headset worry

Picked up an interesting project, one of the main problems was the thread was knackered on the 1" steerer. Spare fork & headset came in the deal, no worries. Took it out for a test run & the headset loosens pretty quick. All the parts seem in the right order (tag ring between the nuts, etc) I'm just worried because the original fork was knacked, is this going the same way? tightened as much as seems sense with normal spanners. Is it just taking a long time to bed in? Would Loctite help? can any one recommend an easy to source early 90's replacement set (this is a no-name steel set, last time I tried for an early 105 it was a real problem)?
Is it economical to have a frame builder fit a new steerer? Or maybe it's ok to have a little movement in some bearings? (uncomfortable feel though)

What do the headset threads look like?

Look fine on the new fork, bearing parts on the original had destroyed the fork thread while keeping theirs.

Likely the threads on the headset are also damaged.
Do you have a picture of both parts?

I've had a similar problem with my old 1" Deore XT headset. It always started to loose. After I replaced the aluminium top nut of the headset with a steel one (costs about a half pound in a LBS), the problem is gone.

Several things to check:
1 The headset lock nuts have to be done up dead tight together - turning the lower one looser onto a held top nut works best for me.
2 If it has run loose for any time, the bottom cup may have ovalised, in which case it is scrap.
3 Fit new bearings: missing, worn or poorly toleranced balls may be the problem. While you are at it check for pitting or brinnelled dents in the lower race, which will make the headset notchy and impossible to adjust. Swapping to loose balls can cure it.

You may need a thicker spacer/washer under the top nut, it's possible the nut is butting against the top of the steerer tube.
Good luck

What tatra said sounds most likely, but didn't actually check that on the original set-up. All parts there were NOS, so wear wouldn't have been an issue just poor quality. By this point I'd found some Tange parts further back in the cave, at least they have a name so I guess a period upgrade! There's a gap above steerer with this set. Had a quick blast down the Chocolate Path (notorious local loosener!) one quick adjustment & back again throwing in a few more cobbles & curbs seems fine now.
Also found this:



Top nut with 2 opposing grub screws & a spring wire around inside the thread. Has FSA logo on the seal, think it came off a Giant road bike. Would it have worked? Any experience of these?

It will work but it could / will mash the threads :-(

This type won't damage the threads at all :





WD

WD Pro, that's a neat solution, where are they from?

Spoke too soon on the Tange set up. Still couldn't get it quite right, even with new loose balls somehow there were tight spots. Got me thinking about the '94 Rockhopper I had new, & that headset would never stay tight. Cured it with an STX cartridge bearing. Remembered I had a spare set of this so gave it a try. Being a cartridge bearing the stack height's a bit more so I couldn't quite fit the tab washer in there - checked the old Rocky frame (just returned from long term loan!) & that headset had obviously been running without tab washer for some time. Can't remember if it was me or Circus Freak fitted it like that but seems like it worked so did the same on this bike, took it out for a shaking, still tight so I guess I'll run with it & be happy!
Anyone know what year the cartridge type headset was first available from Shimano, & any in stock anywhere?