Should I lap my heatsink?

[scrawnypaleguy]

Just got my new Scythe Ninja and the finish on the bottom is pretty much the worst I've ever seen. wtf. So I wanted to try lapping it (first time I've ever done anything like that). So I drove all over town today and went to four different stores and only came up with 300, 400, and 600 grit. I've read a lot about lapping, and it seems that you're supposed to also use 800, 1500, and 2000 grit.

Would it be ok to just use the ones I have, or does the finish on the heatsink get worse before it gets better when lapping?

 

[Appledrop]

I agree with you on the ninja ... Mine looked as though it wasn't meant to be a flat surface, it had a "fingerprint" type pattern all over, ridges everywhere. So i bought some 80+180+400+800+1200 grit (used one after the other), and temps decreased by maybe 3 or 4C at idle/load. However, i lapped it very lazily- on my knee and not checking for overall flatness besides shoving it against a mirror (which didn't really help). So with a good job, maybe you can reach 5C improvements or so...

I would suggest buying some higher grade grit to finish it off with, but i am no expert so...

 

[scrawnypaleguy]

Well I know I should use higher grit sandpaper, I meant that I couldn't find any

Will I be all right using just what I have now?

 

[GalvanizedYankee]

N/M

 

[scrawnypaleguy]

I heard you weren't supposed to change directions while lapping. Aren't you just supposed to go one way the whole time?

 

[GalvanizedYankee]

N/M

 

[soydios]

Go to any home-improvement store, you can pick up some 1200-1600 grit sandpaper there.

 

[Brahmzy]

Auto stores have the high grit stuff for auto painting.

And yes, lap every heatsink.

 

[scrawnypaleguy]

No, they really don't. I've been to two home improvement stores, and three auto stores. Nothing.

 

[GalvanizedYankee]

N/M

I should have known better than to post in another lapping thread.
With Howard posting links you have the help you need OP.


...Galvanized

 

[Howard]

I figure you'd get better results sanding parallel to the clips (if it mounts with clips) so that even if the bottom of the base isn't parallel to... the whole thing (can't really explain it), the clips will compensate.

Anyway, that's what this guy recommends:

http://www.overclock.net/faqs/15897-info-want-lap-your-p4s-a64s.html

 

[furballi]

Pep Boys...plenty of +1000 sandpaper.

 

[VinDSL]

Here's what I do...

Take some fine wet/dry sandpaper (the finer the better), soak it in water (to make it soft, and keep it from moving around), then lay it on a FLAT surface, like a sheet of Plexiglas, or whatever. Then 'hone' the copper face until it's totally flat, by rubbing it back and forth on this sanding surface. You'll be able to tell when the HS is flat... when the 'marks' are nice and even across the whole thing.

Then, to finish things up, and bring it to a 'high gloss', e.g. mirror finish, polish it with a soft rag and your favorite metal polish, until you can see your face in it. That's it...

Personally, and I can't recommend highly enough, I use Happich Simichrome Polish. It's one of those 'miracle products' the Germans come up with from time-to-time! It isn't cheap, but it works on everything, rings, mag wheels, pots n' pans, and... CPU coolers! You can get it at most motorcycle shops, and a lot of auto shops too...

Have fun!

 

[Howard]

Why polish?

 

[MadScientist]

Look in Walmart's auto section, Advance Auto, or Autozone, get 3M Wet&Dry. There are plenty of lapping guides around. Google them. This is one of the better ones. Lapping Guide

Opinions differ on whether to use a figure 8 or back and forth motion to get the best results. Your objective is flat, not shiny. Lapping higher than 600 grit may not be necessary. Link

I would not lap your heatsink unless you are absolutely positive it is not flat. Poor Man's Flatness Test

Read Cathar's Thread at OCForums

My Artic Cooling Freezer Pro 64 heatsink's base is rough, but flat, and I'm pleased with it's performance.

 

[Zepper]

IMO, a good lapping can get you a degree or two - sometimes more. Few are really flat.

You don't want a "mirror finish" on a heatsink - it can end up reflecting the infrared back into the device. Supposed to lap on a flat surface or what's the point... A fairly thick scrap of float glass is good. Probably don't really need more than 800 grit. A random sanding pattern will give the most even results. I have a few surface blocks that my father made here that are good to less than a thousandth of an inch. A machinist's straight-edge can do it too. Send your sink and I'll test it...

.bh.

PS. note I didn't mention anything about sending it back...

 

[Navid]

Make sure you need to do it before you do it.

What you want is a flat surface. You do not necessarily need a shiny surface. A flat rough surface is much better than a shiny surface that has a curve. It is very easy to unintentionally give the surface a curve by lapping.

