Re: Digest Number 4217

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Dave Shiels <dshiels@e...>
wrote:

>
> One also needs to consider the possiblity of "charging" the cast

iron

> when lapping. Generally lapping in a precision machine shop is a

hard

> steel surface being lapped by a charged cast iron one. Cast iron is
> pretty soft and the surface can become embedded with lapping

compound.

> Be afraid of abrasives on your cast iron parts. Lapping compund

can

> actually bite into the surface of cast iron.
>
> R Rogers wrote:

Excellent point and one I have not seen addressed completely.

Very fine and hard grit may charge the cast iron. but regardless of
the method employed, we are talking about fixing a poor fit on a cast
iron part. if grit is used, there is the very real possibility of it
charging the cast iron.

If that occurs, the parts never stop lapping themselves. The tell-
tale black oil would indicate the situration.

Sure puts a big plus into the scraping category.

Dave