This may sound dumb but... What's Lapping?

I'v never heard that term before I found these boards?

It is sanding down the base of a heatsink to make it totaly smooth and get rid of ridges and stuff so you get better heat transfer. You cna get up to a 6c drop in temperature.

It would probably be better to click on the search button and do a search for Lapping if you really wanna read about it.

Or.............. lapping is basically "smoothing" out the bottom of the heat sync by either "milling" it (with a machine) or "sanding" (sand paper ((about 600 grit and above)) taped to a very flat surface (((usually a large piece of glass))) and using "figure 8" motions) the base smooth.

I hope this helps but honestly it would probably be best to do a search on the forums as MANY other's have explained (probably in more detail I might add) on how to do it.

Rob

Constantinos said:

You cna get up to a 6c drop in temperature.

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Dont bet on getting a drop that big. Not even half of it. A degree of 2 is what most peolpe get if the HSF is lapped badly from the factory.. Most high quality commercial blocks aren't that bad.

Would that actually be necessary on an SLK-900 That thing look pretty smooth to my untrained eye, but I know the ridges are microscopic.

Honestly tho, sand paper would make the surface worse i think.

Well depends wut grit sandpaper you use. You should use these grits in this order 600-->800-->1000-->1500-->2000. That should give it a mirror finish.

Please, do a thorough search on lapping before you attempt it. I'll outline some of the things you're looking for (by no means a complete list!):

The base of most factory-produced heatsinks is not perfectly flat. Aside from the microscopic ridges, the base could be warped, concave (bent inward), or convex (bent outward). The main purpose of lapping is to flatten the base to get better contact with the whole of the CPU core/heatspreader.

Most of the benefit from lapping comes at grits coarser than 1000 (the less the number, the coarser the paper). At mirror-finish shine, the thermal paste can actually hurt if it's applied to thick. Having 1000-grit microscopic ridges for the paste to seep into can keep you from insulating the CPU with grease, while still allowing for a nice tight fit.

The mirror finish you might see in pictures on these forums is not true mirror finish, except in the case of those obsessive few that use polishing compound (I don't recommend it - do a search to find out why). Notice that in every picture you see, the heatsink is at an angle to the camera. Looking at it straight on, the lapped surface is apparent (but it's still usually better than straight from the factory, and you can't feel the texture).

There are lots of other suggestions, including making sure to clean the base immediately after lapping with rubbing alcohol or another solvent, to remove any oxidation-causing fingerprints; how to make sure your sandpaper is indeed on a flat surface to begin with; and what heatsinks need how much lapping.

You can see a benefit from lapping your north bridge if you have a board like the 8rda+, where the nb isn't flat.

Seems like an interesting adventure, I read some guides it doesnt seemd too hard.

Does anyone know it Strauss Stores would sell the Sand Paper needed?

The wet or dry micro fine stuff.

Any auto parts stores should have the stuff that you'll need. Or you can try a home improvement store such as Lowes.
Rob

Just out of curiosity, does anyone here know what the cascade is lapped with?

n3xu5 said:

Just out of curiosity, does anyone here know what the cascade is lapped with?

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Procedure is this:

Initially they are fly-cut flat, but moving to being ground flat for all future blocks. The fly-cut bases are not flat at all really (~50 micron variations), but the ground bases with a properly dressed grinding wheel produces flatness down to around 3 microns across the entire 80x50mm base - hence the switch to using this as the new first-step flatness method.

After the first-step flattening, the blocks are then finished off by hand using:

A polished flat marble slab
240-grit paper to remove gross non-flatness (240-grit won't be used with the future ground bases)
600-grit paper
Low-smell kerosene as a cutting agent.

I used to do a final dry (no kero) lap with the 600-grit all clogged up to get a fairly shiny finish which was reflective enough to shave with if you wanted, but I no longer do this on current blocks as I had too many complaints by people with too high expectations on receiving a perfect mirror finish, which was never my intention on producing, so I opted for a matte finish.

Now I just wet lap to 600-grit with the kerosene. This produces a matte finish to the surface that is vaguely reflective in that you can see your larger facial features (eyes, nose, mouth, etc) if you look at the base straight on, but you couldn't shave using it as a mirror.

I found that this finish produces the best results for me in my testing.

If one wanted a near mirror finish from my blocks, all they need to do is a follow up lap using 1000-grit, then 1500-grit, then 2000-grit paper. As Restorer points out above, doing this may actually be detrimental to thermal transfer performance in various scenarios, which is why I do not do this.

n3xu5 said:

Just out of curiosity, does anyone here know what the cascade is lapped with?

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I'm sure Cathar would be able to answer that question.

Ffats said:

I'm sure Cathar would be able to answer that question.

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I thought I just did.