10.13 Taper Turning
Micky R. Jennings
What is it?
Taper turning is the process of producing a taper on the workpiece. Tapers can come in many forms and can be cut with multiple different methods. Short tapers can be cut using the compound rest, where long, shallow tapers will need to be made with the tailstock offset method or the use of a taper attachment. Taper turning is generally performed with multiple roughing cuts and at least one finishing cut.
Tailstock offset method
The tailstock offset method is a way of moving the upper portion of the tailstock out of line with the center rotation of the lathe spindle. The body of the tailstock can be moved in and out independent of the base by loosening and tightening bolts on the front and back of the tailstock.
Step by step process for creating a taper using the tailstock offset method:
- Hold a part between centers. It helps if the center drills used are of the bell type. This is because the part will need to pivot slightly on the centers as it revolves. This is easier on the rounded portion of the bell center drill mark.
- Calculate the taper per inch of the feature to be machined.
- Apply that taper per inch to the entire length of the part. Half of this amount is approximately how much the tailstock should be offset.
- Use a magnetic base to apply a drop indicator to the side of the tailstock and adjust it by the amount calculated.
- Mount the work between centers.
- With the spindle static, run a drop indicator along a measured length and observe the taper per inch. This is only half the amount of taper that will exist when the part is cut because, when machining on a lathe, the material removed on one side of the part is also removed from the other side.
- Readjust and recheck until the taper per inch is correct.
- Now the part can be machined with a standard carriage turning operation, and because the part is held crooked to the centerline of the spindle, a taper will be created.
Taper attachment method
A taper attachment is a device that attaches to the back of a lathe and aids in making shallow tapers by automatically moving the cross slide while the carriage is feeding axially. It does this by disconnecting the nut that normally creates the movement for the cross slide and replaces it with a shoe that rides on a bar that is adjusted to a precise angle or taper per inch. Taper attachment types and the mounting method vary with each machine, for this reason, it is preferred to refer to the operator’s manual for proper setup and use.
Compound rest method
The compound rest method is the simplest and most versatile way to create a taper. An angle anywhere between 0 and 90 degrees can be created. A couple of the downsides of the compound method are that the length of taper is limited by the movement length of the compound rest, and there is no power feed option.
Step by step process for creating a taper using the compound rest:
- Chuck up the part that needs to have a taper.
- Calculate the tap