Cutting BB threads before vs after welding in practice

[hans736]

Think of chasing like sharpening a blade only you’re sharpening the tiny threads.
So when it is finished, the threads look clean. If there was paint or rust or anything that would inhibit installation of the BB, it is removed by the chasing tool.

...and reaming is different from this?

[TonyP]

...and reaming is different from this?

Yes, an unthreaded tube is reamed while threads are chased and flat surfaces are faced.

[hans736]

Yes, an unthreaded tube is reamed while threads are chased and flat surfaces are faced.

Ok. What would you do the the unthreaded tube (by reaming it)?

[Rich Beaudoin]

Ok. What would you do the the unthreaded tube (by reaming it)?

Reaming it makes the inside round again after welding so the seatpost or headset fits correctly.

[hans736]

Reaming it makes the inside round again after welding so the seatpost or headset fits correctly.

I think my picture is complete now:
+ Tapping = cutting threads or recutting threads.
+ Chasing = removing paint,rust or metal shavings from threads.
+ Facing = making the BB surfaces level.
+ Reaming = makes the inside round again after welding.

[VertigoCycles]

I think my picture is complete now:
+ Tapping = cutting threads
+ Chasing = removing paint,rust or metal shavings from threads. this also makes the bore roundish again
+ Facing = making the BB, or head tube faces level. and parallel
+ Reaming = makes the inside round again after welding.sort of. Reaming is cutting a hole to a specific size. In basic machining, the hole is usually very round because of the amount of material surrounding the hole that supports it during the reaming operation. We'd all like to think that reaming a HT, BB or ST makes a perfectly round hole, but the reality is that it often doesn't. What it does is make a hole with a relatively precise I.D. into which a bearing assembly can be pressed or a seat tube can be inserted.

notes in red

[hans736]

notes in red

Excellent thanks!