Hardness testing of saw plates

[Rob Streeper]

Hi Mel,

The Atkins saw I tested that has the Silver Steel blade is a pattern makers saw. It is very hard but not brittle. It's hardness may be due to the relatively unique design of the saw.

Cheers,
Rob

[David Weaver]

Hi Mel,

It is very hard but not brittle.

if it was 61 or even 58 hardness, you wouldn't be able to flex it. It would break just like high end japanese saw plates break when they are flexed (and those are often yellow steel, which is much like 1095).

Find a thin chisel, bend it (or a knife) and let us know how it turns out. They are heated past spring temper, and most pocket knives are a touch softer than chisels.

What you're perceiving as a magic combination of hardness with ductility is due entirely to the fact that the saw is not actually 61 hardness.

[Brian Holcombe]

I don't post much here any more (because like this thread, the discussion doesn't advance and there isn't proper credibility given to the people who actually know what they're talking about), but I'd like to point out that George is correct and you're wrong. You need to test the saws on something like a versitron (or trade for some time on one) if you want to assert their hardness. Right now, you're just wasting your time.

I had the saw that was light straw temper, it couldn't be filed. Period. The very tips of the factory teeth cracked off because it was overhard and then what remained got rounded over (worn) by some tough handed but weak minded individual and that is how the saw stayed until I got it. It was a disston 7 (not a metal cutting saw or anything, just a defective 8 point crosscut saw - maybe someone pulled it off the line as a spoof before it got tempered to spring temper).

There is little discernible difference between old saws brand to brand and 1095 at 52 hardness is harder than any old saw that I've filed (save the one), except those old enough to have been hardened inconsistently (where most of the saw is fairly soft and there are surprise hard spots that kill files). There are not many saws like that in use, and they don't say atkins on them.

Silver steel is a marketing term. It means nothing at this point other than in old things, it was a generic term for high carbon water hardening steel, commonly used on razors (I guess it assured the buyer they weren't being slipped medium carbon steel in a low quality good). Only the original alloy coined by some brit had silver in, and then not that much (silver does nothing for the steel) - nothing you find modern enough to use will be any different than any other generic water hardening high carbon steel. Not coincidentally, every saw made by disston and every other maker at the time was high carbon water hardening steel. When specialty steel was actually used, the mill and the alloy were specified (see schoeller Bleckmann razors, or "phoenix steel").

If those saws have ever seen a file that left marks in them on all of the teeth, they are not high 50s or 60 hardness, and not even mid 50s. They would've been thrown aside/away in favor of a saw that was easier to file. Not to mention, at mid to high 50s, spring temper is gone and the teeth would snap at set.

Most of the old saws I've filed are probably mid to high 40s in hardness.

Find yourself a chisel that's 60 hardness, stone the bevel off until it's about saw width, and then file five full depth teeth in it with a saw file and let us know how it goes.

I don't think the NIST is wrong, I think you're missing the difference between theory and practice and you need to give your saws to someone who can test them competently.

I was starting to wonder where you were.

PS the Snow white is workin' like a charm.

[Winton Applegate]

Hi gang,
I am having a great time reading this thread and learning.
When I heard the term superfical I thought that might mean case hardened.
At least I was right about one thing today.

The term gray metal . . . that's the English term right?
As far as I know in America black is iron and white is aluminum. As in Black Smith.

For a bit there I was guessing silver steel was stainless; I recall reading in his book that Norm Abrams had a nice stainless steel panel saw that some one stole from him. Any way . . .

George,
I stay up too late as well.

Thanks guys for hammering all this out !
I'll just shut up and learn something.

PS: in this day and age, the last ten years or so, of flagrant incompetence, I wouldn't even be surprised that the Standards Institue (in America) was full of beans.

[Rob Streeper]

if it was 61 or even 58 hardness, you wouldn't be able to flex it. It would break just like high end japanese saw plates break when they are flexed (and those are often yellow steel, which is much like 1095).

Find a thin chisel, bend it (or a knife) and let us know how it turns out. They are heated past spring temper, and most pocket knives are a touch softer than chisels.

What you're perceiving as a magic combination of hardness with ductility is due entirely to the fact that the saw is not actually 61 hardness.