Edit:
Mad scientist,
I read your post after I posted mine.

 

[VinDSL]

Originally posted by: Howard
Why polish?

Yes, sorry... a word of explanation...

While 'they' call it a polish, it's actually a very fine abrasive -- and I mean f-i-n-e! You just have to take your time and let Simichrome do it's thing. When you're done, it'll look like a mirror -- and this is with ANY metal, not just copper.

A small amount goes a long way with this stuff. Get the smallest tube you can find. It'll last you for years!

*edit*

You know what? Thinking about it, maybe the reason they call it a polish is because it leaves an anti-corrosive agent on the surface when you're done -- and I forgot to mention that above. So, if you use Simichrome on your HS, make sure to clean the surface with ISO, or whatever, just like normal, before mounting it on your CPU.

This should be obvious, but it never hurts to point these things out...

 

[VinDSL]

Originally posted by: Zepper
You don't want a "mirror finish" on a heatsink...

Heh! Yes, I do...

The more 'mirror-like' the surface, the less the imperfections. Less pits and scratches mean better heat transfer with less thermal compound. It's a win-win-win situation, IMHO!

 

[VinDSL]

Originally posted by: Navid
Make sure you need to do it before you do it...

True! For instance, I can't see much sense in lapping a nickel plated HS. To my way of thinking, filling-in and/or covering-over the imperfections is the whole reason for plating it... but that's just me!

 

[GalvanizedYankee]

Originally posted by: VinDSL

Originally posted by: Zepper
You don't want a "mirror finish" on a heatsink...

Heh! Yes, I do...

The more 'mirror-like' the surface, the less the imperfections. Less pits and scratches mean better heat transfer with less thermal compound. It's a win-win-win situation, IMHO!

A well used sheet of 800 will bring up enough luster to see one's reflection, this is good
enough...Period.

Never introduce anything to the virgin surface but TIM. overclockers.com did testing that
indicated a 0.5~1.5C loss by polishing for a Kodak moment.

You come off knowing too much about everything Vin.

...Galvanized

 

[Howard]

Originally posted by: VinDSL

Originally posted by: Navid
Make sure you need to do it before you do it...

True! For instance, I can't see much sense in lapping a nickel plated HS. To my way of thinking, filling-in and/or covering-over the imperfections is the whole reason for plating it... but that's just me!

Plating is rarely to cover imperfections unless you count primer (the painting kind). Cardinal rule in finishing is that plating magnifies imperfections, not cover them up.

If your base is perfectly (like, flawless single-crystal) flat, where does the TIM go? That's right, it becomes an insulator.

 

[scrawnypaleguy]

Thanks for all the advice guys, I'm learning a lot. I'm going to lap this with what I have since it can't possibly be worse than the poor contact this thing is going to have if I just throw it on there. I'll post some updates when I'm done with everything.

 

[VinDSL]

Originally posted by: scrawnypaleguy
Thanks for all the advice guys, I'm learning a lot...

Yep, good points -- all!

Now, to whom it may concern (ahem):

Look, when it comes right down to it, this is all academic, isn't it? Just a matter of opinion -- and I stated MY opinion.

I didn't interject somebody else's opinion (as if it were my own) into this thread -- some phantom authority -- someone that isn't even taking part in this discussion -- someone that can be questioned, and so forth. That's a dishonest debating tactic, but I'll give YOU the benefit. I don't *think* you were trying to be malicious, and neither am I!

After all, we're just having fun, right? How about 'we' keep it on that level, and not turn this into a pi**ing contest. Nobody wants that (or do they?)...

 

[Henny]

Originally posted by: VinDSL
Here's what I do...

Take some fine wet/dry sandpaper (the finer the better), soak it in water (to make it soft, and keep it from moving around), then lay it on a FLAT surface, like a sheet of Plexiglas, or whatever. Then 'hone' the copper face until it's totally flat, by rubbing it back and forth on this sanding surface. You'll be able to tell when the HS is flat... when the 'marks' are nice and even across the whole thing.

Then, to finish things up, and bring it to a 'high gloss', e.g. mirror finish, polish it with a soft rag and your favorite metal polish, until you can see your face in it. That's it...

Personally, and I can't recommend highly enough, I use Happich Simichrome Polish. It's one of those 'miracle products' the Germans come up with from time-to-time! It isn't cheap, but it works on everything, rings, mag wheels, pots n' pans, and... CPU coolers! You can get it at most motorcycle shops, and a lot of auto shops too...

Have fun!

Plexiglass is a poor choice for flatness!!

Get a granite tool room plate like these:

Text

Or you could use a piece of 1/4" plate glass.