Now, there's a machine that you won't find in many hobby shops. For some reason, I've always found lapping to be interesting.
I remember reading the account of Johannson making his first set of gage blocks, and some years later, Dick Moore making his first set on his kitchen table, lapping them by hand.
These accounts would be interesting. Do you recall where you saw them?
Johannson's patent is from 1907 or so.
For a nice description of how such things were done 100 years ago, see ³Accurate Tool Work², Goodrich and Stanley, First Edition, Eighth Impression, McGraw-Hill
1912, 217 pages. The last two chapters are on the then recently invented Johansson Blocks, with microinch precision .Joe Gwinn
Very interesting info guys. I was thinking about spotting them with bearing blue to see how close to each other they are. There wouldn't be a problem with that would there?
As far as needing gauge blocks goes. All of my work so far(very limited and not in the same league accuracy wise) is what I call "comparison measuring", so my mic's could be calibrated in westernwigets for all it matters. As long as they are consistent.
I would not try that. You want to minimize sliding of anything on top of these to prevent scratches. Besides, it will not tell you much. These plates should be flat to better than 300 nanometers which is probably a little thinner than the dye layer. You really need optical methods to test them. If you are interested, google "making optical flats", some of those pages outline test methods an amateur can do.
Try it. If you can't get a good read, use jeweler's rouge. That's what's used for checking iron surface plates that have been scraped; it may or may not work better than blue on lapped surfaces.
It's difficult to spread an even coating of rouge. If you have some in a stick, for use with a buffing wheel, take a rag, wet it with paint thinner, and rub it good on the rouge. Then, while the rag is still wet, try wiping an even but thin coating on one of the plates.
This is easier said than done, but it works well with finely-scraped surfaces.
That's the way it is with most hobby work. For lathe work, I just use spring calipers most of the time.
That's true. My suggestion of using rouge is probably of no use on such flat surfaces.
The account of Johannson was in a book I borrowed from Mitutoyo's collection. It was a rare book -- I don't recall the title.
About Dick Moore, we had all of his books at _American Machinist_, so I don't recall that one, either. I think it was either one of his first, about jig borers, or the late one by his son Wayne, titled _The Foundations of Mechanical Accuracy_.
Look at the bibliography of the Wiki entry mentioned below: does it ring any bells?
I think I have read this one. A coworker lent me a copy. It's still in print, sold by Moore, but at an astonishing price.
Joe Gwinn
That book sounds familiar; I think I read it around 30 years ago. However, that's not the book that had the Johannson story I'm talking about. That book had a title that said something about the history of metrology. Sorry, it's not coming back to me.
You're reminding me that I have to call McGraw-Hill in New York and find out what happened to all of the old metalworking books they had in their library. M-H sold _American Machinist_ to Penton Publishing sometime in the '80s, but the books that had been accumulated in the corporate library via AM may still be there. Probably not, though, because M-H no longer owns any metalworking magazines.
I'll call and check.
Thanks,
Joe Gwinn
Would be nice but the postage to AU would be killer.
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