Cycling UK Forum

Brucey wrote:as has been mentioned before, old style loose-ball BB cups are made from hard steel and can be 'modified' to make thread chasers quite easily, using an angle grinder.

I guess a note of caution concerning these (or indeed, any tool which doesn't use a guide of any kind) is that it is easy to go cross-threaded. The posh tools make this much less likely.

cheers

A good idea, helped of course if you're able to clamp an axle or some threaded stud to the improvised chaser, to act as a guide for a straight entry.

I'd pay the LBS the £35 this time.
I'd make sure the threads on any future frames are protected by fitting an pair of old style BB cups or even an old BB cartridge.
That IMHO is your cheapest option.

Cheapest option is to do what I did.

Use an old pair of BB cups and slowly rotate back and forth with oil until the threads are clean.

reohn2 wrote:I'd pay the LBS the £35 this time.
I'd make sure the threads on any future frames are protected by fitting an pair of old style BB cups or even an old BB cartridge.
That IMHO is your cheapest option.

On the occasion that I decided that I couldnt manage to do a job myself and took it to the LBS, they did more harm than good. Now my classic frame has a rattlingly loose headset and forks.
This is an LBS with a lot of engineering level experience and equipment.

Mick F wrote:Cheapest option is to do what I did.

Use an old pair of BB cups and slowly rotate back and forth with oil until the threads are clean.

It is if the OP has the old style BB cups to hand and the confidence to use them.

meic wrote:

reohn2 wrote:I'd pay the LBS the £35 this time.
I'd make sure the threads on any future frames are protected by fitting an pair of old style BB cups or even an old BB cartridge.
That IMHO is your cheapest option.

On the occasion that I decided that I couldnt manage to do a job myself and took it to the LBS, they did more harm than good. Now my classic frame has a rattlingly loose headset and forks.
This is an LBS with a lot of engineering level experience and equipment.

The OP's LBS has done the job once,if he has confidence in them he can trust them to do it again.

reohn2 wrote:

Mick F wrote:Cheapest option is to do what I did.

Use an old pair of BB cups and slowly rotate back and forth with oil until the threads are clean.

It is if the OP has the old style BB cups to hand and the confidence to use them.

No,i don't have the old cups i'm afraid . And your correct about the confidence thing .
I think that if the BB housing was steel and not aluminium,then i might have given MickF's method a go . But i'm abit cautious where aluminium is concerned .
Just as a point of interest . . i've always assumed (rightly or wrongly),that manufacturers used such a fine thread in the BB housing to enable bearing adjustment with the old style cup and loose ball system .
I also fully understand why cartridge manufacturers still use this thread size today . . there will be tens of thousands of machines out there that use that size .
But from an engineering point of view, does such a fine thread still need to be used,bearing in mind that most cartridges i've seen are non adjustable anyway .

I think you could use a coarser thread, but it would have to be toleranced differently to normal in order to work OK. Also both parts would have to be thicker and heavier to accomodate the screw thread.

In most engineering circles, the conventional approach to an application with this loading on it would be to use a couple of bearings which are a press-fit into the BB shell, a bit like the viscount BB design.

In general fine threads are good for bicycles because they can allow high clamping loads and good resistance to loosening with modest torque values.

A DIY thread chaser will work really well in an aluminium frame, if you can make it so that it is held square.

cheers

Collected frame from LBS today . Shop owner had to clear threads out . He seemed to think that the BB housing was possibly distorted . I did get the impression that he wasn't a fan of aluminium frames . Anyway all is now well .
We three would like to thank everybody who contributed to this thread . The advice and suggestions have been more than helpful as always .
Anyway,watch this space . I have another frame at the P/C's at the moment . Maybe third time lucky with the BB cartridge fitting .