slowtwitch73
Well-known member
Saw this today.. pretty cool.
Mute it and skip towards end to see it in action.
Mute it and skip towards end to see it in action.
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Polygon maker/cutter for lathe video
- Thread starter slowtwitch73
- Start date
mark-NJ
Well-known member
Crazy mad skills! I can't begin to wrap my head around it!
OP
slowtwitch73
Well-known member
I guess it's a function of spindle rpm, feed rpm, and 3 cutters placed at a certain geometry. Might only work at certain speeds/feeds?
American Locomotive
Well-known member
The industry term for this is called "polygon turning".
The cutter has to spin at a ratio compared to the main spindle, and the ratio is determined by how many flats you want on the part, and how many teeth your cutter has. For example, a 3 tooth cutter will need to spin at a 1:2 ratio (so twice as fast) relative to the main spindle to achieve 6 flats. If you cranked that up to a 1:3 ratio, you'd get 9 flats on the finished parts. Basically Number of Flats = (Number of Teeth * Speed Multiplier).
Polygon turning is super cool, and it's a very fast way to crank out parts with hex or square (or any polygon shape really) features using lathes. It's used very often in the high production world.
However it's not perfect. The flats are not perfectly flat, and actually have a radius (or rather an ellipse) shape to them. So if you put a straightedge up to it, you'd see they're slightly dished. IIRC, the error gets worse the less flats you have, and the smaller diameter your cutter is. For most applications, the error isn't a problem. Although I suspect in this guy's case, his universal joints are probably adding some additional error. Likely not a big deal if you just want the flats to put a wrench on it.
The cutter has to spin at a ratio compared to the main spindle, and the ratio is determined by how many flats you want on the part, and how many teeth your cutter has. For example, a 3 tooth cutter will need to spin at a 1:2 ratio (so twice as fast) relative to the main spindle to achieve 6 flats. If you cranked that up to a 1:3 ratio, you'd get 9 flats on the finished parts. Basically Number of Flats = (Number of Teeth * Speed Multiplier).
Polygon turning is super cool, and it's a very fast way to crank out parts with hex or square (or any polygon shape really) features using lathes. It's used very often in the high production world.
However it's not perfect. The flats are not perfectly flat, and actually have a radius (or rather an ellipse) shape to them. So if you put a straightedge up to it, you'd see they're slightly dished. IIRC, the error gets worse the less flats you have, and the smaller diameter your cutter is. For most applications, the error isn't a problem. Although I suspect in this guy's case, his universal joints are probably adding some additional error. Likely not a big deal if you just want the flats to put a wrench on it.
and he didn't put seals on those taper bearings. seems like a lot of work to miss a step like that
RoninB4
Well-known member
The basic process of this is how ball-end hex keys are/were made most of the time now. I worked for Eklind Tool as a die maker that spearheaded the ball driver project. I believe Eklind was the first to use this process in 1995, others soon followed. Prior to this, Bondhus was using an opposed broach method that indexed 3 times for the hex. The new process cut cycle times to about 10 seconds with no re-sharpening of the expensive form broach. Cutter rotation has to be synchronize with the headstock spindle for the desired shape. I stumbled upon this same process turning off the spindle of a BP using a fly cutter while still cranking the rotary table. Wasn't smart enough to figure out how to apply it.
rattle_snake
Well-known member
just synchronous movement of tool and workpiece....
Impressive.
Impressive.