What methods do you use to lap your stuff?

[kendellrt]

Read my experiences w/ a q6600 here. Get wet/dry high quality sand paper. Cut it into thin strips and tape the strips down to a piece of glass or mirror (something flat). Lap using front-to-back motions with minimal pressure; let the sandpaper do the work and remember: the key is FLAT. You can do about 20-30 strokes, then rotate 90

[Verran]

I've done a couple of my sinks now and my method was very similar to nrg's. It's actually pretty much word for word from the lapping guide that's here at OCC somewhere.

 

Also, I'd have to say the idea of a "kit" seems a little silly to me. It's just sandpaper. I guess they could throw in a few drops of dishsoap to make it a "kit" Just head over to Home Depot or Lowe's or whatever equivilent you have in your area and get some sandpaper packs. I got everything I needed from 400 to 2000 for less than twenty bucks, and there's enough there to do more than a few sinks as well.

 

I set my paper on a mirror, wet it with a bit of water with dishsoap, and started "swiping". 10 swipes in one direction, rotate 90 degrees, 10 more. etc etc etc. Took me about an hour to do my XP-120 (at a leisurely pace, and it was quite concave).

 

If you're unsure of the process, I'd recommend trying it on an older sink first. If you go the "buy it yourself" route, you'll have plenty for a few "test" runs. I did it on a fairly crappy sink first just to get the hang of it. It didn't make a big difference, but I'm still glad I practiced first.

[kendellrt]

I'm doing an IHS, not a HSF. Is there a difference?

[Verran]

I wouldn't think so. The process should be the same regardless. I've never lapped mine (decapitated the last two instead ), but if I were going to, I would basically treat it the same as my XP-120. Maybe set up some sort of grounded case nearby with a wrist-strap if you want to be real careful...

[LeBronville]

lap?

[oblivescence]

lapping is the process of sanding the bottom of a heatsink to make it smoother for better heat transfer. Think of it this way, nothing is perfectly smooth, Ther are always microscopic valleys and hills on the surface of everything. When 2 surfaces touch, the valleys do not make contact, therefore, without contact there is no direct heat transfer, that is where thermal paste comes in, it fills up those valleys, Now if you keep on sanding the surfaces, the surface becomes more and more smooth on a microscopic view. This allows for more direct heat transfer. For lapping, you use very high grit sandpaper, 1000 grit, 2000 grit and the like near the end.

[kendellrt]

Ok, so here is the plan. I will use the same method for both the CPU and the HSF. I will simply cover the business end of the CPU with the black cover it came with, just in case. Please let me know if this makes sense. I use some wet/dry sandpaper with a dab of dish soap. I will hold the unit lightly and let the paper do the work and keep it even on whatever flat surface I choose to get. First, move the HSF/CPU forward and backward ten times, then rotate 90 degrees and do it again, until I have made a full circle. Do that ten times for each grit of sandpaper, rinsing off the residue often to keep it clean.

 

Am I on the right track? Also, what grit should I start with, 400? In my poll most people answered that they go up to 2000 grit before they finish, but some go to 1600. What do you think?

[hardnrg]

i would recommend rotating 180

[kendellrt]

i would recommend rotating 180

[Verran]

nrg's 180 / 90 explanation makes a lot of sense. That's a really good way to make sure you know when you're "done" with a particular grit.

 

Also, if it were me, I'd be a bit concerned about ESD during all of this. I'd set up my case near wherever I planned to do the work. Then I'd plug in the power cord to the wall and switch the PSU to off. That way it just gets the ground from the wall and no juice. Then, I'd wear a wrist strap and clip it to the case. It's a fairly easy precaution to make sure you don't kill your chip with static.

 

Also, I only went up to 1600 grit, but that was mostly because I couldn't find 2000 in any local stores.

[kendellrt]

nrg's 180 / 90 explanation makes a lot of sense. That's a really good way to make sure you know when you're "done" with a particular grit.

 

Also, if it were me, I'd be a bit concerned about ESD during all of this. I'd set up my case near wherever I planned to do the work. Then I'd plug in the power cord to the wall and switch the PSU to off. That way it just gets the ground from the wall and no juice. Then, I'd wear a wrist strap and clip it to the case. It's a fairly easy precaution to make sure you don't kill your chip with static.

 

Also, I only went up to 1600 grit, but that was mostly because I couldn't find 2000 in any local stores.

Good idea.

[mazakman]

I would like to add something here.

 

Many years ago I worked as a machinist in a shop that made parts for communication sattelites. A lot of the parts required lapping to achieve a maximum of 0.0005" (yes, ten thousandths of an inch on parts up to 2 feet square) flatness per inch. A to and fro (or back and forth if you preffer) motion would yield horrendous results. The leading and trailing edges of the lapped surface would get rounded because of the build up of loose particles of abrasives and material that were being lapped and accumulating at the edges.

 

The best results were always achieved using a figure "8" motion while applying only the necessary force to keep the part in complete contact with the lapping surface or medium (paper or compound on a granite surface). The preffered lubricant that we used was mineral spirits (oil based paint thinner). If you're using sand paper, a mix of dishwashing soap (yeah palmolive or the likes) should tield satisfactory results.

 

Hope this can help.