As a follow up.
I did try the Bosch quick release set up that came with my Bosch 1617EVS kit, and which I mentioned that I already own, but thought it looked ill conceived, kludgy and klutzy. I have confirmed to myself that the Bosch OEM quick release bayonet mount holds the Bosch OEM template guide in a loose fitting sloppy manner. This system seems like a bad idea that was manufactured poorly.
I received the Jasper M 575B universal plate and installed it on both the RA 1166 plunge router base and RA 1161 fixed base that came with my Bosch 1617EVS kit. The mounting holes do line up with the respective bases, but not in a position that allows for proper concentric mounting of the Router Template Guide. The correlation between the mounting holes is "off" by a good margin which makes the base unsuitable for the task which I purchased it for. I was able to attach one mounting screw and rotate the plate so that the center hole was centered but then the other two mounting holes were not available for use.
I purchased a Bosch RA1151 Router Sub base Centering Device and found that after careful assembly the conical mandrel exhibited run out that was easily visible without the use of measuring indicators. The Bosch centering device does not help find the center, it just sort of looks like it does.
The Jasper plate came with an included aluminum mandrel, which promised "precision" in its description. It too exhibited run out that precluded its usefulness.
FWIW, I have been asking about using a guide bushing with a Plunge Base, because I would not use a guide bushing if I were not plunging. I would happily use a template bit with a bearing if I did not want to plunge. I have plunged with fixed bases enough times to know that I do not want to do so in some circumstances.
Making a custom base plate is beginning to seem like the only practical option. I wonder if the power tool factory bases are made with enough variance to cause makers of after market parts to provide precisely fitting components.
I have made base plates in the past, but had hoped to find a product that provided both precision and ease of use while working with guide bushings.
Last edited by Ben Dado; 09-06-2019 at 12:17 PM.