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When
the kit arrives it becomes clear you're not paying for the
packaging. Suits me, it's not like you'll be using it again.
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The
Kit
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The
long strip of lint free cloth needs cutting into three pieces
for use with each of the lapping compounds. I'm no textiles
guru but this appears to be your reasonably expensive microfibre
cloth which increases its effectiveness and greatly reduces
its tendency to mark the surface.
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The
Kit
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Finding
a suitable subject to lap wasn't too difficult, though I
figures softer aluminium was too easy and went for copper
instead. Surprisingly, this woeful base is from the sink
supplied in an AMD retail CPU kit. It came with the usual
phase change gum applied which I had already scraped off.
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The
Candidate
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PCViper
recommend you mark up the base to give a quick indication
of where the low spots might be. If you've seen our previous
lapping reviews you'll know we've always done this anyway,
but make sure you use a permanent marker. If you don't the
water will wash the marks off when what you actually need
is for the paper to sand them off.
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Base
Marked
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Which
paper you kick off with depends on the state of the base.
I decided to go for the roughest 400 grit first though if
you think you can get away with it go for the medium 600
or even the fine 800 grit paper.
My
biggest complaint with this kit is that PCViper suggest
you start by taping the sandpaper to a table. This might
be okay if it's a good table but it's hardly the best way
to get a precision flat finish. What you need is a piece
of glass or a very hard, very true surface to work on. A
table will do at a pinch, moreso if you're using an exposed
core CPU as the smaller surface area is unlikely to be affected
too much my small surface deviations, but for anything with
a heat spreader fitted I'd try and find a piece of flat
glass.
To
be fair, PCViper explained that including glass would push
up the price as the postal service insist it be shipped
in its own protective box, not to mention the very real
risk of it arriving in a greater number of pieces than it
left in.
Before
you start, choose a well lit location and lay out plenty
of newspaper or tissues around and under your work area.
Don't work on an important polished surface.
There's
actually too much water on the paper in the shot below,
I did this to make sure it showed up properly. Using too
much water actually slows the lapping process by creating
a skin under the base kind like a car tyre aquaplaning.
It also makes it moor difficult to get a good, smooth motion
going.
Circular
motion or linear? There's a lot of argument over which is
best and in my experience it doesn't seem to matter much.
Linear seems a bit easier but you also collect more swarf
under the base so choose which ever you prefer making sure
you wipe the base with a paper towel and rinse the paper
regularly.
PCViper
suggest a linear motion to get started moving them a linear
or figure-of-eight motion once you get into your stride.
Some people swear that a linear motion gives a finer finish
but having never compared the two I really can't say.
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Paper
Prepared and On Glass
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After
the first cycle on your starter paper, take a long, hard
look at the base. If you still have pits, low spots or plateaus
stay with the same paper. There's no point wearing out you
next paper on flattening when it should be polishing. If
the grit fractures and gets finer, and it will, use the
edges of the paper more and use a linear action. At this
stage you're still aiming to get a semi-smooth but more
importantly, flat surface ready for the next stages.
If
you've decided to do the entire surface as I did, then don't
worry if the outer edges kick up and don't touch the paper.
This is often the case and doesn't do any harm as it's not
in contact with the CPU. If you want them to look good too
you can sand them using the paper under your finger so they
have the same finish. They just won't be flat.
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After
the 400 Grit
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