# Preparing a granite surface plate



## blue_luke (Jan 12, 2018)

Hello all! 
In the next few weeks I will buy a few more tools for my hobby machining shop and I intend to buy a granite surface plate.

I have been gathering informations about this subject and it seems that for my purpose I shall be happy with a 12"X18"X3" grade 'B' (tool room)
I intend to build a welded square tubing base for it and use a three point leveling system to set it perfectly level.

Funny enough I can't find much information about how to treat the surface initially when it's new, and then at routine maintenance intervals. Maybe since these are very simple devices there is simply not much to say about them? But without being maladively perfectionnist, I like to know and understand these basic things!
So the questions are:
-  is there an initial treatment to be given to a new stone?
-  Are there some products I should never touch the stone with?
- Other considerations I am ignorant of?

Thanks, Luc


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## Moderatemixed (Jan 12, 2018)

I have a Starrett 24 x 36 x 4 plate. I watched youtube videos regarding "Bessel and Sperry points" which helps sort out your mounting. There are formulas online which I found helpfull. Too, I watched "Suburban Tool" and they suggest using "ammonia" to clean the plate. I went to Canadian Tire and got a $3 jug and it works amazingly, just make sure you ventilate the shop when you use it. I keep my plate covered when I am not using it with a vinyl Starrett cover. I am just a basement shop so I have not had the plate resurfaced or re-calibrated yet, but for you that won't be an issue. Good luck. 


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## woodchucker (Jan 12, 2018)

well, I have never treated my plate.  I clean it with simple green.   Don't sand  or file on it. Don't hammer on it.
Clean it, cover it with some tempered hardboard when not in use. It will protect it from the crap that normally winds up finding it's way to that surface.


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## Ulma Doctor (Jan 12, 2018)

Hi blue_luke,
a thorough cleaning is recommended for a new stone.
granite dust can create all kinds of scratches on the plate and instruments
i use straight dollar store ammonia, after seeing a great video by Don at Suburban Tool Co  
Tom Lipton at Oxtool uses Starrett brand surface plate cleaner
i have heard of people treating their surface plates with lanolin, it is an acceptable practice and recommended by some


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## eeler1 (Jan 12, 2018)

Hey Mike, does that apply to newly-reconditioned stones as well?  Mine just got re-done, should it get a good clean with ammonia?


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## blue_luke (Jan 12, 2018)

Hmmmmm....
That is exactly what I was suspecting. A new plate was probably fairly well cleaned after manufacturing but there must be still some dust, particles and whatnot on it. 
So this has to go somehow. I did not know about using amonia on granite.

Also while on the subject, a 'B toolroom grade" plate is surfaced to 0,0002" which is is about twenty times better than my abbility at machining right now! I will buy one from a machine tool distributor, I 'need' the comfort of buying something certified, but just out of curiosity, how flat are the granite found at countertop or toombstone fabricator ?
Also, again out of curiosity, I had some belgian, french and austrian colleagues at one point or another in my career and contrary to us north-american as where we refer to a 'surface plate, or a 'granite', they refered to a 'marble plate' or simply a 'marble'
Is it just because granite is more common in America, and marble more comon in Europe, or this is just a semantic quirp?

Luc


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## Eddyde (Jan 13, 2018)

In my opinion marble would make a poor surface plate, It is soft and porous. So my guess it's a case of translation. 



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## Bob Korves (Jan 13, 2018)

Granite is stable and long wearing against abrasion.  Ammonia is a great choice for a cleaner.  Some surface plate cleaners contain lanolin, which makes the rock look nice, but builds up a film that compromises the accuracy, which is the sole purpose of the plate.  Your measuring tools should be be accurate to an order of magnitude higher than the work you want to calibrate with them.  For some work a yard stick is close enough...


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## toploader (Jan 13, 2018)

While watching some Vintage Machinery videos on YouTube.  Richard King advised the guys in the class to use windex. I have Starrett surface plate and it seems to work well.


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## Ulma Doctor (Jan 13, 2018)

eeler1 said:


> Hey Mike, does that apply to newly-reconditioned stones as well?  Mine just got re-done, should it get a good clean with ammonia?


Yes,
I got quite a bit of diamond dust to come off onto the white rags when i cleaned mine after calibration 

Ammonia will not compromise granite.

you can spend more money if it makes you feel warm and fuzzy, but there is no magic in other cleaners , rather only preference


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## Ulma Doctor (Jan 13, 2018)

blue_luke said:


> Hmmmmm....
> That is exactly what I was suspecting. A new plate was probably fairly well cleaned after manufacturing but there must be still some dust, particles and whatnot on it.
> So this has to go somehow. I did not know about using amonia on granite.
> 
> ...


I can’t say for tombstone, but i have checked countertop granite- it failed when blued up on my A plate
It’s better than the garage floor but not precision by any stretch .


