Re-lapping over a machine lap?

[CoW]8(0)]

Apparently the WC block I have has been lapped flat to within 5 microns, but when I reflect it against light, the reflection clearly shows ALOT of scratches that have developed over time. The mirror finish is still there...

Would it be a good idea to do a hand lap? The finest wet/dry paper I have is 2000 grit, but I don't think that's going to give me <5 microns...

 

[SpoogeMonkey]

You could probably do a quick lapping with 1200 grit, then jump to the 2000....I wouldn't over-do it though. Your local Napa auto parts store should sell single sheets for $0.78

 

[zer0signal667]

What company lapped your block? I assume 5 micron means they used a 5 micron polishing compound, which doesn't say much of anything about flatness.
Anyhow, 1200 grit converts to 15 micron, 2000 grit is about 8 micron. If you're going to be completely anal about the finish, you're going to have to work hard to get it back to the original 5 micron polish. You won't see a difference in temps unless you change the flatness of the base, whether it be for better or for worse.

 

[DFI Daishi]

2000 grit paper is the finest that i have used, and it gives a more reflective surface than the finish that has come stock on any heatsink i have had, or on my waterblock. starting from a tool finish i usually start with like a 400 grit and move up by incriments of whatever grit the hardware store has in stock, up to 2000. if the scratches in the block aren't too deep, and there are no tool marks on it, you can probably start with more like 800 grit.

perhaps more important than having a fine grit paper is having something REALLY flat to use for your lapping surface, and carefull technique. a bit of mirror glass is reasonably good, because you can at least visually verify that it is reasonably flat, looking at something's reflection with it. someone suggested graph paper last time i read a thread like this. seems like a good bet. go slow, with fresh paper and plenty of fluid (water with a bit of soap, low odour kerosene or whatever else you like to use) and make sure to keep even pressure on the block.

there have been a few threads on the subject of proper lapping technique around here......it's not going to gain you much, if anything, in terms of cooling. all the same, it's cheap, and it helps to reassure you that both you and your system are really hardcore.

 

[SpoogeMonkey]

When I was polishing some 1" lexan plaques, we finished by buffing it with a talc like powder, similar to baby powder to remove the tiniest of scratches.

 

[CoW]8(0)]

What company lapped your block? I assume 5 micron means they used a 5 micron polishing compound, which doesn't say much of anything about flatness.
Anyhow, 1200 grit converts to 15 micron, 2000 grit is about 8 micron. If you're going to be completely anal about the finish, you're going to have to work hard to get it back to the original 5 micron polish. You won't see a difference in temps unless you change the flatness of the base, whether it be for better or for worse.

Well apparently a Peter Wolters AC 500 lapping machine was used for the lapping...

And is it safe to assume that the base is probably made flatter in the factory than I could ever possibly get it? I do have sheets of glass, but not mirror glass, so I can't verify it being completely flat.

 

[DFI Daishi]

Well apparently a Peter Wolters AC 500 lapping machine was used for the lapping...

And is it safe to assume that the base is probably made flatter in the factory than I could ever possibly get it? I do have sheets of glass, but not mirror glass, so I can't verify it being completely flat.

it probably is, though there's always the chance that you got a poorly machined block that slipped through the QC cracks. you can try the reflection trick with the base of the block as well, to see if the lines on graph paper get distorted.

and, to be clear, mirror glass = a piece of a mirror. i picked up some at the hardware store for a few bucks, and a glass cutter to trim it to the size i want.

i guess that this is one of those occasions that i'm guilty of "doing it because i can"......however it really is cheap, and seeing the product left me feeling reasonably satisfied that i had made that block as good as it was going to get.

got a few hours to kill? sand.....sand.....polish.....polish......and it looks really good when you're done.

the kitchen table and wall panels that i did this summer turned out pretty well too.

 

[MikeP]

Everyones going on about reflective surfaces. Cathar , who knows more about blocks than jsut about anybody says blocks should have a smokey finish when lapped properly.

This si taken directly from his Little river website:" The satin-like dull reflective finish on the block.s base is intentional. A highly polished finish is not indicative of a flat contact area, just as a polished metal ball is highly reflective but absolutely is not flat. It is strongly recommended that you do not lap or polish the base-plate of the Storm water-block as you will make it less flat and degrade the quality of the CPU to water-block contact area. "

Id assume this will translate to most blocks.

 

[DFI Daishi]

Everyones going on about reflective surfaces. Cathar , who knows more about blocks than jsut about anybody says blocks should have a smokey finish when lapped properly.

This si taken directly from his Little river website:" The satin-like dull reflective finish on the block.s base is intentional. A highly polished finish is not indicative of a flat contact area, just as a polished metal ball is highly reflective but absolutely is not flat. It is strongly recommended that you do not lap or polish the base-plate of the Storm water-block as you will make it less flat and degrade the quality of the CPU to water-block contact area. "

Id assume this will translate to most blocks.

you don't end up with a mirror finish with the steps that i outlined. it's reflective, but not mirrored by any stretch.

what goes for the little river blocks does not go for te whole industry. cathar's blocks are known to be 1) machined precisely flat and 2) EFFECTIVELY machine lapped. i believe that the machine lapping is up to about a 1200 grit in fact.

not all waterblocks are machined terribly flat (look up threads on A-C blocks with concave bases) and quite a few aren't lapped at all.

if you are patient and carefull, with a really flat surface upon which to lap you can do some good quality work by hand.

here's the thread where cathar weighed in on the subject: http://www.hardforum.com/showthread.php?t=925741&page=1&pp=20&highlight=lapping

 

[Top Nurse]

I went to 2,000 grit with my AC blocks and they are not mirror finished like the kind a real mirror provides. What you get is an extremely flat surface that when tilted at a slight angle will reflect like a mirror (much like a fine table top). Of course what you are looking for is an absence of wavy reflected lines when put near a grid. Actually on my block sides I went to about 3,000 grit by using the back side of a piece of 2,000 grit sandpaper. I then applied some Meguire Yellow wax to the sides of the block for some real bling bling.