Bicycle Mechanics - Rear hub cones keep loosening

First the history:

Built a new set of wheels for my commuter. I used a NOS Shimano 600EX hub I purchased on eBay. It was new in a box and had never been laced. Took the cones and bearings out just to see the condition of the grease and it was fresh (not dried out). I added a bit of extra Phil Wood grease as it went back together, adjusted everthing correctly, built the wheel, and began to ride it.

Now the problem. Every hundred miles or so I notice that the cones seem to be loose. There is excessive play in the bearings. The first time or two that this happened I just snugged the adjustment up and rode on. It has happened three times now so I dismantled it and had a look. The bearings are all there and still look like brand new. The cups and cones are like new too and no visible signs of wear. The axle is straight and is not cracked/broken. I washed out all the grease this time and regreased with new Phil Wood grease. Again checked the bearing play as it went together and it is perfect. As before the bearings feel very smooth. I've checked each time to ensure I didn't forget to tighten either of the cone locknuts.

I'm at a loss on this one...any suggestions?

Go through how you tighten the lock nuts step by step. It sounds like the axle is spinning when you tighten the lock nut to the cone.

Go through how you tighten the lock nuts step by step. It sounds like the axle is spinning when you tighten the lock nut to the cone.

I tighten the freewheel side cone first with its locknut and the spacers (and the outer locknut, I hold the cone and tighten the locknut against it to jamb it...typical process). I load all the bearings, greased then thread on the opposite cone, place the washer on the axle then thread on the locknut. I adjust the cone on that side so there is just the tiniest bit of play perceived in the bearings. When I install the wheel on the bike and tighten the quick release the play goes away (axle compression). Basically this is how I do all my wheels but I've never had one loosen up after 50 - 100 miles.

Any chance your axle or locknut threads are stripped? You might not notice just tightening them, I'd do a visual inspection.

You dont mention jamming locknut against the cone on the nondrive side.

Try taking the cone just past tight, before you tighten the non-drive side locknut. The axle tends to slip with the locknut sometimes when your turning it, and when it's done the cone is in the right position. Make sure the Axle vise is real tight before you start too. I've had this problem with some older exage 600 hubs. That always seems to fix it. You might have to have a helper use a wrench on the drive side to hold the axle while you tighten the non-drive side to get it real good and tight.

Any chance your axle or locknut threads are stripped? You might not notice just tightening them, I'd do a visual inspection.

I checked for that. The threads aren't stripped. After I've ridden for a bit and the hub feels loose I check the cone adjustment. The locknuts are still tight against the cones. That's the wierd thing about this problem is that the cones themselves aren't loosening on the axle...its the bearings that end up having more play. The adjustment is correct when I install it in the bike but gets loose after riding for a while.

I only had one other wheel do this and when I took it apart the cone was worn out. It was the wear on the cone and bearings that resulted in the increased play in the wheel. The 600 hub I'm describing has no visible evidence of wear and the cones aren't rotating on the axle. It is a very strang problem.

Try taking the cone just past tight, before you tighten the non-drive side locknut. The axle tends to slip with the locknut sometimes when your turning it, and when it's done the cone is in the right position. Make sure the Axle vise is real tight before you start too. I've had this problem with some older exage 600 hubs. That always seems to fix it. You might have to have a helper use a wrench on the drive side to hold the axle while you tighten the non-drive side to get it real good and tight.

I've done that. The problem isn't that I can't get the bearings adjusted properly prior to installing the wheel on the bike. It also isn't that the cone/locknut is rotating on the axle. It is just that the bearings end up loose after 50 - 100 miles. I've even ruled out practical joking coworkers (it's a commuter bike).

I don't know this hub at all, but does it have removable cups like some of the fancy hubs have? If so, could the cups be loose after you overhauled the hub, and then they shift around as the bike is used?

I don't know this hub at all, but does it have removable cups like some of the fancy hubs have? If so, could the cups be loose after you overhauled the hub, and then they shift around as the bike is used?

I wondered that myself although I think the cups are pressed in. I guess if this problem persists I'll have to tear it down again and see if one or both of the cups are loose. I think that would mean the hub is no good. I've got a spare one just like it but wanted to keep it as a spare...

I wondered that myself although I think the cups are pressed in. I guess if this problem persists I'll have to tear it down again and see if one or both of the cups are loose. I think that would mean the hub is no good. I've got a spare one just like it but wanted to keep it as a spare...
Try this: overhaul the hub again, but OVERTIGHTEN the cone that keeps loosening up, say by 1/8. Then lock the locknut good and tight again. Obviously now the axle will be binding, but ride it anyway for a bit, and see if it "loosens" up to the ideal point.

Was this hub a take-off or OEM? or was it sold to retail?

Was this hub a take-off or OEM? or was it sold to retail?

Sold to retail. It was a hubset new in box of NOS Shimano 600EX hubs. These are older style thread on freewheel hubs (well the rear one is anyway...) made for 126mm O.L.D. spacing for 6 and 7 speed bicycles.