bimetal

April 22, 2002 07:45 - Model 3861 Sandflex(R) NF(TM) bimetal bandsaw blade lasts 8 to 10 times as long as common milled carbon steel blades when sawing wood, plastics, and metals from foundry metals through alloy steels. Bimetal blade has high speed steel teeth beam-welded to spring steel back. Suitable for job shops and tool rooms, blades are available in sizes from 1/4 to 1 in. with 3 to 24 teeth-per-inch pitch.

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It's amazing what Google can find.

I had that experiance today in fact i wiped out a plan steel one on 5 cuts of stainless ! I cut 50 pcs with a bimetal thats what the diffrence is! matrial is 3/4 round stock.I ran it slower with bimetal 29.00 for blade 64.500 .500 wide blade .020 thick

I wonder if this "bimetal" concept is close to the concept of damasque steel.

Is that the deal where back in the middle ages they ran the hot blade through a slave to temper it? Damascus steel, if I'm not mistaken. Always wondered if that story had any truth to it.

Garrett Fulton

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Probably did; brutal times, 'twere...

But damascus specifically refers to the method of forge-welding two different materials (in those days, probably high and low carbon steel from the uneven nature of the bloom iron used), flattening, folding and rewelding ad nauseum to get many layers (often hundreds) of alternating material to even out the properties a bit.

Come to think of it, how thin would the layers have to be before they diffuse into each other reasonably at the temperatures used for forging, and become homogenous? Say, alternating layers of 1020 and 1090, and a long anneal (several hours) at 2000°F or so. Anyone?

Back on topic, what's the advantage of bimetal over HSS? I noticed the yellow-painted HSS hacksaw blades are cheaper at Ace than the bimetal (carbon steel of course is cheapest, but nuts to that!). I haven't had one break on me after the usual abuses of normal uses, just a few teeth chipped as any would.

Tim

-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @

Less likely to snap. I bent over a few of them a couple of days ago, in a Sawzall. 'No way that solid HSS would have taken that without snapping off.

So, why doesn't the narrow HSS strip on a bimetal blade snap, you ask? I don't know. I think it's something like the metal strap you use on the outside of a piece of wood you're steam-bending to extremes. Constraining one edge of it may make the difference.

-- Ed Huntress

No truth to it whatsoever. But it plays well to the rubes along the way. Helps to explain things to the ignorant, without leaving them any less so. Particularly, it explained away the reasons that godless heathens could make a sword steel that was so far superior to the stuff made for and by gods own holy crusaders.

Slaves were worth a lot more for the work they could do (labor, not just skilled) in 20 or more years of use.

And besides, all the caustic crud from inside any one of us would be pure nastiness to have to clean off of a blade, once it burnt on, and writhing bodies don't make for a consistent quench, methinks.

Lots of info online. Search for the term "Wootz" as well as "Damascus Steel".

AFAIK Bimetal blades are just that, two metals. IIRC HSS is used for the cutting teeth and a short distance behind them, and a tough but not hard steel is used to provide the flexible support.

I would say that the bimetal blades had more in common with some laminated knife blades (such as used on some Japanese and Finnish knives) than they would have with any form of Damascus.

Cheers Trevor Jones

As I stated in another post. Unlikely.

The actual term damascus was first used to refer to a type of steel known also as Wootz. It was a crucible steel that got at least some of its useful properties as a rsult of some of the trace elements in the make-up of the ore it was smelted from. The Europeans first encountered it in the region of Damascus.

Now the term is used to describe what would be more accurately called pattern welded steel.

The Japanese smiths used a process more along he lines of what you describe above, sorting fragments of higer and lower carbon steels and welding them together to achieve their end product. Some old sword blades from there exhibit paterns that show the layers clearly, while others do not. A lot of the variations can be accounted for by the master/ apprentice training system, and that the variuos makers kept their techniques secret from one another.

It takes very few folds (from personal experience)to get a homogenous product. Or at least one that does not readilly show its layers, when etched. Many, if not all the folks doing pattern welded steels today are using at least one high nickel alloy in the mix to prevent the layers from homogonizing. Several makers are welding knife billets up out of layers (lots of layers) of shim stock thickness, to avoid having the losses that come from repeated heats and welds.

Two straight carbon steels such as you propose above would not show much if any pattern after about three weld cycles, if you were dealing with work of a size suitable for a blade.

There is a really good book out called(IIRC) The Craft of the Japanese Sword that has a reaaly good series of photos of the entire process, starting with mining the ore, right through the final finish, with an explanation of the tradesmen involved in all the steps along the process. Shows good pics of the selection and sorting of the various carbon content chunks that get welded into the billet. It also shows a good representation of the economics involved in multiple welds in the forge, as it discusses the losses due to scale, etc that are assosciated with the forge welding process. While it deals with Japanese swords specifically, it does show some of the problems that any smith must deal with to produce a decent sword blade in the forge.

Cheers Trevor Jones

Actually that's a lousy way to temper a blade -- unless you can get it all the way in at one time.

Well, not exactly. Or at least not originally.

We have to distingush three things here which are all called 'damascus': True damascus, or wootz, steel; pattern welded steel now commonly called 'damascus'; and damascene, which is a surface treatment.

Damascus (from the city that was the terminus of the silk road -- most of the original blades probably came from India) was a homogenous crucible steel with was worked in a superplastic state to produce exceptionally fine blade. The crucible steel, called 'wootz' was made by a process which originated in India and India remained a major source for the metal. However the process of forging damascus blades (and I believe the technique for making the steel as well) spread to the Middle East.

