well i wanted to lap the intel processor. but 1st i thought i would try it on the heatsink & see how one goes about it.
got various 3M polish/sand paper - 800, 1000, 1200, 1500, 2000 & 2500. cost of each was Rs.35/-
took around 25-30min to do all of them.
here is the closest i got to a mirror finish on the ultra120. dont know how good or bad this is. inputs are welcomed.
http://img266.imageshack.us/img266/8926/ultra120lappedtc9.th.jpg
^ That’s quite nice I must say. You could probably have used a bit of oil on the sandpaper, and I hope you used a glass surface 
All that aside, what are temps like ? If there’s a big drop, I’m lapping right away 
Little more to do…
To check if the base is perfectly flat after the lapping hold a metal rulers edge against the heat sinks base and hold this in front of a bulb and see if there is any light leakage between ruler and heat sink - this will indicate if there are any uneveness on heat sink surface.
Did you get “wet” type sand paper and do the lapping under water ? Did you lap the heat sink in figure 8 pattern motions ? Recommendation is to wrap sand paper on a flat piece of glass and rub the heat sink over this in a figure 8 pattern under a tap with water flowing over sand paper.
@Anish … my experience has been that lapping hardly makes more than 1 - 2 C temp difference - unless the heat sinks base is pretty warped to start with 
Stormy … I think it may have been better NOT to have lapped the Ultra-120 heat sink as the Nickle platting they have put on top of the copper should protect it from Mumbai’s polluted air - copper heat sinks tarnish and get horrible black and green marks with Mumbai’s air pollutants. I have a Zalman and a Thermalright copper heat sinks which look terrible after a year in Mumbai. The Nickle plating should be good for stopping this tarnishing.
What were the CPU temps before and after Lapping ?
no did not use any oil. & ofcourse i did do the lapping on a glass surface. as far as the temp goes, there wasnt any drop in temps as the e4300 surface is really bad. this was an experiment by me b4 i start lapping the e4300. i am sure when i lap the e4300 the temp drop will be huge cause now its just too high. sad that a company like intel cant deliver flat ihs on their chips.
yes i checked the hs on a flat glass surface after lapping & it was perfect. also the mumbai humidity wont be a huge prob as the comp is going to be in office in close room inside ac most of the time. i did not lap under a running tap. i got a glass surface. stuck the sandpaper on it with celotape & started lapping the hs vertically from 800 all the way to 2500. & when u say that temp drop is just 1-2deg u are wrong. temp drop is huge especially when u lap the processor & hs both as u can pretty much count on intel not to deliver a flat ihs on c2d.
@easy & anish - cpu temp 62-63 TAT load b4 lapping & the same after lapping. the blame for this is the cpu as i checked it & it was far from flat. cpu = e4300 @ 2.8ghz @ 1.275v 24/7
I dont have any experience lapping a CPU’s IHS so I dont know how much difference it will make… but are these IHS thick enough to be lapped without an risk ?
The reason the MAD MODDERS recommend the WET Sandpaper is that lapping under flowing water moves away the sandpapers grit and small pieces of metal which have been scrapped off - if this is not done you get fine lines on surface which are created by these debris rubbing against the Heat Sink. Not all Sand Paper can be used under water - the ones that can be used are marked like so …
http://img175.imageshack.us/img175/2117/sandpaperym0.jpg
I understand that it is not the moisture in Mumbai’s air which causes problems with copper surfaces but the sulfur and other pollutants in the air. If you have only lapped the base of the heatsink and bared the copper there … and … you will apply AS5 on this area than I think you should not have a problem - as AS5 acts as a protective barrier - in fact the only part of my Zalman copper cooler which does not have any black and green marks is the part which gets covered by AS5
Nice job.
Honestly lapping to a mirror finish will give you 2-3C Higher temp’s, than a Non-Mirror Grit 1000/1200 finish.
Dont worry, and go ahead with ur Lapping of the E4300. 
^im sure u meant 2-3 lower..
