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Am I lapping it wrong?

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iLLestOne

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Dec 13, 2003
Location
San Jose, Cali
I've searched and read MANY reviews on lapping.

The one that's I've seen the most people agree on is to keep pulling the hs in the same direction. Never rotate it at all. Just pull, lift up, put back, pull again.


I did this for about 10-20 mins. I started with 600grit, then went to 1500.

I noticed that the SIDES are getting a lot smoother then the center or the front and back. If anything, i'd figure that the front and back would be the wones that should be wearing down faster, but it's the sides.

I stopped, fearing I was doing more harm then good. I wet the paper and used a little dishsoap for a lube. Can anyone tell me what I'm doing wrong? Or will it all start to be smooth some? I just don't wanna mess up my new sp-97.

And to anyone who is going to suggest not to lap it, the bottom of mine looks the the top of a record. I can HEAR sounds when i rub my nail over. You wouldn't believe how bad it is, at least I didn't at first. :(
 

L337 M33P

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Jun 5, 2003
Location
TEH INTERNETS
rubbing in one direction? Won't that make the base at an angle?

The reason it didn't work is because you didn't do it for long enough. A good lapjob is 2-3 hours worth of elbow grease.
 

crull

Member
Joined
Dec 19, 2002
Its tough to say what is the best way to get it flat. There are a few ways to do it, but I can't say which is best.
The way you posted doesn't sound right though. It does sound like you would be sanding more metal off one edge unless your turning the heatsink every now and then.
The way I do it and I think it works pretty well. You need a surface that is fairly flat like a mirror or even a piece of glass. I tape the sandpaper to the the glass. Then I put the heatsink on the paper. I place my hand over the heatsink and apply even down pressure and twist the heatsink with the palm of my hand.
I'm not sure if it's the best method, but it seems to work fine for me. You will see a nice circular sanding pattern on the bottom of the heatsink if your doing it right. When you start going up with higher grit sandpaper, apply less pressure to get a nice finish.
 
OP
I

iLLestOne

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Joined
Dec 13, 2003
Location
San Jose, Cali
Thanks for the quick response. I intended to lap longer, but wanted to make sure I was doing it wright.

From what I've read, if u rotate it every once in awhile that will cause the hs to become convex, since the outside edges will wear down faster.

This is why I only did it in 1 direction. It might make it at a slight angle, but it will be the flatest it could be.

Since this is my first time lapping, you know more then me. I'm just stating what i've read.

Alos, the sp-97 uses spring loaded screws, and I've heard you don't wanna take TOO much copper off of the base or else it won't put enough pressure on the cpu die.

I will be buying some 400, 600, 800, and 1200 grit today, and I will lap it again tomorrow.

I lap it on a marble/granite countertop.
 

crull

Member
Joined
Dec 19, 2002
iLLestOne said:
Thanks for the quick response. I intended to lap longer, but wanted to make sure I was doing it wright.

From what I've read, if u rotate it every once in awhile that will cause the hs to become convex, since the outside edges will wear down faster.

This is why I only did it in 1 direction. It might make it at a slight angle, but it will be the flatest it could be.

Since this is my first time lapping, you know more then me. I'm just stating what i've read.

Alos, the sp-97 uses spring loaded screws, and I've heard you don't wanna take TOO much copper off of the base or else it won't put enough pressure on the cpu die.

I will be buying some 400, 600, 800, and 1200 grit today, and I will lap it again tomorrow.

I lap it on a marble/granite countertop.

It really comes down to what works best for you. Something else to remember. The cpu core only sits on a very small center area of the heatsink, so why should the edges matter? You would be better off rotating it every now and then in my opinion though.
 

clocker2

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Dec 5, 2003
Location
Mile High
You have to lap the surface in ALL directions to achieve a flat surface.
I think that people confuse polishing with lapping and they are not at all the same thing.

If you are polishing a surface you must maintain the same direction so that the (ineveitable) scratches are all parallel. This makes the surface appear smooth.

