Golf Equipment News 2010: The secret of the Miura forging process

The secret of the Miura forging process

		The first part of the manufacturing process is the cold cropping of the carbon steel which is supplied to Miura in bar form.

		The cropped billet is passed through an induction heating process which heats the metal to 1200ºC.The operator has 14 seconds to move the heated billet to the air hammer for the first strike.

		The 1 tonne air hammer in the forge is isolated 1 km from the main factory. The hammer hits the heated billet 3 times; once to flatten it, again to make the first press in the die, and the third to make the second press.

		The operator has 5 seconds to move the offered billet from the first strike to the third strike.

		The die used with the air hammer. First strike to flatten the billet.

		Second and third strikes to form the head.

		The grain structure of the metal used in Miura heads changes during the forging process with the removal of carbon deposits. Black areas are carbon deposits. The smaller and tighter the deposits the more solid the feel.

		After the billet has been struck three times during the initial forging stage it is then passed through a press to remove the excess metal from the formed head.

		The die and cutter used to remove the excess metal from the formed head.

		After pressing the formed head is allowed to cool. This is the end of the initial forging.

		When the heads are returned to the main factory a final forging process is initiated. The formed head is heated in a furnace.

		In the final forging the press changes again the density and grain structure of the metal.

		The final strike changes the grain structure of the metal again and removes further carbon deposits. Black areas are carbon deposits. The smaller and tighter the deposits the more solid the feel.

		In the final strike there is a further change in the composition of the metal and a small flange which will be removed later is formed.

		The die set used in the final forging.

		The press used in this process exerts 200 tonnes of pressure on the head. As can be seen clearly the formed head does not have any hosel at this point.
Miura is unique in pressing the grooves into the head. This is seen by Miura San as important as there is no material loss and no temperature changes. It is his view that a cutting process for grooves increases the temperature of the metal and adjusts the temper of the metal in the head.
		The hosel is manufactured in a CNC machine with a tool post containing 6 cutters. These cutters centre, bore and chamfer the finished hosel.

		In this operation the stalk on the head is prepared to meet the hosel with an end milling cutter. The hosel which is housed in a collet within a high speed clutch is presented to the head and spin welded onto the head.
The spin forging of the hosel onto the formed head is another unique part of the Miura manufacturing process.
		A grinding belt prepares the profile of the head. This is the only mechanical grind in the head manufacturing process.

		Hand grinding of the head is undertaken by a Miura trained craftsman grinder who is seated to provide stability when grinding.

		During the grinding process the head is weighed for a finished weight tolerance of +/- 0.5 grammes.

		The first part of the finishing process is to tumble the heads in a tumbler containing stones for hours before the heads leave the factory for plating.

		Final check and hand painting of the head before packaging and dispatch.