Another fixture is a base plate, to hold the engine frame during various steps. It is milled square, and drilled for a precise fit to the engine frame base. This assures alignment when re-positioning the frame. I used 1/2" thick Aluminum for the plate. Some of the extra holes are there from a previous project.
The compound was removed, and replaced with a sub-base for the fixture. The sub-base attaches using the bolts used for the compound. Here, the base plate is fastened to the sub-plate, and checked for alignment to the carriage, to assure that the cylinder will be bored straight relative to the frame..
A flycutter is used to square up the front of the cylinder, prior to boring. The magnetic-back dial indicator is used to determine an accurate depth of cut.
The frame, attached to the base plate, is tilted at 25 degrees, for milling the bearing faces. It was necessary to use an extra-long endmill to provide the clearance with the water hopper.
A 1.249 diameter test bar was inserted into the finished bore, and tested with an edge finder, to guarantee parallel, when milling the space between the bearing caps. The base plate was supposed to be parallel, using the fixed jaw of the vise. The test bar just provided an extra measure of caution.
