The Shop > Finishing
cheapo flat surface lapping
srm_92000:
--- Quote from: bry1975 on May 18, 2011, 08:10:21 AM ---Ring Taylor Hobson and ask if they've got any unused or slightly marked flat surface blocks! :D
--- End quote ---
Hi I did my apprenticeship at Taylor Hobson and 12 years after!
We used to use a reference optical flat about 5" diamter for setting up interferometers that was just over of lambda/10
i.e. 1 tenth the wavelength of light IIRC.
Did you have anything to do with them? (Taylor Hobson that is)
'oops just noticed the thread date :palm:'
vtsteam:
To produce a flat surface for a reference, traditionally 3 plates were used.
Call them A, B and C.
A&B were lapped together first. This would tend to make a complementary pair -- convex and concave to a small degree.
Then A and C would be lapped together. C would will tend toward the form of B (as a complement to A).
Finally B & C would be lapped together -- since they have nearly identical irregularities rather than complementary ones, these irregularities would be lapped away.
Presumably if the degree of flatness wasn't then acceptable, I imagine the process could be done by using 4 plates yielding additional flats after the first round, and then these lapped together to further refine it.
All of the above can be done with plate glass and corundum powder in the home workshop. The 3 plate method for glass is given in the Gingery machine building books.
philf:
--- Quote from: vtsteam on February 11, 2013, 01:39:08 PM ---To produce a flat surface for a reference, traditionally 3 plates were used.
Call them A, B and C.
A&B were lapped together first. This would tend to make a complementary pair -- convex and concave to a small degree.
Then A and C would be lapped together. C would will tend toward the form of B (as a complement to A).
Finally B & C would be lapped together -- since they have nearly identical irregularities rather than complementary ones, these irregularities would be lapped away.
--- End quote ---
For which we have to thank Joseph Whitworth - born 210 years ago about 3 miles from me in Stockport, Cheshire.
Phil.
vtsteam:
Thank you, Mr. Whitworth! :bow:
Also for a probably unrelated but awe inspiring bit of joinery, the Incas. :bow:
http://travelblog.mtsobek.com/2012/03/14/the-craftsmanship-of-the-incas/
Dawai:
OR used fixing a hillbilly with a "leaky harley" spraying oil out on the ground.
Using a trick learned from a old machinist, I laid a piece of "glass" down on a table, a piece of emery cloth upside down, figure 8'ed the warped oil pump housing around and around till it was as flat as the glass. A manual surface grinder. dyekem stain showed it was evenly wearing off. It fixed the pump.
I tried to study the ancient methods of cutting those blocks so close, or how they placed them, them being different sizes locked it together during earthquakes, making a structure that outlived the race of people who built it. MY research went into "sun and moon worship", "Levitation", "resonant magnetism", then "MOLOCK" worship where I drew the line and quit reading. (human sacrifices) I don't really want to move big stones that much.
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