Help fork disaster

[Joolstacho]

Yuck... old shagged fork sliders eh!
Trouble is they get 'belled-out' in the middle by the lower bush so new bushes will never fit correctly.
On BSA sliders I wonder if it's possible to renew the tubing. I recently restored my Velocette sliders, using new seamless steel tubing (I believe it's used for hydraulic rams etc). With the Velo though, the top and bottom lug sections are soft-soldered to the tubing.

[Rich]

tried the swaging method, did not work, so I managed to win a pair from eBay, managed to get a mortgage for them, lets hope they are ok, described as superb condition, if they are no good then I will seek Ebays money back guarantee, will find out the week after next, as away next week to get over the stress of parting with so much money

[RDfella]

Rich - sorry to hear swaging didn't work, which surprises me. Had that been my workshop I'd have guaranteed good or better than before. But the mortgage How much did you pay . Ones I saw recently on ebay went yesterday for just over a hunderd £. Can't remember postage.

[Joolstacho]

I'm a bit confused in this thread. (Nothing unusual then!...)
Are we talking about swaging the tubing out because it has shrunk/distorted because of welding or brazing of the mudguard lug?
The vast majority of slider problems are caused by wearing and/or 'belling out' of the slider tube so the lower bush is a sloppy fit.
(Or have I got on the 38D to Oblivion when I should have got on the 21A to Farningham!) 

[RDfella]

Jools - as I understand the original post, the problem is having welded mudguard lugs onto the sliders, the bushes are a tight fit to get past the area. Swaging in to take up wear from the bushes would be a job not worth the trouble (easier to make new).

[Joolstacho]

Yes mate, that's what it sounds like. But IMHO once that sort of distortion damage is done ya'd never get the internal bore accurate enough eh?.
That's why I mentioned the possibility of re-tubing the sliders with nice new tubing.
Has anyone looked into this? As I said, you can do it with Velocette sliders.

[Swarfcut]

Rich.. At least you won them, if they were the ones mentioned they looked the part, ready to fit and from a seller who is a long standing eBay member, with an established reputation. Like I said, some are made of precious metal. I think you will be OK, but its always a bit of a worry when you open the box.

   If you have not done already, get yourself a Nectar card and link it to your eBay and PayPal Accounts. The way you are going the points will soon add up, and you can spend the points on eBay and get a few quid off your future purchases.

 Jools... As to the wear pattern, it all take place on the loaded side of the slider and bush, as in use the slider and bush are under  constant sideways load.  So as long as the slider doesn't rattle or knock I would be happy, and accept a little slop, taking into account  the age of these parts and my pussyfoot "cloak of invisibility" riding style.*
   That extra bit to get perfection is the bit that costs the most.
   You could say a few minor rust pits will hold oil and improve the lubrication and have a marginal effect on damping compared to other factors.
   As to re-tubing, if the spindle lugs and oilseal holder thread parts could be salvaged without damage, anything is possible. You need your own toolroom, skill and time. Paying the going rate would make Rich's  look positively cheap, but when serviceable originals have all gone, the Indian or Chinese entrepreneurs will step in. They may have already done so, but I would be a bit wary of these safety critical parts made from re-cycled Oil Tankers.

 In manufacture I would assume the last step would be to bore, hone or broach the final ID, to remove any distortion from welding on the mudguard mounts. The early types look to be brazed on, but even so there is always the risk of heat distortion, so I doubt if this was done to the pre- finished tube.

 Any production engineers in the house?

 Swarfy.

  * Ride with the mind set that no other road user has seen you, and that guy up ahead is gonna pull out, turn across you, run a red light....put your own scenario.   You folks, the survivors, know exactly what I mean.

[BSA_54A10]

Yes mate, that's what it sounds like. But IMHO once that sort of distortion damage is done ya'd never get the internal bore accurate enough eh?.
That's why I mentioned the possibility of re-tubing the sliders with nice new tubing.
Has anyone looked into this? As I said, you can do it with Velocette sliders.

Eeer why not get the tubes line bored then fit oversized bushes .
Done it dozens of times

[Joolstacho]

Well it's good to know there's enough meat on the tube walls to line bore them.
(Though I've got at least one pair that would be perilously thin if bored enough to get the 'belling' out).

[BSA_54A10]

A surprisingly small amount of wear makes a massive difference.
Anything much more than ,020" would allow the wheel to move near 6" for & aft when you brake & make the bike unridable.
From memory the last set I got done needed .005" machined ( ,010" diameter ) and that was a wrench out of your hands front end.

[chaterlea25]

Hi All,
How do you bore down past the tapered damper plug that's welded to the bottom of the fork slider?
John

[muskrat]

G'day John.
I've never done it but if I had to, the boring bar would need to be shaped the last 2" to clear it. To overcome flex and chatter the bar it would need to be almost as thick as the stanchion.
The next question is how would you measure it with that lump in the road?
Cheers

[RDfella]

Musky – exactly my thoughts. With fifty five years mechanical engineering under my belt, I’d really scratch to do that one. How do you centre it or hold it true? The best way would be to take all the lugs off (bar top & bottom fixings) and put in a chuck. But then you’re back where you started. And as you say – with that length of boring bar, what about chatter? Suppose you could bore it in a lathe with a 3” or bigger headstock, but we’re getting a tad agricultural now. Honing is really the only option, but then there’s a danger of taper and, unless it’s a Delapena (which probably wouldn’t be long enough) the hone would likely follow the ovality. Using a pilot is not feasible, as it’d rattle in the worn part.

[terryg]

Given BSA's background I imagine the sliders were gun drilled as part of the original manufacture. If that's correct it's presumably not an option for reworking owing to the 'missing' supporting material.
Can someone familiar with the method comment?

[duTch]

 

Musky – exactly my thoughts. With fifty five years mechanical engineering under my belt, ...........

 And with 10 minutes of experience after reading the original post I decided it was gunna be a shitfight so opted out while I was ahead