Cast Steel

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Bedrock

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Having gone in search of an old chisel to "Bill Carter", I chanced upon a 1"Marples firmer chisel, without a handle, in the damaged chisels drawer, which cost me £1. Having cleaned it up and had a better look, I am now thinking it deserves more respect, and probably a new boxwood handle.
The thing I'd like some advice on is that the bolster is nicely round, rather than forged, and the tang has clear mould marks, across the horizontal axis, which suggest to me that it may well be "cast steel".
How was this made and of what? My current assumption is that the steel was cast and the blade section then forged to shape and ground.
The imprint is very clear "Wm Marples & Sons Sheffield. Eng." with a trefoil flower stamp. All very neat and clear, not the product of a heavy thump with a stamp.

What are the advantages/disadvantages of cast steel.? Also any thoughts on age, and what shape of handle would be most appropriate. I like the look of the London pattern, but not the feel.

Regards Mike
 
Cast steel was a process used to make steel not a method of chisel manufacture, it was a process used before blast furnaces.

I have a 1/2" chisel with the same round bolster and its good steel well worth re-handling.


Pete
 
Thanks Pete
Nevertheless, the tang and the bolster are clearly "moulded" rather than forged, so I am puzzled as to the method of manufacture.

Mike
 
I don't have my Salaman's Dictionary of Woodworking Tools on hand at the moment, but I think it says "cast steel" was made as a molten metal and then poured into casts, in contrast to the previous type of steel which was "blister steel", made by heating iron with a source of carbon like charcoal, the carbon would diffuse into the iron.

This is modern chisels being made:
https://www.youtube.com/watch?v=MnBrxv-kgq0

they stamp the metal between dies, (is it stamping or forging?) which leaves a line along the chisel.

Yes as mentioned, "cast steel" refers to the metal not how the tool was made.
 
Are you sure it's cast and not just hot die forged, I.E. stamped out of bar stock.
 
In the early 18th century, the main method of manufacture of steel was by cementation - taking carefully selected low-phosphorus wrought iron bars and packing them in charcoal in large, sealed containers. The containers were then heated for a week or more, until the low-carbon wrought iron had absorbed carbon from the charcoal. The aim was for about a 1% carbon content, though the carbon concentration varied through the thickness of the bar. The result was 'blister steel', which was them broken into pieces, piled into bundles, heated and forge-welded to get a more even carbon distribution. That made 'shear steel' - used for the making of sheep shears and other edge tools. A better grade was made by folding and forge-welding again - 'double shear steel'. Even this had some variation of carbon content, making it less than perfect for some applications. In 1740, a clockmaker by the name of Benjamin Huntsman developed a method of breaking cementation steel into small pieces, placing them in a small crucible, and heating them until they melted. The molten steel was cast into small ingots - this was a much more homogenous material, called 'cast steel' or 'crucible cast steel'. The small ingots were then forged into bars suitable for toolsmiths to further forge into edge tools, cutlery etc. It wasn't cast direct into tool shapes - the tools were forged from cast steel stock.

The crucible cast steel process was the only way in which 'steel' (which meant high-carbon tool steel) was made until Bessemer perfected his converter in the 1860s. That allowed the bulk production of low-carbon 'mild' steel. Later, electric furnaces were developed for the refining of special steels, and their use really took off during World War 1. Crucible cast steel production declined, the last being made by the Huntsman process in the 1960s. By that time, most 'tool steels' were produced in electric furnaces.

The process of making a chisel is by forging, using either multiple-strike forging (either by hand or by a small power hammer of about 1cwt capacity). There are several stages in forging the chisel, first forming the bolster, the tang and neck, then drawing out the blade. It's a skilled process, still used by Ashley Isles. The more recent method is to use a drop-stamp or hydraulic press with two dies as shown in JohnPW's link above. That's a much faster process, but requires a far higher investment in tooling.

From the OP's description of his chisel, it's been made by drop-forging, a process used extensively in Sheffield from before WW2. The chisel would most emphatically not have been made by a casting process, but drop-forging of crucible cast steel may have happened.

There's some debate about the relative merits of multiple-strike forging and drop-forging. Some are of the opinion that the gentler urging into shape of the multiple-strike forging process aligns the steel grains better than the brutal strike of drop-forging, giving a tool that will take a sharper edge. However, the majority of modern chisels are drop-forged, and most perform adequately. That said, many people have remarked that older (especially 19th century) chisels - all of which were made by multiple-strike forging - will take a sharper edge than many modern ones, so there may well be something in it.
 
Casting can leave a pretty uneven surface maybe the chisel was cleaned up on some kind of lathe before being handled?

But I know little about forging or casting and may be talking ball puffins.
 
If its a Marples with a round bolster it will be a later 20th century chisel - and a very good one at that.

The marks on the tang are from die forging, hot steel bar rests in one half of the die, the other half is attached to the drop hammer which comes down and forms the tang and bolster with one almighty thump.

