Originally Posted by wootang
Hey everybody was wondering how to lap a cpu waterblock and and my custom gtx block what materials would i need? I have a huge glass piece from my old house it looks pretty flat and what kind of sand paper do i need?
There are multiple ways to go about it, and some people fancy certain methods more than others.
- 100% Flat surface (not something you just think is flat), glass probably the most used
- Sandpaper: 3M Wet/Dry Automotive sandpaper works good, grit sizes ranging from 120-2000 grit, I'll cover a bit more on that later
- Good tape to tape the sandpaper to the surface, duct tape works, but not if you're doing wet sanding, and it's a bit painful taking duct tape off when you have to change the sandpaper sheets.
- Razor blade
- Compressed air
- Isopropyl Alcohol
- LOTS of time
The key to lapping is taking your time. Set aside more than a few hours for 1 item alone. I've spent up to 3 different 5 hours sessions lapping some quite uneven heatsinks.
Grit sizes are important only to your task at hand. There is no "perfect" grit to start with. It depends more or less if the base is nickel plated, and if it's very uneven, or if it's already copper and some what flat. If it's a bad base, start with 120 or 220 grit. A more flat base you can still start with 220 grit, but don't spent a lot of time on that as it'll chew through it quick. Just get it flat with 220 and move on. You could start with 320 or even a little higher, but I prefer lower grits to get it perfectly flat first. You can then skip to 600 grit and then work up slowy to 800 grit, or go straight to 1000 grit. In order to save money, I like to go from 220 grit to 600 grit to 1000 grit. There isn't any need to go higher than 1000 grit, the rest is purely for the look/shine on the base, which some people like even though it won't be seen again.
As for sanding, you want to apply only minimal pressure to the item. Lapping a tower heatsink is harder not to apply pressure since it wants to fall over, but something like a waterblock or CPU is very easy to lap with just guiding it. Some people like to wet sand, and it does tend to sand down the base better and quicker, but I find it makes too much of a mess for my liking. Some people even lap under running water. I personally just stick to dry sanding, and if I can't get a nice finish on it, wet sand on the ending grits. When lapping, you want to start with one side in a back and forth motion, and do this anywhere between 10-25 times, then turn it and do that same amount again. The less times between turning, the better, but that gets very tedious so doing it 25 times isn't terrible, but it's best to do 10-15. When the sandpaper is getting noticeably dirty (even a minor amount) just blow it off with compressed air. When it feels like it isn't cutting much anymore, change to the next sheet of sandpaper (not grit). If it still feels like it isn't cutting much, then check with a razor blade and if it's perfectly flat, move to the next grit. You can spend ~30 mins or so on higher grits just to get off any scuffs and scratches.
Once you're satisfied with your lap dance (you will be dancing when you're finished), clean the surface of the cpu/waterblock/heatsink with isopropyl alcohol.
Hope this helps.