Hi David,

The hardness and brittleness are critically dependent on the alloy used. As I said I don't know what Silver Steel is but the saw and box look like they might have been made in the 50's or 60's. For instance, I tested a Lenox carbide toothed bandsaw blade just now. Thickness is 0.022" and I don't know what alloy is used for the blade body but 5 replicate measurements on the 15 kg and 30 kg N scales indicate that the hardness is 58-60. The blade is of course quite flexible. Another Lenox blade I have, a 14/16 Diemaster II, gives hardness readings in the range of 32-35. This blade is M42 according to Lenox literature. Both are great blades but each is obviously very carefully engineered. The CT blade is designed for heavy duty cutting of large pieces of hard metal. The Diemaster II, which has teeth sharpened into the body of the blade, is also a heavy duty metal cutting blade, especially thinner stock.

So, given that we don't know yet what Silver Steel is I think it best to reserve judgement on the question of whether it can be simultaneously hard and flexible.

Cheers,
Rob

[Patrick McCarthy]

[QUOTE=David Weaver;2359714]I don't post much here any more (because like this thread, the discussion doesn't advance and there isn't proper credibility given to the people who actually know what they're talking about),

DAVID, good to see you post. I for one, would encourage you to keep posting, as I am one of the silent majority out here who has benefitted from your breath of experience. I understand the frustration with getting sucked in (or under) by some of the posters, but I think most out here who appreciate the comments are reticent to say "Great post" and, on the other hand, equally reluctant to do a "Dear dunce head" post to some of the "always certain, but seldom correct" posters. Like everything out here in real life, the vast majority of us are open minded and appreciative of those who answer our questions. Also like the real world, there are also those that seize upon facts and beliefs without the depth of knowledge or experience to really understand the nuances necessary to make some of the blanket statements they utter.

BTW, saying George is correct is kinda like saying the Pope is Catholic. Of course he is correct; not even sure his wife could find fault with his knowledge, skill and experience.

[Rob Streeper]

There quite likely was as George says a much wider historical usage of the term silver steel, but it surfaces these days in the UK and environs as a very specific form of brightly finished ground rod as described here - so it probably has specific applications for production of easily hardened parts: http://en.wikipedia.org/wiki/Silver_steel

It's a very definite designation, the subject of a British Standard. It hardens to 64 HRC according to the link. It's quite a high carbon tool steel (0.95 - 1.25%), with a decent amount of chromium, manganese, silicon and vanadium in there too. e.g. http://www.westyorkssteel.com/tool-s...ver-steel-bar/ It's possibly not a lot different in some ways to O1 steel - has a bit more carbon, a bit less manganese, similar chromium, a bit less vanadium, a little silicon and no tungsten - but i don't know enough to know what the differences are likely to amount to.

It's a very common tool room supply item. I don't know enough about the metallurgy or usage in practice to say much about its characteristics, but experience says that even in the annealed form in which it's normally supplied it's quite awkward to handle. e.g. it doesn't thread well, because bits chip out, and it's likewise not keen on being more than moderately bent - it tends to crack.

Hi Ian,

Thanks for the additional information. The additional elements, if they represent what Atkins used of course, may explain some of the apparent discrepancy between hardness and flexibility of this particular saw blade. When I say flexible I mean that I can deflect the tip of the saw relative to the centerline of the blade by 50 mm or so and the blade doesn't break.

Cheers,
Rob

[george wilson]

Rob,NIST is not wrong. You are just not using it correctly. You are apparently ignoring the stated metals and conditions of those metals to be tested with the scales your machine has access to. I suggest that you study the chart carefully,in a non emotional way. You have only a specific type of tester,and it is not suitable for the saws you are testing. I am sorry to burst your bubble,but this is factual.

About silver steel again,it means every type of steel that has carbon in it. That includes everything in use. Mild steels still have a silvery appearance compared to grey looking wrought iron.

I have tested many a tool,especially punches, that I made from W1 steel. Fully hardened,it reaches to 67 RC,much harder than HSS,which is normally about 63 RC. These were tested on my Versitron. I don't know where that figure of 64 RC maximum hardness was arrived at for silver steel,of which W1 is a member.

. I always got 67 RC as a maximum hardness.There are many types of HSS,though,so a blanket statement about them cannot be made. Some,like M 42 HSS has a lot of tungsten in it,and the weight and color it has can look a lot like carbide.

After hardening my W1 steel letter or number punches,I had to be careful about tempering them neither too soft nor too hard. I found that heating them to a purple color gave the best balance,so they could stamp a crisp impression onto soft steel,or un hardened tool steels,without shattering or quickly getting dulled. This left them at about 54 RC. Letter and number stamps have a finite life. I have forgotten how many impressions a normal letter stamp is expected to make,but it is in the thousands.

