Few Lapping Questions

[Zaskar]

Would really appreciate a bit of info on Lapping, a few of the guides ive read on the net don't seem to cover it enough or have info that is contrary to what many here advise.

First off, when lapping a CPU with a beveled edge like this, would you lap it till its 100% flat edge to edge, or till the center is flat and there is still remains of the nickel plated beveled edge on the side?
http://img183.imageshack.us/img183/2608/cpuprelapsp2.jpg
You can see more of what im talking about in this pic (I know it needs more sanding at higher grit levels)
http://i32.tinypic.com/2qdst4h.jpg
Would you go further down on the lapping to make it 100% edge to edge flat/copper?

Do you tape the CPU up or just use the plastic backplate that came with the cpu, then use compressed air/air compressor to get rid of any dust that got where it shouldnt (like under the cpu or around/under where the IHS meets the board)

Next, Ive read that figure eights with little to no pressure, just using the CPU weight for the entire process is recommended, and that you also shouldn't use any water on the sand paper. How much of that is wrong? What would you recommend instead?

Lastly, I cant find anything over 500-600 grit in my local stores, I had a mini kit with some low quality very tiny sheets of micro grit sandpaper (one of each kind) and they didn't work out too well at all. What kinds/brands of sandpaper would you recommend if I had to order online (any difference between really high grit sandpapers and micro grits?)

Any places you would recommend ordering from?


Thanks allot guys.

[leuler]

Do you have any auto parts stores around there that sell painting supplies?
You should be able to find higher grit paper at a place like that.

Don't worry about the edges. Just get the top smooth and flat. If you
sand enough to get rid of the bevel, you will decrease the heat spreading
ability of the IHS.

[Xilikon]

Do you have any auto parts stores around there that sell painting supplies?
You should be able to find higher grit paper at a place like that.

Don't worry about the edges. Just get the top smooth and flat. If you
sand enough to get rid of the bevel, you will decrease the heat spreading
ability of the IHS.

Yes and make it more prone to crushing the core. Just sand till the whole surface (beside the edges) is a nice copper color.

[walshlg]

personally, I'm more consistant with back and forth strokes then turn 45 degrees. You are done with any given direction when the pattern is now all in the direction you are troking. More stroks does not equal better. When you get realyfine and you feel a "catch" that's a clump on your paper and you've just put a deep gouge into the surface. DON'T WORRY, it doesn't matter just stop and move to a new spot on the paper. After a while you will put more scratches in then take out. = Time to stop!

[[cTx] Nooc]

Anything beyond 600-800 is a waste.

I bought my stuff at Ace Hardware for like $2 a sheet. They have all grits up to 1200. Go nuts.

[billb]

Wet sand. If you don't the paper will just clog up really fast and have a tendency to "grab".
Add a few drops of dish soap (liquid!) to a 1/2 cup of water. Or use kerosene.
Throw out the water and rinse out the container. Rinse off the paper (for reuse again).
Clean the CPU/block to remove any "grit" left behind. And rinse off whatever you're using under the paper (glass plate?) too. You want to make sure none of the "grit" from the previous paper gets onto the new, finer grit paper.

Use a magnifying glass (microscope is even better) to determine when to change grits. When all the sanding marks are the same depth/width (ie. all the larger grooves from the previous grit are gone) then change to the next grit.

Use a black Magic Marker and put an wide X on the CPU/Block to check for even sanding.

And, yes, you want to remove as little as possible of the CPU heatspreader.