Shars Surface Plate - 'certificate' Not Inspiring Confidence...

You are not any better off if you buy a nice looking used USA surface plate instead of an import plate. Both are equally unknown quantities, even if one is a used Starrett or other highly regarded brand plate. You have no idea how it was used and treated. Any plate you are using as a reference for calibrating your tools or testing parts to meet stated tolerances must be a known quantity. The used 18x24" plate I bought, a well known American product, was .003" out when I got it. In the surface plate world, .003" is a bowl, not a plate. I did not have any way of actually testing it, and knew it was well used, but bought it anyway for a core price and had it calibrated and certified. Now I am happy. Do not spend a lot of money for a used surface plate, make sure you know what it takes to get one calibrated and certified where you live, and add that to the total cost.
 
if you are using this surface plate to master your mini lathe, you would be improving it's accuracy regardless of the calibration of your plate.
you will in effect be mastering one part, then transferring that flatness (or lack thereof) to the next part.
you will be scraping the parts to a matching plane
it would be ok for you to use this plate on your mini lathe that may never send parts to Saturn.
is it book of Hoyle correct?- absolutely not!!!
but you are a hobbyist.
i saw your pictures of the mini lathes' machined surfaces :eek:
if the plate turned out to be only .001" on the mark, your precision will undoubtedly be better, i assure you.
 
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I paid $400 for a 4'x6' plate, I had a friend check mine and it was within 50 millionths high to low. I had to build a stand and I would like to get it lapped in but its not really necessary for what I use it for. Tim
 
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