Some good questions have been raised about alignment/parallelism of other surfaces/components, mostly associated with the various surfaces on the saddle, and how that affects the function/operation of the tapered gibs.  One of those questions is the parallelism between the inverted V-way and the "L" bracket mounting surface.  This would pertain to both the front and rear ways, although determining that parallelism is much easier for the rear way.

Checking It Out

I attempted to determine the parallelism between the saddle V-groove and the "L" bracket mounting surface, for the front way.  At the same time, due to my setup, I was able to examine the same for the rear way.

I started with a 1/2" reamer blank clamped to the V-groove.  I reasoned the V-groove is the primary reference surface.  It is what I used for determining parallelism for the bedways, and it just makes sense to me.  By clamping the reamer blank into the V-groove, and then inverting the saddle and resting the reamer blank ends on a set of V-blocks on a surface plate,  the various flat surfaces in question could be examined.  This did require some further setup.

I verified that the reamer blank was parallel to the surface plate, at the middle and at both ends.  Then I used a Master Precion Level to level the saddle to the same level readings as obtained directly on the surface plate (my surface plate has not been perfectly leveled).  To do this it was necessary for me to use an adjustable parallel on the back side of the saddle.

What I found was comforting and puzzling.  I found that the outer areas of both the front and rear "L" mounting bracket flats were very close to what they should be, very close to zero.  However, the middle of both the front and rear flats were 2-3 thousandths HIGHER than the outer areas.  This was also true of the rear flat that the saddle rides on, on the rear flat way.

At this point, I'm not sure what difference this makes, if any.  It feels like these discrepancies are something that should be corrected.  But, it also feels like the tapered gib conversion is a major jump from some undefined level to somewhere near the 90% level and improvements beyond that begin to lose their relative/marginal value, especially given the machine and what I may do with it. It remains an open question.  Perhaps some answeres will come from using the lathe with the tapered gib conversion and seeing if anything more is needed.