Infill Irons Harder than Other Irons in Vintage Types?

[D_W]

Or maybe I should ask if parallel irons are harder than taper irons typically?

I've only used a couple of parallel irons in vintage types so far, but in each case, they are very hard. One is a mathieson and one is a ward. I'd expect the ward to be hard, but the mathieson is harder than any of the taper mathiesons I've tried, and I've had quite a few of them.

Just curious.

https://s28.postimg.org/h537mjbf1/20161223_160405.jpg
https://s28.postimg.org/r3o690kul/20161223_160428.jpg

(I can't find a picture of the plane that I have with the mathieson iron, but it's nothing spectacular - it was a craftsman made infill, though quite well done. The infill plane in this picture is branded Buck, presume it may have been a norris plane...and also not sure that front bun is stock. The back handle was broken and glued and the horn is a replacement horn - I'm sure it was dropped. I worked the seller over pretty hard about it and he gave me a huge amount of the purchase price back to the point that I told him that I'd settle for a little less - so the plane didn't really cost me much).

Anyone know about the hardness spec for irons? I have a third parallel marples iron, but I have to make a plane for it yet and haven't tried it.

 

[Mr_P]

Guess the parrallel iron are made by different people than the tapered ones even if they are badged the same.

Also the irons you are comparing could have 50+ age gap.

 

[AndyT]

Over in the discussion about Record irons, Custard quoted this statement, written by C &J Hampton. Although their book was helping to sell their modern planes, I think it's true to say that as manufacturers they would have known quite a lot about the subject.

"Within living memory...the purchase of a satisfactory plane iron was largely a matter of luck. It might be too hard or too soft; it might hold its edge or it might not."

So your sample of one could be harder by chance, or it could be by design - a special iron for a special plane - or it could be by natural selection, if the iron took longer to get used up.

 

[D_W]

I'm a little confused by the time periods. I gather that crucible steel made the good irons, that before them everything was chance. If the book is from 1934, and crucible steel came about in the 18th century, I guess they're suggesting irons weren't made with it? (re: the comment about plan irons within living memory).

I do have a fairly small sample of infill irons, but the others are pretty uniform and all but two that I've gotten (out of maybe 50? or more?) have been good - speaking about the tapered irons. I've noticed preferences by manufacturer - freres irons are soft, dwight and french irons are soft, ward irons are hard. I'm excluding irons that seem to have been made after 1900 or so as I don't have a lot of faith that they were made by the mark that's on the iron.

If the makers intended infills for finer work, it would make sense that the irons would be harder whereas a slightly softer taper iron would be handy for site work and coarse work such that it could be maintained more easily and reground if damaged with nothing other than bench stones.

 

[AndyT]

Cheshire Chappie can probably give more detail, but my understanding of the chronology is that although the crucible process was old and labour intensive, it continued in use alongside other more efficient processes (Bessemer, Siemens/Open Hearth) because it was the best way of making good hard steel for cutting edges of tools, right through until about WW2 or a few years afterwards. This was a long time after the other methods had taken over for ordinary bulk production - Bessemer steel was invented in 1856 and well established by 1870; the Siemens process took off after 1879 when Thomas Gilchrist invented the basic process for eliminating phosphorus from the mix. *

It might be debatable whether it really was better, or whether conservative customers had been trained to demand "cast steel" (ie crucible steel) in the tools they earned their living with, so conservative manufacturers continued to supply it, but I don't have any real evidence either way on that question.


* Source - Sheffield Steel by KC Barraclough - an excellent little book which I bought on CC's recommendation.

 

[Cheshirechappie]

It's entirely possible that there is some variation in the hardness of vintage plane irons. Indeed, it would be remarkable if there wasn't, given the following.

There are two contributing factors; steel composition, and heat treatment practice.

Steel metallurgy is a vastly complex subject, and it can't really be boiled down to a few words. During the 19th and early 20th century (which realistically is the period from which most vintage plane irons originate) tool steel making practice developed quite a lot. The first change was the addition of manganese from about 1860, which improved steel quality. The next big change was during WW1, when the shortage of skilled labour (conscription) drove the installation of small electric arc furnaces for specialist steel making. Even the smallest of these makes half a ton or so per heat, against a crucible's 100lb or so - about as much as a strong man could lift.

The next factor is carbon content, which could be varied from about 0.8% (or less) to about 1.4% for 'straight' carbon tool steel, the different compositions suiting slightly different applications. For example, R.A.Higgins in 'Engineering Metallurgy' Vol.1 gives 0.9-1.0% as the ideal for axes, 1.1-1.2% for woodworking tools, and 1.3-1.4% for saws and razors among other applications.

Then we come to hardening and tempering, which in Sheffield was done by very basic methods until well into the second part of the last century. Hardeners judged everything by colour - no temperature controlled furnaces or quenching baths. You can well imagine the variation that might arise if the colours were judged on a dark January morning or a bright July noon, and quenchant temperature could vary significantly between the depths of winter and the height of summer. All that would add variations - perhaps quite a lot; and never mind the effect a couple of pints too many the night before might have!

Given the above, it's actually quite remarkable that the vast majority of tools turned out of Sheffield were eminently fit for purpose - and perhaps not at all surprising that modern tools tend to be much more consistent!

 

[Vann]

Or maybe I should ask if parallel irons are harder than taper irons typically?...

