4th axis taper

[hmatyas@wi.rr.com]

I can't figure out what is wrong.
I tried "turning a cylinder that is 2 inches in diameter. What I got was a piece of wood 8 inches long that went from 1.9 inches to 2.18 inches.
I have a Shark HD 3. My lathe front radius is 1.723 and the tailstock radius is .25 inches.
In Vcarve I turned a 2 inch cylinder, from zero to 8 inches here are the dimensions.
1 inches 2 inches 3 inches 4 inches 5 inches 6 inches 7 inches 8 inches
1.9 1.95 1.97 2.01 2.06 2.09 2.14 2.18

I have set my zero first on the top of my front chuck and then moved it down to the tail stock, where I zeroed the
machine on top of the tail stock. I wonder, if I should zero it off of the tail stock 1/2 inch pin.

When I checked z zero, it looked like it was in the correct place for both the head stock and tail stock.
However, zero at the head stock was at zero but z at the tail stock was .2XX (I did not write it down).

Thanks for any suggestions.

[hmatyas@wi.rr.com]

I found one mistake. I had the front radius at 1.725 not 1.75 inches. I still have a small taper about .04 inches over a 8 inch length.

[Rando]

hmatyas:

Sorry nobody's responding to your query. I don't have any 4th axis equipment, so I'd only be guessing.

Just didn't want you to think we're all just ignoring you....though I guess technically we are

To me, it sounds like either the gantry isn't really parallel to the bed (bed misaligned?), or one of
the 4th axis parts isn't "on" the bed. Though 0.040" is a lot for "stuff" to be under one or the other,
ends, but only you can tell what's going on.

Hope you figure it out!

Rando