Lapping a H/S..(sand, sand..sand!!)

[Bovon]

Here is something interesting I thought some of you might like to read.

I have been running a K6-2 500 sence late `98. I bought it retail, and it came with the AMD heatsink. Its been inservice sence then...I was fiddling around in the case today, after the puter had been on all day, and running several cpu intensive apps, I just closed everything down...and put my hand on the side if the sink. It was cold...not cool, cold. (the sides are off the case)...anyway, I thought this unusual, so I pulled the sink. I touched the top of the cpu, and it was quite warm..I got a straight edge, put it across the bottom of the sink, slid a 0.005 (5 thousants) feeler gauge between the straight edge and the sink bottom...that thing was very concave, and was only touching the metal cap of this K6-2 out on the edges. I have so far, worn out two sheets of 400 grit wet/dry automotive sandpaper...and still have a little anodize finish right in the middle. I slapped another sink on the cpu til I get this AMD sink sanded flat.

Maybe we should all be checking our heatsinks better before installing them...and, this could also be a reason some guys are having heat problems with their new systems, even tho the core of an Athlon is much smaller than the metal cap on a K6-2..a concave bottom of a heat sink still wont contact the core properly.

[Sterling_Aug]

Use 400, 1000, and finally 1500 grit to get a mirror smooth finish.

[Target]

Seems like the guy that wrote this article agrees with you....oh wait, that was me <lol>.

http://www.sysopt.com/articles/lap/index.html

Even though that article has been around for a while, and processors and heatsinks have changed, it still applies.

[Bovon]

Hi Sterling_Aug, yep...I do that to get the mirror finish, but if I had known this sink was this bad, I would have started off with a file, instead of 400 grit sand paper

Goor artical, Target.. this sink was flat...(to the eye), it took a straight edge and a feeler gauge to actually "see" the concave bottom. I suspect many guys (and gals) are simply placing a heat sink on the cpu in their haste to get it up and running, and do not check to see if the sink bottom is actually flat. These things are not machined to a specific tolerance like a part for the Space Shuttle LOL...so, we need to check these things out first, and lap them at least flat, even if we do not try for the mirror finish.

If a heat sink does not contact the core of a HOT Athlon completely, heat problems are sure to plague us.

[NavyDood_ F/A18_Mech]

I'd have to disagree on using the 1500 grit from my experimenting.

Start with a 220 or so grit. Takes it down quick. Then 400 or so then finish it with 600. I did this once stopping at 600 on my old celeron 366 heatsink. Slapped it on with Arctic silver and ran it. I don't remember the temps. I then removed it and sanded it all the way up to 3500 grit. (Yes i have access to these grits) Spent a long time to get up to that grit. It didnt change my temp at all. I did this becuase everyone always talks about getting a mirror finish.

Like I said though. This is what I found out experimenting.

Jim

[Banti]

My cousin use to use the 3500 grit on his fingernails. Got rid of the natural grooves in his nails so cleaning grease of his fingers was a snap... appparently the women liked the smooth nails as well... then again he hung out with strange girls.


Banti

[NavyDood_ F/A18_Mech]

LOL Banti.

I have access to 5500 grit also, but i wasn't about to waste my time.

Jim

[knucklebusted]

5500 GRIT! Man, what do you work on, Jet Engines?

I stopped at 1000 grit for my Duron and Athlon HSF and then applied some Wenol metal polish. It was mirror slick. I never tested at anything other than stock and mirror. It was good for 4F idle and 5F at 100%.

I also did a K6-2 HS for my brother with what he had available. We only had 80 and 220. Just getting the nasty grooves out dropped his K6-2 by 3F at 100%.

[thekingofpain]

Ive seen some sinks that appeared they chucked a rock in the mill to smooth them---(ive ground on them till my hands were blistered)--- beware of finishing with any sort of "metal polish" it can pollute the surface fouling benefits of good compounds like Arctic silver...

[NavyDood_ F/A18_Mech]

He he he why yes i do work on jet engines.

Actually we have kits for re-conditioning the canopies and windscreens for the Jets. They have those grits in the kits. What is left over just gets tossed.

Jim

[Banti]

Yup that is where my cousin use to get his supplies, from the waste.... That boy never was quite right.


Banti

[Bovon]

I don't try for a mirror finish either. The main criteria is to get it flat, and remove the anodized finish. Engineering heat sink manuals teach students in this area of their training that an anodized finish impeeds heat transfer. Removing the finish on the bottom of a heatsink will help greatly. Removing the finish from the fins is entirely a different story, and probably not feaseable.