correct hsf prep

[plowd1]

Since I am new to OC I hear alot about lapping and polishing. I went and got some 800 grit, 1000, and 1500 and worked my way up using a flat surface and sliding the sink across it . It seems to still be alittle scratched but smoother than it was Am I doing this right ?

 

[Nagorak]

I think you should probably start with lower grit...

Start with say 200 or so, then 400, then 600, then 800, etc...

Bear in mind that the finer the sand paper, the less of the heatsink surface it removes (thus allowing you to get it closer to being completely flat). If there is a big gouge (big being relative, on the bottom of a heatsink a "gouge" can be quite small) you will only be able to practically remove it with a lower grade sand paper (it would take FOREVER with 1500 grit, for example). The idea is to get the larger imperfections out first and then finish sanding it smooth with the finer grits.

 

[plowd1]

I do understand the concept of using a lower grit and I was able to start with 800 and remove and grooves that were in the sink but after I finished with the 1500 there seemed to be scratches or lines that the 1500 was leaving or maybe it just looked scratched because when I sanded the other way it would put them going the other way. When you say mirror finish I assumed it should just be shiny and consistent without visible lines . I see lines but don't really see any grooves and it feels smooth is that the results I am looking for?

 

[kat]

using wet/dry paper and honning oil will produce better results. finish up with rubbing compound on an old dish towel ;D

 

[Hoot]

If you're referring to the "spider web" stuff left after the last lap step, don't concern yourself with it in terms of impacting performance. However, if you are just trying to get that final finish cosmetically appealing, flip over that trimite sandpaper and spend a few minutes on the plain paper. It will strop away most "spider web" marks. the faster the motion, the better the result. Make sure you clean the final surface several passes with a good solvent, basically until a paper tower comes away as white as when you started. Use lots of solvent and lots or rubbing pressure to work it in. No matter how clean the surface looks, you should see some grey stuff come off on the paper towel the first pass or two.

Hoot

 

[LimeyGreg]

The scoring you see is due to the 1500 becoming clogged, you are getting a build-up of aluminum (aluminium in english english ???) which is in turn scoring the surface. As Kat said "honing oil" will help - or some soapy water is okay, it will help stop the wet and dry getting clogged.

I found that using 1000 or 1500 and my finger tip with light pressure as a final polishing works well - you don't need to worry about not leaving it flat at that point as you won't be able to remove enough material to cause that, unless you do it for a few hours of course.

 

[plowd1]

That answers my question concisely thanks for all the input from all I will follow the directions given. This forum is great

 

[Phil]

why do people buff the heatsink after they have lapped it? surely it leaves a residue that will slightly impair the transferance of heat between the thermal compound and the heatsink, it's like when they tell you not too spread AS with your fingers because it leaves grease on it.

 

[kat]

Phil (Mar 10, 2001 06:48 p.m.):
why do people buff the heatsink after they have lapped it? surely it leaves a residue that will slightly impair the transferance of heat between the thermal compound and the heatsink, it's like when they tell you not too spread AS with your fingers because it leaves grease on it.

hum ?

 

[plowd1]

I worked on the heatsink some more with the oil . That did the trick I see no need to buff it I will just wash it good with a solvent and call it a heatsink day Thanks again