Mark Waite (http://www.corrismineexplorers.co.uk/) has given me what looks like a slate off-cut which appears to have been cut by a Hunter Saw.

From measuring the curvature of the toothmarks it looks as if the saw diameter was around 2 m (though it's only a small piece of slate so the calculated diameter can be only approximate).

The well-known picture of the Hunter Saw at Delabole looks as if it was something like 1.5 m diameter - does anyone know what sizes Hunter Saws were made in? (For that matter is there any record of Hunter Saws at Braich Goch?)

Also of interest, the slate fragment was found some way underground - so it is assumed that waste from the mill was being carried back underground for tipping in worked-out chambers.

Dave

Have you read Hunter Saws / Thoughts on Saws by Rodney Weaver (additional notes by G. Isherwood) ? It's in the Technical Documents section of this site.
He states that blades were made as large as 13' diameter. I'm not sure if they were made in standard sizes or increments but I wouldn't be suprised if they were made in size and ganging to suit the power available on a particular site.
I can't see any mention of Braich Goch. It could be possible that one was obtained second or third hand. I'd have thought well suited to Corris slate.
Cheers.

Thanks for that - I'd not spotted that paper before.

Dave

The very thick (c.5") slate plaque commemorating the incorporation of the Van Mining Co Ltd, from above the deep adit portal at the mine, now in NMW, shows on its lower edge, evidence of having been sawn with a sandsaw from both ends and the remaining central portion smashed through and then dressed tolerably flat with a pick. See WMS newsletter 49, item 40 for the inscription and other information.

Sandsaws, as I understand, preceded better known mechnaical saws in the slate industry.

Mark Waite (http://www.corrismineexplorers.co.uk/) has given me what looks like a slate off-cut which appears to have been cut by a Hunter Saw.

From measuring the curvature of the toothmarks it looks as if the saw diameter was around 2 m (though it's only a small piece of slate so the calculated diameter can be only approximate).

The well-known picture of the Hunter Saw at Delabole looks as if it was something like 1.5 m diameter - does anyone know what sizes Hunter Saws were made in? (For that matter is there any record of Hunter Saws at Braich Goch?)

Also of interest, the slate fragment was found some way underground - so it is assumed that waste from the mill was being carried back underground for tipping in worked-out chambers.

Dave

GrahamI should be able to cast some light on that, but a 6' blade sounds about right.

Interesting that the waste was seemingly tipped inside chambers - I'm sure I've come across this somewhere else, but I can't for the life of me remember where.

It may be something to do with mineral rights and land ownership being two different things, ie the land owned by the quarry company on the surface was much more limited than their underground ownership?

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Some underground tipping has been carried out at Maen Offeren, is that where you are thinking of?

Tipping inside chambers i.e. backfilling became more commonplace towards the later years, principally to save the cost of haulage to the surface. However, this was usually mining/quarrying waste rather than mill/dressing waste. Tipping space was certainly an issue in the peak times of the quarries - but was usually resolved by using some kind of up-haulage and higher level tipping over existing tips.

Regarding the Hunter saw blade diameters etc. they could obviously be made any size - they used "standard" teeth and holders - however there was a limit to the actual size which could be fitted to any given machine because of the height of the saw axle which was fixed above the moving table. There was (as far as we know) no provision for moving the axle up and down, and given the massive gear wheel drive, would have probably proved fiendishly difficult in any case. If a smaller saw was used it was merely a matter of supporting the slabs on suitable blocks of timber to raise them to the required height for cutting.

Curious - there were certainly several saws made and given their weight, cost/value etc. they were probably a saleable asset when a quarry went under. Braich Goch is of course just down the valley from Cooke's venture at Abercwmeiddaw where as well as the tunnelling machine, there was a Hunter planer and (I speak from memory of the sale list in the Corris Slate book) I think a saw as well. Perhaps Braich Goch bought one from there?

Cheers

Grahami

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A photo of the off-cut in question ...

