Damn, no mirror finish even with 2000 grit

[Glumy]

Hey guys, just seeking advice again:

Ok I stepped the sandpaper grits from 400,600,800,1000,1500, and then 2000 whilst lapping my *cough* waterblock (actually its my Geforce 5900 Ultra GPU but im just trying to avoid the "dont lap your GPU" replies hehe). Anyways the 'waterblock' is now flat and smooth, very smooth. But one thing that bugs me with the effort that i've put forth with each grit sandpaper is that i still dont have a mirror finish. My gawd I used 2000 grit (and Im talking, using soapy water, rinsing the paper every 20-30 seconds, wiping off the 'waterblock', etc) for like 45 minutes and whats left is a smooth surface, but the finish is i guess what you could call "murky" or brushed looking.

I know the mirror finish is probably not necessary as I have read in many posts. But humor me, after that much labor I want to be able to see all the cuts and bruises sustained on my hands from this endeavor in that fabled mirror finish.

But I just CANT get there with 2000 grit. I sanded and sanded and sanded, but just couldnt get there...

Anyone have advice? Maybe a different material to use to get that mirror finish?

Thanks!

[ukdan]

how about polishing it with different grades of car polish to get the shine you want?

[Jex]

i have heard that it takes several hours to get that beautiful mirror finish. g'luck

jex

[vonkaar]

You should take note that even those with 'true' mirror finishes aren't really looking at it like it's a mirror. The best way to SEE the great finish is to lay it flat against a surface and see the reflection...

like, the bottom of my SS:
http://www.euphoriaguild.com/oc/cascade-ss1.jpg

[Cathar]

To get 2000-grit to give you a mirror finish you need to dry lap it.

If you wet lap with 2000-grit, you will get that murky finish that you describe. After lapping to satisfaction with the 2000-grit, push down fairly firmly while lapping. This wears away the grit making the paper effectively finer than 2000. Now take your block off and dry it off. Wait for the paper to dry out. I use low smell kerosene as it dries off without leaving crazy residue like soap does.

Now that the paper is dry, put the block back on and do small circular laps while pushing down very firmly. After about 10-15 laps you should now have a near-perfect mirror. I don't like doing this though because the action required to get that mirror finish often makes the base less-flat, even if it does give you the mirror shine.

[ogboot]

listen to Cathar, if i do know one thing it's that he knows his stuff :D

[BladeRunner]

To get a mirror on my blocks I use down to 1200 grade, (wet), then T-Cut (used for restoring dull car paintwork) and finally car polish (autoglym). on non contact surfaces I coat with clear celulose lacqure to prevent tarnish. also worth keeping in mind that a mirror polished contact surface may not give the best results..

http://www.zfz.com/pictures/temp/splitter-x032m.jpg (http://www.zfz.com/pictures/temp/splitter-x032.jpg)

[eXCeSS]

damn you guys posting nerd porn

(that mirror SS and bladrunners cpu block)

brb gonna go cry :(

[Seven]

Haha eXCeSS.

Very useful guide Cathar.

I thought that finish doesn't really matter as long as the contact surface is clean and flat for heat transfer...

[NavyDood]

I only go as far as 600 grit. Anything finer than that I haven't had any difference in temps.

[Cathar]

Originally posted by eXCeSS
(that mirror SS and bladrunners cpu block)


Q) What's better than one mirror SS?

A) 2 mirror SS's! :D

http://www.employees.org/~slf/images/mirrors.jpg

[feyd83]

Lol.
That's just ludicrous shiney :p

[BladeRunner]

Originally posted by Cathar

Q) What's better than one mirror SS?

A) 2 mirror SS's! :D


No>>>>>>>>>> the item in my reflection :p

http://www.zfz.com/pictures/jpg/hdd3small.jpg

[skidooosl]

why do people say not to lap the GPU??? i just did mine today on my TI4200 in my sig, they are not even close to flat... it took me FOREVER to get it down... but now i only need a small amount of AS5 instead of like a gallon to make contact with my water block.... also while i was sanding i noticed it is all copper under the aluminum WOO HOO! this should help my temps quite a bit. i just tested the card after i finished and it still worked to, lol!! now when i finish my upgrade i can see if it made a difference. i went up to 2000 grit also and had the same result, it leaves scratch marks... but you can still see a reflection... i just dont really want to get the card wet...

[BladeRunner]

Getting it wet isn't an issue but drying it fully is very important. Also water with a high mineral content may leave unwanted deposits on the card. I regularly wash cards mobos and cpu's and never killed any by washing them. I usually use an airline and hairdryer to dry them straight away and leave them over night on a warm place to be sure all traces of wetness are gone.

GF3 / 4 were notorious for having poor concaved GPU surfaces, and the silver you sanded away would have been some form of plating on the copper not aluminium I think.

http://www.zfz.com/pictures/dusty/dusty7.jpg

[Diggrr]

You Go Blade!

I'd told people here that we used a dishwasher after wave soldering on circuitboards (at a former job) and no one believed me.
We too used a dry line (filtered, dried compressor line) and let sit overnight in a warming rack before installing them in lasers the next day.
Best way there is to get flux and other crudies off the boards.

I used some 2500 grit paper from AutoZone on the tops and sides of my blocks, and got great results. I just let the copper sit on it's own weight (ie NOT pressing downward) and lapping in a small circle the size of a dime. I always wet lap mine on a piece of glass over the sink basin, with the water tap slowly running on one corner of the paper at all times. That keeps removed copper from causing scratches, and the water will "hydroplane" the block for an even lighter lapping, also effectively making the grit "smaller".

Have fun ya'll!

[BladeRunner]

Yeah those cards were just from a mate's wife's mums PC, It was the most dusty PC I've ever seen, not been cleaned since new (Pentium 2)

Recently I gave it a clean / refresh and made it neater inside. The pics are here for a laugh and run from dusty1 to dusty11, just change the number on the url.

http://www.zfz.com/pictures/dusty/dusty1.jpg

Another funny thing she had no disk space left on a 4.3 gig HDD running Win ME. I found over half the disk was full of weekly system restore files going back to Sept 2002 :p

On the GPU lapping you will end up with a slightly convex GPU doing it manually.There is just no avoiding it without surfacing on a machine, but whatever it should be better than some of the concaved ones I came across, and at least the centre of the GPU should be making contact now.

[wannaoc]

Heres a little trick I figured out to give it the final mirror finish. After you sand it down to the 2k grit like usual take a dry piece of 2k and litely sand over it again. Change out your piece a couple times because without the water it gets clogged up fast. I use around 2-3 small pieces to do it and it looks perfect when finished.

EDIT: I now see Cather also brought this up. :p

[Camacho111]

Originally posted by ukdan
how about polishing it with different grades of car polish to get the shine you want? I manage to do a three stage lapp. 600-1000-1500. The trick that I've found is to use either MOTHERs POLISH or Eagle ones' NEVER DULL buff to shine. apply three coats. That should do the job.