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why doesnt anyone use metal polish to "lap" heatsinks?

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nbx2

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Mar 14, 2003
im a car person... with 30 mins you can make any metal shiny, provided you use the right stuff.. which is mothers mag and aluminum polish.

i dont see why you guys use that sandpaper crap... 1 rag and some polish out of your garage...

stock intel heatsink + 15 mins =

intelhsf.jpg


anyone out there try the metal polish method, as opposed to the hour of wet sanding method? more time and it would be perfect, if you had a buffer wheel it would take <5 minutes..

id do this on my aeroflow but im not sure if it needs it..
 
OP
nbx2

nbx2

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Mar 14, 2003
i just checked with a razor blade and it is indeed flat..

going perpendicular to the ridges smooths them all out.

the fact its machined means its most likely flat to begin with, if it was stamped, that would probably be another story, cause molds do deteriorate, most of the time however, machines that do "machining" dont really do shoddy jobs..
 

john240sx

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Sterling IL
there's imperfections that you just can't see with a naked eye, it may look flat but it might not be. just polishing the metal might actually have a negative impact on the heat transfer properties of the heatsink.

what's your before and after temps?
 
OP
nbx2

nbx2

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a mirror shine is a mirror shine. if its smooth it will reflect perfectly, mine isnt perfect, then again i spent 15 minutes on it. i wasnt trying for anything cause im not using this, i just wanted to see if it was possible.

there are no tests, its a stock intel hsf and im not using that crap on an oc'ed celeron, especially when i have no idea what the cpu temps are cause theres no way to tell :)

i just wanted to know what the reasoning behind wet sanding vs. polishing was.

remember, polishing is really similar to wet sanding, the 'grit' is contained in paste form, instead of glued onto a paper.

its the same principle, it just seems (so far) to be quicker and easier.

i refuse to believe that a metal can have a perfect mirror shine but be physically different cause you used wet sand paper and i used metal polish. polishing metal until it shines IS removing imperfections. this HSF was very "ridgey" as you can tell by the untouched sides, now there are like 2 ridges in the cpu contact area that i could get rid of the same way you guys do.. spend some more time on it.
 

slater3333uk

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Dec 8, 2002
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john240sx said:
there's imperfections that you just can't see with a naked eye, it may look flat but it might not be. just polishing the metal might actually have a negative impact on the heat transfer properties of the heatsink.


Thats very true

tests have showen that finishing the sink to a mirror finish has a negitive effect on heat transfer. this is belived to be caused by the fact the a hsink lapped with say 600 grit wet n dry has a higer surafce area on its base then a hsink that has been lapped with 1200 grit due to the slight microscopic ridges that form.

thats just 1 hypothisis but it has been showen that going further than 600-800grit wet n dry paper brings no gain in performance and maybe eaven a slight loss

the method that you are trying to use is not lapping at all it is just polishing the surface as it has been stated before that purpose of lapping is to make the surface as flat and eaven as possble this method dose nothing at all to make the surface eaven it just makes it look good!

if you want to see the best way to lap at home without the use of machines then i would do a serch and find out a bit more info on the situation - take note of the methods described by BillA or Graystar
 
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nbx2

nbx2

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http://forum.oc-forums.com/vb/showthread.php?s=&threadid=135548

then why is every other picture in that thread of a waterblock on its side with the mirror finish showing? surely those guys knew having a shiny surface was a stupid idea.. should they break out the sandpaper and rough it up? even though the whole point of 'lapping' is to smooth the surface out, to a point where the imperfections are so tiny that the surface reflects images perfectly? I wish I could do a comparison cause im betting that when you put a mirror finished hsf/waterblock that was done by lapping, and one that was done by polishing, that the results would be the same.

i dont think you guys realize polishing is removing metal from the surface the same as sanding does. i have a rag that is now black and was once white to prove how much metal was removed.
 

BoB NaPaLm

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I see your reasoning that if there were ridges, then the light would refract? and cause a distorted picture. A mirror finish with a perfect picture means that the surface is flat so that all the light reflects nicely like on a mirror.

However it could be a mirror shine and angled to one side...but seeing as not a great ammount of metal would be removed, it is most probably flat.

Maybe you can test this theory out on another heatsink that is currently in use!
 
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nbx2

nbx2

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and i quote.. the lapping sticky:

So we lap the heatsink to make it smooth so you get the best possible contact between the heatsink and CPU for maximum cooling. There will always be peaks and valleys, but lapping changes Mt. Everest to a small hill. Thermal grease fills these micro-voids, but the smoother the better.

thats the exact same thing ive done with polish. almost all the ridges are gone (more will be if i decide to spend another 15 minutes on this), there are peaks and valleys, yet the peaks have been lopped off to sea level by the liquid sandpaper, oh, i mean, polish, and the valleys are subsequently not as deep.