The obvious characteristic of a damascus blade was the patterning on the surface produced by the process. This became a mark of a high-quality blade.

Pattern welding by welding bars of different steels together is an ancient technique practiced just about anywhere steel was made and worked, including northern Europe. The Europeans couldn't make true damascus, but they could imitate the patterning and produce superior blades with pattern welding.

When the process of pattern welding enjoyed a resurgence in the 19th Century, the pattern welded still was referred to as 'damascus'.

The thing that causes most of the confusion is that modern smiths refer to pattern welded steel as 'damascus'. Knowledgable smiths and collectors use the term 'true damascus' for real damascus steel and simply 'damascus' for pattern welded material.

Damascene is a surface treatment that can be applied to any metal to produce a repeating pattern. It is a common decorative technique in jewelry makings.

If you want the full low-down ask over on the knives group.

--RC

"Sometimes history doesn't repeat itself. It just yells 'can't you remember anything I've told you?' and lets fly with a club. -- John W. Cambell Jr.

This pokes at one of my hobby horses, which I'm going to address with a short message, rather than at length. (I wrote an article for a metalworking magazine on the subject once). Quickly, the term "damascus" is not properly used for any form of pattern-welded blade (Merovingian, Japanese, Indonesion, or the modern custom knives that the makers call "damascus"). The blades that were originally sold to the west through the markets of Damascus had a grained pattern not entirely disimilar visually to pattern-welded steel, but were never pattern-welded. The material was manufactured by a controlled melt, very slow cool process that precipitated large carbide crystals within a eutectoid matrix. The material is also known as Wootz. The Victoria and Albert museum has a wonderful collection of true Damascus blades, if anyone happens to be visiting London. The Royal Ontario Museum in Toronto also has a few examples, I'm sure there are examples in many other museums in North America, that just happens to be where I've seen them.

This is not to be taken as a criticism of pattern-welded blades, or pattern-welding, which is a worthy activity (though over-hyped), it is just to get it on the record that true damascus steel and pattern-welding are completely unrelated.

See "A History of Metallography" by Cyril Stanley Smith, which is, by the way, an absolutely wonderful book, though very hard to find. Available for use in most decent size university libraries.

Regards,

Adam Smith, Midland, ON

snipped-for-privacy@TAKEOUTmindspring.com wrote in news: snipped-for-privacy@4ax.com:

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So...which one of these discriptions apply to "damascus barrels" that's an honest question BTW.

granpaw

True damascus barrels are made by winding a strip of metal around a mandral, and hammer welding them. They are not particularly strong and great care should be used in fireing them. Black powder is the recommended propellent. Ive a barrel someplace in my Stuff that came from a very nice, early Greener that was fired with a modern high based shotgun shell. Its a nice piece of modern open helical sculpture that resembles a spring.

After nickle steel barrels (drawn etc) were developed, many shotguns were damascsened for looks. The only true way to tell the difference is with a bit of nitric acid applied under the forend over one of the "weld lines"

Gunner

"Gunner, you are the same ridiculous liberal f--k you ever where." Scipio

What makes you think they don't snap?

John Martin

"Damascus barrels" are pattern-welded.

--RC

"Sometimes history doesn't repeat itself. It just yells 'can't you remember anything I've told you?' and lets fly with a club. -- John W. Cambell Jr.

I would offer that "pattern welded steel" is perhaps the closest description.

I suspect that the pattern was a byproduct of attempts to mfg. barrels from less than high quality metals, at least when they started making them in that manner.

Most of the shotgun barrels I have seen had quite an obvious pattern that appeared to me to have been formed by welding several layers, twisting it, then wrapping it about a mandrel and welding it together.

Cheers Trevor Jones

Pattern welded steel has been called damascus for hundreds of years now, not because of modern bladesmiths. It was just in recent years what your'e refering to as "true" damascus is now what most call wootz.

Forger

I would disagree that pattern welded steel and "true" damascus are completely unrelated. Isnt the belief now that the relationship was that they were two types of steel of similar appearance? And wasnt there some theories that while trying to duplicate the one form of steel, the other was created? Isnt it also true that we really dont know the "true" origins of damascus steel? It would also be interesting to know how long pattern welded steel was referred to as damascus, and how long it has been thought of as something other than damascus. The one other thing that puzzles me is if damascus is not pattern welded steel, it is really wootz... then why call it damascus, why not call it wootz?

Forger

That's certainly true. But the relationship pretty much ends there. See, for example.

I don't see how that could be as pattern welding pre-dates true damascus, at least in Europe and damascus gets its pattern naturally.

Here's an example of true damascus:

Not to my knowledge. I thought it was quite well established that true damascus (wootz) steel was invented in India before the birth of Chirst and the technique of superplastic forging for wootz was invented in the same place not too long afterwards.

I suspect strongly there was a lot of misleading advertising associated with the confusion in the Middle Ages. Kind of like the running wolf mark on sword blades.

Because the steel and especially the blades entered the West through the city of Damascus, which was the the western terminus of the Silk Road. 'Wootz' is a corruption of 'ukku', the word for it in several Indian languages. That was applied to the material independently at the end of the 18th Century as Europeans, especially English, became more familar with the centers of its production.

For a more complete explanation of just what the stuff is and some of its history, see:

--RC

"Sometimes history doesn't repeat itself. It just yells 'can't you remember anything I've told you?' and lets fly with a club. -- John W. Cambell Jr.

I bent six of them over in the last week. They didn't snap. Also, I've used bimetal blades in my bandsaw for years, and they don't snap.

Ed Huntress