rhb
Aluminum
- Joined
- Apr 27, 2019
- Location
- A small town in central Arkansas
After lots of investigation and thought I think I'm ready to "grind" the spindle and thought it might prove useful to document the method and results here.
I've determined that I need to remove 0.00005-0.0001" from the rear journal and 0.00025 - 0.0003" from the front journal to bring them within the +0.0/-0.0002" ABEC 7 spindle tolerance.
Because of the extremely light cuts I've concluded that a tool post grinder is neither needed nor desirable. Instead I intend to hand work a small whetstone against the journals while the lathe is running much as one would a file. The rear journal will just get the medium Arkansas stone. The front will start with the corundum stone and finish with the Arkansas stone. Both stones have been lapped flat using silicon carbide paper on a surface plate. I plan to run at minimum speed and measure often. When the front journal gets to a tenth oversize I'll switch to the Arkansas stone.
The spindle is mounted on an MT 2 test arbor which has been wrapped with copper wire and placed in a 4 jaw independent chuck. It will be indicated to a tenth or less TIR. The chuck jaws look to be in excellent shape with no discernible wear.
I considered a number of other approaches and this seemed the most controllable. Maximum drag corresponds to being parallel to the existing surface.
Reg
I've determined that I need to remove 0.00005-0.0001" from the rear journal and 0.00025 - 0.0003" from the front journal to bring them within the +0.0/-0.0002" ABEC 7 spindle tolerance.
Because of the extremely light cuts I've concluded that a tool post grinder is neither needed nor desirable. Instead I intend to hand work a small whetstone against the journals while the lathe is running much as one would a file. The rear journal will just get the medium Arkansas stone. The front will start with the corundum stone and finish with the Arkansas stone. Both stones have been lapped flat using silicon carbide paper on a surface plate. I plan to run at minimum speed and measure often. When the front journal gets to a tenth oversize I'll switch to the Arkansas stone.
The spindle is mounted on an MT 2 test arbor which has been wrapped with copper wire and placed in a 4 jaw independent chuck. It will be indicated to a tenth or less TIR. The chuck jaws look to be in excellent shape with no discernible wear.
I considered a number of other approaches and this seemed the most controllable. Maximum drag corresponds to being parallel to the existing surface.
Reg