Lathing, Sanding, Smoothing...CPU

How much lapping can the core take before you kill the cpu? Just wondering?

The core? Not much at all. And anyways, you won't be able to make the core any flatter by lapping it, since cores themselves are typically extremely flat.

a bit of mother's metal polish from the auto parts store and a finger's worth of elbow grease will get the thing smooth to a mirror finish, be sure to get polish, not a "filler" because the polish is "3000 grit or so sand paper" in theory and will put the smoothest finish on it. do the same to the heatsink. results will be greater than any sandpaper. dont forget to seal that combo with Arctic V

there is also less risk involved

cool I think I just read a new project to do.

CeleronO/C'D said:

a bit of mother's metal polish from the auto parts store and a finger's worth of elbow grease will get the thing smooth to a mirror finish, be sure to get polish, not a "filler" because the polish is "3000 grit or so sand paper" in theory and will put the smoothest finish on it. do the same to the heatsink. results will be greater than any sandpaper. dont forget to seal that combo with Arctic V

Click to expand...

without sanding?

Lapping the IHS is not a good idea, here's why. The IHS has a phase change tim material under it which compresses under the load applied when attaching the heatsink and the die becomes hot when first used. If you notice, a brand new processor will actually be convex (or protruding) out from the center of the IHS. When load is applied, the phase change material under the IHS has a certain amount of presure applied to it. If you remove this bulge in the new IHS by lapping, not the same amount of presure will be applied to the phase change material and a thicker tim will result between the bare die and the underside of the IHS. The edges of the IHS will transfer the full load to the chip package and not to the phase change material on top of the die.

Claims of 1 or 2C improvement are within the margin of error between mountings. Nobody ever reports an increase in temp, they just remount till they get a better reading.

I stubbornly lapped one and was proud of how "flat" I made it, thinking how shoddy Intel was for making a wavy topped IHS. In reality the only thing it did was make me feel better at the time. I ask you, what good is having the secondary tim improved if the initial tim is degraded?

You are correct when you say that 1-2 degree differences could be mounting error differentials, but that is mostly with air cooling, and it also depends on how far you actually lap the IHS. the IHS plays the part of protecting the acutal core of the CPU, some people just pop off the IHS completely, BUT you are at a much higher risk of crushing the core and rendering your CPU useless. When I use my before and afters, Im using a few methods, I use air cooling (the least though), water cooling, and a prometeia mach I and mach II unit. I notice the largest improvements with the vapor cooling units, due to the fact that I lap the s**t outta them, polish them up to a mirror shine... but it all depends on how far your willing to go for those few extra mhz, or to cool it just that little bit extra...

You missed my whole point, you degrade the first tim joint to improve the secondary one by lapping an IHS.

quote "but that is mostly with air cooling" end quote

Waterblock mounting will have just as much error as air heatsinks between mounts.

lol I think you missed what I was saying, when I said that using air cooling a 1-2 degrees difference is very small, and can be blamed for by mounting, but when you lap the CPU and use water cooling or vapor cooling and the tempurature differences are more along the lines of 8-10 with water or 10-12 degrees with vapor, then it goes beyond calling it mounting mishap...

irregardless of the tim, whether it is not anatomically flat, you are essentially shaving off more metal inbetween the core and the heatsink or waterblock or Vapor unit copper block. If it was a bad method then macci or G-Vex, or any of the top world reknown overclockers who blow away futuremark or 3dmark scores...wouldnt use this method.

The reason they achieve high results has nothing to do with their lapping abillities, it's their circuit board modifications, and it probably makes them feel better if they do any lap jobs to an IHS.

I guess we just have a difference in opinion...

My lapping
SLK-947U

Used 300, 400, 800, 2000 wet/dry sandpaper. Then the red dremel polish.

Awesome Job, thats how I get my CPUs looking, i use 220, 600, 1200, then polish it up with some blue magic and a buffer wheel , then i thouroughly clean it with isospropyl acohol. Very nice job..

Lapping your IHS does very little for temps and next to nothing worth do it for the max OC. All it does is void your warranty.

All I know is that I shaved 3 degrees when I lapped mine.

tellis100 said:

My lapping
SLK-947U

Used 300, 400, 800, 2000 wet/dry sandpaper. Then the red dremel polish.

Click to expand...

Looks great!

To be completely honest, the more testing that I do the
more I think that getting a perfectly mirrored surface is a
waste of time. At least when the CPU still has the rough
"stock" surface.

Getting a mirrored surface isn't as difficult as some
make it out to be. * my slk-900a *

Many times I have observed posters saying
they didn't get any noticable results after a certain grit.
It may be where many less expereinced "lappers" have trouble is
that they don't clean sheets to remove the particles
from the previous grit, or even from the last few passes.
This can be especially important when working with 2,000
and/or 10 micron sheets. Cleanliness is paramount!

