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Thread: Marble Slab !
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26th Nov 2020, 02:47 AM #1
Marble Slab !
Hi Guys,
I got a nice gift this morning !
A friend dropped off a piece of white marble plate 30 mm thick, about 30" by 20 " inches in size. I can barely lift it up, but at least it will be flat or at least flat enough to be useful. It is rough sawn on the back but has a lovely bright polish on the top. Apparently it is an off cut from a marble kitchen work top.
25-11-2020-01.jpg 25-11-2020-02.jpg
I'm going to have to find something to sit it on because if I put it on the floor I will never be able to pick it back up !
Maybe I can retire my 13" square trusted floor tile.Best Regards:
Baron J.
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26th Nov 2020, 01:45 PM #2
How do I get friends like you?nooidea.gif
Great score.
Ratty 05/2004 -05/07/2010 COOPER 01/08/1998-31/01/2012
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26th Nov 2020, 07:55 PM #3
Hello Mark,
Nice to hear from you, its been a while...
I guess that its part of just being there when someone needs a hand ! Its saying Good Morning and how are you.
To be honest its something I've never given any thought to !
I consider people on these forums as friends, people that share experiences with each other.
As far as the marble plate is concerned, I repaired the guys lawnmower last year. He thought that it would be useful to me and brought it over.Best Regards:
Baron J.
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26th Nov 2020, 09:46 PM #4Member: Blue and white apron brigade
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My Marble slab story.
About 25 years ago the uni was decommissioning a laboratory that included a polished marble and concrete microbalance pedestal.
The sides of the pedestal were polished marble very similar in total size to the ones you showed in your photos and these weighed about 60kg each
The polished concrete top was about 600 x 600 mm x 150 mm which was impossible for me to move by myself (I estimated it must have weighed ~150 kg)
The top also had short stubs of 18?mm diameter steel embedded into the underside of the concrete that poked out about 40 mm to act as locators that went over the edges of the marble sides
On decommissioning the lab, no one wanted the pedestal so it was marked for disposal and put outside the building next to the space where the skips are parked for waste disposal.
I immediate grabbed two of the sides and took them home where they leaned up against the side of the hour in my side garden for many (20?) years.
I had many big plans, including a marble topped dough bench for the kitchen, but I finally decided I was never going to get around to using them so decided I would sell them last year.
Looking on line I was disappointed to see even this size of slab was quite common and could be purchased as a new off cut for ~$50.
The same adds ran for many weeks, even months so it was pretty obviously there were few buyers.
I also advertised mine for $50 each but months went by and I got no phone calls so eventually I advertised them as $50 for the pair and they went within hours.
Here you can see the slabs, the one on on the RHS still shows 20+ years off accumulated dirt from standing in the garden. The LHS one was after a bit of a wash.
They were still in quite good condition with no nicks out of the edges.
Marbleslabs.JPG
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27th Nov 2020, 08:52 PM #5Senior Member
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Does anyone know how accurate or not, composite granite countertops are. I have a couple of sink cutouts that I use with wet and dry sandpaper to flatten and polish bits of metal on.
Rgds,
Crocy.
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27th Nov 2020, 09:33 PM #6Most Valued Member
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No. After all the only way to know would be to test it.
I'm sure some are better than others. I have a peace of headstone granite. Is it as flat as a surface plate? Certainly not my peace. But how far off it is I really don't know. It has waves in it that are deep enough that blue only transfers to the crests and that's over about 150mm if I recall correctly, to long ago for me to guess at the minimum depth of the wave. There used to be a picture on here but I wouldnt even know where to start looking for it.
But what do you call accurate? and how accurate do you need?
It may well be the flattest thing in your shed and that may well be good enough for starters.
Unless you are trying for "black polish"
The way I look at it is along the lines of "can I sharpen a knife on a concrete floor?" "sure, if the knife is blunt enough you can improve it, you just need to know when to stop trying to make a razor blade" Sometimes all you have is a concrete floor.
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28th Nov 2020, 12:20 PM #7Golden Member
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- May 2020
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I happen to have access to three large marble floor tiles. I know they would not have the rigidity or accuracy of a proper surface plate but for some things the last tenth is not critical.
I was thinking of doing the three plate method to make them flat.
What would be a good media to use as a lapping paste.
I was also thinking that they may be able to be bonded together with something to increase rigidity.
Thanks
Steve
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28th Nov 2020, 02:57 PM #8Most Valued Member
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How you want to spend your time is up to you, some would say its more constructive than golf
As far as thickness goes, just remember "proper" plates are only as thick as they are so they can take X weigh on the plate and stay within 50% of the flatness spec. A very quick google says 50lbs per sq ft. You got anything that heavy in mind?
Bonding them together worries me, at least in our sheds. Sure there is a lathe made with pieces of granite bonded together but I'm pretty sure its in a climate controlled room. How would you know it wasn't "moving all over the place"?
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28th Nov 2020, 09:10 PM #9Senior Member
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28th Nov 2020, 09:37 PM #10Most Valued Member
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Well you cant take it back now, I saw the request and thought it was about my other post. So I went looking. In case anyone was wondering here they are
Damn it was 9 years ago and its not exactly like I remembered it.
First pic a 150mm x 100mm block spotted on a carbatec surface plate.
Second same block spotted on headstone granite.
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1st Dec 2020, 01:29 AM #11
Hi Guys,
I've just discovered that the piece of marble, still has the plastic film over the surface ! Still its got to be better than a floor tile.Best Regards:
Baron J.
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1st Dec 2020, 11:53 AM #12Senior Member
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- Jul 2017
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you would not believe the amount of people I've had arguments with both online and in person RE granite offcuts being as flat as surface plates, its positively bizarre how stubborn people are on the subject. one fellow claimed his to be flat within 0.002mm and when queried how he measured it he apparently used his manual mill with an indicator.
that's not to say they're not handy for the hobbyist on a budget, they are of course a lovely option for scribing layout lines and doing the rough marking out work that is best kept away from a surface plate but the flatness varies by more than a few thou and changes drastically depending how it is supported and what load is on it. so its simply a case of knowing its limitations. for comparison the granite square dan imported for me a few group buys back has a parallelism deviation of about 0.5 micron on the non working faces and when compared for squareness to a master square they both had the same reading on a tenths indicator.
117889683_3215426955213093_7100373639129475756_n.jpg
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2nd Dec 2020, 07:41 PM #13
Hi Marcuschrist, Guys,
My take on this subject of flatness is this ! I have been using an 8 mm thick porcelain floor tile for a long time, for the sort of things that I do its been fine. So the marble slab has to be at least as good, and I would expect better.
I don't have any way of testing or determining how flat it really is.
For what its worth laying the floor tile on the marble surface face down it doesn't rock that I can tell, so either is good enough for me.Best Regards:
Baron J.
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