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| Author | Shotholes |
peterrivington Joined: 28/10/2011 Location: Dalton View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 07/11/2011 18:56:45 Reply | Quote Hi, I have heard it claimed that triangular shotholes are hand-drilled and round ones are machine drilled. Is there any truth in this? Any written source, reputable or otherwise? Thanks, Peter IP: 92.26.193.187 |
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Ty Gwyn Joined: 30/10/2009 Location: Lampeter View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 07/11/2011 20:11:17 Reply | Quote None at all. Hand and Machine are round If you think about it,what ever shape Hand drill you have,between blows with a sledge,you have to turn it,to stop it sticking on the hole,hence ,always round. IP: 86.141.201.218 |
RJV Joined: 16/03/2008 Location: Cleveland View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 07/11/2011 20:13:23 Reply | Quote Ty Gwyn wrote: If you think about it,what ever shape Hand drill you have,between blows with a sledge,you have to turn it,to stop it sticking on the hole,hence ,always round. Can't move for perfectly triangular shotholes in Cleveland. I'll try and find a pic. Jumpers though, not mechanical drills. IP: 82.5.181.65 Edited: 07/11/2011 20:15:44 by RJV |
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Ty Gwyn Joined: 30/10/2009 Location: Lampeter View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 07/11/2011 20:19:00 Reply | Quote Yes,a photo would be good,intrigued, When you say Jumpers,what do you mean? IP: 86.141.201.218 |
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Buckhill Joined: 08/04/2008 View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 07/11/2011 20:33:12 Reply | Quote I would tend to agree with Ty Gwyn on this one - there shouldn't be any difference. I have seen hole mouths, even from machine drilling, which look triangular (or even elliptical) but that could be down simply to movement of the rod (whip) around that point as it is usually slightly greater in diameter than the rest of the hole. It probably depends on the driller how the hole looks. And on the question of not getting the rod stuck - I knew quite a few men who couldn't get it into their heads that the air leg was for holding the drill's weight, not forcing it into the hole - that often resulted in the bit punching an ellipse through a softer bit and taking an age to get back out. IP: 86.159.132.200 |
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RJV Joined: 16/03/2008 Location: Cleveland View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 07/11/2011 20:33:30 Reply | Quote Like a long chisel basically. Either thrown at the rock or hit with a hammer. http://www.redcar-cleveland.gov.uk/rcbcmuseums.nsf/Web?ReadForm&id=889B17EEE770A2E8802576730057CD13 Can't immediatley find a photo of a triangular hole but there are at least a few others on here who will be able to post one when they turn up I expect. IP: 82.5.181.65 |
christwigg Joined: 20/02/2008 Location: Cleveland View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 07/11/2011 20:47:10 Reply | Quote RJV wrote: Can't immediatley find a photo of a triangular hole but there are at least a few others on here who will be able to post one when they turn up I expect. I've seen Simon and Dave trying to get a good shot before, i'm sure one of them will oblige when they read this. IP: 82.5.179.238 |
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christwigg Joined: 20/02/2008 Location: Cleveland View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 07/11/2011 20:55:04 Reply | Quote Found a couple of photo of Simons that shows the triangular profile. http://www.flickr.com/photos/simonrail/5070892387 http://www.flickr.com/photos/simonrail/5873795239 IP: 82.5.179.238 |
AR Joined: 07/11/2007 Location: Knot far from Knotlow in the middle of the Peak District View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 07/11/2011 20:56:19 Reply | Quote I've got a bit of slate I found at Coniston with a triangular hole running through it lurking outside the back door..... I've always been told that the triangular ones were due to the drill not being turned evenly during drilling. The cross base on Monyash village green has both round and triangular holes in it, apparently from miners and quarrymen testing their jumpers after having them sharpened at the smithy. -- I am currently out of the office on leave and travelling through time but will respond to your message when I return last week. IP: 217.43.190.3 |
Edd Joined: 02/07/2008 Location: Alderley Edge View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 07/11/2011 22:19:58 Reply | Quote We have a lot of examples at Alderley of different shot holes over the years. From very wide triangular holes (up to 2" on the flat sides) to rounded triangular ones to perfectly round ones. One even un fired   From what i have been told the very wide tringular ones are due to the chisel being a flat bar, or a round bar with a very wide chisel end. Some one the ones we have found are 3/4" bar with 1 1/2" end. These tend to offer more rounded shot holes with slight tringulation, and often a twist down the bore. The later round ones were air drilled so are much straighter and perfectly round. -- 'having a spiffing adventure underground!' IP: 86.16.18.46 |
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John Lawson Joined: 09/12/2010 Location: Castle Douglas Dumfries & Galloway View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 07/11/2011 22:21:36 Reply | Quote Never seen any of these triangular shot holes. Can only assume that they could be used in a softer type rock, as hand drilling in hard rock in this manner would be almost impossible. You can tell a lot from drill marks the earliest hand drill marks are small eg those in Tynebottom Mine Garrigill and a larger one about 1820's onwards as seen in Smallcleugh. Machine drilling used much larger holes and generally a lot longer, so obviously more efficient. In modern mining many drill holes are often drilled simultaneously using a rig,and the blast pattern produced seems to eliminate the signs of the drill marks,but perhaps other contributors will enlighten us. IP: 86.131.185.178 |
