Scooterotica

My original Innocenti rear hub is in decent nick, but one of the studs has at some point come loose and 'bored' its way out. I.e., there is now a distinctly larger hole for the stud than there should be, with no visible threads. And NO - I didn't do this, it was bought as a barn find...

Is it feasible to weld the hole and have it tapped for a replacement stud? Too risky?

I have just bought a genuine NOS SIL rear hub as a replacement. TBH, it's pretty rough - the casting around a few of the fins looks absolutely shocking. Is this normal? The rest of it seems ok, I suppose.

Opinions please.

Cheers,

Dan

Its certainly possible to have the hole rewelded by a competent welder...... but its a very uncommon thread to re-tap it and not many people would have one....


But to answer your question... yes it would certainly be possible.

You've got PM about a welder in Sydney.

Tapping odd metric threads.

To find the size of the tapping drill for any ISO metric or BA thread deduct the thread pitch from the diameter of the stud.
ie M6, dia 6x1.00 pitch > drill size is 5mm
M8, dia 8x1.25 pitch > drill size is 6.75mm
M10 fine, dia 10x1.00 pitch > drill size is 9mm
etc. etc.,

Buying very odd taps can be a pain, but I have always found SKF Dormer very helpfull even with left hand threads. send them a letter telling them you are an engineering student on a degree course and you need the tap for a project (lies ).

In theory it is possible to convert a high tensile bolt or stud into a single use tap.
Use an angle grinder with a fine cutting disk or a dremmel (etc) to cut a couple of flutes along the length of the stud,
then use a pedistal grinder to put a slight taper on the start of the stud.

It is difficult but possible, if you get it right it works for a couple of uses.

As Paul says the welding is not too much of a problem.

Try getting the tap first.

paulmgreen wrote:Its certainly possible to have the hole rewelded by a competent welder...... but its a very uncommon thread to re-tap it and not many people would have one....


But to answer your question... yes it would certainly be possible.

i do

Thats because you are a top engineer!!!!!!!!!!!!

Thanks people - I think I'll prepare both hubs, if possible, and choose which one to use later on. Although it will be intersting to see how readily available the tap will be (in Sydney...).

As I said, just really disappointed with the casting qaulity of the SIL hub - and I believe this is a genuine one, too. Probably works fine but just looks so ugly; I'll have to build up the edges of a couple of the fins as they're missing so much metal from the mold. (?)

Dan

are the changes in the mechanical properties of the heat affected zone in the cast alloy when electric arc welding (TIG/MMA/MIG) acceptable for the application?

as a welder of 31 yrs i wouldnt weld an item like this for highway use , castings are an unknown quantity you never know what there made of unless you do a burn test and even then each batch can vary, as just mentiones the HAZ is an area were all sorts of things go on with reguard to grain structor, others will disagree but why scrimp on safety this part cost very little compaired to what your scooter is worth and more importantly yours and others lives should a failiour occure ............ if you have children ask yourself would you feel safe letting them get in a car or on a bike with a welded hub/wheel ?

shocky wrote:as a welder of 31 yrs i wouldnt weld an item like this for highway use , castings are an unknown quantity you never know what there made of unless you do a burn test and even then each batch can vary, as just mentiones the HAZ is an area were all sorts of things go on with reguard to grain structor, others will disagree but why scrimp on safety this part cost very little compaired to what your scooter is worth and more importantly yours and others lives should a failiour occure ............ if you have children ask yourself would you feel safe letting them get in a car or on a bike with a welded hub/wheel ?

Thanks Shocky,

Appreciate the feedback. It is sometimes difficult to know the 'right' thing to do with stuff like this without any background knowledge.

The reason I bought the SIL hub was because my gut instinct told me it would be a bad idea to weld the original, but as you can see - as ever - there are always different opinions! Just trying to work out the best option, really.

Cheers,

Dan