When lapping, appearance is secondary to absolute flatness. A circular or figure eight motion will most quickly achieve this.
 

Cypress

Member
Joined
Jun 22, 2003
Clocker...how does rotating get absolute flatness? One direction gets a slight angle but absulute flatness. The processor only covers a small area so the angle won't matter. If you do the figure 8 or rotate you'll get an ice cream cone shaped heatsink(hyperbole). You're doing it right just keep going at it, make sure you push down lightly and in the middle.

Also, try doing it on a mirror or a piece of glass, it helps.
 

crull

Member
Joined
Dec 19, 2002
You better off having no angle. Everything should be as flat as possible. If the angle runs the same way as the clips then the pressure from the clips will make up for the angle so that might be OK. If the angle is the other way there really isn't any spring tension that way so the heatsink might sit on the core at an angle. The center of an average clip is flat so the heasink must be flat to sit flat. If the center of the clip was a point then the angle wouldn't matter but its not. This also really depends how the heatsink is attached with clip or bolts.

Lets look at this from turning the heatsink. You take some metal off one side. It gets turned you take some more off another side. Because your not taking a lot off the surface off every time. you should never end up with one side having a lot more surface taken off then another.
 

DOHCrazy

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Nov 19, 2003
Location
The Colony, TX
iLLestOne said:

Alos, the sp-97 uses spring loaded screws, and I've heard you don't wanna take TOO much copper off of the base or else it won't put enough pressure on the cpu die.

Find some of those plastic washers that you put under the standoffs on the motherboard, the clear, VERY thin ones.

Put them under the springs on the screw, that should fill enough space to put enough pressure on the die.
 

Cypress

Member
Joined
Jun 22, 2003
Lets look at this from turning the heatsink. You take some metal off one side. It gets turned you take some more off another side. Because your not taking a lot off the surface off every time. you should never end up with one side having a lot more surface taken off then another.

except for the huge mountain in the middle right? Point is when you look at a properly lapped(then again anything done propperly isn't a problem) push/lift HS you won't notice the angle. You set it down on the mirror and it looks like it has no angle. The whole idea is to shave off all those little mountains on your HS, the angle really doesn't effect the clips and such. You want to be FLAT so you can transfer as much heat as possible, you don't want to have some of the heatsink not touching the processor.

*edit* stuck the quote to clear up this post some
 
Last edited:

crull

Member
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Dec 19, 2002
Cypress said:


except for the huge mountain in the middle right? Point is when you look at a properly lapped(then again anything done propperly isn't a problem) push/lift HS you won't notice the angle. You set it down on the mirror and it looks like it has no angle. The whole idea is to shave off all those little mountains on your HS, the angle really doesn't effect the clips and such. You want to be FLAT so you can transfer as much heat as possible, you don't want to have some of the heatsink not touching the processor.

*edit* stuck the quote to clear up this post some

Its tough to explain what I mean, but having an angle is not good. I'm sure your not gonna take that much surface off that it will make a big difference, but better to play it safe and have no angle at all.
The angle does effect the clip depending which way the angle is. If you look at a clip really well the surface of the clip making contact with the heatsink is flat. So you have a flat surface(Clip) that is pushing an angled surface(Heatsink) against another flat surface(core) sitting flat in a socket. There is no way possible the three surfaces can be flush with each other if any one of them is not flat.


If you are laying that heatsink down flat everytime when you turn it you shouldn't end up with a mountain in the middle. You should also be applying pressure to the whole base evenly.
 

