?How to cut spherical wedge for lathe tool post lantern?

I ordered one from J&L, but the Armstrong 89-441
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the right width for my .56" slot, but is too short for the 3"
diameter dish it sits in.
So I made one yesterday with a radius of ~ 2.85" and a height of ~ .75".
I hack sawed out a 3" x 1.5" x 1" piece of steel from a length of
1.5x1.5 steel.
Then I drilled holes in it, mounted it on a rotary table on the vertical
mill and cut the radius.
It works, but now I realize, the dish is sits in is spherical.
I can't even imagine how I could have done it right.
Reply to
Clark Magnuson
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The rocker to sit in the bottom of the spherical washer could be made by a) turning a convex surface on the end of a piece of bar stock, with the correct radius to match the washer.
Then mill the sides to leave a rectangular portion at the end, the width that you want the rocker to be. Then either saw, mill, or part off in the lathe to remove from the end of the bar stock.
When I made one of those, I just did it by hand, offhand grinding to get the lower surface close to the correct radius. That was for a small AA products lathe lantern toolpost.
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Reply to
jim rozen
That's exactly what I'd recommend for the home shop type. Once you've established the proper radius in one plane, you radius the rocker side to side by hand. A belt sander does a great job on such things. You cut a thin template with a divider to gage your progress, and work to a centerline scribed on the rocker. Working carefully, you can achieve good results, and it's a good learning experience.
If you have a radius cutter, or a tracer, it could be done on a lathe fairly easily. You have to duplicate the sphere of the rocker base. Needless to say, a CNC would handle it in stride.
Reply to
Harold & Susan Vordos
The rocker on my dad's SB 9" is just a segment of a cylinder, works just fine. I've made them by just bandsawing out a chord segment out of a suitably-sized disk turned on the lathe. I think if you made it a segment of a sphere, you'd get more rocking than you'd want, sideways. Hey, if it works, don't sweat the details. Have you tried it out yet? My homemade block-type toolholder is more rigid, but the lantern post gets a workout now and then on some odd jobs where the block just won't work.
Reply to
Stan Schaefer
I haven't made one of these, but if I needed to, I think I'd try to cut a convex disk that matches the washer with a ball turning attachment, then cut the bar out of the middle of the disk. I suppose a double radius could be cut with a ball turning attachment, in a piece of bar stock securely attached to a faceplate, but the interrupted cut could provide less than desireable results in the final finish.
WB ................
atheists that will destroy the society. It is Darwinian.
Reply to
Wild Bill
I realize now, that if instead of mounting to my big rotary table, if I mounted to a small rotary table and mounted the small rotary table to the large rotary table face plate, I could do it properly.
Reply to
Clark Magnuson

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