Keith- Assuming that you got the right diameter and count of balls the next likely cause is the technique to screw the second cone down with out dislodging balls. If any rotation is allowed between the second cone and the shell/balls WITHOUT cone/ball contact the churning action will lift a ball out of position very easily. So what I do is to hold the cone stationary in respect to the shell and press the axle/first cone up against those balls while turning the axle. The turning action is only allowed between the first cone tightly held against it's balls to contain them. The second cone is drawn up the axle with our turning, settling against their balls with no string of the pot to speak.
Some hubs are more sensitive to this possibility. Shimano at one time did make noise how their hubs used a different bearing geometry (the ball's contact point angle to the axle) then the "old" designs. Hope this helps.
> Message: 1
> Date: Mon, 13 Jul 2009 13:21:44 -0500
> From: <firstname.lastname@example.org>
> Subject: [CR] 1st gen. Dura Ace front hub overhaul problem.
> To: <email@example.com>
> Cc: firstname.lastname@example.org
> Message-ID: email@example.com
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> I am trying to overhaul a 1st Gen. black Dura Ace front hub. I got 20
> 3/16 grade 25 ball bearings from my LBS. Even with Campagnolo sticky
> grease, I couldn't get them all to sit in place while I tried to get the
> second cone screwed on. The rear was no problem.
> We verified that the old BB were 3/16 and double checked in a Barrett's
> I don't remember any other hub being this difficult to overhaul. I'll
> admit that I wasn't using a vice due to the heat in my garage. Is there
> something that I'm missing?
> Keith Kessel
> Shreveport, La.