Ge|atinousFury

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May 26, 2002
Location
Scottsboro, AL
I received my SP-97 from HeatSinkFactory today, and I have run into the exact same situation upon trying to lap it. The edges are being lapped but the center isn't. All I've used so far is 800 grit sandpaper (wet sanding). I'm lapping on the same 3/8" piece of flat glass that I've lapped 3 other heatsinks on, so the glass isn't the culprit.
Also, what was said in the initial post about the texture of the HS is right also. It is definitely textured as a record would be. You can actually drag your fingernail across it and hear that same sound that you get if you drag your fingernail across a big record or similarly textured surface. Also, there was glue residue when I peeled the protective plastic off of the contact surface. I was going to clean it, but lapping would do that for me.
I don't know if there's a reason for this, but I don't like it. I've lapped about 5 heatsinks before using figure 8 motions and rotating every few minutes and achieved great results. However, this is the most non-flat heatsink I've lapped yet. I'm on my way to wally world to pick up another pack of 800 grit sandpaper to go ahead and finish the job that I started. This thing will be flat before the nights over....
 

crull

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Dec 19, 2002
Did you try putting a straight edge on it. Maybe it's taking more off the edges because the surface of the base is concave which is quite possible.
 

Ge|atinousFury

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May 26, 2002
Location
Scottsboro, AL
crull said:
Did you try putting a straight edge on it. Maybe it's taking more off the edges because the surface of the base is concave which is quite possible.

The surface of the base is concave and has a rough texture. This is what I'm not comfortable with. I don't think that this concave a surface is required to offset the force of the 4 screws that hold down the SP-97. My goal is a flat surface. I'll know this weekend when my AS5 comes in if the lapping paid off or not.

Still though, it's got me wondering why Thermalright, knowing that a good bit of people lap their heatsinks, would not give us information if they desired the surface to be concave and textured.
 

rhino56

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Dec 11, 2003
Location
Arkansas
crull said:
Did you try putting a straight edge on it. Maybe it's taking more off the edges because the surface of the base is concave which is quite possible.
thats how mine was, now i just did my stock heatsink so the quality probably isnt as good as whatever you guys are doing but
when i started it was only hitting the edges because it wasnt flat
with the first grit you use, (which i used 400 to remove it fast) take it down till its flat and the center is as scratched as the sides.
it took me a little bit to get that much off. i would say it was about .5 mm that had to come off. (educated guess) then from there it was a matter of just removing the surface scratches.

if your heatsink is 3 inch by 3 inch then go in a circle like you are going around an object as big as the heatsink. dont go too fine though because if it starts to shine then it wont transfer heat as well.
 

rhino56

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Dec 11, 2003
Location
Arkansas
Ge|atinousFury said:


The surface of the base is concave and has a rough texture. This is what I'm not comfortable with. I don't think that this concave a surface is required to offset the force of the 4 screws that hold down the SP-97. My goal is a flat surface. I'll know this weekend when my AS5 comes in if the lapping paid off or not.

Still though, it's got me wondering why Thermalright, knowing that a good bit of people lap their heatsinks, would not give us information if they desired the surface to be concave and textured.
is your cpu convex and textured? you want it flat so more area is contacting. a convex heatsink would be a unlapped heatsink is all.
 

Ge|atinousFury

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May 26, 2002
Location
Scottsboro, AL
rhino56 said:

is your cpu convex and textured? you want it flat so more area is contacting. a convex heatsink would be a unlapped heatsink is all.

That's precisely the reason why I've been lapping this thing for a long time now:)
 

rhino56

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Dec 11, 2003
Location
Arkansas
Ge|atinousFury said:


That's precisely the reason why I've been lapping this thing for a long time now:)
you need to remove the flatness, if its taking forever then drop down 200 grit. like if your doing 600 do the removal with 400 until you see the center area getting scratched, then go back to 600 and up from there.
 

Ge|atinousFury

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May 26, 2002
Location
Scottsboro, AL
rhino56 said:

you need to remove the flatness, if its taking forever then drop down 200 grit. like if your doing 600 do the removal with 400 until you see the center area getting scratched, then go back to 600 and up from there.

I'd very much like that myself but I'm afraid I'm out of luck. In my earlier post when I said I was headed to wally world to pick up 800 grit it was because I went earlier to get the first bach of sandpaper and 800, 1000, and 1500 was all they had in stock at the time :(

So, 800 it is, but it's ok since I have nothing to do tonight besides reading one chapter of one of my textbooks.