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bollie7
11-05-2012, 09:07 PM
G'day All
I came across a small bit of granite that had been turned the other day and that started me thinking about how it was done. ie what sort of lathe, tooling etc.
I''ve just done a quick search on this forum but nothing jumped out at me.
I don't want to do this, I'm just curious to find out how its done.
Any thoughts?
regards
bollie7

KiddZimaHater
11-05-2012, 09:15 PM
http://wickeddark.smugmug.com/Photography/The-Black-and-White-Collection/PC113167/1123572202_Qo4Vj-M.jpg
.
Here's a picture I found of an abandoned Granite Lathe from the Redstone Quarry.
(Wherever that is).
Abandoned in the 1940's. Notice the tree growing up between the bedways.

Dr Stan
11-05-2012, 10:24 PM
I understand old planners were used to surface stone after they were of little to no use in the metal industry. However I have no idea as to how the cutting tools were ground. Today most of the work is accomplished with diamond saws.

Duffy
11-05-2012, 10:48 PM
Virtually EVERY processing method or technique for working stone is an abrasive process. Proof of this statment is that the product of these processes is always stone dust or grit, never "shavings." All this to say that to turn a piece of, say, granite, it is necessary to wear it away with an abrasive such as a diamond single point, or even a diamond composite. Marble or alabaster can be worn away with hardened steel tools.
Even drilling a blast hole is really a wearing process, except the tool produces fairly coarse chips. I dont think anyone can say that the shape of the chip relates to the "cutting angle" or "rake" of the tool bit. The actual tip design is intended to ensure that the tool wears away MUCH slower than the stone.
Someone here will doubtless have a more technical take on the process.

mickeyf
11-05-2012, 11:05 PM
On some of the limestone/sandstone islands in this part of the world, millstones were sawn out with what looks a lot like a regular hole saw - but several feet across. Limestone is pretty soft as stones go, and I'm not even sure the saws were hardened. I saw some abandoned ones years ago on Gabriola Is. Some photos and discussion here. (http://www3.telus.net/jenni_gehlbach/quarries.html)

oldtiffie
11-06-2012, 04:41 AM
http://www.google.com.au/#hl=en&sugexp=les%3B&gs_nf=3&cp=10&gs_id=37&xhr=t&q=machining+marble&pf=p&rlz=1W1IRFC_enAU360&sclient=psy-ab&oq=machining+marble&gs_l=&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.&fp=3a3ea9713b9f1163&bpcl=37189454&biw=1920&bih=884&bs=1

http://www.google.com.au/#hl=en&sugexp=les%3B&gs_nf=3&cp=15&gs_id=46&xhr=t&q=machining+stone&pf=p&rlz=1W1IRFC_enAU360&sclient=psy-ab&oq=machining+stone&gs_l=&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.&fp=3a3ea9713b9f1163&bpcl=37189454&biw=1920&bih=884

kf1002002
11-06-2012, 01:27 PM
Just got done end milling some soapstone. This material is very soft, you can work it with your fingernails if you try. The chips do cut off, it appears but they are so brittle they break into tiny pieces and you then have a pile of coarse talc.
For drilling, I've used copper tube with an abrasive/water mix and I've seen big gang saws with 6 or 8 steel blades in parallel washed with a water sand mix used for cutting architectural stone. The idea in both cases is that the sand or abrasive grains get imbedded in the copper or steel and even if their life is short there are lots more where they came from.
In Egypt I saw the local people using what looked like carpenter's tools for cutting the local limestone to use on various monument repair jobs. It would require a lot of patience but they have been at it a long time so probably have learned more than we give them credit for.

Anyway that's my 2 cents worth.

Ken

Fasttrack
11-06-2012, 02:45 PM
Great question!

I was recently given a copy of Machinery's Handbook from the early 1940s and I noticed there was a section on speeds/feeds and tool geometry for cutting special materials including rubber, slate, granite and marble. I was astounded! I never considered machining slate, granite or marble! I just assumed it was always a specialized abrasive process, but the handbook suggests otherwise. They do note that great care must be taken to prevent brittle pieces from breaking during machining. That made me pucker a bit ... I just imagine the slate flying into razor sharp bits!

Northernsinger
11-06-2012, 03:13 PM
I'm pretty sure you can see stoneworking on lathes on Youtube. Many old lathe handbooks had short sections on marble, alabaster, etc. When I obtained a fair sized patternmnaker's lathe in the mid-1970's a smart, local machinist thought I ought to try marble turning. I didn't but have always remembered his thought.

Also in the 1970's I had an informal tour of a slate working concern up here and saw their planer in action. I can't now recall whether they cut dry--I believe so, though--or wet6. I do know that they certainly had a settling pond for some process water.

Bob Fisher
11-06-2012, 05:38 PM
When we were purchasing a granite counter, I had occasion to see their shop and see some of the operations. It's all done at speeds much higher than I would have imagined. Router cutters about 4in in dia and coated with diamonds. Lots of water , slow feeds, high RPM. Lots of water to cool the bit. Bob.

rohart
11-06-2012, 06:03 PM
I think the key point on the text in mickeyf's link about cutting pulp stones on Gabriola island is that they used ball bearings cut into quarters. The large 5 ft cylindrical cutters only had seven or eight teeth (27" apart) and they would drop half a tobacco tin of quartered ball bearings into the trough to be used as an abrasive.

I don't know who's going to spend their life cutting ball bearings into quarters, but it takes all sorts.

Dr Stan
11-06-2012, 06:24 PM
Keep in mind the Egyptians only had copper & bronze tools and they managed to build the pyramids and other very large stone structures cutting blocks that were fitted together without mortar.