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The setup
for grooving or thread relieving is critical. Grooving
creates high cutting forces; therefore, maximum rigidity in
the setup must be maintained. The parting tool holder must
be kept as close to the tool post hold down screw as
possible and the parting blade must not stick out further
from the holder than is absolutely necessary. Parting tools
must also be set on centre and square to the work.
Maintaining centre height is crucial when grooving (Figure
When using a high-speed steel, pre-formed parting tool, the
back rake angle should be neutral. This will ensure that the
tool does not try to pull itself into the work, causing the
tool to over cut and snap off. Apply cutting oil to the
point of the parting tool. This will aid the cutting process
as well as keep the tool from binding in the groove. When
using a pre-formed parting blade, never grind on the sides
of the blade.
The RPM setting for grooving varies with the width of the
parting tool, but a good rule of thumb is 1/3 to 1/2 the
speed you would use for turning.
Procedure for cutting a groove:
- Layout or measure the groove location.
- Set the lathe to the proper R.P.M. setting.
- Mount the workpiece in the machine.
- Set the parting tool on
centre and square (remember: maintain maximum rigidity).
Locate the tool to the work. - Touch off on the diameter of the part.
- Set the cross-feed graduated collar to zero.
- Lock the carriage down using the carriage lock.
- Calculate how much the cross feed dial must travel to cut the groove to the proper depth.
- Slowly feed the tool bit into the work using the cross feed handle.
- Apply cutting fluid.
- Before cutting to depth, stop and check the depth of the groove.
- If a wider groove is needed, move the tool over and repeat operation
