New method for lapping?

[dipan]

My brother in law paid me a recent long visit over the holidays and I've learned something from him. I thought I might share it and get everyone's input. BTW, he's a materials science PhD working in research for Motorola.

Anyways, I needed to lap an SK6 again and he immediately jumped in and gave me some tips. It seems he did a lot of lapping (grunt work) when he was just starting out on his degree(s). They needed perfectly flat surfaces for some sort of electron microscopic evaluation of the material and they used lapping to start.

Anyways, his method is to only go side to side with the sink with any particular grit. When going to the next finer grit, rotate the sink 90 degrees and lap again only side to side. You know when you're done when you don't see anymore of the perpendicular coarser grit scratches. Then you're ready for the next grit ...

The methods I've heard of so far include using a circular motion, figure 8 motion. Also some have mentioned marking the base with a permanent marker (never worked well for me). What I like about his method is that it defines a definite endpoint for each particular grit rather than subjectively deciding how much is enough ...

Comments? ...

[ButcherUK]

I use that, seems to work well and gives a nicely polishled surface.

[The Overclocker]

for uncarefull people (me) might be a problem with the heatsink rocking and making a rounded base

[dipan]

Originally posted by the overclocker
for uncarefull people (me) might be a problem with the heatsink rocking and making a rounded base

If you're not careful, you can end up with an uneven surface with a circular or figure 8 motion also. The thing with this method, going only in one direction, you will see if you are raising a shelf on the base very easily. I actually did this with the 1000 grit. It looks like a fuzzy line going perpendicular to your scratch lines all the way across the sink. If you keep going, this shelf could get bigger. If you're careful, you can make it migrate to the edge so you'll have attained flatness again. Or you can just go back a grit to 800 or 600 and wipe out that 1000 grit shelf. That's what I did. Took more time, but the finished product was nice and seems to have taken around 3 degrees C off load temp.

[rivercom9]

Hmmm. Interesting technique. I gotta try that next time. Sure will be nicer on your hands.