Inexpensive (cheap) Surface Plate

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Silvergoose

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Although I have had a Mill and Lathe for some time only since I 've retired have I found time to use them. I have built a wobble plate engine based on Elmer's design and found that it is a lot of fun along with being a challenge. I read the forum with great interest and admire the talent that I fear the young will never know.

But to the point of the post. I needed a surface plate, the granite plates while being time tested, proved to be a bit spendy. I did not want a metal plate, living in Arkansas were the summer months bring the "air you can wear" the metal would prove to be a pain to keep clean.

While driving home one afternoon, I passed by a monument company. I turned around and went in to ask about grainite. After explaining what I was looking for I noticed a few broken headstones. I asked about the stones. Most all had highly polished surfaces, at least on one side. Found a piece, broken. I bought the stone for $20.00. The stone is a bit thick at 8 inches, but warping will not be a problem. The usable surface is about 18 X 16 inches. The surface is smooth and for the work I am doing it will be perfect.

Just thought I would pass on some information, I ran a search, but could find any post for this, forgive me if you all have done this and it is old news.

Thanks for the forum and the vast wealth of information.
 

kquiggle

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I think you are right in saying that it will probably work for you, but I would also caution that "smooth" is not the same as flat. Unfortunately, to really test for flatness you need a surface plate, but a couple of things you might try at a bare minimum:

- test with a straight edge steel ruler, with a light shining from behind; kind of a crude test, but will certainly show any serious issues
- if you can fit the stone on your mill, test it with an indicator while running the table back and forth (you will need to shim the stone to get the top parallel to the table surface)

Just a couple of things I can think of off the top of my head.

I had some small "surface plates" made for me at the local glass shop by having them cut some rectangles of thick float glass for me (any thick plate glass you buy nowadays is likely to be float glass). This is also not a true surface plate, but also good enough for the work I do.
 

gus

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Surface Plare.
Here's mine -----a recycled but brand new Ingersoll-Rand Model 3000 Air Compressor Valve plate which is cast iron and lapped to flatness to function as valve plate with finger valves.
For the small jobs that I scribed, it meets my requirement. Along with it ,I bought a Starrett Digital Surface Gage. Same is M.I.C. (made in china).

The Webster,Rupnow,Namett-Lynx & Howell V-2 Engines were scribed with same surface plate.

IMG_3256.jpg
 
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Theclockworks

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Had mine from Tesco cooking department £14.00 they say it's a chopping board but it's made of granite about 14x10 inch.
 

Silvergoose

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Kquggle, You made a very good point about shiney vs flat. I checked the surface with a straight edge, result, no light. When checked on the mill table the result was still very good. For the model steam/IC hobby I feel this is in line. With my skill and equipment dealing in more than 4 decimal places is out of my realm.

Thanks for the input
 

barnesrickw

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I used to pick up pieces to use for sharpening my woodworking tools. I would tape fine grit automotive sandpaper over them. I found them to be very flat. Just the same checking would be a good idea.

On a side note, I used to teach Geology, briefly, but I got some of my samples from a headstone company. Some had parts of names in them. Had a great deal of fun letting the students think I was a night time sample collector before letting them know the real origin.
 

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