Method and apparatus for balancing a rotary tool assembly

In a rotary tool assembly having a rotary tool holder having an outer housing and means for receiving and securing a cutting tool within the rotary tool holder, the improvement comprising a readily adjustable external ring balancing mechanism for balancing the rotary tool assembly and cutting tool secured therein, comprising:

• a) an outer cylindrical ring bearing surface formed around the outer housing of the rotary tool holder such that the ring bearing surface is exposed about the outer housing;
• b) a pair of cooperating balancing rings journalled around the outer cylindrical ring bearing surface and operative to assume both an unsecured mode and a secured mode;
• c) each balancing ring being unbalanced about its longitudinal axis and rotatively confined on the outer cylindrical bearing surface such that in the unsecured mode each balancing ring may be freely rotated completely independent of the other such that the rings may be selectively positioned to balance the rotary tool assembly;
• d) in the unsecured mode each balancing ring being freely rotatable by hand around the outer ring bearing surface such that in the unsecured mode the balancing rings may be freely rotated and positioned by hand to balance the rotary tool assembly;
• and
• (e) retaining means for securing the respective balancing rings in the secured mode to the outer cylindrical bearing surface at the selected position, said retaining means including a radially threaded bore formed in each ring and a threaded set screw secured within the radial bore and operative when screwed into engagement with the underlying rotary tool holder for fixedly securing the respective balancing rings to the tool holder.

A method of balancing a tool holder assembly having an outer housing comprising the steps of:

• (a) forming a circumferential ring bearing surface completely around the housing of the tool holder assembly;
• (b) rotatively mounting two completely independent closed balancing rings about the circumferential bearing surface such that the respective balancing rings may be rotated about the bearing surface independently of each other;
• (c) balancing the two rings about the tool holder assembly and securing the rings to the tool holder assembly in their respective balanced positions;
• (d) determining the magnitude and angular position of the unbalance of the tool holder assembly;
• (e) rotating the balancing rings independently of and relatively to each other to form a ring unbalance about the longitudinal axis of each ring whose magnitude generally equals the magnitude of the determined unbalance of the tool holder assembly, and then rotating the rings together to where the unbalance associated with the rings lie diametrically opposite the determined angular position of the unbalance of the tool holder assembly;
• and
• (f) securing both rings to the tool holder assembly such that the unbalance associated with the rings counters the unbalance of the tool holder assembly.

A method of balancing a rotary tool holder adapted to receive and hold a cutting tool comprising the steps of:

• (a) forming a cylindrical ring bearing surface around the tool holder,
• (b) forming a pair of unbalanced rings and referencing like points of unbalance on the rings, each ring being unbalanced about its longitudinal axis;
• (c) journalling the two closed balancing ring completely around the cylindrical bearing surface of the tool holder such that each ring can be rotated independently of the other;
• (d) axially confining the balancing rings on the cylindrical bearing surface;
• (e) balancing the two rings about the tool holder by positioning the rings such that like unbalance reference points lie 180 degrees apart and securing the rings to the tool holder thereat;
• (f) inserting a cutting tool into the tool holder;
• (g) determining the magnitude and angular position of the unbalance of a tool holder and cutting tool;
• and
• (h) rotating the balancing rings relative to each other to form a ring unbalance whose magnitude generally equals the determined magnitude of the unbalance of the tool holder and cutting tool and positioning the balancing rings such that the unbalance associated therewith lies directly opposite the position of the determined unbalance of the tool holder and cutting tool.

A method of retrofitting a rotary tool holder with a ring balancing mechanism without the retrofit exceeding standard tool envelope criteria, comprising the steps of:

• (a) forming an outer cylindrical ring bearing surface about a housing structure forming a part of the rotary tool holder;
• (b) journalling a pair of unbalanced balancing rings, each ring being unbalanced about its longitudinal axis, on the outer cylindrical ring bearing surface such that the rings in an unsecured mode may be freely rotated completely independently of the other about the ring bearing surface;
• (c) manually rotating the balancing rings with respect to each other to a tool holder balanced position where the rotary tool holder is balanced;
• (d) axially confining the rings to the retrofitted outer cylindrical bearing surface of the tool holder;
• (e) securing the respective balancing rings in a secured mode to the outer cylindrical bearing surface of the retrofitted tool holder at the selected balance position by radially boring and threading the rings to form radial set screw openings and threading set screws therein that can be moved selectively into contact with the tool holder;
• and
• (f) confining the retrofitted ring balancing mechanism to an area about the rotary tool holder such that the tool holder as retrofitted with the balancing rings falls within the standard tool envelope criteria.