On 2010-11-11, wrote:
On 10 Nov 2010 04:39:20 GMT, "DoN. Nichols"
wrote:

[...]

Windows Live Mail has done it again. Not only did it swallow my
original post but also your reply. Fortunately I now have two other
news readers.

Hmm ... not from Microsoft I hope? :-)

Hmm ... sounds like a tramming error -- the axis of the spindle
is not perpendicular to the bed. And likely the column axis as well.

[ ... ]

Get a machinist's square (a blade with a heavy right-angle
piece) and resting that on the bed, check for a slight angle between the

[ ... ]

Is yours one of those whose column has a pivot at the bottom, so
you can drill holes at an angle? If so, have you checked that the
column is truly vertical?

That's the one. Last time I did this it was within 0.001" from
end-to-end and front-to-back.

And with the head moved up and down?

I will do this again - but first have to
clear things off the table. Oh, joy! The opportunity to re-align the
vise. Again :-)

:-)

[...]

I tried a different No. 1, I tried both ends, same result. Looking at the
slowly rotating point with a magnifying glass it describes a small circle
which is not obvious when I bring it down on the metal.

That is either runout in the chuck, or a bent arbor for the
chuck. I forget -- does your machine use R8 collets? If so, how are
you holding your drill chuck? An R8 arbor, or a straight shank arbor
held in a collet? In either case, the arbor might be slightly bent.

Before I read your post I checked the run-out just under the chuck. No
dowel pins or drill blanks here so I used the drill shanks. I did two
just incase. Both (3/8" and 9/64") showed TIR 0.0005" about 3/8" under
the chuck.

Pretty close. What happens to the runout when you shift from
light to tight tightening of the chuck?

BTW Drill shanks are soft, and the chuck's jaws can bite into them
so they won't slip. End mill shanks are hardened and ground
smooth so they work well in collets or end mill holders, and are
*not* best used in a drill chuck. (The same applies to the
center drills, FWIW.)

The soft shanks on drill bits also means that it is possible for
the shank to bend, so the tip will describe a circle even if the chuck
is prefect.

And -- you are unlikely to find a long drill bit which has a
shank long enough to allow runout measurements. (Aircraft drills are
the exception -- but they may be too long for your machine.)

BTW my spindle is MT3. I have never had to take the chuck
off so I am not sure how it is attached at the other end. I just
change the whole thing for a collet chuck when I need to.

O.K. So R8 is not in the game. It is possible that the arbor
(MT-3 to whatever Jacobs taper the chuck uses) is bent -- but less
likely with that 0.0005" TIR. This then suggests that the jaws in the
chuck either have burrs in them, or there is wear in the body of the
chuck. Different brands of chucks have different quality levels. The
Albrecht keyless chucks are very accurate and can handle a long service
before they start showing problems. (But they are larger, so they leave
less space between the spindle and the table, so check for that too.)

What happens if you use collets for the center drill and the
plain drills? (Assuming that the plain drill is of a size which matches
a collet which you have.)

I was out of town today and took the opportunity to look for dowel
pins etc. No luck.

They are hardened and ground -- but fairly short usually. The
best thing is drill blanks, which are hardened and ground to precise
diameters -- but much longer. (And quite expensive, which is why I
don't have an index full of the standard sizes. :-) But that length
makes it easier to check for the drill chuck holding the drill at an
angle, thus causing the circle. Measure runout just below the chuck,
and close to the end (but before the diameter starts to fall).

[ ... ]

Did you try a runout indicator on the shank of the drill? How
about with a longer rod (best would be a drill blank -- or an unusually
long dowel pin, but you might get away with some drill rod if it has not
been bent.

I shall go through the drawers and see if I have any unusually long
drills or anything else which might do the job.

Aha! This is what I was answering somewhere above. You are
unlikely to find a drill whose smooth shank is long enough. Usually the
extra length is in the flutes.

[ ... ]

I presume that you started with the wiggler a bit off center,
and pressed a finger against the side until it stopped wiggling? *That*
is what sets it on center.

Yes, but then you have to bring the point over the mark. I find that
challenging without the magnification.

So -- use magnification -- and a small LED flashlight for
illumination.

Even using the other center
finder (this one, so there is no confusion:
http://www.busybeetools.com/products...RE-FINDER.html )
the alignment of the two parts of the barrel are tricky and much
easier with a magnifying glass.

And if the axis of the chuck is not parallel to that of the
spindle, you will still have the point wandering in a circle. One of
the reasons for the sliding offset is so you can push it while spinning
slowly until the point stops moving in a circle. That is the center of
the spindle axis -- but perhaps not the center of the chuck's own axis.

BTW I thought that the wiggler should be more accurate. However, it
was the other one that was consistently agreeing with the center drill
entry point.

But both of those are longer than the center drill, so you will
have had to move the head up to get them in the space. And, BTW, it is
possible that your column is truly vertical, but the head is slightly
off so its axis is at a tiny angle to the column. Another reason for
measuring with a machinist's square and a drill blank.

Yes -- as someone else suggested, hardened steel rods from dead
printers (or some older dead disk drives) can be used in place of the
drill blanks -- if not badly worn.

[...]

I was wondering about the way the drills are clamped in the chuck and I
tried different degrees of tightening.

The proper way is to tighten equally using all three holes, one
after the other.

I would go round al of them 2-3 times. With the No. 1 the feeling is
of never really tightening enough.

Give in the chuck somewhere -- a jaw with a chip under it, or
something similar. Try another chuck. Or check with collets.

With, say, 1/4" drill you go around
and you know when the thing is tight. There is a definite "stop". With
the No. 1 there is a sort of springy feeling even after you have been
around 3 times.

Your No. 1 is not fully deep in the chuck, so you are only
holding it with the tip of the jaws -- and they may be flexing in their
ways. Try another chuck. Yes, more money for a chuck *does* mean a
more accurate one.

That is what made me wonder about the possible
distortion caused by the chuck. I thought this was supported by the
fact (yet to be confirmed) that if I tightened only lightly the center
drill run straighter (see the last effort where the center finder,
center drill and the twist drill all managed to coincide).

Yes -- flex of the jaws in the body when you don't have a shank
contacting the jaws the full length into the chuck is a possibility.

Again -- try collets.

Good Luck,
DoN.

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