What Size Surface Plate

ddickey

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I'm considering a surface plate purchase. Looking at a 9" x 12" that Lee Valley has for sale.
Checked E-Bay and see a lot of 12" x 18" plates. What size do you guys have? Is 9" x 12" considered a very small plate?
 
I put in a very good ebay bid on one I think 18x24 BECAUSE I could go there and pick it up BUT it took two people to load and unload safely.
 
I would like to learn how to properly use one, layout & measuring parts to check flatness on various projects. I have a surface grinder now so think it would be a nice addition for checking ground parts. So far my projects would work fine on a smaller plate I think. The plate would be kept indoors.
 
i'd get the largest plate that's convenient for your shop space and scope of work.
there is not much worse than needing a larger anything! :)
the cost difference between a 9x12 and a 12x18 are negligible if broken down over the lifetime of the plate.
unless you are doing high precision work a grade B will be sufficient
 
To check parts and tools you will probably need some kind of height gauge for dimensions, a surface gage with indicator to compare parts with each other or with gage blocks, and a cylinder gage or granite square for checking squareness. For layout you will need the surface gage with a scriber and the height gage and some spring calipers. Not all of that stuff needs to be on the plate at once (or even ordered right away), but there needs to be room for whatever part you want to work on as well as the tools for layout or testing. You will run out of room pretty quickly on a 9x12" plate unless you only work on really small stuff. I have a 18x24", it has comfortably handled everything I needed to do so far. The biggest thing so far has been spotting my 8x16" cast iron surface plate for scraping it in. I have also calibrated straight edges up to 24". I assume you are looking at Chinese import surface plates. They can be really good, but not always due to lack of quality assurance, and there is no way to know, and no reasonable way to test it yourself. The small plate is fine for starting out, but at some point down the road you may want a bigger plate to handle bigger parts, and one of known and tested accuracy so you can calibrate your tools properly and with confidence.

Edit: The smaller Chinese plates make good lapping plates for general shop work.
 
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I have a 9 x 12 from Lee Valley. Nice enough plate and I'm not dissatisfied with it, but it is small. To give yourself an idea, put an ordinary piece of printer paper on your bench and play with your layout tools on it and maybe a dummy part. The paper is 8-1/2 X 11, the plate is 9x12. If you find the paper area is feeling cramped, so too will the plate. Using bluing (for scraping) would be a challenge too without covering the entire plate surface.

Like I said, I'm not unhappy with the 9x12, but it will not be my one and only.

-frank
 
I've got a 12x18, I don't inspect parts a lot but I personally wouldn't want anything smaller. Put a height or surface gauge on it & a lot of space is taken up. Mine has ledges so it's easy to pick up & move around if you need. Mine just sits on my workbench.

I do also have a 9x12, as mentioned it's basically the size of a sheet of paper which is why I bought it. I use it for lapping, perfect size to glue or tape a sheet sand paper to it. I have this one sitting in an aluminum baking pan to catch the water when wet sanding.

I'd really like to have an 18x24 but they cost a lot more. My 12x18 is a grade A that I got for $37 at Enco. My 9x12 is a grade B, $33 from MSC. Those are Chinese grades though. :)
 
If you plan on measuring parts that are 60" long then you will need 60" of surface, no less no more.
If you are a hobbyist you probably do not need a surface plate of any size, what kind of work do you do anyway?
 
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