Scraping straight down and datum points

I'm in Maryland.

Back to the mill, it is ready to be laid back once I take the column screw out. There will be a slight delay in progress as I will be out of town this weekend. I'm determined to figure this alignment and scraping thing out.
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After you clean the knee up set it ways down on a surface plate and check things out. They are normally worn on bottom flats and top dovetails. Also set the coulum back on 3 points. 2 on bottom and 1 in center about where the electrical box is or just under the top of the wide flat way directly in the center of casting. then lay your plate on and do some measuring. Will add a few pic's on a smaller mill, being scraped.

Pic. checking column dovetail for parallel while scraping as shown below.

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Question for you Rich:

I have a mill that I've been working towards scraping, much like ThunderDog here, and I've read many of your descriptions of checking a mill table here and on PM. I don't have a giant surface plate, just a little baby 18x24, so I can't lay the mill table on it and work from a datum surface. If I have a big wooden workbench and three spherical washer type stands (Unisorb leveling feet for bigger, nicer machines with spherical washers for uneven floors), how would I go about setting the table up on three points to go about checking it? I'm not sure mine has any unmolested factory surfaces at this point, other than perhaps the back vertical edge of the table...

Thanks,
Will
 
Hi all,

Finally got setup to measure. Critique and correct the process as you see fit. Video explains all that I've done thus far.

 
I made an alignment jig. It's ugly looking, but it gets the job done.

 
Well, here goes nothing.
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More roughing.
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Many evenings later... (I'm at 10-12 p.p.i.)
You can still kind of see what used to be the low point on the top.20180523_133748.jpg

For those wondering, the knee doesn't ride on the entire surface. It was just easier to scrape the whole thing flat. At least that's what I did. Bottom view of knee.
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Progress continues.
The scraping of the knee has been slow. I think a lot of it had to do with moving it on and off the column to match the dovetails.
Anyway, the back of the knee had significant wear at the bottom of the slides. The top slides of the knee had .003" worth of wear in the middle and a little more than that from back-to-front when measuring squareness to the column. The gibs have significant bow in them. When I did some checks of the back sides for each gib on the surface plate I could slip a .006" shim under them. They have now been scraped flat on the back sides. I now need to fit/scrape the sliding sides of the gibs to match the dovetails. The column gib needs a shim due to the cumulative amount of scraping of the column/knee/gib. No video for this part because, well I just needed to focus on the task at hand. But, I took a few pics along the way.
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