depend upon the ore used. This material is commonly called "cast iron", or "pig iron" and has a carbon content beyond that necessary for steel. In the time referred to by Harry, that cast iron would be further processed in a forge where it would be repeatedly heated and hammered. Carbon has a high affinity for oxygen so the carbon would be "burned" out of the cast iron, leaving a low carbon iron, generally known as wrought iron.

It's possible to process the cast iron so that not all of the carbon was removed, but it was a difficult, hard to control process.

The first decent technique for making steel from wrought iron was blister steel. First, the wrought iron had to be made from special ores from Sweden which had very low levels of phosphorus. Phosphorus causes the resulting metal to be brittle.

Thin strips of this wrought iron were placed in clay boxes with carbon bearing material, such as charcoal. The strips were layered with the charcoal and the box was sealed so that air could not get in. The box was then placed in a furnace and heated for a long time, perhaps a week. During that time, the carbon diffused into the iron, leaving the characteristic blisters on the surface.

When removed from the furnace, the strips were not uniform in their carbon content - there was much more carbon in the outside than on the inside. The strips were then hammered together, and sometimes folded and hammered, as Harry mentioned, in an attempt to make the steel more homogeneous, but the general result was material that had layers of high and low carbon, leading to difficulties in hardening the steel.

Huntsman was looking for steel that could be used for clock springs and invented the crucible process. He took pieces of blister steel and put them in an air tight crucible which was then placed in a furnace which got hot enough to melt steel. Other materials were placed in the crucible to remove (into the slag) elements which were not desired. The melting of the steel allowed the production of steel with homogeneous carbon content.

This long process made steel very expensive, compared to cast or wrought iron, but until the Bessemer process came along, it was about the only way to produce steel in any quantity (and that quantity was small). Because cast steel was so expensive, it was not used for the whole tool - the tool was made of low carbon steel (wrought iron) and the cast steel was "laid on" (forge welded) to the wrought iron for the cutting edge. That why you see "layers" in a cast steel tool - the cast steel edge usually take a brighter shine than the wrought iron.

Bessemer's process allowed the production of steel in mass quantities but it did not produce good steel. The primary product produced from Bessemer steel was railroad rails. Bessemer steel suffered from phosphorus contamination due to the ores used.

The basic open hearth process came along shortly after Bessemer's process and it could produce decent steel from phosphorus containing ores.

Through this all, the crucible process endured, producing the best steel until the electric arc furnace came along. The last crucible process furnace was shut down in the 1960's.

Mike

[added note - modern steels are generally better than crucible steel because there's much better process control today - the steel is consistent batch-to-batch. In the 1800's the steel produced was variable due to the poor process control - both from the raw material to the heating and melting steps. The one good thing about old steel is that "only the best survived" - meaning that our ancestors probably scrapped the worst steel and kept the best. So your cast steel chisels are likely to be very usable, fine tools.]

[Don C Peterson]

Thanks Jr. and Mike,

Your posts filled in a few gaps in my understanding. It all makes much more sense now.

[Dan Racette]

Thanks guys.

Would it be too bold to say that this is a rudimentary comparison to the Japanese laminated steel process, or about as close as it gets for EAST to WEST comparison?

The reason I suggest it, is the working of the elements together to create a stronger product, and the keeping of the softer product just off of the cutting edge. Or is it much different and that's why the Japanese process still is used today?

Just trying to bring sense to the whole metallurgy, in an almost basic sense. Of course the Japanese process is very much more handworked, and I mean no sense of dishonor to the craftsmen, if the comparison is inappropriate.

Dan

[David DeCristoforo]

In a very, as you say, "rudimentary" way, yes it's the same principal. A thin layer of harder steel is laminated to a softer one.

YM

[Mike Henderson]

The Japanese process of layering is done for a different reason than cast steel was layered. Cast steel was layered on only for the cutting edge because it was expensive - if it had been low cost, the whole tool would have been made of cast steel. The steel the Japanese use for chisel edges is not expensive - it's pretty ordinary commercial carbon steel.

The reason Japansese chisels are layered is that the carbon steel edge is heat treated so that the carbon steel is much harder than western chisels.

Now, let me divert for a minute. To make a good cutting tool, you need two things in the steel: Hardness for edge retention (so the edge doesn't "mush" or "roll" in use), and Toughness to stand up to shock (being pounded on without chipping). If you heat treat steel to be very hard, it loses toughness and becomes brittle - when you pound on, or pry with, the tool, the edge may chip. Western chisels choose a level of hardness that also provides a decent amount of toughness.

Japanese chisels, on the other hand, choose a level of hardness for the edge steel that sacrifices toughness. If the Japanese chisel was made just of the high carbon steel, and hardened to the level that Japanese chisels are, the tool might fracture in half if you dropped it on a hard surface, or pried with it.

So what the Japanese smiths do is make the bulk of the tool from low carbon steel (which won't harden) and lay on an edge of carbon steel. When the tool is heat treated, only the working edge hardens.

