best technique for using an SE for a surface longer than it is?

The 30" SE thread made me think of this.... No matter how big an SE you have (or do not have), there is likely to be a surface longer than it that you want to scrape. So overlapping spotting is likely to be required, unless you resort to surveying equipment.

So, what do you recommend?

Some suggest scraping one area the size of the SE, then "stepping down" by overlapping about 30% onto the next area, scraping the next to match the first, and so forth until complete

Some seem to suggest s similar approach, but stepping down earlier, so all the area improves at once, instead of stepping when the first area is nearly done,

Others ?????

We just talked about that at the last class. I do it pretty much the way you said. Overlapping distance would depend on how long the SE is. I do a bit of detective work first by flipping it upside down and use a precision level. Starting in the middle after I get it level in the middle of the straight edge and then move the level middle to the end one side and then middle to the other side. After I am done doing what you said I would do it again with the level and it should be with-in .00005" as you move along. Another way would be to set it on perfect 1 2 3 blocks and measure the surface between them with a surface gage and .0001" indicator. Again depending on how long it is. super long ones will not balance right unless you scrape it upside down using the plate and level together. Rich