I'm getting in this late, I can tell, but as an old practicing engineer from a job shop background, I was taught that part
being assembled (generally the pulley) should be a light push fit while the part over which the part was being fitted
(generally the shaft) should be press fit to the key. With this kind of fit a single pass with an end mill will not get the
job done on any kind of consistent basis. This kind of fit is the only way to prevent wallowing of fits under reversing
loads..which are most kinds of driving loads anyway. The amount of time taken fitting the key, keyway and keyslot directly
reflect on the life of the joint, as much or more than the fit of the bore. A one pass keyway, broached keyslot and a
chopped off piece of keystock, filed to fit, will get a joint that fails that same as an oversized bore will fail. Some
places, the joint requirements are not very high and an oversized joint can be tolerated but even then, it kind of reflects
on the craftsmanship of the person making the joint.
R. Wink


On Sat, 15 Jan 2005 22:42:16 -0800, "Harold & Susan Vordos" wrote:


"Gene Kearns" wrote in message
.. .
snip-----

...another arguable point is that an endmill is a poor choice for
cutting a keyway, unless it can't be performed otherwise.....
--

After reading your last post, I realize that you and I aren't necessarily
talking the same keyway. My experience is in job shop and missile
industry, where cutting a keyway was not something that was done
repetitively, or routinely, so, naturally, the tools used for the job were
those that were at hand. The tools of choice for me, and the shops where
I was employed, just happened to be end mills, and I suspect that unless
most folks are engaged in machining key slots routinely, that would be their
tool of choice, too.

While one may provide a little "Kentucky windage" when cutting a keyway, the
amount of deflection is up for grabs, regardless of the type cutter used.
Feeds and speeds create a myriad of conditions that can't be anticipated.
I think my point is that those of us that prefer to "do it right" and not
abuse, or ignore, tolerance, would not make the cut in one pass, nor would
we expect it to be as good as one cut by our preferred method. Key slots
are tight tolerance, too tight to risk cutting in one pass as far as I'm
concerned. I agree, the key likely fits tightly when the seat is cut in
one pass, but not because of the precision involved, but more so because of
the variations in the key seat. Overall the key is a press fit, but is
likely hitting on the highs alone. The key seat is likely not on (proper)
location, not square, nor a constant width. That kind of work wasn't
acceptable in the industry from which I came.

I took a quick look at your site. Nice job! I'm impressed with your
background.

Harold