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Before building up a new frame, it's crucially important to ream/face the headtube and crown race seat (and the bottom bracket, if using press-fit cups). You should also ideally chase the threads of the BB and the derailleur hanger.

But why don't manufacturers (e.g., Surly) do this before they leave the factory? Surly in particular mentions that they do in fact face their head tubes, but they do so before painting the frame, requiring new frame owners to re-face them.

Why wouldn't they just do this before shipping the frame out? It seems like a no-brainer.

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I've read that it's not crucially important and that you can do without facing. –  user973810 Jan 18 '12 at 21:49

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up vote 7 down vote accepted

First thing that comes to my mind is labour costs.

Second thing that comes to mind is that once you break that paint seal by reaming/facing you are allowing contact with the air and elements. As a good practice you should coat the threads with a little grease before assembly, meaning that when you get that new frame, you tap out the mounting holes and then screw in the mounting bolt with grease that will re-seal the exposed metal.

Third..tradition. New frames never came faced in the old days as it was expected that the professional bike mechanic would be doing all that as it was their job.

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Agree, and add one thing: the frames should be perfectly raced "just in time", because they can suffer some impact during transport or handling. I, for one, never raced any frame, but I think this is a good idea to do that (I didn't even knew it was possible until recently). –  heltonbiker Jan 19 '12 at 15:35

It is important to note that most manufacturer's of quality frames do face and ream their frames before they assemble or ship. They often do it before paint because they do it with machinery to build/assemble their frames, which allow a level of precision which wasn't possible with a locally produced hand built frame. So facing to raw metal isn't necessary anymore.

In addition, the components installed on a modern bicycle often require a level of precision in frame specifications which can be destroyed by hand reaming or facing a frame after purchase. Campagnolo Ultra Torque cranks in particular, when installed, require a very specific shell width for the bottom bracket to be installed and function correctly. The tolerance range is less than .5 millimeters.

So it is not always automatically a good idea to face your frame in a shop or on your own.

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+1! I dont ream/face frames unless there's an issue that leads me to believe that reaming or facing is necessary. If you feel you must, 99.9% of the time it's best just to take the paint off and nothing more. I have seen instances where mechanics take too much metal off when facing a bb and have to compensate by using an extra spacer. That's bad. –  joelmdev Jan 22 '12 at 19:50

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