🔗Personal-Album-166-Image-60188[linkphoto]Personal-Album-166-Image-60188[/linkphoto][/link]

Dave

Is this the only sample that has been found?

i measured the bores at corris and they were about 2 meters diamiter see hunter tunneller posts a while ago for dimentions i posted

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Is this the only sample that has been found?

It's the only one I saw there (and I did look around for more). I probably would not have noticed it in the first place if I hadn't been looking at the floor as I put SRT kit on.

Dave

It looks more like the result of blasting a pillaring hole to me you get some weird patterns sometimes, the ridges are to sharp and the "valleys" (cant think of the right word) to grainy it would all be a bit smoother if it was cut by a saw; but without getting my paws on it I cant be certain :flowers:

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If this was from a quarry where a Hunter Tunneler was used, I would be wondering if this couldn't be a piece of rock that split off from the cutting face. What does the face look like at the end of a blind Hunter Tunneler bore?

The "face" of a blind bore produced by the trepanning tunneler would show no marks.

Looks much more like saw waste to me. As for the sharpness of it, un-weathered cuts would be sharper than the samples we see in buildings etc. (e.g. Hafod-Las) which have been weathered for something like 100 years.

Cheers

Grahami

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Presumably the feed rate for the saw would be controlled by an automatic (possibly adjustable) power feed?

Sorry to spoil the party but I am dubious that this is actually from a Hunter machine. In one of the last chmabers to be worked at Braich Goch they appear to have used something like a coal cutter to open up a foot joint and I suggest that this is what the fragment came from. Alternatively they could have used the Korfmann saw which was used at Aberllefenni although I am currently uncertain as to whether this was ever used at Braich Goch. I'll try and find out. One thing I am on clear on is that it took a long time to get the correct teeth for the Korfmann saw.

... I am dubious that this is actually from a Hunter machine. In one of the last chambers to be worked at Braich Goch they appear to have used something like a coal cutter to open up a foot joint and I suggest that this is what the fragment came from.

That's an interesting suggestion and considering where the fragment was found (the east end of floor 5) seems very reasonable.

Two more pictures showing (a) curvature of marks (about 2 mm in 100 mm)

🔗Personal-Album-166-Image-60344[linkphoto]Personal-Album-166-Image-60344[/linkphoto][/link]

and (b) the profile of the grooves.

🔗Personal-Album-166-Image-60345[linkphoto]Personal-Album-166-Image-60345[/linkphoto][/link]

Dave

Just seen the last two pics, I am now almost certain that this is the result of a pillaring hole and not made by any saw or machine; the ridges aren't parallel and its to grainy. The saw teeth would have made it smoother, weathering does not come into it if it was underground; I once found a similar piece (square) ; and almost convinced my new rockpartner that it was a fossil of a dinosaur's tooth 😉

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OK - the Jury's still out on this one.
The marks certainly look curved, rather than straight as they would be from drilling. Not sure of the geometry and drive of the machine Jon refers to that could produce the effect - nor the "coal cutter" thingy - my gut feeling is that it would produce a much smoother cut than this, even if left in place for some time. Most odd.
I've got shot somewhere of a piece on the bottom floor at Braich Goch where they've used a channelling machine, the bores are, as you would expect, very much larger and the breaks between them caused by the broaching much more obvious. Ahaa - found it!

🔗Corris-Mine-Explorers-Image-44977[linkphoto]Corris-Mine-Explorers-Image-44977[/linkphoto][/link]

Maybe scouring what's left of the tips at Abercwmeiddaw would throw up some Hunter cut bits there. If anyone was inclined, I suppose it's an academic exercise.

Cheers all

Grahami

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I have uploaded a photograph to the BG user album showing the marks left on the rock.


🔗Braich-goch-Slate-Mine-User-Album-Image-60527[linkphoto]Braich-goch-Slate-Mine-User-Album-Image-60527[/linkphoto][/link]


(pic added by Vanoord ;))