By the way ... where does "lathing" come into play?
thread title = "Lathing, Sanding, Smoothing...CPU"

ol' man said:

Lapping your IHS does very little for temps and next to nothing worth do it for the max OC. All it does is void your warranty.

Click to expand...

I'll agree, since the P4 IHS is already quite smooth, and perfectly flat. The older S370 PPGA Celerons on the other hand are quite rough, those WERE worth lapping..

Non-flipchip chips like southbridges and graphic chips are also worth lapping since they're extremely concave.

my 2.53 was not flat at all. i lapped it carefully and made it very flat, along with my heatsink and had great results.
i now use a very little amount of AS5, like half of what i had to before to have it reach the edges of the chip before i lapped it.
to say that its concave because it heats up and expands then comes in contact with the heatsink is about the most ridiculous statement ive heard yet.
that would make the AS5 about useless. thats the equivilent of taking off your HS and remounting using the same AS5 or any TIM
every time you turn it on and run a program.
you want perfect surface to surface contact with the right amount of pressure to hold them that way.
a not so perfect surface like a concave one is relying on the paste for heat transfer. which is fine and works but the better the surfaces mate the better the heat transfer will be between them.

there may be some chips that have very nice flat heatspreaders on them and the gains will not be noticed by lapping, but how many times do you hear, i lapped my heatsink, i mounted it 5 times very carefully and cant figure out why its so hot still.
sometimes a heatspreader IS the problem and its always overlooked.
i had a very concave 2.53, i lapped it for a 5C temp drop.
1 or 2C drop is worth doing to me.
however i would recommend not just doing it to a new chip. run it for sometime and put it thru all the paces, if you are willing to then lose your warranty then that is the biggest downfall of lapping the heatspreader.

Hmm.. if u are so worried about that "bulge" then mount the HS to "flatten" it and to spread the TIM around so that it is thiner then do that then lap the IHS and the HS but take ur temps b4 and then after u WILL notice a large diff. Also u are removing material so that in itself will lower temps the smother the surface the better the heat transfer. Also if u have a Cu core and an Al Hs then u can only take away as much heat as the Al will take away from the Cu. So if the Cu can radiate 80w of heat but the Al can only radiate 60w then u have 20w that is left to raise ur temp. then u have to also take into acount thickness and interface material to get the best temps u must use something that can remove more heat then what it is in contact with. So if it goes Cu Ag then Al 80w for Cu 100w for Ag and 60w for Al then it will act as though the Ag wasent there and tarnsfer like it was copper save for it will loose(loose as in make it harder for heat to pass through) when transfering surfaces materials. Then once agian to the Al or Cu. So by lapping u are making it easer for all of these things to tranfer thus lowering temps. And getting rid of TIM making it thiner for less material to transfer through also helps. So if u have a HS that is pressed together it will not cool as good as the same HS that is Ag solderd together. As it will have to go from surcae to surface then material to material with the solder it will have to go from material to materil only as it will all be connected. So lapping will help temps as it takes away IHS material, lower use of TIM, polishes surfaces smoother for better heat transfer. All that adds up to lower temps. So lapping will and does help temps maybe not very much 1-5 deg c but that could be the differnce between stable and not stable.

As for the motions the figure 8 WILL "round" the sides off and make them a little lower then if u did it in a stright forward motion with even preesure then turned it 90deg to the other side and so on this gives nice flat "sharp" edges instead of rounded ones. But the gains here in contact (in terms of heat) will be very very small as u are gain very little surface area by doing this but it does take a shorter amount of time to do it push then turn 90deg then it does to go figure 8 and "can" lower temps by a slight margin as u will have slightly more area that can be used to transfer heat.

Also clamping presure will effect how well heat is transferd. Some ppl go as fare as putting JB weld on the IHS and then the hs on top of that and using a 25+ pound weight as presure to let it dry. This yeild very very good results when lapped. The JB weild is a very good heat conductor and when combined with lapping the IHS and HS b4 can yeild upwards of 7-10 deg drops. But mind u IT IS VERY VERY PERMENANT and CAN'T B UNDONE. so once u have done it and it is dry that is all. It makes very good surface to surface and material contact due to the high mounting presure and the exelent thermal dynamics of JB weild. *these drops where from systems with just TIM on there hs and mounted in the mobo. and then lapped and JB weilded together with the large weight(25lbs+) on them to acheive spreading the JB weild and to get very high mounting pressure between them that when removed acts as though it is still clamped at that pressure.

If words are spelt wrong or even missing srry but it is late here i have a cold i'm dead tired and the keys are blurry. So i hope this helps to show what lapping does and why and so. If u want i can get in to why the atoms allow this to happen and so on but 4 now good night all.