This forms a 'mood' (piece of bar with a tang and bolster forged on it) which is then passed to a smith for hand forging (spring hammer) into whatever you want it to be. As soon as it is flattened out it is no longer a mood and is referred to as a blade. In the case of your chisel the neck and bolster would have been turned on a lathe before the blade itself was ground - hence the round shape.

As John says, 'Cast Steel' was a mark used much earlier to differentiate superior 'crucible cast steel' from the less consistent 'blister steel'. The introduction of the blast furnace meant that you could make cast steel in huge quantities for a fraction of the cost, so all steel from Bessamer onwards is cast. The wording was dropped around this time as there was no longer anything for cast steel to be different to.

Earlier chisels would have had a tapered four sided tang similar in shape to the tang of a round file. This would have been drawn down by hand (hammer and anvil or spring hammer) and the bolster formed by upsetting or welding on a collar that was then carefully hand filed into an octagon. You can see how one big thump and a spin on the lathe getting your skilled blacksmith halfway there was attractive, especially since most of it was going to be buried in the handle anyway. This was proper industrial cost saving, using technology appropriately with no sacrifice of quality.

Modern steel, as a raw material, is actually far better than crucible - we can now dial in the exact chemistry of the melt while it's hot and adjust it to a fraction of a %. The benefit that you feel with old tools (and the better modern ones) comes from proper heat treatment, which brings out the beneficial characteristics that the material is capable of.

From the 1970's onwards, after yours was made, the demand for ever cheaper tools that the sheds (spit) could sell for tuppence a bucketful, led to widespread adoption of impulse hardening. The chisel is held by a robot inside a coil for a moment and heated insanely fast, then it drops into a bath of oil to quench it. The problem with this is that the result after tempering can be anywhere from RC55 (mush) to RC65 (chippy) and in some cases both issues within the same blade. If a chisel chipped, people were more likely to return them to the sheds, so they asked for softer blades to reduce their return rate. Result - good ones and bad ones with an excellent chance of mush, even though the steel itself was capable of being outstandingly good.

There were a few manufacturers who were isolated from this nonsense. Ashley Iles proudly independent and tucked away in Lincolnshire quietly ignored it and carried on making good ones. Narex, tucked away behind the iron curtain had 'no expense spared' central government investment and a mandate to make the best possible quality for the workers at minimum unit cost. And Japanese Saw manufacturers like Gyokucho, who saw the potential of impulse hardening if done correctly and developed it into a process for hardening saw teeth that is still unmatched for accuracy to this day.
 
Excellent information in this thread.

I have a couple of those round bolstered Marples and they are lovely to work with.

As far as multiple strikes vs single forging, materials science tells us that the same amount of deformation at the same temperature will have the same effect on the grain structure so I would venture that there is probably very little difference in the finished article between the two processes, if there were a difference I imagine the range of temperatures at which the blacksmith works would promote more grain formation and a smaller grain size (almost always seen as a good thing, Hall-Petch effect).
 
I am somewhat overwhelmed by the speed and information of all of your replies, so thanks to you all.

In regard to the chisel, the tang is exactly as Matthew describes, having a tapered four sided profile. There is about 3 1/2" of blade left so it should have years of use left.

Any ideas as to age and what the handle shape might have been?

Mike
 
Sorry Matthew, didn't read that properly at first. Did you mean late 19th Century?

Mike
 
Hi Mike,

No 20th century, if Pop Larkin had bought a new Marples chisel it would have looked like yours.

The handle would be a 'carving' handle, not to be confused with a larger 'carver' handle. Same pattern as you find on todays AI's but in boxwood.
 
matthewwh":2wrk2s2w said:
From the 1970's onwards, after yours was made, the demand for ever cheaper tools that the sheds (spit) could sell for tuppence a bucketful, led to widespread adoption of impulse hardening. The chisel is held by a robot inside a coil for a moment and heated insanely fast, then it drops into a bath of oil to quench it. The problem with this is that the result after tempering can be anywhere from RC55 (mush) to RC65 (chippy) and in some cases both issues within the same blade. If a chisel chipped, people were more likely to return them to the sheds, so they asked for softer blades to reduce their return rate. Result - good ones and bad ones with an excellent chance of mush, even though the steel itself was capable of being outstandingly good.

That's interesting - because the usual advice when hardening steels (of any grade) is to ensure they are heated through before quenching, by soaking at hardening temperature for long enough to ensure an even heat right through - one hour per inch of thickness is one 'rule of thumb'. The speed of impulse hardening would presumably mean the case was hardened, but the core remained soft. Fine for some duties, but not necessarily ideal for a high quality edge tool.

Further to the notes on 'cast steel' - the straight carbon steel of about 1% carbon content with no alloying element additions - this is a material that is quite hard to harden; it needs a fast, aggresive quench in water or brine, and even then, it only hardens to a relatively shallow depth. It has another couple of problems, too. Firstly, it can change dimensionally when hardened; not a lot, but measurably. This isn't a problem to edge-tool makers, but it is to engineering gauge-makers. The second problem is that because of the very fast quench, it is prone to the locking-in of quite severe internal stresses which can cause items to distort, or in extreme cases, crack.