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## blue_luke (Jan 13, 2018)

My dad was an artisan bookbinder and I remember as a kid he had this big piece of granite from a friend who made tombstone, monument bases, and that sort of things, hence the question!  
That stone was used as a surface where one operation required that the book spine be hammered to give it the roundness. 
Just hamering on a bench, no matter how sturdy it was built,  did not produce the required results.


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## Moderatemixed (Jan 13, 2018)

I tried the "piece of countertop" option first and found it to be within .003. It was 
small however and when I got a piece that was 14" x 14" the error was "bad" to say the least. I paid $250 for a Starrett 24 x 36 x 4 on Kijiji (Craigs List for Canadians). If you are a bit patient you can get a "name brand" for a decent price. That said, a buddy has a 12 x 18 "Chinese" plate and it is as accurate as my Starrett. (.0005 over 18 inches). I think marble was used because of a lack of granite overseas (rampant speculation). Good luck..... let us know what you end up with. 


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## Bob Korves (Jan 13, 2018)

toploader said:


> While watching some Vintage Machinery videos on YouTube.  Richard King advised the guys in the class to use windex. I have Starrett surface plate and it seems to work well.


I have used Windex (well, actually generic cheap Windex substitutes) and it is a great and cheap cleaner for surface plates and for scraping cleanup.  The downside is that some of it causes iron and steel to rust pretty badly and quickly.  BTW, the water soluble Canode spotting inks will also cause corrosion if you leave them on your parts or tools.


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## Bob Korves (Jan 13, 2018)

Moderatemixed said:


> That said, a buddy has a 12 x 18 "Chinese" plate and it is as accurate as my Starrett. (.0005 over 18 inches).


.0005 is not accurate enough for a 12x18" surface plate.  On a 18x24 the entire surface should be within .00015 for a grade A plate of that size.  Names like Starrett mean nothing on a used surface plate, and there is no reasonable substitute  for having your plate professionally inspected and calibrated so you know what you actually have.  Anything else is guessing and hoping.  Shiny does not mean flat.  Small dings do not compromise the flatness.


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## Moderatemixed (Jan 13, 2018)

Bob..... I missed a zero. But thank you for correcting me as you seem to do so for everyone, I feel honoured. 


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## woodchucker (Jan 13, 2018)

Ulma Doctor said:


> Ammonia will not compromise granite.


Why would lets say simple green compromise granite. I wipe it off as soon as I use it.


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## middle.road (Jan 13, 2018)

Back to Old Carl here. (The Tool & Die Maker that I first worked with and should have paid better attention to...)
Back to work after the two week summer shutdown, he was removing the cover from the surface plate in the shop
and asked if there was any coffee left in the pot. (I had brought in a Bunn-O-Matic when I first started there.)
'Sure' says I, and he asked me to fetch it. He then proceeded to use the coffee, black, no cream, to clean the surface plate.


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## Ulma Doctor (Jan 13, 2018)

i agree, simple green will not compromise granine either,
but simple green can leave residue that doesn't flash off

fretting over, protecting and cleaning a piece of flat rock would be considered heresy by any other profession or pastime


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## Bob Korves (Jan 13, 2018)

Moderatemixed said:


> Bob..... I missed a zero. But thank you for correcting me as you seem to do so for everyone, I feel honoured.
> 
> 
> Sent from my iPhone using Tapatalk


You are quite welcome, and I hope you and others will return the favor whenever I or anyone else spreads information that may be incorrect.  We are all learning here, and incorrect information does not help anyone.  I really want to be part of the solution and not part of the problem, so please let me know when I am mistaken or out of line.


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## KMoffett (Jan 13, 2018)

Windex contains ammonia.

Ken


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## gradient (Jan 13, 2018)

Hmmm, I think people who practice the sport of curling also fret about how clean and flat their rocks are, not only machinists


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## Dabbler (Jan 13, 2018)

As a curler, you are tight!  we fret about how the different rocks slide!

I use ammonia wipes in a pop up container.  That way I have a clean cloth every time, and they are lint free.


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## Ulma Doctor (Jan 13, 2018)

gradient said:


> Hmmm, I think people who practice the sport of curling also fret about how clean and flat their rocks are, not only machinists


I stand corrected!


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## petertha (Jan 25, 2018)

What is it about ammonia (either as a concentrate or ingredient within Windex or whatever) that makes it good for granite to begin with?


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## kev74 (Jan 25, 2018)

petertha said:


> What is it about ammonia (either as a concentrate or ingredient within Windex or whatever) that makes it good for granite to begin with?


Just a guess, but ammonia is an effective solvent that is relatively safe and non reactive with granite and steel tools. It also leaves no residue behind.


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## Bob Korves (Jan 25, 2018)

Ammonia is an effective and inexpensive cleaner that cuts oil and grease and does not leave a residue.  It does not harm granite.


