How tennis rackets are made

Cut the cold prepreg

Graphite sheets already carrying uncured resin, called prepreg, come out of cold storage and are cut into shapes. Each piece has a set fiber direction, and that direction largely decides how the racket plays. One Head model uses 15 pieces.

Roll a tube around a bladder

Workers arrange the pieces on a table and roll them around a mandrel and a polyurethane tube. The mandrel sets the wall thickness, and the tube becomes the bladder that air will inflate.

Preform the hoop

The tacky tube is bent around a metal form shaped like the racket head, and reinforcing pieces go on at stress points such as the throat bridge. Careless shaping leaves wrinkles once the tube is in the mold. A plastic piece in the handle end lets air into the bladder.

Inflate in a hot mold

Inside the heated mold, compressed air blows up the bladder and pushes the layup against the walls. Resin turns so fluid that some leaks out, then it hardens.

320 °F for 10 to 15 minutes

Sand off the resin

Hot from the mold, the frame carries cured resin along its edges. Workers sand it until the frame is clean and smooth.

Drill the string holes

The hoop is drilled for its string pattern, such as 16x19.

Paint the frame

A production frame then gets paint and decals.

Fit grommets and grip

Grommets line the holes so strings do not rub on sharp edges. A butt cap and a grip finish the handle.

Weave in the strings

Strings are threaded across and through the frame in a grid. Synthetic strings of nylon or other polymers have partly replaced natural gut, and a professional may have a racket restrung after every match.