It's the best *gliding*-surface, not rolling surface.
And an ideal fitting surface too. I've read in a book, that the overall
damping is by magnitudes better with scraped and oiled surfaces compared to
milled ones. That damping has an higher effect than the damping of single
parts (cast iron vs. steel).
The "real" frosting is achieved by simply scraping to a plate. With enough
passes and short strokes (2 .. 3 mm) it is frosted. Decorative frosting is
I do have a cast iron plate that I scraped that looks frosted:
For size reference, that a cap of a beer bottle. :-)
But I only scraped it to 20 dots per square inches. ;-)
Ha! It floats on the granite plate! Just a slight push and it slides along.
Takes a minute or so until it sucks itself to the plate. Took me about 6
hours to scrap (200 * 300 mm).
The other decorative scraping I know of is flowering (we call
it "butterflying"). I tried that, but don't have the *slightest* clue how
it works. Despite the description in "Machine Tool Reconditioning".
One day, I'll find it out too.
Oh, and here's a surface map of that Camel Back:
In fact, it is better, because I didn't subtract the error introduced by my
plate (IIRC 4,2 µm). Gonna have to write a program that does better tilting
of the plane (another 3 µm) and correct with the known error of the
measuring plane. The output is made with gnuplot.
Good God that looks just like my shop except for...........
The quality of the machines
The complete absence of clutter
The lack of swarf on the floor
The missing leak in the roof
The missing pile of scrap waiting to be turned or milled into
But I am happy <G>
Note that what I and Nick referred to as flaking (the half-moons on the work
piece) is what Connelly refers to as frosting. and What I referred to as
frosting (regular, light scraping patterns like the frost on a window or in a
chess-board pattern) is what Connelly refers to as flaking...
After the work is finished, one last pass is made all over the work. A grid is
drawn on the work with a pencil 1/4"-1" square as appropriate to the part.
Alternate squares are gently scraped over their entire surface in one
direction and the other squares are scraped all over at right angles to the
first direction. It is entirely a decorative effect, but if done carefully and
consistently, it will damage the finish by less than a micron (0.4 tenths of a
thou). This is perfectly adequate for the top of a milling machine table:-) No
point in doing it on a non-visible sliding surface or a standard, since it'd
wear off the sliding surface in a very short time and standards don't need to
Using deep half-moon gouging for decoration, as Bridgeport do, just looks like
crude butchery to my eyes.
Funny confusion. Maybe triggered by me. :-)
Or maybe the reason is, that different countries do have different names. I
do have my names from the US (and I think I got them right).
Frosting is irregular (90° diagonal) short strokes. Either functional (but
with the same appearance) or purely decorative (without flatness)
Flaking functional or decorative.
flowering, purely decorative (at least never seen on a guide)
I have no word for this. And frost doesn't make a regular square pattern on
my car's window (maybe because I don't have a car <G>).
I tried that once -just for curiosity- and you even can keep that pattern
without a last "destructive" pass. But it's a bit of a pain. Scrap to
flatness and then continue with maybe 3 passes -still touching- but keep
the scraping direction within the square boxes. Looks very nice.
OK. But then, there are people that can make shallow half-moons (unlike me)
that look nice. The ones I made are quite deep. Didn't measure them, but I
estimate them to be almost 0,01 mm. Oil pockets should be 6 .. 8 µm for
heavy load, about 4 µm for light load.
I think that Connelly is wrong on this one! While frost does not make exactly
square patterns on windows, it can make similar patterns with different areas.
Another example is the pattern of the zinc crystals on galvanized iron. Again,
it isn't regular, but that is the general appearance.
I think that flowering is engine turning by hand :-)
I had been trying to explain the principal without trying to convince anyone
that it could be done without damaging the accuracy. There are examples of the
manufacturer's name/logo being made in the centre of the surface table using
this technique :-) Note:- I haven't tried it myself, it's enough work getting
things flat without decorating them as well!
Every time I look at a Bridgeport I get angry about the mindless damage :-(
Not mine, and not the best according to the scraper. Rectangles are about
square and 2 .. 5 mm long. Scraped in 45° directions.
Yes, its a bit destructive, but not that much if you touch and modify the
pressure at high spots.
I wouldn't buy a Bridegport anyhow. It's like the Robinson for helicopters.
Works, but ugly. :-))
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