My Lapping Experience with an SP-94

[photogearjunkie]

First off, I'll say that I'm new to lapping. However, I did read several of the better lapping guides and combined the best procedures from each of them into my own procedure. I'm also familiar with machining and using tools, so I'm not a total newbie at working with metal.

If you've read any of my recent posts, you'll know that my SP-94 was likely one of the worst as far as machine jobs go. The bottom surface was not only uneven (I only found this out during the lapping process!), but the base was full of ridges from the machining process. When I ran my fingernail over the base, I could clearly hear a zippering sound. And since my load temps were quite high (around 55° on an IC7 Max3), I thought my HS would be a good candidate for lapping.

I won't bore you with the entire lapping process. I went from 400-grit, to 600, to 800, and finally to 1000-grit, to achieve a near-mirror finish. The process took about 2 hours, spending most of time using the 400 and 600 grit sandpaper, to even out the base. I have to say, I was quite impressed with how flat and shiny the base came out after I finished!

I reset the HS with AS5, using the rice-sized-blob-method. After about 100 hours of burn-in, loading and unloading, the verdict was in... this was a waste of time. At Idle, I dropped 1°C, and at load I dropped about 2°C. And yes, my case temps are fairly cool- usually about 27-28°C whether at idle or load (I have 10 fans working it, baby!)

Maybe this just testifies to how awesome and efficient AS5 is...I don't know??? My SP-94 base was in worse shape than ANY of the pictures that I saw around the net reviews and forums. I really expected more of a difference from lapping it, but oh well.

For some, a 1-2°C difference might be worth it, but not for me. And as I suspect that most HS bases aren't in as bad of shape as mine was in, the temp drops likely may be negligible.

Take this as you will...

 

[LED]

I've lapped many atime using close to your methods and yes the cooling performance is minimal but it sure looks good !, even though no one can see it...Reminds me of RAM HS purposes but at least they can be seen through a window

 

[MichaelD]

Strange. The last HS I lapped was a FOP32, way back in the day. My idle temps went down a full 5C.

That said, that was back in the days when there were no HS' that took an 80mm fan. So you either had a 60mm 9,000rpm Delta sawmill or a 2,000rpm whisper-quiet fan that did absolutely nothing.

I had the "Nothing Fan." Lapping made a big diff for me.

Flash-forward to today: My SLK900A came with a mirror finish on it's copper base. Combine that w/AS5 and a quiet 92mm Panaflo fan and you've got pretty much the best cooling system you can buy. (air)

 

[xbassman]

A few months back I was watching Yoshi on TechTV show how he lapped all his heatsinks.
He took them all the way to 2000 grit then used polish to get a mirror finish. This went in contrast to most guides I had read which talked about the oils in the polish messing up heat transfer with thermal paste.

Well, thinking I had nothing to lose, I decided to give it a try.
The first victim was a Thermalright AX-7 that was sitting atop a TBird 950. I lapped to 1200 grit (finest I had). Then scrubbed with alchohol. Then I worked the base with Brasso until not much black was coming up from the surface. Then I scrubbed it again with alchohol. After that I applied AS5 and reinstalled the heatsink.

The result was a temp drop of 5C @100% load from readings taken before removal. That was not only the biggest temp drop I have gotten, but it is the lowest load temps I have had with this processor/HS combo.
On a side note.... other than the polish job, the thermal compound was also upgraded from AS3 -> AS5. I'm not really sure how much drop can be attributed to the thermal material.

Since then I have done 4 or 5 more heatsinks the same way and have had excellent results.

 

[LED]

I think it's all relative to how coarse the HS was before and after the lap job.

 

[photogearjunkie]

I think it's all relative to how coarse the HS was before and after the lap job.

Although that is what makes sense, I don't think this is the case. My HS base went from mountains to a mirror, with minimal temp improvement. I now think it has more to do with how incredibly effectice AS5 is.

 

[wkwong]

did you mount ur sand paper on a flat surface or used your hands? because it can look smooth but still be uneven if you were applying pressure with just your fingertips. well im sure you know what your doing, but i'm guessing that could be a problem with lapping. just my 2 cents