To me this sounds like a case of "he must be wrong because he did it a different way than we usually do it"

I'm not trying to start some kind of .. well i dont know, but the reasons you guys are giving me arent based on fact, theyre based on your opinions. "because" is not a reason.

removing the high points so as to make the lowest points "not so low" is the purpose of "lapping" and "polishing"

the better job you do, the shinier the bottom will be. thats common sense.

in fact, wouldnt the BEST yet impossible scenario be where you have 100% metal to metal contact, and we put heatsink compound companies out of business?

that being, no peaks and valleys to an atomic level, every single possible point of contact is used.

in that scenario you wouldnt want any more "surface area" because for you to have more surface area, you would have to have peaks and valleys, which are inefficiencies that have to be filled with AS3.

since we cant make it perfectly flat, we can only try, its the law of diminishing returns however cause its not going to make a measureable difference past.. well, what is the general idea right now? a "600 grit" level of polish? in that case, my job would be "better" in a sense, being a mirror finish (or really close to), but the difference in performance between it and a 600 grit finish wouldnt even be noticeable.

right? :D
 
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slater3333uk

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i can see where you are coming from and your right that alot of people do put a mirror finish on there blocks but thats because they dont relly think about what they are doing they just go with the flow. if people like you post telling them not to bother lapping there sink and just to polish it then thats wot they will do.

it hard to explain why lapping is better than just polishing so i did a quick drawin to give you a vague idea

lap.JPG


its by no means a accurate drawing but it shows the main principals of it. the surface that has been polished using you methord will be smooth therefore it will reflect light like its polished but it will not be eaven and that means that it will have less area in contact with the chip and that the heat will have to conduct a long way through the gaps witch will be filled with hsink paste witch is a poor conductor.

on the lapped suface it is not smooth so it dosent reflect light very well but it is very eaven and that means that it will contact the chip in more places and the gaps are smaller than if you was to polish it

the main problem with your method is that there is no flat surface inolved so the base of your sink will be no where neer flat. correct lapping uses a flat surface so that the base of the sink comes out flat thats what lapping is! not just polising with a bit of rag

sorry to put you down :/
 
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nbx2

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Mar 14, 2003
polishing doesnt remove that much metal though,

lapping removes a certain set of grooves and replaces them with another set of grooves

polishing simply removes the high points, it is a much softer method and it removes less metal, there is no way your diagram could be correct, for that to be true i would have had to polish for more than 15 minutes :)

you cant remove the high and the low points because the high points "go" first. in other words you cant create bigger valleys without touching the peaks.

polishing is easy and gets progressively harder approaching the mirror shine because youre just removing the tips of the peaks, and then once its close to a mirror shine, you have to actually remove more and more metal, which gets much more difficult to do.
 
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slater3333uk

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Well it depends on how flat the sink is to start with

if your polising is removing enough metal to remove the machining marks then its is removing alot of metal

however if the polising is not removing the machining marks then its not having enough effect

a good point about lapping is that it will remove the machining marks and leave you with a surface that has more area in contact with the chip and smaller gaps for paste to fill

where as polishing will leave you with a smooth surface wich is not flat - if you dont have any flat surface involved then it cant be flat
 
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nbx2

nbx2

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how about a fight instead? :attn:


hehe kidding.

youre right, we'll never know unless i could test it out myself. and since im a broke-assh foo then thats probably not going to happen.
 

Jah Warrior

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hmmmmz strange coincidence this thread....


I lapped my SLK900u last night because it had machining grooves, anyway i couldnt find any really fine sandpaper so I finished it off with Brasso and my temps dropped by 2 - 3 degrees (measured at same room temp)

Hence polishing with metal polish works - heres the data if you are interested...

CPU speeds:- 217 x 11 = 2389 @ 1.79v (actual)

Temperatures pre-lapping
Idle:- 36 celsius
Full Load (prime 95):- 43 celsius

Temperateures After Lapping
Idle:- 33 celsius
Full Load (p95):- 41 celsius.

For both tests the room temperature was 22.5c and both tests were conducted using Arctic Silver Ceramique applied in the usual manner.



oh btw...
I think that just polishing would do little good, a combination of the both would seem to be best as you are removing the worst of the ridges with the sandpaper and then smoothing thise ridges further with the polish. Ultimately polish will not remove large ridges as per the diagram that dude posted, but it will smooth each of the remaining ridges.... now i'm lost too:D
 

slater3333uk

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lol :)

i think its a very hard thing to test because the differance is too small but your welcome to try.

everyone has a differant onpinion on lapping and stuff so dont worry that we dont agree. thats why we could argue all day there is no universaly agreed answer to this one... yet;)
 

slater3333uk

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Dec 8, 2002
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Jah thats a valid point but we need a test to tell the differance between stock, lapped and polished and maybe lapped then polished not just stock and polished but thanx neway:)

1 tip: if you need to test something its a good idea to repeat it 3 times or more. the differance in the way you seated the hsink makes a huge differace to temps so just 1 yest of each is not very reliable

Have a nice day!:D