In use, the softer low carbon steel absorbs shock and does not fracture. It's an attempt to get the best of both worlds, hardness and toughness.

And now, some personal observations and opinions. I bought some Japanese chisels in my never ending quest for the perfect chisel. I did not find that the edges held up any longer than my western chisels, or at least not so much longer that I noticed. I also found that it's easy to chip the edge of a Japanese chisel, which puts you back to the coarse stone to take a fair amount of steel off to repair the edge.

My present "best" set of chisels are the LN chisels. They have certain shortcomings but (1) they take a good edge, (2) retain that edge for a decent amount of time, and (3) have a socket for the handle which allows you to easily make your own handles to suit your hand.

#3 is one of my complaints about Japanese chisels. They're hooped on the end which makes them uncomfortable in my hand, and the way the handles are joined to the iron it's very difficult to make new handles. I wish the Japanese smiths would try new things and offer their chisels with sockets so that the customer could easily re-handle them for comfort.

Mike

[David DeCristoforo]

"I wish the Japanese smiths would try new things..."

GASP!!!!

YM

PS It's true what you say about the Japanese edge tools being almost "too hard" and therefore "too brittle". But remember that most traditional Japanese woodworking was done in much softer woods than were commonly used in "the west", lots of pine and cedar which is much easier on the edges.....

[John Holland]

Thanks for that information, based on that it's got to be worth cleaning them up and sharpening them for use.

Also tools like this are still abundant at boot sales and the like and cheap to boot, so i shall fill in the gaps.

[Pam Niedermayer]

...But remember that most traditional Japanese woodworking was done in much softer woods than were commonly used in "the west", lots of pine and cedar which is much easier on the edges.....

And then there are Japanese white oak, red oak, hon red oak, gumi, tsugi, .... Are these woods are used in applications that don't need planing and/or chiseling?

Pam

[Pam Niedermayer]

...And now, some personal observations and opinions. I bought some Japanese chisels in my never ending quest for the perfect chisel. I did not find that the edges held up any longer than my western chisels, or at least not so much longer that I noticed. I also found that it's easy to chip the edge of a Japanese chisel, which puts you back to the coarse stone to take a fair amount of steel off to repair the edge....

Who made your chisels, Mike?

Pam

[Mike Henderson]

Who made your chisels, Mike?

Pam

Don't know/remember, Pam. Two sources, though.

Mike

[Mike Henderson]

[snip]PS It's true what you say about the Japanese edge tools being almost "too hard" and therefore "too brittle". But remember that most traditional Japanese woodworking was done in much softer woods than were commonly used in "the west", lots of pine and cedar which is much easier on the edges.....

Yes, I'm sure the Japanese chisel was developed to best meet the needs of the craftsmen who were working in that wood. My woodworking instructor commented something similar - he said that soft wood requires a very hard edge, while hard wood requires a softer edge. Maybe what he meant was that working hardwood requires a chisel with more toughness, rather than a harder edge.

Mike

[Dan Racette]

My experience has been different.

I have not liked my experience with A2 steel, of which the LN chisels have. I have found that they are initially sharp, then after about two slices, they are at about 80% capacity, and they stay at that capacity for a very long time.

I have found that HCS gets a much keener edge, remains at "100%" much longer, but you have to go back to the stone much sooner, than A2. For example, time and time again, I've seen the two cherries chisels not be able to get as sharp in the same techniques as a marples or a ashley iles. The marple, being of pretty mediocre quality.

I have also found the opposite to be true with Japanese chisels. The one or two experiences that I have had with "marked" chisels, that is chisels that are marked with a makers mark, and sold in Japan, have been nothing short of stellar. The one mokume, unbelieveable. I should underscore that the person that sharpened these had years of experience that I do not have. NO gadgets, no guides, etc. I have a couple of "western" and couple of "japanese" chisels but they come from various dotcom sources and they would be what I represent as the "bud" and the "miller lite" of the finer chisels (so I guess in beer terms, more the sam adams, higher up than bud). So I guess I am saying to Mike, that I wouldn't judge 'all japanese chisels' based on an American dotcom purchase of a sub $100 chisel. (no offense Mike if that's not what you did).

Why I posted about cast steel, is that my great grandfathers swedish cast steel plane recently came into my possession and I noticed that it wouldn't sharpen on my PSA paper, and only my waterstones/diamond stones. I also noticed it held a great edge and I haven't quite determined it's quality of cut. I was wondering about the rudimentary comparison to Japanese method of hammering and combining metal for strength of edge characteristics to see if that's why I might be getting the same results.

So, right now I am pursuing one paring chisel, based on experimentation, trial and error, buying and selling, I would say that there are several candidates and the only "western" candidate is a Barr Tools, at least that I have found. The others are all Japanese, and need me to be saving for some time.

Just my feelings and observations so far.

I'd welcome friendly comment.

dan