Methods for threading sinterable materials and related apparatus and systems

A method for manufacturing a spinal implant, the method comprising the steps of:

• selecting a mold having a sufficient size larger than a desired size of a spinal implant so as to account for an expected shrink rate and further to account for an expected layer of cracking during a subsequent tapping process;
• inserting a silicon nitride ceramic powder into the selected mold;
• compressing the silicon nitride ceramic powder into a spinal implant block;
• determining an expected shrink rate of the spinal implant block upon undergoing a firing process;
• applying a scaling factor using the expected rate of shrinkage to select a tap having a size larger than a desired thread size, wherein the scaling factor is selected such that the selected tap has a size that is between about 19% and about 20% larger than the desired thread size;
• tapping the spinal implant block with the selected tap to form a threaded opening in the spinal implant block, whereby cracks are formed in the spinal implant block from the tapping process;
• identifying a thickness of a layer of material in at least one surface of the spinal implant block in which at least substantially all of the cracks formed during the step of tapping the spinal implant block are present;
• removing the layer of material having the thickness so as to remove at least substantially all of the cracks formed during the step of tapping the spinal implant block;
• and
• firing the spinal implant block after the step of removing the layer of material and after the step of tapping the spinal implant block, wherein the firing reduces a size of the spinal implant block and reduces a size of the threaded opening.

A method for threading a sinterable material, the method comprising the steps of:

• inserting a powder into a mold;
• forming the powder into a green block;
• determining an expected rate of shrinkage of the green block upon undergoing a firing process;
• applying a scaling factor using the expected rate of shrinkage to select a tap having a size larger than a desired size of a threaded opening in the green block after firing;
• tapping the green block with the selected tap to form a threaded opening in the green block;
• identifying a thickness of a layer of material in at least one surface of the green block, the layer comprising at least substantially all cracks formed during the step of tapping the green block;
• removing the layer of material having the thickness so as to remove at least substantially all of the cracks formed during the step of tapping the green block;
• and
• firing the green block to form a finished block.

A method for threading a ceramic material, the method comprising the steps of:

• inserting a ceramic powder into a mold;
• compressing the ceramic powder into a block comprising a spinal implant;
• determining an expected rate of shrinkage of the block upon undergoing a firing process;
• applying a scaling factor using the expected rate of shrinkage to select a tap having a size larger than a desired thread size;
• tapping the block with the selected tap to form a threaded opening in the block such that the threaded opening extends to a hollow interior of the spinal implant;
• machining the block by removing material from the block comprising cracks formed during the step of tapping the block;
• firing the block, wherein the firing reduces a size of the block and reduces a size of the threaded opening, and wherein the step of tapping the block is performed before the step of firing the block;
• and
• removing material adjacent to the threaded opening within the hollow interior prior to the step of firing the block.