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Jared Smith




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PostPosted: Thu 06 Aug, 2009 3:12 pm    Post subject: historical emergence of hollow grinds?         Reply with quote

I am wondering when hollow grinds on; knifes, swords, and similar cutting implements began to appear commonly in Europe?

I would theorize that grinding wheels facilitated fullers as well as hollow ground blades. (Possibly early wheels were very large diameter and this was not the case.) As far as I know in Western Europe, pronounced fullers began to appear more commonly sometime around 11th century (early, but credibly close to known mining and production of greenstone for grinding wheels.) In the texts on swords of the same era, the hollow grind does not seem to be mentioned much.

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Jeroen Zuiderwijk
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PostPosted: Fri 07 Aug, 2009 4:18 am    Post subject: Re: historical emergence of hollow grinds?         Reply with quote

Jared Smith wrote:
I am wondering when hollow grinds on; knifes, swords, and similar cutting implements began to appear commonly in Europe?
Strictly speaking, in the copper age. Most copper and bronze age weapons had hollow hammered and ground edges. I know there's hollow ground blades on certain iron age swords as well, not sure about Roman blades.

Quote:
I would theorize that grinding wheels facilitated fullers as well as hollow ground blades. (Possibly early wheels were very large diameter and this was not the case.) As far as I know in Western Europe, pronounced fullers began to appear more commonly sometime around 11th century (early, but credibly close to known mining and production of greenstone for grinding wheels.) In the texts on swords of the same era, the hollow grind does not seem to be mentioned much.

The hollow edge can be achieve in various ways, including forging, scraping etc. They are a lot more difficult to polish and sharpen compared to flat edges though, where you can simply use a flat wetstone. Getting the hollow shaped edge isn't the difficult part, but bringing it to full sharpness and a high polish is the really tricky part (particularly on the few mm wide hollow edges on bronze age swords f.e.).

Jeroen Zuiderwijk
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Arne Focke
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PostPosted: Fri 07 Aug, 2009 11:51 am    Post subject:         Reply with quote

Adding to that what Jeroen pointed out, hollow ground blades can be found on roman daggers as well.
Germanic lance heads are hollow ground as well.

So schön und inhaltsreich der Beruf eines Archäologen ist, so hart ist auch seine Arbeit, die keinen Achtstundentag kennt! (Wolfgang Kimmig in: Die Heuneburg an der oberen Donau, Stuttgart 1983)
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Ken Nelson




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PostPosted: Fri 07 Aug, 2009 12:05 pm    Post subject:         Reply with quote

Hollow grinds seem to have gone in and out of fashion in different places and times. Much of it has to do with use and how and where it was made. For example, in De Re Metallica, there is a woodcut of French blade grinders working with 6-8 foot (1.8-2.7m) water powered grinding wheels. Technically that is a hollow grind, but of such a slight degree that with a bit of corrosion, it may look now as if it were flat ground. Also, I have had the opportunity to examine a pair of early viking blades, and it appears that they got their fullers by forging and scraping, as the bottom of the fuller is much flatter than the sides. a wheel cuts a much more uniform radius in the fuller.

Flat versus hollow versus convex also has to do with the intended use. for example, for a razor, which only needs to be thin and sharp at the edge, as the hair falls away, is almost always hollow ground, and with wheels that would be too small for a using knife. A knife or sword that had to move the material aside as it is cutting through, may want a flat or convex edge, as those tend to move material aside more readily with the sides, and don't stop like many hollow ground blades can.

I admit I do not have much experience scraping out a fuller, but draw filing can turn a forged bar into a blade surprisingly quick.

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Boyd C-F




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PostPosted: Fri 07 Aug, 2009 4:23 pm    Post subject:         Reply with quote

Speaking of grinding out fullers

Check out the two guys on the bottom left of this page

http://image.ox.ac.uk/images/bodleian/ms.bodl.264/49r.jpg

Doesn't really like that fun of a job... Big Grin

Cheers

Boyd
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Jared Smith




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PostPosted: Fri 07 Aug, 2009 6:04 pm    Post subject:         Reply with quote

Wow! That image is a great find. I have seen a photo of bench and tool that looks like it was for a similar purpose. (I think it is in Barta's workshop.)
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Jared Smith




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PostPosted: Fri 07 Aug, 2009 6:13 pm    Post subject:         Reply with quote

Ken Nelson wrote:
A knife or sword that had to move the material aside as it is cutting through, may want a flat or convex edge, as those tend to move material aside more readily with the sides, and don't stop like many hollow ground blades can.


I was thinking in the opposite opinion for things like seaxes which may have been all around utility knifes in addition to backup or finishing weapons in combat. Hollow grinds tend to be easier to resharpen if there has only been only minor dulling of the edge. I don't recall seeing many images of hollow ground seaxes or "knightly" medieval daggers though. I suspect combat duty may have favored the flat ground profile's strength behind the honed edge, and ability of more average owners to properly repair the blade themselves.