[David Weaver]

It's not 60 hardness. There is no spring steel that is 60 hardness. We will wait for you to find and confirm the error in your tooling or interpretation of how to use it. You are getting far too swept up in trying to get more precise about how your tool was used, but ignoring the fact that the results aren't possible. If they were, everyone would've had saws that hard, and files would've been another 10-15 points harder. I don't know if you don't know enough about metallurgy to understand why there are not 60 hardness or 58 hardness 0.8% carbon water hardening steels or what, but you have made an error at some point and everyone here with enough knowledge of tools, tool steels and the temper of the same knows that you've made an error. You're digging yourself a hole.

Even a razor is only about 60 hardness, possibly a touch harder, and they are thin and would benefit enormously from ductility, but they don't have it because it doesn't exist at that hardness level. Simply tapping a straight razor against a faucet can cause a section to break out of it.

If the saw is from the 1960s, it's just going to be some low dollar mid to mid-high carbon steel that is more highly alloyed. The term spring steel (which originally intended water hardening and probably then later oil hardening carbon steels - used a generic term, often of british origin) was completely defiled later on by adding a lot of chromium or manganese and still using the term.

[Steve Voigt]

There quite likely was as George says a much wider historical usage of the term silver steel, but it surfaces these days in the UK and environs as a very specific form of brightly finished ground rod as described here - so it probably has specific applications for production of easily hardened parts: http://en.wikipedia.org/wiki/Silver_steel

It's a very definite designation, the subject of a British Standard. It hardens to 64 HRC according to the link. It's quite a high carbon tool steel (0.95 - 1.25%), with a decent amount of chromium, manganese, silicon and vanadium in there too. e.g. http://www.westyorkssteel.com/tool-s...ver-steel-bar/ It's possibly not a lot different in some ways to O1 steel - has a bit more carbon, a bit less manganese, similar chromium, a bit less vanadium, a little silicon and no tungsten - but i don't know enough to know what the differences are likely to amount to.

It's a very common tool room supply item. I don't know enough about the metallurgy or usage in practice to say much about its characteristics, but experience says that even in the annealed form in which it's normally supplied it's quite awkward to handle. e.g. it doesn't thread well, because bits chip out, and it's likewise not keen on being more than moderately bent - it tends to crack.

Ian, thanks for posting this. I was sure I had heard the term, in the specific sense you're using it, bandied about on knife (or maybe razor?)-making forums, but I wasn't aware of the link to west york. .95-1.25% carbon is very high, on a par with Japanese white.

[george wilson]

Steel that is actually sold to be used as spring steel,is generally .80% carbon. Old saws can run between .70 and .80% carbon. Blacksmiths like to use .70% carbon if they are forge welding bits into softer bodies as in making bitted plane irons,or large timber framing chisels. Higher carbon steel catches fire and burns up at welding heat. Since steels were hand processed in the old days,makers were frugal about making tools from solid high carbon steel.

The old saws were made with .70 to .80 carbon steels. They really cannot compare to the boutique saws being made these days from .95% carbon steel. 1095 carbon steels are pushing the boundaries of spring steel. It is not real difficult to break a tooth off while setting teeth on 1095 saws. I had to recut a number of the saws we made for the museum. When they were done,though,they were said to be better than any other saws the craftsmen had ever used. Now,nearly ever small maker is using 1095 spring steel shim stock.

As I have said several times here,steel hardness vs toughness is a balancing act. Gain hardness and you lose toughness and flexibility. You can't have both,except in the case of the Ancient Wootz steel. Their secret was to only reach a red heat in forging a hockey puck size ingot of very high carbon steel into a sword. By not exceeding a red heat,the carbides in the steel were not melted(to form,when they cooled,into large crystals). The smiths crushed the still solid carbides into a fine matrix inside a body of soft iron. That is how they made such superior weapons. We don't do it that way,but ought to. The reason we do not is,high carbon steels at red heat,are VERY hard and a big chore to forge. I have done that myself,making some nearly indestructible engraving tools.

