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Hullo Bob....reading your post interested me, however I have more questions than answers1. we see the green faced block in the red vice.....is the vice held on a magnetic table? Yes 2. is the block supported on parallel strips in the vice? No it was not necessary, see ans 43. is the block cast iron or cast steel? [red sparks or yellow sparks?] Cast Iron4. how did you set the block to be best Law of Fit for initial flatness to start with? Block in the vise was set on a surface plate, the unworn four corners of the block were set to within .0005 of each other5. is the white grinding wheel A60 or A120 [aluminium oxide?] I do not know I would have to pull it off6. if red sparks were evident, did the wheel surface load up? no red sparks7. are you using coolant when grinding? No coolantIn your first paragraph you mention 0.25 inches........so we assume all other dimensions are also in inches! YesPoint 4. is critical........it is always best to start with a flat clean surface.....the photograph suggests another 0.41" is required for this an so the offfset is 0.082"....[or have I misunderstood?] I think the problem is with my writing on the block, the dimensions were all the same, ie first photo .020, second photo .030, third photo .041, just sloppy writing.The - negative dimensions shown are different between images......nearly as though the block was not adequately supportedeg., right hand top corner = - 0.030, then - 0.091 in another image for the same location!? See above anshow are you measuring the negative depth dimensions? On the surface plate ie I recorded the start dimension and simple subtraction to get the removed (negative) amount.In some ways, a larger 0.82" would be easier to manage than an offset one 1/2 of thisI have no personal experience with slip steel shim plates, however the prospect is not sitting well in my mindDerek