Facing and chasing – why?

Not 'why is it needed' but why doesn't the manufacturer do it in the first place?
I just wondered coz the owner of the nice green Ragley on another thread is taking it to be done – when it's brand new. Seems odd. It's not like there are people out there who won't be fitting a BB.

It takes time. When a frame's being built in a factory in Taiwan (or anywhere else, for that matter), the quicker it can be built the better. If most frames will be built up in shops by mechanics with the right tools, why duplicate that at the factory when you can save a few quid as a manufacturer?

I don't necessarily think this is best, and also most frames direct from the manufacturers are pretty much chased and faced anyway, but that may be why the Ragley needs it doing…

: P

Most manufacturers do.

Brant doesn't have the Ragleys done because he reckons that after a few thousand miles of shipping the BB will be no longer faced.

Is the facing to get rid of corrosion as well as paint then?

some aluminium frames come faced, i wouldn't want a steel one coming off a boat from taiwan with exposed metal though!

That's interesting re the shipping, I always figured it was more of a cost / time issue, and considering the price of the frame I'm not overbothered. Plus I quite like spending the odd bit of money at the LBS.

Facing just takes everything (paint, corrosion, burrs, unevenness) off the faces of the BB shell and makes sure they're flat, parallel and exactly perpendicular to the BB axle. Chasing cuts the threads properly at the right angle and makes sure they're clean and free of all the above things.

: P

Never bothered for years, never had any issues.

I understand why you might want, or need, to face the BB shell.

However there shouldn't be any need to chase the BB threads other than to carefully clean them up if they're damaged or clogged with something that can't be cleaned off with a degreaser.

If you're chasing for "cutting the threads properly and at the right angle" you need to ask questions about the manufacturing process. Besides, if you chase too aggressively or not straight the thread can become baggy and the BB caps will have a) play between the mating surfaces of the threads on the BB cap and those on the BB shell b) increased risk of stripping the BB threads due to a combination of ham-fisted tightening and a).

"If you chase too aggressively"

…not if you're using a good tool. If the threads are right and clean, the tool won't have anything to cut and will just spin in and out.

Even if you _face_ aggressively, you'd have to do an awful lot to make a significant difference from 68mm (or 70, 73 or 83, or whatever).

: P

Fair enough Pierre, I'm sure you're right. With the right tools being properly used there won't be any issues.

I guess that if you have to face up the shell and that results in any significant removal of material you'd want to run a tap down the threads anyway to clean up any burrs and to ensure that the thread's start is clean.

Depends which tool you're using. I have the Park Tool set which has screw-in guides which also protect the threads when you're facing. Even if you've had to take a fair bit of material off the faces, take out the guides and quick blow to check there's no swarf loose in the shell and you're pretty much good to go…

: P

Lets be honest, if you're frame was manufactured properly in the first place you wouldn't need to chase the threads unless they get damaged in transit. If your BB area was manufactured correctly you wouldn't need to face it, unless you damage it in manufacturing or transit. If they are damaged you need to fix your shipping and manufacturing problem, or hand it on to someone else.

Never chased or faced any frame I've owned, and never had a problem.

The mmmBop needs doing 'cos there's paint in the threads / faces. I could probably do it myself with a scalpel and a bit of time, but since I'm buying a headset from the LBS and they're fitting it I may as well get them to do a proper job of the facing / chasing while they're at it 🙂