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jaiyls Joined: 20/01/2010 Location: off of wales View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 07/11/2011 23:40:10 Reply | Quote Triangular holes are hand drilled and is the result of precise hand turning of the drilling chisel, strike the chisel with the hammer or sledge and turn the chisel 'one wrists worth' ie one third turn...strike..one third turn..strike..one third turn..strike..one third turn, a quater turn will do but is not as efficient and makes rounder bores, less causes the chisel to snag as you turn as the chisel digs into the slate but not as much in harder rock.   -- Have you got any blocks boy? IP: 86.158.166.117 |
Mr.C Joined: 23/03/2008 Location: North Staffordshire View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 08/11/2011 00:04:02 Reply | Quote Over the years i've seen lots of triangular shotholes (as well as round ones of course) & allways gone with the "hand drilled theory". Asked around at the club tonight & no one can think of any quotable referance to support this though. But one came up with the idea that they can be the result of machine drilling with an off center ground steel - plausable. One thing I would say is that the short narrow 1' x 5/8" holes you see, seem to be the early ones. I've test fired such holes myself, & they seem to be the optimum size for drilling effort v effect when hand drilling in hardish rock & firing with black powder. -- If things dunner change - the'll stop as the' are. IP: 2.27.39.138 Edited: 08/11/2011 00:09:04 by Mr.C |
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Buckhill Joined: 08/04/2008 View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 08/11/2011 00:11:37 Reply | Quote christwigg wrote: Found a couple of photo of Simons that shows the triangular profile. http://www.flickr.com/photos/simonrail/5070892387 http://www.flickr.com/photos/simonrail/5873795239 The first of these photos shows a hole which has been drilled along the junction of two joints which explains the flat right and bottom faces but...the left side shouldn't be flat.. so there could be something in the idea after all. As jaiyls explains a precise 1/3 turn would of course make a triangular hole, but this also suggests several successive strikes at each position in order to form a continuous side. With percussive air drills the rotation rate depends on the pitch of the splines on the twist bar - usually around 10-12 strikes per rotation, maybe slightly more if in very hard rock which would produce a smoother and more rounded profile. IP: 86.159.132.200 |
Roy Morton Joined: 09/10/2007 Location: Redruth Cornwall View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 08/11/2011 04:54:30 Reply | Quote I have to agree with Jaiyls. Here in Cornwall I've seen many examples of triangular shotholes and they have all been in older mines or in mines that have been run on a shoestring. All in all I have always viewed them as hand drilled, and the method described, concurrs with my personal theory. It's all in the wrist action.  -- 'Bid me discourse, I will enchant thine ear' IP: 86.150.101.209 |
Morlock Joined: 31/07/2008 View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 08/11/2011 06:06:05 Reply | Quote If you hand sharpen an ordinary twist drill you can get a similar effect in metal if the point angle or lip length vary between sides. IP: 82.27.15.59 Edited: 08/11/2011 06:09:02 by Morlock |
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RJV Joined: 16/03/2008 Location: Cleveland View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 08/11/2011 06:38:46 Reply | Quote Morlock wrote: If you hand sharpen an ordinary twist drill you can get a similar effect in metal if the point angle or lip length vary between sides. Not sure you could do that with a Cleveland shothole. They don't just resemble triangles, they are perfectly triangular with sharp 60 degree internal angles. IP: 149.254.187.125 Edited: 08/11/2011 06:41:19 by RJV |
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christwigg Joined: 20/02/2008 Location: Cleveland View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 08/11/2011 11:10:13 Reply | Quote Buckhill wrote: http://www.flickr.com/photos/simonrail/5070892387 The first of these photos shows a hole which has been drilled along the junction of two joints which explains the flat right and bottom faces but...the left side shouldn't be flat.. so there could be something in the idea after all. There was no joint there, the Cleveland ironstone doesnt have that. I believe what happens is the force of the blast fractures the rock from the three points of the triangle, so you're seeing three cracks radiating out in those directions. I think we need to keep an open mind about the term "hand-drill" because in later years they did use rotary hand-drills in the same mines that give the circular holes you would expect. The earlier triangular holes were still 'drilled' by hand, but with a chisel point being turned around a 1/3 each time to give the shape seen there. IP: 145.8.104.65 Edited: 08/11/2011 11:11:32 by christwigg |
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Morlock Joined: 31/07/2008 View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 08/11/2011 11:27:09 Reply | Quote RJV wrote: Morlock wrote: If you hand sharpen an ordinary twist drill you can get a similar effect in metal if the point angle or lip length vary between sides. Not sure you could do that with a Cleveland shothole. They don't just resemble triangles, they are perfectly triangular with sharp 60 degree internal angles. Do the holes look something like this, constant diameter triangle easily achieved with a flat drill? http://en.wikipedia.org/wiki/Reuleaux_triangle IP: 81.107.137.179 Edited: 08/11/2011 11:31:09 by Morlock |
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Ty Gwyn Joined: 30/10/2009 Location: Lampeter View Profile View Posts View Personal Album View Personal Files View all Photos Send Private Message |
Shotholes
Posted: 08/11/2011 11:27:59 Reply | Quote Very interesting indeed I cannot visualise that photo of a Jumper very well,the Drill bar above yes,but that other piece,is it on the same principal as a lorry tyre remover? What type of rock was drilled in the Cleveland mines,was it softish? I can visualise triangular being drilled in Slate,being a softer material,and using a narrower drill to increase speed of drilling,one wrist turn right then left.and the use of Black powder for firing. Have you boys ever found a Triangular Rammer on your travels? IP: 81.158.20.170 |
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