6/23 - Abrasives and Polishing, 383-387 Flashcards
steps after wax-up, investing and casting:
- preliminary finishing
- try-in and adjustment
- precementation polishing
- cementation
- postcementation finishing
studies show that the more you___, the less plaque accumulates
polish
when doing preliminary finishing, should you start with less abrasive instruments than continue to coarse abrasives?
NO! start with coarse abrasives then continue with increasingly less abrasive instruments
should you spend more time with coarse or fine abrasives
coarse abrasives
when finishing, should the surface have an even amount of roughness
YES
what is a disorganized surface layer of highly polished metal produced by a series of abrasives of decreasing coarseness
Bielby layer
the Bielby layer is anagolous to what layer
smear layer
what are exceptionally hard materials that can be chipped, glued to a shank or disc and used to gradually smooth a surface
abrasives
T/F: the abrasive must be softer than the surface on which it is being used
FALSE! abrasive must be harder than surface on which it is to be used
what are the units the determine that hardness of abrasives
Knoop hardness number
what is the softest on KHN scale? hardest?
softest: cementum
hardest: diamond
what is the hardest of all abrasives
diamonds
what abrasive do we typically use on enamel or porcelain
diamonds
what is the other name for green stones
silicon carbide
what is the basic material of carborundum
silicon carbide “green stone”
does silicon carbide exist as discs or points
BOTH! silicon carbide aka green stone
what is the other name for brown, coral, and white stones? which is most abrasive to least abrasive?
aluminum oxide
most abrasive: brown
coral
least abrasive: white stone
what are the abrasives found in sandpaper kit
emery, garnet, sand, cuttle
what are powders combined with wax to form a cake
tripoli and rouge
what is tin-oxide
a fine powder
what must you always have on when working with abrasives
eye protection
what is bonded to a paper backing or mixed with a binder and pressed into various shapes (points, wheels, etc.)
abrasives
separating disks are also called what
Joe Dandy discs
what are stiff, brittle and coarse; used for cutting off sprues; and very abrasive yet can leave an even surface
separating disks/Joe Dandy
what is the most abrasive thats not a diamon
separating disk/Joe Dandy
should separating disk/Joe Dandy be used at slowspeed?
YES
What are sandpaper disks (emery, garnet, sand, cuttle)
Moore’s disks (E.C. Moore)
should you use soflex disc in fixed?
no - only used in operative to polish resin
do you use high or slowspeed for Moore’s disc
slowspeed
what are extremely coarse and used for bulk removal
heatless stones
what abrasive is used for porcelain
silent stones
pink stones are also called what
aluminum oxide
white stones are also called what
fine-grain alumium oxide
what are examples of rubber wheels and points
Shofu points (brownies, greenies and super greenies)
what bur to use to place initials in metal ingot
2 round bur in high speed
what do you roughen both ends of the metal ingot with in the beginning
heatless stone
coarser abrasive = [more or less] pressure = [higher or lower] speed
more pressure
lower speed
finer abrasive = [more or less] pressure = [higher or lower] speed
less pressure
higher speed
order to use:
white stone, green stone, coral stone
- green stone
- coral stone
- white stone
what should you use to remove scratches on metal ingot
rubber wheel - should end up with a mirror like image
which is coarse, which one is fine: grey compound vs. green compound
grey: coarse (pressure w/ slow speed)
green: finer (less pressure w/ higher speed)
can you use the same robinson wheel for both gray and green compound
NO! use one wheel each
if you can’t make it right…
at least make it bright
if you can’t make it fine…
then make it shine FML
what are useful abrasives for gold
sand, tripoli, rouge
