Help! > Machines, Tools and Fixtures
How would You Do it?
Jo:
Make yourself a D bit with a square end out of a bit of silver steel or HSS, then cut a slight Vee shape into the centre of the square end leaving an inner and outer cutting edges. If you want to be really posh you can slightly relieve the sides of the steel dowel and then you can cut the inner and outer rims as well. Heat treat as appropriate ::) You now have a nice tool for cutting the flat face.
I regrind old centre drills to make these ;)
Jo
PaulR:
--- Quote from: Jo on February 12, 2025, 02:19:54 PM ---Make yourself a D bit with a square end out of a bit of silver steel or HSS, then cut a slight Vee shape into the centre of the square end leaving an inner and outer cutting edges. If you want to be really posh you can slightly relieve the sides of the steel dowel and then you can cut the inner and outer rims as well. Heat treat as appropriate ::) You now have a nice tool for cutting the flat face.
Jo
--- End quote ---
Sorry, being thick, as per.... you mean a regular D-bit with a vertical notch on the semi-circular end?
PaulR:
Didn't know that was called trepanning (thought that was boring holes in skulls!). Just found this, which is what I was hinting at with a parting tool.
EDIT: Although I was thinking of moving it left and right as well :D
http://www.youtube.com/watch?v=6PcEBaset1I
Jasonb:
I usually do it much as you describe except I don't swap between left and right hand tools. I work out towards the hrimwith the lathe running in the usual direction and in towards the hub with the lathe running in reverse. Saves time and you feed in to the same handwheel depth to get a flat bottom. Careful if you have a screw on chuck when runing backwards.
If the topslide is angles a few degrees you can also mimic the draft angle of the cast looking flywheel you are trying to make.
A mill and rotary table or a CNC are other options if you have them.
Jo:
--- Quote from: PaulR on February 12, 2025, 03:05:49 PM ---
--- Quote from: Jo on February 12, 2025, 02:19:54 PM ---Make yourself a D bit with a square end out of a bit of silver steel or HSS, then cut a slight Vee shape into the centre of the square end leaving an inner and outer cutting edges. If you want to be really posh you can slightly relieve the sides of the steel dowel and then you can cut the inner and outer rims as well. Heat treat as appropriate ::) You now have a nice tool for cutting the flat face.
Jo
--- End quote ---
Sorry, being thick, as per.... you mean a regular D-bit with a vertical notch on the semi-circular end?
--- End quote ---
See attached.
On a D bit there is only one cutting edge, on these there are two. It is worth radiusing the cutting corners.
Jo
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