I will be interested in what the senior wizards have to say about this
as I am experiencing the same problem. In my situation it appears as
if it's the hole and not the shaft since I can measure the shaft along
its length.

I get the feeling that the drill is having a little trouble early in
the hole and kind of wanders around making the early part of the hole
bigger than the later part -- where there the drill gets a little more
discipline from the sides of the hole. I suspect that drilling of
sequential pilot holes might help -- as would keeping drill length down
to a minimum. Or maybe it is a poorly sharpened drill since, in my
case, many of my drills are three generations old having belonged to my
grandfather.....

I recently retired from engineering with electrons, but took ME201
years ago in college and got a taste for making chips. So now I have a
little lathe and mill and have been reading this group (and the
archives) from start to finish. There is so much to be learned and so
many 'unusual characters'.

Thanks Guys

Rye

Proctologically Violated©® wrote:
Awl--

I'm sure I can "solve" this by being more vigilant, but that it happens at
all seems sort of strange.

Briefly, I'm drilling a 3/16 hole 3/4" deep in 1/4" round brass: face,
c-drill, then a 3/16 drill (tailstock/drill chuck, 5C collets).
Then, I'm turning down a piece of 1/4" round brass to 3/16" OD, for abouta
3/8" insertion into the other piece w/ the 3/16 hole, for a "nice" fit.
Using a live center.
Have DRO, Aloris tooling, good for half a thou, I'm pretty sure--at least
the DRO says so!

Problem is, the 3/16 OD pc gets in only about half way before it hits some
kind of "step"!!!
To achieve the full 3/8" insertion, the fit winds up being far too sloppy!
Still works, but annoys the hell out of me.

Seems like a simple no-brainer, and I'm sure I could solve it w/ sequential
drill sizes, reaming, etc., but it doesn't seem to me like this should be
necessary, as there is nothing complicated or exotic here.

I would have anticipated any other type of problem--holes too big, holes too
small, ragged/jagged sides, holes off-center, etc.
But an invisible step??

Any idears?
Mebbe on my next have-at-it here, I'll test the female portion w/ a 3/16"
dowel, to at least try to identify the offending piece/operation.
It's pretty clear what the problem is (diameters!), but puzzling as to *why*
this problem is occuring.

TIA.
----------------------------
Mr. P.V.'d
formerly Droll Troll