Went through 2 sheets of 120 grit to lap in SVC GC68

Squisher

Lifer
Aug 17, 2000
21,204
66
91
I took me 1/2 an hour just to get the bottom of this thing flat with the 120 grit. Of couse the worst indent was right where the cpu goes. What do they make these things with, a chisel,? Or, maybe an axe :|

 

cheap

Senior member
Sep 30, 2002
399
0
0
Same with my volcano 9 cooler, middle where cpu goes was the hardest to get to. Went through the whole 2000 grit sanpaper bag and spent like 2 hours on it.

Originally posted by: Squisher
I took me 1/2 an hour just to get the bottom of this thing flat with the 120 grit. Of couse the worst indent was right where the cpu goes. What do they make these things with, a chisel,? Or, maybe an axe :|

 

Jeff7

Lifer
Jan 4, 2001
41,596
19
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Originally posted by: Lizardman
sorry to tell you this but the indent is supposed to be there:(

Which indent? Found a pic of it here, 2nd pic down. I see no indent there, except for the one on the side that runs the length - that's there to clear the socket itself. But as for an indent where the CPU core goes, the only thing I'd figure that Squisher means is that the heatsink was concave. I found that a power sander with rough grit is good for getting heatsinks flat. I do the actual lapping manually with the finer grit sandpaper.
 

Lizardman

Golden Member
Jul 23, 2001
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Originally posted by: Jeff7
Originally posted by: Lizardman
sorry to tell you this but the indent is supposed to be there:(

Which indent? Found a pic of it here, 2nd pic down. I see no indent there, except for the one on the side that runs the length - that's there to clear the socket itself. But as for an indent where the CPU core goes, the only thing I'd figure that Squisher means is that the heatsink was concave. I found that a power sander with rough grit is good for getting heatsinks flat. I do the actual lapping manually with the finer grit sandpaper.



Maybe the bottom of the heatsink is supposed to be concave?? And you cant tell from that picture.
 

Squisher

Lifer
Aug 17, 2000
21,204
66
91
Originally posted by: Lizardman
sorry to tell you this but the indent is supposed to be there:(

Ahh, I don't think so.
rolleye.gif


What I'm talking about was like a .005" deep pucker inward.

Taking off .005 with sandpaper=not fun.

If I had known that it was that bad I would have chucked up in vise and milled it smooth first.
 

Jeff7

Lifer
Jan 4, 2001
41,596
19
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Originally posted by: Mikewarrior2
under no circumstances is a heatsink supposed to have a concave base.

Mike

Yeah. Back before I knew anything about CPU temps or cooling, my P2 300 ran at 60C. Yes, that's about 140F. Well I found out that that was WAY too high for a CPU (probably explained the BSOD's I'd get occasionally) - took off the heatsink, and found that it was bowed in about a full 16th of an inch! I put it in a vice and actually bent it straighter. I just gave up on it then; it would have taken way too much work to make it half decent - it also had ridges on 2 sides; that would have made it very difficult to flatten the interior.
And of course, convex wouldn't be much better. Got to be completely flat to match the CPU core, though even that can be a little off too.

Did you take any pics for us?
LilHen, that's not the Anandtech way to ask. I think the proper way is more like:

PICS???

:D
 

Squisher

Lifer
Aug 17, 2000
21,204
66
91
Sorry no pics, I was in too big of a hurry to get this cpu installed. Besides, when I started I thought it would take the usual 5 to 10 minutes starting out with some 400 grit. Well, I backed up to 180, then to 120. In retrospect I should have started with 80 grit(whew).

As for performance the GC68 is doing just fine. Temps are 41C running a 1600XP at 138Mhz FSB(more later) and I downgraded the fan to the 80mm Panaflo L1(from 28cfm to 21cfm). I wonder what performance would have been like without the lapping?

This for my 2D machine I was really looking for silence.
 

Engineer

Elite Member
Oct 9, 1999
39,230
701
126
I've got about 5 of the GC68's and the first 3 were mirror finish and very flat....but the last two had several flaws. The groove for the clip was cut deeper than the previous models (I didn't mic it, but a side by side comparison showed the groove to be cut deeper in the newer models, causing much less pressure from the clip. The clip had to be bent to get any amount of pressure at all on the CPU. Also, the bottom looked like it had been cut with a saw....very rough.....took 30 minutes of sanding to get a flat surface with no deep scratches (saw marks?). I don't think the new batch would have cooled anything, except the false readings it gets from most motherboard thermisters from the air flow around the GC68 to the motherboard! (Sorry, had to throw that to MW2....it makes perfect sense now! ;) )

Good Luck all....

(P.S. Yes...the surface was concave at the CPU when it arrived)....
 

BZeto

Platinum Member
Apr 28, 2002
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I lapped a GC68 awhile ago, it wasn't too bad, I got it pretty flat. The bottom wasn't too smooth when I started. I started with 400 grit, then went to 600, then to 1000 grit (I was too cheap to buy a sheet of 800), then to a 1500 sheet to finish it off.
 

BZeto

Platinum Member
Apr 28, 2002
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I was in the same situation as you. No place logical had a big variety. Turns out good ol' Walmart had it all. Look in the automotive department, They should have 3m Imperial Wet or Dry. Lots of different grits, it can get pricey though.
 

Jeff7

Lifer
Jan 4, 2001
41,596
19
81
Originally posted by: LilHen
I went by Home Depot to pick up some Wet & Dry sanding paper and the highest they had was 800 grit. Where are you guys gettting the 800+ grit? I heard Pep Boys carry them, but none around here.

K-mart has up to 2000 grit sandpaper - that's in the auto department; a few auto stores I checked out only had up to 1000 grit. If you have them where you are, Ollie's might have some; they had 1500 grit sandpaper for about a fourth the cost of regular retailers.
 

Mday

Lifer
Oct 14, 1999
18,647
1
81
ya, for like 1000 grit or higher, it's auto stuff stores. you can always check online.
 

randomboy

Senior member
Aug 18, 2002
668
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I just cant believe you guys start with anything that low in grit, lowest I'd go probably is maybe 400 to start, cause I wouldnt want to have to sand out all those deep scratches afterwards :)