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Lapping troubles

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zoopa_man

Member
Joined
May 24, 2001
Location
NY where the cows out number the people
I just got my Danger Den water block in the mail !! I pulled it out of the bubble wrap and took a look at the bottom and it looks horrid. It needs to be lapped...

What I did was find the flattest thing i have in the house. I got a piece of plexi glass on my dinning room table. I put some soap in water just like all the tutorials say. and started lapping with 1000 grit sand paper. After about 20 minutes of figure "8"'s I can see a mirror finish all around the edges but there are still scratches in the center. I thought maybe i was pushing on the outsides of the block...so i lapped for another 10 minutes of 8's with little pressure on the block and i kept rotating it so no one side kept going in the same direction for more then 10 passes...looked at the bottom and still i see scratches only in the center!!!

Could it be that my block is concave and i need to keep going ? Or is there something wrong with my setup ? I don't want my arm to fall off if I’m doing this wrong ? Can someone help me please ?
 

IFMU

The Xtreme Senior Nobody
Joined
Jun 21, 2001
No, the way you are doing it is correct. However it looks as though it is a little concave. I would suggest backing down to say, 600 grit paper, to get it closer to where it needs to be. Then switch to the 1000 grit your using. Just some elbow grease is needed. Luck!~!
 
OP
zoopa_man

zoopa_man

Member
Joined
May 24, 2001
Location
NY where the cows out number the people
I forgot to add the reason for my concern... I have the block with the built in cold plate..so no i've lapped the bottom of the block and now both sides of the cold plate with the same setup...and all three sides have the outside perfectly smooth and the middle scratched still...that's why i question my setup. It could be that danger den's tools that cut the copper always make a slightly concave cut ? It's a possibility, and would make since to always lapp your blocks then. Thanks for the advice....*Pulls out his elbow grease here we go 600 grit. Bye bye shiney..hope to see you soon...hope i'm doing this right...156w peltier is driving me crazy looking at him all lonely with nothing to cool. Hehe soon, soon. MUhahahahah *evil laugh, runs back to the laboratory to lapp some more.*
Thank You IFMU for the quick reply.
 

JFettig

Hey! I showered! Senior
Joined
Jan 5, 2002
Location
MN
plexiglass bends, i suggest you use a old window or a mirror, and that mite be why.... or the block couuld be concave...
 

Tecumseh

Member
Joined
Feb 26, 2002
Location
Ohio
Go find a piece of glass or a mirror. You should also
start and possibly end with 600 grit wet/dry sandpaper.
Why work so hard when you don't need to? Maybe just
kiss it with the 1000 grit when you are done.
 

rivercom9

Member
Joined
Dec 24, 2001
Location
Sacramento, CA
I agree with maskedgeek, the plexiglass doesnt provide a solid and sturdy surfance. Try your bathroom counter, thats what I use since its made out of some kind of rock and its perfectly flat and very solid, no bending.