This is a really cool idea! I'm still wrapping my mind around this. I am still contemplating how to calibrate it. That is, find the exact pivot point, in order to make the tool accurate.
The smaller scale, z axis, parallel to the length of the tool, I take it you set that in the center for no radius, closer to the wheel for convex radii and away from the wheel for concave.
I too want to make very accurate half round nose or quarter round nose lathe tools.
Thanks for sharing this.
Yeah, it can definitely be confusing.
I had a hard time with it myself until I modeled it in Fusion 360 with slider and pivot joints.
The main purpose of the new pivot locating tool was to extend the pivot point of the knuckle up to the work head so I could set the radius point of the work piece without having to guess at it.
Now, the easiest way for me to use it is to picture everything as if it were on a flat plane from above to set the radius I want, then worry about the relief angles afterwards.
The main thing I have to remember is that the center point of the radius I want on the work piece "HAS" to be located directly above the pivot point of the knuckle under the work head.
I also have to remember that the radius point of a concave shape is located in the cutaway part of my work piece while the radius point of a convex shape is located in the part not being cutaway. That's the way I think of it anyway, maybe it will work for you too?
If it's a concave shape, the radius point and pivot point will be under the edge of the grinding wheel profile while the radius point and pivot point will be away from the edge of the grinding wheel profile for convex shapes.
The easiest way I know of to find the exact pivot point on the knuckle is to use a test indicator with a pointer type stylus mounted on a mag base and mounted to the table in front of the grinder, make sure the pointer is almost touching the knuckle near what appears to be the center point, then rotate the knuckle left and right while continuously moving the pointer until it is stationary on a single point on the casting of the knuckle while it is being rotated. I used that point as the datum for transferring measurements to the work head via gauge blocks.
After I made the tool, I used the test indicator again but this time on the tool to make sure the pivot point was on the inner corner of the block, then I done the "0" mark and other graduation marks. I hope that makes sense.
I hope this helps!
Joe
