- Joined
- Aug 13, 2020
- Messages
- 1,342
I've got a Jen-u-wine Bridgeport rotary table. It has a smoothly ground, 1.000" hole in the center that I figure I could put to good use. I turned a dowel that is a tight sliding fit into the hole, and about .75" on the other end to fit an ER-32. Took me a good three hours and as many attempts to get that one together, but I turned it as one piece to guarantee concentricity.
Set it up on the mill. Indicated the body of the R8 collet adapter, and the needle didn't move. Indicated the inside, and still perfect. Put the dowel in, and get 7 thou runout. Replace the bearing nut with a plain one, and the runout drops to half a thou. Good 'nuff.
Drop the dowel into the rotary table center hole, jiggle the table a bit, and snug the nuts up. Now, you'd think that would be the end of it. But, I can't leave well enough alone. Put the indicator on the table, indicate off the collet body (that I just verified had no measurable runout), and spun the table with the crank. The needle went around the world. Made a full sweep of the dial. At least 30 thou runout.
I spent the next hour getting the table situated so that there is about half a thou runout, with a plan to true up the center hole by dropping a boring bar through it, followed by a grinding stone. I figured I could touch the side and spin the table till it was all clean.
Then I thought to myself, "Self, you're fixin' to destroy this heavy piece of American iron. Go ask those guys on HM if this is a good idea." Self, is a purty smart fellar at times, so here I am. Is this a good plan? Or should a rotary table have some sort of adjustment for concentricity?
Set it up on the mill. Indicated the body of the R8 collet adapter, and the needle didn't move. Indicated the inside, and still perfect. Put the dowel in, and get 7 thou runout. Replace the bearing nut with a plain one, and the runout drops to half a thou. Good 'nuff.
Drop the dowel into the rotary table center hole, jiggle the table a bit, and snug the nuts up. Now, you'd think that would be the end of it. But, I can't leave well enough alone. Put the indicator on the table, indicate off the collet body (that I just verified had no measurable runout), and spun the table with the crank. The needle went around the world. Made a full sweep of the dial. At least 30 thou runout.
I spent the next hour getting the table situated so that there is about half a thou runout, with a plan to true up the center hole by dropping a boring bar through it, followed by a grinding stone. I figured I could touch the side and spin the table till it was all clean.
Then I thought to myself, "Self, you're fixin' to destroy this heavy piece of American iron. Go ask those guys on HM if this is a good idea." Self, is a purty smart fellar at times, so here I am. Is this a good plan? Or should a rotary table have some sort of adjustment for concentricity?