Machining error on fork slider?

SteveBorland · Jan 8, 2015

I've been playing with the forks on my 850, and I tried a newish LH slider that I received together with the bike when I bought it.
However the damper end will not fit into the recess in the bottom of the slider, where the securing bolt passes through. I've tried various combinations of damper and slider (both original Norton and the lovely Landsdowne bits), and the recess is simply too small in diameter.

These sliders are fairly expensive at around 160 GBP each, so I was wondering if anybody had experienced this before? I've no idea who the original supplier was. The stanchion and bushes are a good fit, and it seems to be dimensionally correct (other than that damn recess, which is perhaps 1mm too small).

I suppose it's possible to reduce the diameter of the protrusion on one damper (the Landsdownes are alloy), but before doing something as drastic as this, I was wondering if anybody else has had this problem? It's not easy at all to enlarge the recess in the slider, it would need a very long end mill.

/Steve in Denmark.

dave M · Jan 8, 2015

Make sure that your newish slider doesn't have a deformed fabric seal from an old damper rod wedged inside from a previous attempt at assembly.

Egholt · Jan 8, 2015

I have new RH/LH slider , will check today .

Michael from Denmark

SteveBorland · Jan 9, 2015

Actually, this slider is probably at least 10 - 15 years old, so it's unlikely that it's present on any current production.
What I was wondering was if there is any way of salvaging the slider.
Just to repeat, the issue is not the depth of the recess (someone suggested that there was an extra washer in there..) but in the diameter of the recess.

/Steve in Copenhagen

dave M · Jan 9, 2015

Steve, the washers I am referring to are fibre or fabric and could deform causing problems with the diameter and or the depth, try putting a long metal probe in there and see if the limited diameter is due to some foreign body.

kommando · Jan 9, 2015

Opening out the hole will entail mounting in a lathe or milling machining and cutting the hole larger using a very long cutter/spot facer. This will take a lot of setting up to be accurate and doubt an existing tool at the machine shop will do. You are left with cutting the current or the Landsdowne damper body down to fit.

SteveBorland · Jan 9, 2015

dave M said:
Steve, the washers I am referring to are fibre or fabric and could deform causing problems with the diameter and or the depth, try putting a long metal probe in there and see if the limited diameter is due to some foreign body.

Thanks for the clarification. I've had a good look down the bugger with a light, and there is what I took to be a chamfer on the edge of the recess - it's a lighter colour. I'll make up a tool to try to pick up on this through the bolt hole - it _might_ be something left in there, but how , and where did it come from??

Mind you, this is still a more probable explanation than a machining error.

dobba99 · Jan 9, 2015

Steve
If you know someone who knows there way around a lathe, they it should be able to turn up a long counterbore out of silver steel, file the cutting edges in the said tool and then harden it. I have done this numerous times when i haven't got the counterbore of the size required (the last time i did this was to make up a counterbore to drill out the exhaust valve guides on my 850, this allows whats left of the guide to collapse inwards and leave a clean hole in the head, it worked a treat!)
The important thing is that you incorporate the pilot/guide in the tool so that it follows the hole exactly.
You might have to extend the length of silver steel as they are only a foot long. Either sleeve it and join the bits with loctite or weld an extension on.
The drilling could be done with a hand held drill on slow speed. The long length of the tool down the slider will make it easy to keep it centered just by hand.
Regards
Pete

john robert bould · Jan 9, 2015

Steve
The slider damper location Bore should be 24mm, damper dia 23.7mm thats 12 thou clearance. a 24mm end mill[spot face cutter] will require careful application ...a small amount machined off the damper base is easy , just check there s no bur before drastic action.

kommando · Jan 9, 2015

If the cutting tool had an 8mm (5/16") pilot extension this would locate the cutter in the centre and also help locate the slider in the 4 jaw chuck (as the slider is not round a 3 jaw chuck cannot be used).

SteveBorland · Jan 9, 2015

Thanks very much to both of you for the very helpful info. Now just to see if it's practical for me to get a mate to do this.
Worst case is to buy a new slider, so depending on how much I can get done via the back door.....

/Steve in Copenhagen.

john robert bould · Jan 9, 2015

I have seen Seeley sliders with the damper 5/16 hole off center, i think these where drilled from the outside , "bottom up", this cause's problems with the pin/hole pulling the damper to one side.

kommando said:
If the cutting tool had an 8mm (5/16") pilot extension this would locate the cutter in the centre and also help locate the slider in the 4 jaw chuck (as the slider is not round a 3 jaw chuck cannot be used).

850commando · Jan 9, 2015

this sure seems like a lot of work to correct a manufacturing defect , is there any chance to return the slider to the person you acquired the bike from and have them get back to the manufacturer/supplier who made the crappy part?

SteveBorland · Jan 9, 2015

After 10 - 15 years? I rather think not

good plan though.

john robert bould · Jan 9, 2015

Finding and getting the part back to tho original maker will be next to Zero, Steve just machine a bit off the damper base. Or sent it to Madass Don he will put it right.

850dunstall said:
this sure seems like a lot of work to correct a manufacturing defect , is there any chance to return the slider to the person you acquired the bike from and have them get back to the manufacturer/supplier who made the crappy part?

SteveBorland · Jan 15, 2015

Yesterday I had the time to have another careful look at the problem slider and at the original. As you can see in the attached pictures, it looks as if the locating recess has not been machined at all. The rough (cast?) finish is clearly visible, vs. the machined finish of the OEM item, and the difference in diameter can also be seen.

I think what has happened is that this recess is probably done as the last operation inside the slider, and for some reason, this particular slider was never finished. Who knows, perhaps the operator had to break for tea.
to
While this may be a salvageable part for someone with more extensive access to a toolroom than myself, I'll put this one on the shelf and try cleaning up the OEM slider.

Here's a photo of the faulty slider, showing the "as cast" finish of the damper recess.

Here's the OEM slider.

Johnnymac · Jan 15, 2015

I have a nice looking OEM LH slider that I'm not using.

Fast Eddie · Jan 15, 2015

Steve, why not just take some material off of the OD of the damper body base?

john robert bould · Jan 15, 2015

Check it#s not where the stanchion as hit, this will "fold over" the alloy in effect squeezing the hoke smaller :?:

Machining error on fork slider?

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