|1210 $20.10 Radius Turner mounted to the cross slide.
Here's a pretty good way to set it up.
|Chuck a dowel pin or other round rod so that it sticks out at least 1.5" so the tool can swing without whacking into the chuck.|
|Make sure the center of rotation is slightly to the rear of the lathe centerline and move the tool holder so the tool tip touches the rod and tighten the tool holder.|
|Move the carriage back.|
|Swing the tool around.|
|See there is a gap between the rod and the tool tip.|
|Measure that with a feeler gage.|
|In this case it was .036"|
|Move the cross slide in half that gap, in this case .018"
You can use this same method to determine the center line and offset it for radii not on center.
|Note that the tool now has the same clearance on either side. Do not touch the cross slide dial from this point on.|
|Chuck the workpiece. Bring the tool against the face of the work. Set a carriage stop so you don't go much past the face.|
|Move the carriage back a bit.|
|Swing the tool to take repeated cuts, moving the carriage in a bit each time, closer to the face of the work.
Do not go past perpendicular with the work.
|The radius looks ok but there's a flat spot in the center.|
|See the flat spot?|
|Forgot to shim the tool. You won't.|
|A final cut with the tool tip on center.|
|Looks pretty good. You aren't going to get perfect radii to .001" with this tool.|
|Once the hemisphere is formed you can do a bit of a back cut, if you do this before you are finished cutting the front you won't get a full round. Notice the 1210 fouls against the chuck. You can't form that much of a ball past a hemisphere, unless the work is really sticking out. This of course means chatter, etc.|
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