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Jeroen Zuiderwijk
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PostPosted: Thu 13 Aug, 2009 4:21 am    Post subject:         Reply with quote

Boyd C-F wrote:
Speaking of grinding out fullers

Check out the two guys on the bottom left of this page

http://image.ox.ac.uk/images/bodleian/ms.bodl.264/49r.jpg

Doesn't really like that fun of a job... Big Grin

Cheers

Boyd

Just adding to this one, here's a picture of a similar scraper in use, (Cantebury Psalter, 1150):

Jeroen Zuiderwijk
- Bronze age living history in the Netherlands
- Barbarian metalworking
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Bruno Giordan





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PostPosted: Thu 13 Aug, 2009 9:51 am    Post subject:         Reply with quote

Boyd C-F wrote:
Speaking of grinding out fullers

Check out the two guys on the bottom left of this page

http://image.ox.ac.uk/images/bodleian/ms.bodl.264/49r.jpg

Doesn't really like that fun of a job... Big Grin

Cheers

Boyd


that is the most useful image I have seen in years .. only: how was such tool actually made ?
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Jared Smith




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PostPosted: Thu 13 Aug, 2009 2:49 pm    Post subject:         Reply with quote

Pack carburization. Basically, they wrapped the tool in some charcoal and lamb skin (contains the acids associated with carburization in modern processes.) Then covered it in clay and dried it to isolate it from air. It was then heated in a coal forge environment for several days to drive the carbon in. I have a later period (believe it is a translation from 16th century) recipe describing the process for making files capable of working metal and other hardened tools.
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Jeroen Zuiderwijk
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PostPosted: Fri 14 Aug, 2009 3:14 am    Post subject:         Reply with quote

Jared Smith wrote:
Pack carburization. Basically, they wrapped the tool in some charcoal and lamb skin (contains the acids associated with carburization in modern processes.) Then covered it in clay and dried it to isolate it from air. It was then heated in a coal forge environment for several days to drive the carbon in. I have a later period (believe it is a translation from 16th century) recipe describing the process for making files capable of working metal and other hardened tools.
It was animal fat and leather to be precisely (if you're refering to the description Theophilus gives), and heated to high temperature for a relatively short time (experiments have shown that for files 15 minutes or so is sufficient).

But I think that Bruno refers to the construction. It's basically a piece of rod with a hardened steel chisel tip, set into a bar (wood, or iron). The chisel has a large angle at the cutting edge. I'm currently still trying to figure out the most ideal angle, but you'd have to think in the 45-80 angle range. The bar is shaped such, that when the front is ground off at the right angle, the cutting edge has the shape of the groove or fuller you want to cut.

Jeroen Zuiderwijk
- Bronze age living history in the Netherlands
- Barbarian metalworking
- Museum photos
- Zip-file with information about saxes
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Jared Smith




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PostPosted: Fri 14 Aug, 2009 10:02 am    Post subject:         Reply with quote

Jeroen Zuiderwijk wrote:
It was animal fat and leather to be precisely (if you're refering to the description Theophilus gives), and heated to high temperature for a relatively short time (experiments have shown that for files 15 minutes or so is sufficient).


I have it saved, but along with so much that it will take time to dig up. The lambskin was used "freshly slaughtered." It has an effective blend and composition of ingredients; ideal acids, fats, same elements as would be in actual processed leather. If one had access to it, the file was simply wrapped in fresh skin and encased in clay. Then allowed to dry over a period of several days (?, possibly baked at low heat at some distance from a fire?) so that the clay would not burst in high temperature heating. I would have to check the time of heating recommended. In practical terms, the clay encased file/ tool would simply be repeatedly put in the fire while doing other forge work.

I am not sure what the real mystery with blade scrapers is. Some current day makers have web site photos of them in use. At least one asserts that it was the more common method for finishing katanas. ( I have no idea if that is really true. But I have been using similar objects in woodworking longer than I can remember. In furniture working, the wood type scrapers, Sandavick, etc. used to be marketed as a Danish invention.)

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G Ezell
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PostPosted: Fri 14 Aug, 2009 10:16 am    Post subject:         Reply with quote

Jeroen Zuiderwijk wrote:


But I think that Bruno refers to the construction. It's basically a piece of rod with a hardened steel chisel tip, set into a bar (wood, or iron). The chisel has a large angle at the cutting edge. I'm currently still trying to figure out the most ideal angle, but you'd have to think in the 45-80 angle range. The bar is shaped such, that when the front is ground off at the right angle, the cutting edge has the shape of the groove or fuller you want to cut.

The ones I've made so far have a 90 degree cutting edge... its nice because I can flip it over and use the other side, too. I don't think the angle really matters too much, as long as it is sharp...

