OK, the backyard deck is done so the turret project can resume.
First Pic... The block from earlier was carefully setup in the chuck. It's mounted with a 3/8" offset because I want a slight lip to overhang the plate. The block was set perfectly flat and checked ad-infinitum with a TDI lengthwise on all four sides. After that a hole was bored down the middle. In the photo, a travel indicator is setup at the left of the carriage and a TDI riding on the compound. We're setting up the angle for MT 3 taper which is 1.4377[SUP]o[/SUP]. I'm checking by running the carriage 1/2" (as measured by the travel indicator) and watching the deflection on the TDI. 1/2 x TAN 1.4377 is 0.0125" so, the compound angle is adjusted until the deflection reads that amount. This is a basic
Rise-over-
Run Tangent slope calculation... How much the needle
rises when the carriage is
run 1/2". I could have used 1" as the amount of travel but, the Tangent of 1.4377 is 0.025" and the TDI doesn't read that high so, 1/2" was used instead.
After a few adjustments, it was reading dead on. Not shown is the use of a boring bar to start making the taper. I'm just using the compound crank to move the bit in and out. A taper attachment would be a better choice but, it hasn't arrived yet. At the wide part of the taper, the diameter will ultimately be around .98" (around there, can't remember at the moment). For now, I just opened up the hole enough to see how things were looking.
Next pic: I purchased a store-bought MT3 reamer set (I hope to make these in the future for other taper angles) and here, it's inserted in the hole with a little pressure from the TS ram and twisted a few times. This is just a spot check to see if the compound setup agrees with the store-bought taper cutter. BTW, the taper set has both a rough cut (shown) and fine-cut tool.
Third pic: Here you can see things are well in agreement. The reamer is shaving evenly on the inside of the hole. I'll go back to widening the hole with compound cuts to the desired diameter then, I'll clean-up the hole with the rough reamer. After that, the block will need a little milling and holes drilled/tapped -and then a heat treat to about 30 RC. BTW: The block is 4140 so it should harden nicely. Once it's treated, I'll need to touch-up the taper with the fine cut reamer.
Ray