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## woodchucker (Jan 25, 2018)

kev74 said:


> Just a guess, but ammonia is an effective solvent that is relatively safe and non reactive with granite and steel tools. It also leaves no residue behind.


But ammonia is a caustic, so how is that safe with tools.


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## Bob Korves (Jan 25, 2018)

I have never had a problem when using it on my surface plate with tools that I really care about.  I do let it evaporate completely before using the surface plate.  I don't think I would like to leave my tools submerged in ammonia, so I don't.  I actually have had more trouble with generic WIndex type products than with ammonia.


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## kev74 (Jan 25, 2018)

woodchucker said:


> But ammonia is a caustic, so how is that safe with tools.


The only metal I can recall seeing ammonia react with is copper.  Its supposed to harm the iron oxide in steel bluing, but I never left it on blued steel long enough to see the damage.


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## RJSakowski (Jan 25, 2018)

blue_luke said:


> Hmmmmm....
> 
> 
> I 'need' the comfort of buying something certified, but just out of curiosity, how flat are the granite found at countertop or toombstone fabricator ?
> ...


When I had quartz countertops installed in my kitchen, I had some concerns regarding flatness and called several manufacturers requesting a flatness spec.  Only one was able to give me a spec and that was 1/8" over about 12 ft. Natural stone may be better but I have my doubts.  Bear in mind that we are talking about using a product for something it was not intended for so all bets are off.  

Headstones are finished smooth for a mirror-like reflection but again, consider the intended use.  I would suspect that they are ground with a diamond process similar to blanchard grinding and polished for a reflective finish

As far a marble is concerned, it is much softer than granite and it is also etched by any acidic product.  Granite is fairly impervious to most common chemicals.  It is composed primarily of quartz and feldspar (aluminum oxide).  This makes it hard and thus less susceptible to wear. 

I would use the countertop or headstone for setups in the same manner that I would set up on a benchtop.  They should be OK for coarse work but for any precision setups or measurements, I would want to qualify them first.


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## Dabbler (Jan 25, 2018)

When the water carrier of ammonia evaporates, the ammonia is released into the air, and leaves no residue.  Far better than soap.  Since Ammonia is a base it doesn't react with the carbonates [correction] oxides in the granite.  If you spilled  a tiny dot of bleach on your granite surface plate it would cut a hole many thou deep.

-Anything acidic needs to say a  far way from granite.
-never use any kind of soap on granite if you want accurate readings.
-lanolin based cleaners leave a small residue.  I've heard that it doesn't affect readings, but in my experience the film left is readable in the tenths. (just my 2 cents worth)


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## Dabbler (Jan 25, 2018)

Some machinists are 'good enough' machinists - if all you ever do is machine to the nearest .003 or .004 then anything goes.  If you machine regularly to tenths and measure in parts of tenths, then taking care of your primary references is necessary.  

An easy example is to grind to .0002 to square and size.  A dirty, decrepit surface plate just won't cut it.  If you only care to the nearest thou, kindly disregard my advice.


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## Alan H. (Jan 26, 2018)

Granite has no carbonates in it.    I think you are thinking about marble and limestone, not granite.  

Granite is mostly quartz and feldspar.  Granite is more resistant to chemical attack than marble.   Here are a couple of videos of acid being put on each.   By the way, bleach shouldn't have a big effect on granite.  But if I had a nice granite surface plate, I would not be putting any harsh cleaners on it including bleach which is a strong base (alkaline).


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## Dabbler (Jan 26, 2018)

You're right. I did have my geology course  cross-wired.   The acids attack the oxides of potassium, sodium and calcium, rendering the matrix unstable, particularly in fine-grained granites preferred by surface plate manufacturers. Having any acid on a granite surface is going to etch it badly. 

Sorry I misspoke!


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## blue_luke (Jan 29, 2018)

Thanks you all, this is very interesting!
Just to place you all in context, I am French-Canadian so my first language is French.
Most books and information I have read is written in french, but my command of the English idiom is quite good. It is just that sometimes a few expressions are very confusing. Just to give you an example, check the difference of meaning between 'deception' in English and French! Written just with the same ortograph, completely different meaning!
So anyway, I have checked again with some French (as from France) and Belgian fellows, and to them a 'marble' is a reference plate made  most of the time of cast iron or .... granite! I don't know the historical background to this but I guess it closes this aspect of the discussion. It is just an expression, so it seems that if you talk of a 'granite, or a 'marble' any machinist will understand what you are taking about, simply a 'reference plate'
It does'nt have to be always complicated!!


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## blue_luke (Jan 29, 2018)

Moderatemixed said:


> Bob..... I missed a zero. But thank you for correcting me as you seem to do so for everyone, I feel honoured.]
> 
> I'm i detecting a slight bit of sarcasm here!
> I love this place!


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