Lapping...

Sean · Post by **Sean** » Tue Aug 19, 2003 1:15 am

Finally got down the business to use the lapping kit I got almost 2 months ago and my SLK 900u to do some lapping action. At first, I was worried, cause it was looking terrible. I'm pretty much finished now, it feels a bit more smoother (can't feel the machining marks as much) and the base is flat (it holds glass). I sanded it starting with 800 going to 2000, on glass. My problem is, now, that the middle of my base looks a bit foggy, but the outer edges are very reflective. What gives? Was this heatsink concave or somethin??? (I can't imagine Thermalright making a non-flat base).

Should I just try getting the rest of it as shiny starting from, say, 1000 grit again, or should I just call it a lap complete and see how well it handles? I'll show some pictures tomorrow, maybe, if anyone's interested.

PreDatoR · Post by **PreDatoR** » Tue Aug 19, 2003 1:37 am

how did you sand it... lay the paper on a very flat counter top and sand the sink or hold the paper in your hand. the bottoms on most heatsink i have lapped aren't perfectly flat and the outside is always higher than the middle it seems.

Sean · Post by **Sean** » Tue Aug 19, 2003 1:45 am

OMG, not on my hand!!!

I put it inside a huge container, which kept the water near my glass. I put the sandpaper on top of a piece of glass and just moved it back and forth. I tried to move it around in a figure eight movement, but because the base of the SLK's are narrow, it's kind of hard to move it any way but the long way. But, I think I got it pretty even. The base seems pretty flat, since I was able to pick up the glass with water between the glass and the heatsin.k.

nexus_7 · Post by **nexus_7** » Tue Aug 19, 2003 10:59 am

thats what I have done. yea, usually the inside takes a little extra work.

Greg

Lmandrake · Post by **Lmandrake** » Tue Aug 19, 2003 12:18 pm

Even when you do figure 8's, the corners or edges get taken down first and have the most taken off. When you can't do figure 8's, it is even worse.

You probably still havent gotten the center yet. Whether it makes a difference is another question as well. There are some who believe that it is counter-productive to go beyond 400 grit as a surface that is too smooth has less surface area for transferring heat.

I like the latter idea, if only because it gives me an excuse to not spend all the time required to get from a hazy finish to a real shiny one.

sethpa · Post by **sethpa** » Tue Aug 19, 2003 2:05 pm

Lmandrake has the right idea, tests have shown little difference between a shiny and a dull surface, the only place that has to be flat is where the core sits under the sink. Microscopic pores hold the paste better a perfectly smooth surface for best heat transfer.

Shiny looks nice though, but how often you gonna show off the base of your heat sink?

Sean · Post by **Sean** » Tue Aug 19, 2003 6:51 pm

Specially when it's bolted thru the board.

Yeah, the middle part of my base still has the machining marks that the heatsink had before, just not as deep (but pretty close). I think the base is pretty darn flat, because it acts like a suction cup on the glass.

I was going to go over it again, just to get the base smooth, but you bring up a valid point. The edges feel very smooth, and have a mirror finish. Since I couldn't get a figure eight going, I went back in forth in many directions, up and down, side to side, diagnally - it seemed to work ok, but it pretty hard to move. If I can feel the marks with my fingernail, isn't it too much? (which i still can).

I would probably end up using very little paste, most likely. But, what do you all think?

PreDatoR · Post by **PreDatoR** » Tue Aug 19, 2003 7:09 pm

I use to lap mine with 1500 and water to get it to shine... but here lately i just use some good ole 220 grit... its comes out smooth and still leaves it a little abrasive so that the compound holds better on the sink... mostly do it just to make sure the base of it is flat.

Sean · Post by **Sean** » Tue Aug 19, 2003 7:17 pm

My base is probably ok then. I'm pretty sure it's flat, I'll test it a bit more. I know for one, in the reflection, it seems flat. The reflection doesn't look warped or anything. The middle if just cloudy, I can see the reflection a lot better than before.

Pugsley · Post by **Pugsley** » Tue Aug 19, 2003 8:28 pm

I just use lapping compound and a buffer after im sure its flat to give it a nice shine... but then again ive only done it to one HS... if i had a bridgport it finish it on that... but i (like most people) dont have one so good old sand paper to the rescue.

Sean · Post by **Sean** » Tue Aug 19, 2003 9:20 pm

I think I'll just get my whole sink shiny and flat. Since the rubber feet have to be put on, they are a bit hard to ever get off, so I'll do it now so I don't need to do it again.