# Surface plates



## frogesque (3 Nov 2022)

Used fo many purposes including marking out, scraping mating flat surfaces and as an anvil (Arrrghh!!) 

Engineering workshops usually have cast iron tables with decent toolrooms using black granite. Many amateurs and hobbyists have used thick glass plates as a reference surfaces but they are difficult to get now (float glass is not the same!). Smaller cast iron plates are available but are expensive not least because of the carriage charges and, especially in wooden sheds or garages at the end of the garden, prone to rust. 

They aren't perfect, although using the tradionanal 3 plate method with fine grinding paste and a bit of grunt they can be pretty good. What I am talking about are the 3/4 inch thick granite kitchen work top chopping boards. As bought, they have a reasonably flat polished ground surface on one side. Good enough for all but the most exacting jobs and they don't rust or ding easily. Somewhere around 18" x12" in size, perfect for a small bench. 

Anyone else used them and do you bother cementing them to a cut paving slab for better support of heavy jobs?


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## Jameshow (3 Nov 2022)

frogesque said:


> Used fo many purposes including marking out, scraping mating flat surfaces and as an anvil (Arrrghh!!)
> 
> Engineering workshops usually have cast iron tables with decent toolrooms using black granite. Many amateurs and hobbyists have used thick glass plates as a reference surfaces but they are difficult to get now (float glass is not the same!). Smaller cast iron plates are available but are expensive not least because of the carriage charges and, especially in wooden sheds or garages at the end of the garden, prone to rust.
> 
> ...



I use the cast iron surface of my table saw not perfect but does the job.


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## Jacob (3 Nov 2022)

frogesque said:


> Used fo many purposes including marking out, scraping mating flat surfaces and as an anvil (Arrrghh!!)
> 
> Engineering workshops usually have cast iron tables with decent toolrooms using black granite. Many amateurs and hobbyists have used thick glass plates as a reference surfaces but they are difficult to get now (float glass is not the same!). Smaller cast iron plates are available but are expensive not least because of the carriage charges and, especially in wooden sheds or garages at the end of the garden, prone to rust.
> 
> ...


They don't really have a role in woodwork except amongst the tool fiddling enthusiasts.
Even then a piece of MFC is likely to be as flat as you need.
Or machine bed as Jameshow said above


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## Sideways (3 Nov 2022)

18x12" you would usually be looking at a 3" thick piece of granite. Sometimes 4".
Double your kitchen worktop version.
They are not that dear 2nd hand.Just keep eyes open and be patient.
Unless it's just for sharpening woodwork tools in which case worktop is surely fine.


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## deema (3 Nov 2022)

I’m with @Sideways, Granite surface plates can be obtained for very little money. I have two Grade A surface plates c4’x3’ one came with a proper stand and the other came with a nice bench. Together they didn’t break the £100 barrier.


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## Inspector (3 Nov 2022)

Given that here at least they are dirt cheap I would just buy one. 









SURFACE PLATE 12IN. X 18IN. X 3IN.


Precision Surface Plate - Black Granite. Harder than steel and does not nick or burr.




www.busybeetools.com





Not a lot more in your neck of the woods. Shipping might cost more than you like but if nearby then picking up on anything bigger than a moped is easy enough.






Search Results - Chronos Engineering Tools







www.chronos.ltd.uk





Your eBay has a number of used ones.

Pete


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## Dalboy (3 Nov 2022)

I use two one being a granite which I have fitted three pads to the bottom and the second is a cast iron one which I brought second hand this has three feet already cast in. For the more accurate jobs the granite one is used for general use I use the cast iron one as it is smaller and lighter than the granite one


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## hawkeyefxr (4 Nov 2022)

On my second year at college at Croyden we were given a 4in square*3/4 thick bit of mild steel, we had to scrape it till it was flat using engineers blue.
The tutor 'kindly' said we could use the mill to start us off, a few took him up on it. Of course removing one side made it bow like a banana and made the scraping ten time worse as it relieved the tension from one side. I was in the second batch that did theirs.

We were green at 17 years old. Good days though.


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## cowtown_eric (5 Nov 2022)

Some time ago I posted this video

 which shows using an 8"dia deburring wheel to clean planes, and it was commented "why would you use a radiused tool on a flat surface".-Good question- I figured if it scalloped out .0001 or .002 I would be surprised.

But wait, for 30 years or more, I have been aware of the "flat-sole" society of rhikenologists, so surely they must have mensuration data on that,, but nomatter where I searched, only found blanks! No actual data that I could find. 

So I decided to ty and put some measurement data on that....only question remained....how to do that.

One video I watched showed lapping a plane sole on plate glass, but he got a comment that glass bends, and indeed it does so that's where I started. How flat is that? well none of my glass gurus could answer that question. Specifications on flatness tolerance of many materials are impossible to find.

So you gotta measure it I figured, so I cobbled up this glass flatness measurement tool (8" overall length) with a dial indicator measuring in 0001



that video shows a scan of a 36" of 1/2" plate glass showing 2-3 ten thou variance, which is pretty freakin flat, but the slightest bit of debris underneath it causes the glass to bend (the support is a rather complex aluminium extrusion supported on it's 'airy points' all same as longer machinists straight edge) 

Keep in mind-PLEASE-, this ain't to prove or disprove if a really flat soled plane works better or not. It is simply an excercise in mensuration 

and it ain't done yet. This endeavour has taken me down so many rabbit holes

so for the flat sole society, the piece of glass I had would likely yield flatness withing a couple of ten thousands as long as it's adequately supported on a totally flat surface.


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## clogs (5 Nov 2022)

cowtown_eric.....
ur photos never came out here......

an interesting vid on utube for Granite and marble proccesing from quarry to finished sheets.....
the machines are truely big and amazing...
good to watch whilst have ur coffee....
I was in Thassos years ago and it's a place for rose coloured marble......the bad bits were dumped in the sea as a breakwater.....
broke my heart......
practicaly every village here has a marble n granite store.....almost as many as bakers....hahaha


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## frogesque (5 Nov 2022)

Standard 


cowtown_eric said:


> Some time ago I posted this video
> 
> which shows using an 8"dia deburring wheel to clean planes, and it was commented "why would you use a radiused tool on a flat surface".-Good question- I figured if it scalloped out .0001 or .002 I would be surprised.
> 
> ...



Standard test for flatness was the use of a certified optical flat. I forget the conversion from optical interference patterns to 'real' measurements (it depends on the wavelength of light used - usually an orange sodium discharge tube). 

OK, Mr Google knows everything! Way, way OT for a plane but it can be in the nanometer range (billionths of a meter!)


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## cowtown_eric (5 Nov 2022)

optical flats are indeed in the tool box, but I ain't there yet


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## cowtown_eric (10 Nov 2022)

here's the video of the glass flatness mesasurement tool I made (.0001 indicator)


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## Inspector (10 Nov 2022)

Sorry Eric the video doesn't show up. Just a black square. 

Pete


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## cowtown_eric (5 Dec 2022)

lets try again



Eric in the colonises, just west of the inspector!


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## cowtown_eric (5 Dec 2022)

url is""


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## cowtown_eric (5 Dec 2022)

this is so frustrating!


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## AES (5 Dec 2022)

cowtown_eric said:


> this is so frustrating!




Yup, sure is! FWIW, I too am seeing just the same black square in every post above.


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## sploo (5 Dec 2022)

Looking at the BB code for your posts it looks to be a tag/code that I presume will reference a particular video on a website (e.g. YouTube)?



cowtown_eric said:


> ```
> url is"[MEDIA=flickr]2nRhmV7[/MEDIA]"
> ```


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