[R.M.S.]

So I happen to be starting my new build. I plan on retrofitting my G3102 (6x26) and 9x20 lathe .Since I already have my G0704 . Im in no rush what so ever to build both machine.
I happen to come across a very large Rock of Ages Granite surface plate at 4ft x 6ft x 1ft deep made in 83. The plate with out the stand weighs in at 2 tons the tag says.
I believe the accuracy of the plate is A . @ .0006 last re calibrated in 2011 by IBM.. I think its an A correct me if Im wrong. Starretts AA same size is like .00035
So I would like to learn to hand scrape machines(not on my mill at first). My question is if this plate is with in specs still would .0006 be flat enough to scrape my knee mill and lathe?
I have all the ball screws and electronics so I have to start some were. Im thinking making sure I have flat parallel machines would be first.

[Fastest1]

Do you ever watch the videos on youtube by a user MuellerNick? Here is a link to some of his videos.

https://www.youtube.com/user/MuellerNick/videos

I believe he could more accurately answer your questions.

[R.M.S.]

I have watched quite a few of his videos . Forest from PM also has allot of knowledge on the subject from what Ive seen and read.
Im didnt happen to hear or see what level surface plate any one uses or what is recommended for a machine rebuild.
I just acquired Edward F Connelly Machine tool reconditioning and Foundations of Mechanical Accuracy by W. Moore .
Ive read Edwards book is supposed to be the Scrapers Bible.

[SCzEngrgGroup]

The overall accuracy of the surface plate should be a very minor, almost insignificant, factor, since both the machine parts, and the base of any measuring tool, will cover a large-ish area, which will average out any RMS error in the plate itself. Beyond a certain point, you are picking the fly poop out of the pepper. Worrying about errors much below 0.001" in these machines definitely falls into that range, as there are in-fixable error sources inherent in the machine itself and it components (flex, thermal expansion, lead error on the screws, etc.) that are much larger..

Regards,
Ray L.

[R.M.S.]

The overall accuracy of the surface plate should be a very minor, almost insignificant, factor, since both the machine parts, and the base of any measuring tool, will cover a large-ish area, which will average out any RMS error in the plate itself. Beyond a certain point, you are picking the fly poop out of the pepper. Worrying about errors much below 0.001" in these machines definitely falls into that range, as there are in-fixable error sources inherent in the machine itself and it components (flex, thermal expansion, lead error on the screws, etc.) that are much larger..

Regards,
Ray L.

I understand there is a point were im chasing my tail . Im just trying to give it my all .
My last two build I did rather quickly in my eyes . Not that anything was wrong but I wish I would have done things different.
I just wanted to take my time do the best I could .
So I guess that answers my question...
Thanks for the reply Ray.

[mactec54]

R.M.S.

If you could ever get in a class with this Guy, you would learn how to scrape, he is one of the Best in the USA if not the Best in the business

King-Way Scraping Consultants 10855 68th Street South Cottage Grove, Minnesota (MN) USA 55016 Ph 651 338-8141 handscraping.com

[R.M.S.]

He is a ways from me. Im in Connecticut . But thanks for the heads up Ill check out his site
. Im going back to the scrap yard tomorrow to look for cast iron. Keep reading practice makes perfect ,free hand scrapes any one in my area I went to the scrap yard yesterday. I almost cried . There was a huge surface grinder there . Easily twice the size of a Bridgeport.
Beautiful condition . .22 cents a pound. I didnt have the money to spare or I would of grabbed it. I did grab its mag chuck. 10x20 121lbs. paid 20$ . Worked fine . I opened it and cleaned it tonight any ways.
I wonder if its bed would of made a good surface plate after it was scraped?

[mactec54]

R.M.S.

If you look at his web site you will see what accuracy, that they scrape to, for precision CNC machines & for manual machines, .00005 over 12" for Precision & .0002 over 12" for Manual, they have a CD that may help as well