During the later part of the 19th century, a lot of experimentation took place to find solutions to these problems. It was found that the addition of quite small quantities of some other elements had significant benficial effects. One result was the fore-runner of our favourite 01 oil-hardening steel, which because it responds to a slower, more gentle oil quench, is much less prone to distortion (and not prone to dimensional change, which is why it is often called 'gauge plate', since it was much more suitable for the making of accurate measuring instruments than cast steel). Another advantage is that it hardens to a much greater depth. Some feel that it doesn't have quite the supreme edge-taking capabilities of plain carbon steels, but most feel that it gives a perfectly adequate edge. It thus tended to supplant plain carbon steels for edge-tool making from the end of the 19th century onwards. As some of it was still made by the crucible steel process, it might still be called 'cast steel', though. From WW1 onwards, more tool steels tended to be made by electric arc furnaces, producing steel every bit as good as 'cast steel'.

Many other alloy steels came about during this period of experimentation, not all of them of direct use to edge-tool makers. In fact, it's probably fair to say that no steel has ever been developed specifically for edge-tool use (except possibly cementation steel, and that mainly for swords and miitary knives); their main applications have always been for some other application - Huntsman steel for clock springs, 01 for engineering gauges, and so on. However, the edge-tool makers have always used what's available, often to very good effect.
 
Cheshirechappie":1eaiognc said:
Many other alloy steels came about during this period of experimentation, not all of them of direct use to edge-tool makers. In fact, it's probably fair to say that no steel has ever been developed specifically for edge-tool use (except possibly cementation steel, and that mainly for swords and miitary knives); their main applications have always been for some other application - Huntsman steel for clock springs, 01 for engineering gauges, and so on. However, the edge-tool makers have always used what's available, often to very good effect.

How about HSS steel? Or some of these modern powder metal steels like CPM3V. Weren't these designed especially for cutting purposes?
 
Cheshirechappie":23wq0x3n said:
That's interesting - because the usual advice when hardening steels (of any grade) is to ensure they are heated through before quenching, by soaking at hardening temperature for long enough to ensure an even heat right through - one hour per inch of thickness is one 'rule of thumb'. The speed of impulse hardening would presumably mean the case was hardened, but the core remained soft. Fine for some duties, but not necessarily ideal for a high quality edge tool.

I don't think so. Induction hardening heats by the induced electrcal current in the steel, so it is heated from within rather than absorbing heat from its surroundings. Rather like microwave cooking compared with a conventional oven.
 
Corneel":2lo6ucd0 said:
Cheshirechappie":2lo6ucd0 said:
Many other alloy steels came about during this period of experimentation, not all of them of direct use to edge-tool makers. In fact, it's probably fair to say that no steel has ever been developed specifically for edge-tool use (except possibly cementation steel, and that mainly for swords and miitary knives); their main applications have always been for some other application - Huntsman steel for clock springs, 01 for engineering gauges, and so on. However, the edge-tool makers have always used what's available, often to very good effect.

How about HSS steel? Or some of these modern powder metal steels like CPM3V. Weren't these designed especially for cutting purposes?

I was thinking specifically of woodworking and other handtools, but in the case of cutting tools for engineering machinery you're quite right, Corneel. The first advance on plain carbon steel was made by Robert Mushet in 1868, producing (by powder metallurgy techniques, as it happens) an early form of High Speed Steel. Later, in America, a long series of experiments by Frederick Taylor and Maunsel White under the patronage of industrialist William Sellers resulted in the development of what we now know as HSS, first demonstrated publically at the Paris Exhibition of 1900. There's an excellent history of these developments in LTC Rolt's 'Tools for the Job' (published in America as 'A Short History of Machine Tools') in Chapter 10, 'Metal Cutting becomes a Science'. The later development of materials like Tungsten Carbide and the modern Cermets used for metal-cutting followed similar lines, I think. I'm not sure that powder metals (like CPM3V) were developed specifically for cutting tool applications, I suspect a lot of the research drive in this field was about finding economical ways to make complex-shaped items like turbine rotor blades without the need for very complex machining.
 
Sheffield Tony":2wk19ide said:
Cheshirechappie":2wk19ide said:
That's interesting - because the usual advice when hardening steels (of any grade) is to ensure they are heated through before quenching, by soaking at hardening temperature for long enough to ensure an even heat right through - one hour per inch of thickness is one 'rule of thumb'. The speed of impulse hardening would presumably mean the case was hardened, but the core remained soft. Fine for some duties, but not necessarily ideal for a high quality edge tool.

I don't think so. Induction hardening heats by the induced electrcal current in the steel, so it is heated from within rather than absorbing heat from its surroundings. Rather like microwave cooking compared with a conventional oven.

Ah! - Thank you for the correction, Tony. One of the good things about this forum is that there's usually someone around to pick up gross mistakes! I must have been thinking of induction hardening, which is used for surface hardening machine tool slideways, amongst other applications.

That leaves the question - if impulse hardening heats the workpiece through, why the wide variation in final results?
 
Having had a quick Google it looks like my understanding was a bit dodgy. Induction / impulse hardening does heat a surface layer to a depth depending on the frequency.
 
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