The Golden Wrench

A blog about bicycle repair and maintenance by the mechanics at Freewheel Bike.

Tuesday, December 21, 2010

Preparing a Frameset for Building

When building a bike from the frame up, there are certain preparations that should be made to the frame. When a frame is painted or powder-coated, there can be build-up left in and on the headtube, bottom bracket shell, and seat tube. Precision components can be very sensitive to imperfections in frame construction, causing premature wear, binding, and noise.

Before installing any seatpost into the seat tube, it's a good idea to remove any burrs that could scratch or gouge the seatpost.

When the manufacturer makes a relief cut in the seat tube, it often leaves big burrs.

A Flex-Hone gets put in a drill chuck and is spun inside the seat tube to clean burrs and polish the tube.

There is still some excess paint left in the seat tube, but the sharp edges have been taken care of.

The next order of business is to take care of the paint on the faces of the bottom bracket shell. With most external bearing systems these days, the slightest imperfection can cause issues.

Excess paint on bottom bracket shell.

Here is the tool we will be using for this process. This tool does two things, chases the bottom bracket threads and faces the bottom bracket shell.

The tool uses a guide that runs through the center to make sure the threads and face are cut square to the center line of the bottom bracket shell.

Since the frame is brand new, the taps go in pretty easily.

Once the taps are in and recessed within the shell, we can set the tool up with the facing mill.

The tool detaches from the tap and the facing mill snaps right in.

Always apply cutting oil to any tapping/milling/cutting operation.

The shell is 95% faced. You can see the small amount of paint still remaining in the 10 o'clock position. Once this little bit is removed, the shell will be completely faced.

After: A nice, fresh, clean, perpendicular, bottom bracket shell face.

Time to do the same thing for the head tube.

Here is the tool we will use on the head tube.

This tool will ream the inside diameter of the head tube to the correct diameter for the proper headset to fit as well as facing the top and bottom surfaces.

This tool uses a cone to center itself on the side its not cutting.

Nice looking spirals of material indicate that the cutting tool is sharp and material is being removed with ease.

Once the top is finished, the tool is flipped and the bottom of the tube is faced and reamed.

I had a pretty nice spiral of paint on this one, so I grabbed another shot.

After: A nice, clean, perpendicular, faced and reamed head tube.

The final step we will talk about today is milling the fork crown.

There is random paint build up on the surface of the fork crown that the headset race will contact. To ensure good headset race contact, we will face this, as well.

Here is the cutting tool we will use for this operation. The cutting teeth are slightly out of focus. The more important part of this tool is the blue sleeve inside. This is the guide that will make the tool cut square to the steer tube.

Again, this tool provides two functions. It mills the outside diameter of the fork crown to the proper thickness and faces the crown to provide a smooth flat surface for the race to rest.

After: A clean, smooth, fresh, square surface for the headset race to sit.

Most aftermarket parts companies highly recommend facing before installing their components; Chris King, Cane Creek, Shimano, to name a few. As you can tell, there are quite a few, fairly expensive cutting tools required to do a proper frame preparation. Usually, shop rates are fairly reasonable to have this done to your bike. It is a great idea to do this anytime you install a new headset or bottom bracket, too, if it's never been done before. Your components will thank you.