Tool for machining a wall of a workpiece, in particular made from a composite material
A tool for machining a wall of a workpiece, made from a composite material, that can cut a groove in the wall, the tool including a head mounted integrally with a rod having a longitudinal axis and capable of being driven in rotation about the longitudinal axis. The head includes at least one main protruding annular rib with an outer surface covered with abrasive grains of predetermined particle size and with a radial height corresponding to the depth of the groove to be cut, and at least one auxiliary protruding annular rib with an outer surface covered with abrasive grains of predetermined particle size and with a radial height less than the radial height of a main rib. The auxiliary rib includes two circular ridges separated by a ring band that is flat and that can be conical in shape.
1. A tool for machining a wall of a workpiece, or a workpiece made from a composite material, configured to cut a furrow in the wall, the tool comprising:
a head securely mounted on a stem of a longitudinal axis that can be driven in rotation about the longitudinal axis, the head comprising
main projecting annular ribs including an outer surface is covered with abrasive grains of predetermined grain size and a radial height of the main projecting annular ribs corresponds to a depth of the furrow to be cut, and
at least a plurality of mutually parallel auxiliary projecting annular ribs that define grooves including an outer surface is covered with abrasive grains of predetermined grain size and a radial height of the auxiliary projecting annular ribs is less than the radial height of the main projecting annular ribs,
wherein the auxiliary projecting annular ribs comprise two circular edges separated by an annular band that is flat, a separation between the two circular edges of a single auxiliary rib increasing on approaching a longitudinal end of the head,
wherein the auxiliary projecting annular ribs form a frustoconical portion,
wherein the main projecting annular ribs are closer to a free longitudinal end of the head than the auxiliary projecting annular ribs,
wherein the frustoconical portion increases towards the free longitudinal end of the head, and
wherein the radial height of the two ribs closest to the free longitudinal end of the head is a maximum value of the radial heights of the ribs.
2. The machining tool as claimed in claim 1 , comprising between two and six mutually parallel main projecting annular ribs, which define grooves therebetween.
3. The machining tool as claimed in claim 2 , for cutting a furrow of a given pitch, wherein the main ribs are regularly spaced from one another, such that a pitch of the main ribs is equal to a pitch of the furrow.
4. The machining tool as claimed in claim 1 , wherein the radial height decreases regularly from a main projecting annular rib closest to the free longitudinal end of the head, such that radial ends of the auxiliary ribs and of an adjacent main rib are aligned along a straight line that is inclined with respect to the longitudinal axis and belongs to an axial plane passing through the longitudinal axis.
5. The machining tool as claimed in claim 4 , wherein the annular band is aligned with the straight line.
6. The machining tool as claimed in claim 4 , for cutting a furrow of a given pitch, wherein the main ribs and the auxiliary ribs are regularly spaced from one another, such that a pitch of the ribs is equal to a pitch of the furrow.
7. The machining tool as claimed in claim 4 , wherein the abrasive grains associated with a main annular rib have a grain size, or a grain size between 46 μm and 91 μm, which is smaller than the grain size of the abrasive grains associated with an auxiliary rib, or between 107 μm and 427 μm.
8. The machining tool as claimed in claim 1 , wherein the abrasive grains are made of diamond, natural or synthetic, or of cubic boron nitride.
9. The machining tool as claimed in claim 1 , wherein the head comprises at least one internal duct for supplying fluid which opens laterally via discharge openings.
10. A method for tapping a workpiece made from a composite material comprising at least one cylindrical hole, the method comprising:
providing the workpiece made from the composite material comprising the cylindrical hole;
providing a tool, the tool including a head securely mounted on a stem of a longitudinal axis that can be driven in rotation about the longitudinal axis, the head comprising main projecting annular ribs including an outer surface is covered with abrasive grains of predetermined grain size and a radial height of the main projecting annular ribs corresponds to a depth of a furrow to be cut, and at least a plurality of mutually parallel auxiliary projecting annular ribs that define grooves including an outer surface is covered with abrasive grains of predetermined grain size and a radial height of the auxiliary projecting annular ribs is less than the radial height of the main projecting annular ribs, wherein the auxiliary projecting annular ribs comprise two circular edges separated by an annular band that is flat, a separation between the two circular edges of a single auxiliary rib increasing on approaching a longitudinal end of the head, wherein the main projecting annular ribs is closer to an end of the head than the auxiliary projecting annular ribs, and wherein the head is tapered such that a diameter of the head increases towards the end of the head and the radial height of the two ribs closest to the end of the head is a maximum value of the radial heights of the ribs; and
tapping the hole of the workpiece using the tool to cut a furrow in the hole, the tool carrying out a helical interpolation by simultaneously moving circularly in a transverse plane orthogonal to an axis of the hole and moving in translation along an axis parallel to the axis of the hole,
wherein the auxiliary projecting annular ribs are inserted into the hole before the main projecting annular rib.
11. A tool for machining a wall of a workpiece, or a workpiece made from a composite material, configured to cut a furrow in the wall, the tool comprising:
a head securely mounted on a stem of a longitudinal axis that can be driven in rotation about the longitudinal axis, the head comprising
main projecting annular ribs including an outer surface is covered with abrasive grains of predetermined grain size and a radial height of the main projecting annular ribs corresponds to a depth of the furrow to be cut, and
a plurality of mutually parallel auxiliary projecting annular ribs that define grooves including an outer surface is covered with abrasive grains of predetermined grain size and a radial height of the auxiliary projecting annular ribs is less than the radial height of the main projecting annular ribs,
wherein the auxiliary projecting annular ribs comprise two circular edges separated by an annular band that is flat, a separation between the two circular edges of a single auxiliary rib increasing on approaching a longitudinal end of the head,
wherein the auxiliary projecting annular ribs form a frustoconical portion,
wherein the main projecting annular ribs are closer to a longitudinal end of the head opposite a free longitudinal end than the auxiliary projecting annular ribs,
wherein the frustoconical portion is tapered towards said free longitudinal end of the head,
wherein the radial height of the two ribs closest to said end of the head is a maximum value of the radial heights of the ribs, and
wherein a spacing between the main annular projecting ribs is regular and a width of each of the main projecting ribs is the same.
12. The machining tool as claimed in claim 11 , wherein the abrasive grains are made of diamond, natural or synthetic, or of cubic boron nitride.
13. The machining tool as claimed in claim 11 , wherein the head comprises at least one internal duct for supplying fluid which opens laterally via discharge openings.