DIY measuring and lapping a worn surface plate

The everyday problems of trying to live in a sub-ideal Universe.
Another post from another thread comes to my mind:
Attachment 35006
from Karl_H
https://www.homemadetools.net/forum/...534#post155889

A New Year's Gift from Robin Renzetti: DIY SURFACE PLATE LAPPING PART 2

CAUTION, ADULT CONTENT: Nearly an hour of precision workshop pörn!

https://www.youtube.com/watch?v=k82T0T_4UHg

Mmmmmm, slathered compound.....so I watched it.
One part missing [fell sleep], so I'd offer mine as a stand in.
Stunt double?


Ha. Made you laugh!

The cast iron plate he is using in the first frame must be a heavy B***h.
The marble shop where I used to get pieces made was used during WWll to make all kinds of sheet metal parts for the war effort.
It was a three generation shop, Father,two sons, Grand son. The father refused to sell any of the metal machines (punches, breaks shears etc.) after the war. After the father died the son and grand son decided to clean out the shop (they really needed the room the machines were taking up). I was lucky when they were cleaning out. My father had been a customer for 30+ years. I had been going there for over 10.
The grand son and I got along pretty well so on the day of clean out he asked me if I wanted some items, and I said of course.
I got a large welding machine (300+ amp), a large steel machine stand which my mill sits on today, a 30x30 cast iron surface plate that looked as new. and a large box of reamers and countersinks still packed in mill pack cosmoline from WWll.
I believe i missed out on the emptying of a large tool cabinet as I was there about a day late, I hate to think of what went into the dumpster!
The things I passed on were a 1'x4'x8' granite surface plate that had been used as a workbench for years and a 2"x36"x72" piece of steel on steel tubing horses also used as a workbench.
When I moved from NJ to WV, I took both the surface plate among all my shop tools, Lathe, mill, a K.O.Lee cutter grinder (I rescued from a scrap yard in NJ for $100.00) etc. When I moved to NC some things had to go :( so I sold the cutter grinder to my neighbor and gave him the SP. He was a machinist and had a nice shop in his garage. I didn't feel bad because I got a gas forge and nice anvil (130) on a 1 1/2" steel top plate for $250.00 from him a few years before.
I told my wife this would the last move, the next move I would be in would be either an urn or box!

Adam Booth (Abom79) gets a hand (and some impressive tools) to fix his 2 x 3' granite surface plate.

CAUTION: Metrology Pörn! Sure, it's a 50 min video - so you "instant gratification" personalities have thus been warned, and can perhaps try this as a personal "Marshmallow Test"::D

https://www.youtube.com/watch?v=-CM3VWKXasY

*:https://en.wikipedia.org/wiki/Stanfo...low_experiment

Attachment 41479

I read a book titled "The Perfect Machine" about the building of the 200" Hale Telescope. To accomplish the final polishing of high spots on the mirror, they used a light touch with their fingers and a little polishing compound to hit the very smallest areas. It was estimated that if the mirror were the size of the continental United States, the largest deviation of the perfect form would be about 6 inches high.