On 31 Aug 2005 08:32:02 -0700, wrote:



I need to lap a small hole in mild steel. This is a "through
hole"......of about .300 inch ID. I will be using an adjustable
brass barrel lap for the lap.

The hole has been finish reamed to about .2998 inch......and will be
lapped to final diameter of .3000 inch.

I plan on lapping with 3 different grit sizes.......starting with a
150 grit, then progressing to 240 grit, finishing with a 500 or 600
grit.

Will I need 3 different brass laps, one for each grit size? Or can I
use the coarsest grit, then "wash" the coarse grit from the lap,
recharge the lap with next finest grit, lap, then
wash.........etc.......finishing up with the finest grit, the 500 or
600?

If I can use 1 adjustable brass lap, washing it between grit sizes,
what is the best method of washing? Could I spin the lap in a lathe
and hit it with something like a worn-out ScotchBrite pad?

Would that clean an adjustable brass lap in preparation for each
progressively smaller grit?

Thank you Lee Carkenord
Since you only have .0002" left use only the 600 grit. Since this is a
reamed hole you will find that the .0002" will be removed very
quickly. And no, you can't wash the coarse grit from the lap. The way
the lap works depends on the grit embedding into the lap. The lap will
always be the softer metal. So if you use a brass lap in aluminum the
aluminum will be charged with abrasive and will remove material from
the brass.
ERS