"Gene Kearns" wrote in message
...
On Thu, 13 Jan 2005 21:24:27 -0500, "Ted Clark"
wrote:


The foreman of the facility where I work said this was incorrect. He
said
what I should have done was go in with a smaller cutter first, such as
7/16", and then finish with the 1/2" slot drill.

After all, slot drills are made to a minus tolerance. I believe by
taking
two cuts, you run the risk of creating an oversize keyseat.


You are quite correct... it is likely that the keyway will be
oversized...


????? Sorry, I don't agree-----

How so? In the hands of a skilled machinist, the odds of achieving
proper size and location are far better when rouging undersized and then
taking additional cuts. The slot will be on location, straight, and
uniform, all of which are *very* difficult to achieve when taking a single
pass, especially on light duty machines. Regardless of the opinion of
anyone that is more interested in making money than doing the job properly,
cutting keyslots in one pass is generally a poor way to get it done. Tool
pressure is always a factor, as is chip load.

Harold