Granite Surface plates

[ColHParticipant @colh]

[ColHParticipant @colh]

I have obtained three pieces of granite that were cut outs from a kitchen benchtop.  I would like to lap these together to make a surface palte for the workshop.

 

What is the technique used to to lap three plates together and what is the best lapping medium to use?

 

Col H

[David Clark 13Participant @davidclark13]

Hi There

Are you sure they need to be lapped?

They might be flat enough.

Before I bought a proper granite surface plate, I used a granite chopping board from Argos which appeared to be flat enough for model engineering purposes and only cost about £10.

regards David

 

 

[ColHParticipant @colh]

Hi David

Thanks, must admit I haven’t checked them.

I would still like to know how to lap to each other. I know that A is lapped to B, B to C and C to A etc rotating each by 45 or 90 degrees before moving to the next but I have no idea what to use as a lapping compound.

You must work from home like me if you are on the computer so early in the morning.

Congrats on MEW. My first issue was number 2 and I only misse one issue since then. Managed to get a copy of the missing issue and number 1 from Ebay. Not cheap but worth it to complete the set.

regard Col

 

 

[Ruaidhri MurphyParticipant @ruaidhrimurphy46564]

Thanks David – you’ve just saved me a couple of hundred quid!!

 

Guess who’s just back from Argos – and having checked it reasonably thoroughly, it is more than good enough for my needs – 14.50

 

Boy don’t you love good web sites

 

Cheers,

Ruaidhrí

[David Clark 13Participant @davidclark13]

Hi There

I bought a granite Trivet from Tesco yesterday.

It is polished on one side.

About 8 inches 200mm square at a guess and all for about £4.

regards David

 

[John Wood1Participant @johnwood1]

I use a piece of thick plate glass from an old display counter which does the job very well.

 

Regards  John

[BizibilderParticipant @bizibilder]

I also have a granite plate from Tesco.  I checked it with a GOOD straight edge (a new “best” ruler) and could not get a 1.5 thou feeler gague under it at any point on the surface.  I reckon that it is good to a thou over its surface – more than good enough for workshop use.

 

The smaller ones – down to “coaster” size may be useful for confined spaces!

 

Bizibilder

[ChrisHParticipant @chrish]

The managers of Argos and Tesco must be wondering what’s going on, what with all the granite chopping boards/trivets flying out the doors…………….

ChrisH 

[Peter Williams 1Participant @peterwilliams1]

I’ve been using one from Asda for over a year, despite heavy use it’s still like new.

 

Peter

[jomacParticipant @jomac]

Granite slabs that are cut for buildings and monuments, should be dead flat.

I used to work for the largest granite cutting and finishers in the Southern Hemisphere, as a welder and mantainence operater, They produced all the granite for the new parliment  house, so when the 2×3 meter square panels were polished in 1 to 5 grades the tolerances were plus or minus 1mm over 1 m, for the front face only, the backs were left as cut.

But !!!!  when the panels were laid flat and leveled with wooden wedges, because the way the saws could cut ofline, most of the panels varied in thickness from corner to corner, That was not a big problem as you could not see the backs and the fixers would pack them out to fit.

Anyway  if you have a section cut from a large panel to be used as a surface plate etc etc, the top surface should be very accurate, Just make sure you are not trying to level it from the bottom surface ie, there could be a variation in the thickness of the corners. 

Does all that make sense,???  cause trying to type and think at the same time leaves a lot to be desired. Women can knit, talk, watch TV and feed the kids all at the same time.

[Geoff TheasbyParticipant @geofftheasby]

I have a piece of marble intended for a kitchen worktop.   It is too big to use as a surface plate, how can I cut it down to, say, about 1 foot square.   It is about three quarters of an inch thick.

 

I have tried cutting along a line with series of cuts from a cold chisel, but although bits chip off, it shows no sign of breaking.

 

The easy way is to buy a trivet from Tesco, as mentioned above, but I hate to see a bit of useful material go to waste.

 

Regards

Geoff

[chameleonrobParticipant @chameleonrob]

why not spent £20 – £30  on a new one, ideal for scraping and marking are. usual disclaimer.

http://www.rdgtools.co.uk/

Edited By David Clark 1 on 05/06/2009 11:13:39

[ChrisHParticipant @chrish]

Geoff – you need something like an angle grinder with a stone cutting blade I’d say, and probably someone dribbling water into the cut to lubricate and cool.  Be careful not to overdo the water though – won’t do the angle grinder any good or you either.  Use a RCD trip in the electric supply too.

Regards, ChrisH 

[CirclipParticipant @circlip]

Can’t you chat up a bathroom/kitchen tiler?? The circular saws used for tile cutting would help. You can also buy the diamond cutting disks separately. Bonk & quonk  or slewfix??

 

    Regards Ian.

[Graham HorneParticipant @grahamhorne65034]

Many thanks Clark and Holloway. She Who Is Obeyed wanted a layered look low garden wall so each Friday I collected offcuts of Marble, Granit and Ceasarstone from a nearby

Marble grinder to do it.    ‘No not that sort of stone, sandstony stone’.

Couldn’t throw away such beautiful smooth shiny surfaces, so decided to square them and give to student engineers at the local Adult/Further Education school as beginners marking-out plates.

So pleased to hear they should be great for the purpose. Thank you.

 

[ChrisHParticipant @chrish]

Have also bought a granite plate from Tesco’s – 300 x 400 x 12mm for £9.79.  Tesco’s called it a surface protector but for me it will make a very good surface plate to be going on with until I can afford a ‘proper’ one – if I think it necessary then, maybe this will be all I need!

Regards, ChrisH 

[Geoff TheasbyParticipant @geofftheasby]

I bought a “granite” placemat ( a packof two in fact) from Tesco for £5.98.

 

The surface seems superb, according to my straightedge.

 

I am doubtful, however as to to its “granite” constitiuency, since it is limited to a temperature of 90 degrees C, whereas granite melts at about 1300 degrees C.

 

Possibly it is of a granite dust/resin mixture. 

 

No matter, we require its surface properties, not its heatproof ability.

 

SWMBO does not require the extra placemat, so I have two surface plates!

 

Regards

Geoff

[Frank DolmanParticipant @frankdolman72357]

My Tesco seems to have sold out of surface plates, so I went to Sainsbury.  Theirs seem to be the same as the ones Geoff Theasby got from Tesco, ie. a pair and limited to 90 C.  The temperature limitation may be due to the rubber pads and not to the material of the plate.  I am sorry to say that mine are really not very flat at all, to the extent that I am going to try to do something about at least one of them. I have found out that “ATM” stands for Amateur Telescope Maker and that these gentry grind and polish glass surfaces to spheres, paraboli and optical flats!  I shall see about plundering their books and suppliers of grinding paste etc. 

[JimmieSParticipant @jimmies]

The easy way to get granite cut is to take it to your local monumental sculptor ie gravestone supplier.

[Author]

Posts