I'm inclined to think it's just coincidence that your parallel irons are harder than your tapered ones - but I have no experience of parallel infill irons (other than having purchased one - but not fitted - for an old Slater infill I have).

However I guess it's possible that there may have been better testing (or a higher rejection rate) for parallel irons for the prestige planes of the day, than for the the common-or-garden tapered bladed wooden planes.

My tuppence worth.

Cheers, Vann.

ps I don't have a Norris, nor a Speirs, because they're :deer :deer (too deer) :ho2 (a Christmas joke)

 

[D_W]

I think we're discounting just how skilled the workers would've been at doing things like judging temper by color. For example, the half a dozen or ten mathieson irons I've had that are tapered have all been about the same. The texture of the steel on the stone about the same (fairly fine, very fine compared to some modern steels). the hardness, almost identical. There is a much greater difference between manufacturers than within. Of the half dozen ward irons I've used, none have been as soft as any mathieson iron, and thus none of the mathieson irons as hard as any of the wards. None of the mathiesons have been anywhere near the hardness of dwight and french irons (which you could almost roll a burr on, but they do hold up well for trying work - they'd make a pretty disappointing smoother iron, at least the ones I've had).

It's not so much the variation from iron to iron that I'm curious about, but the suspected intentional hardness difference between infill irons and taper plane irons for wooden planes (that difference is something I don't notice on ward irons, they're all hard).

Sometimes it's brought up on other forums that the C scale was developed late as though that would mean that early makers didn't know what they were doing, but I haven't found that to be the case (of the quality makes). By early, I mean in american terms, mid to late 1800s, not earlier than that. I also think that some of the makers intentionally made fairly soft irons (like freres), perhaps due to what was being used to sharpen the irons. Certainly English and japanese irons evolved at much different mean hardnesses because the stones that come out of mt. atago in kyoto are able to cut harder steel, and not sharpening on the job site was considered a desirable trait by some japanese trades.

So that intentionally difference between parallel irons and taper irons is what I'm after.

(I'm sure the difference between bessemer and crucible processes has been discussed at length. I do see the older irons as being finer in structure, but that may not be purely process oriented, it may be due to alloy or expectations/specifications. The good makes of irons in the mid 1800s are very consistent, and very fine grained. There have been long debates on american forums, especially where engineers get involved and have read - but have had no exposure to skilled trades - that the assumption that everything old was inferior and difficult to work with and that none of the old irons were workable compared to modern process steels. Except that in the view of those discussions, anything made late 1800s is "very old" and inferior vs. something made recently out of A2. It's a notion that is probably due to lack of exposure. Both dud irons that I've had were US made - one ohio and one auburn - I can't remember, they were probably both the same company eventually).

 

[Phil Pascoe]

Or maybe I should ask if parallel irons are harder than taper irons typically?...

I'm inclined to think it's just coincidence that your parallel irons are harder than your tapered ones - but I have no experience of parallel infill irons (other than having purchased one - but not fitted - for an old Slater infill I have).

However I guess it's possible that there may have been better testing (or a higher rejection rate) for parallel irons for the prestige planes of the day, than for the the common-or-garden tapered bladed wooden planes.

My tuppence worth.

Cheers, Vann.

ps I don't have a Norris, nor a Speirs, because they're :deer :deer (too deer) :ho2 (a Christmas joke)

Aw, come on - rein them in. :roll:
nadelik lowen ha blydhen nowydh da to all you in Aotearoa - I've just been told in the new year I will become a great uncle (my first "great") to a Jafa boy.

 

[Cheshirechappie]

Two points.

Firstly, I seem to recall various references to moulding plane irons (or at any rate, some of them) being made a little softer than the general run of plane irons, presumably to make them a little easier to shape and sharpen. I've seen one or two forum posts (not all on this forum) complaining about 'soft' moulding plane irons.

I can't confirm - can't find the references despite a couple of hours searching (I'll find them in about a fortnight whilst looking for something else!), and my experience with moulding planes isn't extensive enough to have formed a view.

If (and it is an 'if'!) moulding plane irons were tempered down a bit more than usual, it's entirely possible that some bench plane irons were left a bit harder than usual, too - within reason, of course. Too far, and brittle, chip-prone edges would be a distinct possibility. I'm not aware of any written standard or other documentation to support that, though; it could well have been done by verbal agreement if it happened.

The second point is to pick up my earlier reference to different steel compositions. In the book Andy mentioned ('Sheffield Steel' by K.C.Barraclough), figure 42 shows a circular issued by Daniel Doncaster and Sons in about 1880, entitled 'Recipes'. It shows three main grades of Cast Steel, from which 'other tempers' could be derived if required. No 1 for saw files, etc was of 1.5% carbon, No 2 for Tool Steel for Turning etc was of 1.16% carbon, and No 3 for Saws, Table Knives etc was of 0.75%.

Interesting for a couple of reasons - firstly, the very high carbon content of saw files. I've seen occasional references to the fact that saw files were made of a different steel to the general run of files, and that maybe goes some way to explaining why modern sawfliles are regarded as inferior. Secondly - saw steel at 0.75% carbon, which makes one wonder a little at the modern obsession with 1% carbon (SAE 1095) steel for boutique sawmaking. Were 1880s saws really so inferior?