[Rob Streeper]

If I'm wrong George please tell me how, specifically and instruct me on the appropriate Rockwell scale and indenter to use. This instrument and it's test blocks are traceable to NIST standards.
I think everyone who has been critical of my testing is missing the fact that I am the only one so far to present data. If you have data that conflicts with mine please share it.
Superficial testing is specified for thin materials because the plastic deformation induced by the heavier loadings used on the C scale causes the readings to be anomalously low.
Tellingly, the instrument I have came with two hardness test blocks. The testing of the instrument on those blocks returned values that were within specification. Further, my testing of the 1095 specimens shows very tight readings. The average is about a point higher than the steel manufacturer specification but the specified range is within the tolerance of the instrument.
I am open to well intentioned discussion, even if the discussion is contentious but I ask everyone to please leave the personal attacks out.

[David Weaver]

There quite likely was as George says a much wider historical usage of the term silver steel, but it surfaces these days in the UK and environs as a very specific form of brightly finished ground rod as described here - so it probably has specific applications for production of easily hardened parts: http://en.wikipedia.org/wiki/Silver_steel

It's a very definite designation, the subject of a British Standard. It hardens to 64 HRC according to the link. It's quite a high carbon tool steel (0.95 - 1.25%), with a decent amount of chromium, manganese, silicon and vanadium in there too. e.g. http://www.westyorkssteel.com/tool-s...ver-steel-bar/ It's possibly not a lot different in some ways to O1 steel - has a bit more carbon, a bit less manganese, similar chromium, a bit less vanadium, a little silicon and no tungsten - but i don't know enough to know what the differences are likely to amount to.

It's a very common tool room supply item. I don't know enough about the metallurgy or usage in practice to say much about its characteristics, but experience says that even in the annealed form in which it's normally supplied it's quite awkward to handle. e.g. it doesn't thread well, because bits chip out, and it's likewise not keen on being more than moderately bent - it tends to crack.

i would expect that atkins silver steel probably wouldn't fall in that fairly generous range (which appears to be an industrial standard now, despite being a very large range of carbon that literally occupies three different categories of japanese steels).

I checked around, and there appears to be more than one label that it applies to. Michael Faraday used the term on steel that he put in razors (that had actual silver in it, and then not). Sawmakers used it for steel that had chromium in it because the saw stayed bright longer. They claimed they could make harder saws, too. Perhaps that's true a point or two, i haven't noticed it in saws that I filed, but there may have been more in putting the chromium in for manufacturing - as in good behavior of the steel in hardening and tempering - than necessarily saw characteristics in use or storage. Plus anything you can market as a differentiator in a commodity market is a good thing, it's branding a commodity.

But the fundamental problem still exists with any claim that the saws are substantially harder than any other saw (or that a disston saw is hardness 58), and that's that the saw couldn't be filed and would thus be useless.

It looks like the terminology in the UK applies to a range of things the same way that we would use the term "oil hardening drill rod" (without specifying the carbon level), except where applying it to razors (where it suggests a carbon steel razor that isn't one of the highly alloyed or very high carbon specialty steels)

[Winton Applegate]

Well so much for staying silent.
I think the word flexed and hard enough to break when applied to Japanese high end saws needs a little more massaging for clarification.

What I am saying is you are both right but some where the terms are getting messed up.

There is flexed, a little, and there is bent.

I know that Japanese saws have teeth hard enough to snap off if the filing is too aggressive for the type of wood being cut. Yet every video I see by in the know guys, like Toshio Odate, while handling their saws they can't seem to keep from flexing the saw (some times quite a bit; way past five inches) to feel the spring of the blade. Call is showmanship or compulsion.

No doubt if they were to choke up on the blade and bend it over a short span it would snap or at least crack.

[Rob Streeper]

Well so much for staying silent.
I think the word flexed and hard enough to break when applied to Japanese high end saws needs a little more massaging for clarification.

What I am saying is you are both right but some where the terms are getting messed up.

There is flexed, a little, and there is bent.

I know that Japanese saws have teeth hard enough to snap off if the filing is too aggressive for the type of wood being cut. Yet every video I see my in the know guys, like Toshio Odate, while handling their saws can't seem to keep from flexing the saw (some times quite a bit; way past five inches) to feel the spring of the blade. Call is showmanship or compulsion.

No doubt if they ware to choke up on the blade and bend it over a short span it would snap or at least crack.

So as Clark Griswald says

Hi Winston,

One of the saws I tested was a Japanese style saw with a yellow/gold hued blade. Very hard but still flexible enough to be used.

Cheers,
Rob