Thread forming machine for bone material

A method of forming a bone screw from a bone dowel comprised of a bone material having a central axis, comprising the steps of:

• a) rotating a cutting member at a first rotational speed in a rotational plane that is angled with respect to a central axis to correspond to the angle of the screw threads;
• b) holding said bone dowel in a stationary linear position while rotating said bone dowel;
• c) cutting a thread at a first depth in the bone dowel by transporting the rotating cutting member axially with respect to the bone dowel by using the transporter for said cutting member to rotationally drive the bone dowel holder simultaneously rotating the bone dowel about its central axis at a rotational speed less than the first rotational speed;
• and
• d) cutting a thread at a second deeper depth in the bone dowel by transporting the rotating cutting member axially with respect to the bone dowel by using the transporter for said cutting member to rotationally drive the bone dowel holder simultaneously rotating the bone dowel about its central axis at a rotational speed less than the first rotational speed.

A thread forming machine for forming threads in a bone dowel comprised of bone material having a central axis to form a bone screw, comprising:

• a base assembly defining a planar surface and a camming surface;
• a bone dowel holding and rotating assembly mounted to said base for holding the bone dowel in an axial direction of the thread forming machine and rotating the bone dowel about a central axis;
• a guide assembly mounted on said base assembly;
• a support member moveably mounted on said guide assembly;
• an angle adjustment assembly mounted on the support member and moveably mounted for engagement with said camming surface of said base assembly;
• a cutting assembly mounted on the support member, said cutting assembly being provided with a cutting member for forming threads in the bone dowel, said support member being movably mounted on said guide assembly so that said guide assembly can move said support member in an axial direction moving the cutting member in the axial direction with respect to the bone dowel, said angle adjustment assembly moving the support member to determine the radial distance of the cutting member from the central axis of the bone dowel;
• and
• a timing assembly connected to the guide assembly and the bone dowel holding and rotating assembly so that when the guide assembly moves the cutting assembly in the axial direction, the holding and rotating assembly rotates the bone dowel at a speed that is directly proportional to the axial displacement of the cutting assembly.

A thread forming machine for forming threads in a cylindrical bone dowel made of bone material, comprising:

• a planar surfaced base;
• a threaded guide member having an externally threaded portion, a first end and a second end rotatably mounted on said base so that the threaded guide structure extends in the axial direction;
• a holding and rotating assembly mounted on said base rotatably holding the bone dowel so that the central axis thereof extends in the axial direction;
• a planar support member mounted on said guide member for movement with respect to said base;
• an angle adjustment assembly mounted to said support member;
• a cutting assembly having a cutting member in the form of a burr mounted on the support member;
• means to rotate said threaded guide member, said support member being mounted so that when the threaded guide member is rotated the cutting member carried by said support member moves in an axial direction;
• and
• a timing assembly connected to the threaded guide member and the holding and rotating assembly so that when the cutting member moves in an axial direction the holding and rotating assembly moves the bone dowel angularly.

A thread forming machine for forming threads in a bone dowel comprised of bone material having a central axis to form a bone screw, comprising:

• a base defining a planar surface;
• a bone dowel holding and rotating assembly mounted to said base for holding the bone dowel in an axial direction of the thread forming machine and rotating the bone dowel about a central axis;
• a guide assembly mounted on said base;
• a support member moveably mounted on said guide assembly;
• an angle adjustment assembly mounted on the support member and engaging said base;
• a cutting assembly mounted on the support member, said cutting assembly being provided with a burr cutting member for forming threads in the bone dowel, said support member being movably mounted on said guide assembly so that said guide assembly can move said support member in an axial direction moving the burr cutting member in the axial direction with respect to the bone dowel, said angle adjustment assembly moving the support member to determine the radial distance of the burr cutting member from the central axis of the bone dowel;
• and
• a timing assembly connected to the guide assembly and the bone dowel holding and rotating assembly so that when the guide assembly moves the cutting assembly in the axial direction, the holding and rotating assembly rotates the bone dowel at a speed that is directly proportional to the axial displacement of the cutting assembly.