I believe the grooves on Japanese blades are traditionally done with a scraper, I've never seen or heard of them being forged in.

The tool illustrated is very similar to what one bladesmith I know uses, though he uses a carbide cutting piece. The next one I make will likely use a separate handle/blade setup so one handle can be used with multiple cutters.

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Jared Smith




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PostPosted: Fri 14 Aug, 2009 1:29 pm    Post subject:         Reply with quote

G Ezell wrote:


The tool illustrated is very similar to what one bladesmith I know uses, though he uses a carbide cutting piece. The next one I make will likely use a separate handle/blade setup so one handle can be used with multiple cutters.


I believe that (carbide or pretty hard tool steel hopefully with carbon above 1%) to be the challenging part in making these tools. While simple pack carburizing may get a piece of steel up to the low end of "blade steel" type carbon range, the tool edge probably needs to be much harder than ordinary blade steel for it to last very long.

Whatever they actually did do, they probably knew how a long time ago. The Oxford Journal of Archeology has an article by Vanesse Fell, "Iron Age iron files from England." 7 fine teeth files out of 40 total files (variety of uses expected) were contemplated as suitable for metal working. 5 of the 7 suitable ones had metal particles in the teeth. This was in "pre-Roman era."

Originally my interest in starting this post was to see when actual "grinding machinery" was used to produce hollow "ground", not forged edges. If one possessed the machinery, then I figured it would have been used for similar tasks like fullers in Viking era blades as well. Not knowing for sure, but given their reputation for other elaborate processes like wire drawing, I figure Romans could have actually ground edges and fullers with machinery. (Edit, actually found some examples of Roman grain mills, various power methods, and other articles about ancient gem cutting that assert the opinion that Romans as well as Egyptians had the abrasives and technology to grind gem stones and glass. This capability apparently was interrupted following collapse of the empire.) Production of grinding wheels as a major industry is known in post-viking era, but, I don't know anything about it during 8th to 10th century era. If there is a lack of small utility knifes and other similar cutting objects with true machinery ground "hollow ground" edges during Viking times, my best guess would be that people rough forged and scraped the fullers and edges during that era.

Absence of evidence is not necessarily evidence of absence!


Last edited by Jared Smith on Fri 14 Aug, 2009 3:59 pm; edited 1 time in total
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Dustin R. Reagan





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PostPosted: Fri 14 Aug, 2009 2:24 pm    Post subject:         Reply with quote

Boyd C-F wrote:
Speaking of grinding out fullers

Check out the two guys on the bottom left of this page

http://image.ox.ac.uk/images/bodleian/ms.bodl.264/49r.jpg

Doesn't really like that fun of a job... Big Grin

Cheers

Boyd


Unfortunately, the link seems defunct. Would it be possible to get a direct image?

Thanks,
Dustin
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Jared Smith




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PostPosted: Fri 14 Aug, 2009 3:41 pm    Post subject:         Reply with quote

This is a close up of the bottom left area in the illuminated manuscript.


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scraping.gif


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Jared Smith




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PostPosted: Fri 14 Aug, 2009 3:44 pm    Post subject:         Reply with quote

I have seen something similar in appearance. This was in Barta's shop on one of the articles about him. It looks geared towards one man use. I don't remember if it had a seat as similar rigs ("pony's") sometimes did for other crafts.


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bartasgrindingjig.jpg


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Peter Johnsson
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PostPosted: Sat 15 Aug, 2009 12:08 am    Post subject:         Reply with quote

The tool depicted in the illumination could also be a polishing tool: a burnishing steel set in a handle.
Note the horn set conveniently at the side of the work table: that probably holds oil, or possibly oil and fat mixed with an emery compound.
The blade the work on does not look like it has a fuller. It seems to be a narrow pointy type XV blade. Not that details like this is always very clear in illuminations, but I think that there would have been an attempt to depict a fuller would if they were using a scraper to shape one.

What I cannot understand is the red material they both hold around and under the wooden rest? Something to collect dust? Why?
I´m completely mystified.

Very nice image anyway!
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Boyd C-F




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PostPosted: Sat 15 Aug, 2009 1:55 am    Post subject:         Reply with quote

My initial thoughts for the red thing (hide or textile) was that it would be a way of keeping the scraper or polisher steady.
Although I currently cannot say why I think this - time to sneak off to the workshop and see if I can work out why...
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R D Moore




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PostPosted: Sat 15 Aug, 2009 8:53 am    Post subject:         Reply with quote

Pure guess work here, but maybe the red items were used to regulate pressure/depth of cut? Move the device forward and back until resistance decreased, then grasp the cloth/leather a bit deeper with each change, keeping a somewhat more accurate grind than by solely "eye-balling" it. That could help regulate position as well as depth.
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