The two T-shaped links either side of the engine are the most prominent so I decided to tackle them first. There would be a considerable waste if they were cut from solid as that would need to be 16mm thick due to the central pivot, even if I added material to the pivot so that I could cut it from 8mm thick plate the tee shape meant there was going to be a lot of waste. So I decided to fabricate the basic T-shape that then add some additional material to thicken up the boss.
The first job was to square up some strips cut from 180 x 8 flat black bar and drill holes for locating dowels to keep the parts in position while they were silver soldered.
After a quick pickle I drilled some 3mm holes to use to hold the work down, only the one at the junction is going to be used , the others are in the waste material of the over-length pieces.
The much used machining plate was clamped to the table of the CNC and four matching holes drilled and tapped M3, actually I did six holes so the part could be flipped the other way round to machine the opposite side. This photo shows the arms screwed down and having had an adaptive cut to remove most of the waste material, leaving 0.3mm for the final cuts. 4mm 3-flute cutter used.
I then did a ‘scallop’ finishing path with a 4mm ball ended cutter stepping over 0.2mm per pass which gives an almost paint ready surface, just a bit of needle file work due to a small amount of Z-axis backlash where the cutter changes vertical direction.
After shaping both sides the smaller holes were drilled and tapped and the larger pivot hole reamed for a stepped extension piece.
Here it is in place after JBWelding on the boss extensions and giving it a shoe shine with strips of emery. The counter balance weight was made from two halves so the tapered internal slot could be milled before soldering together and given a final cut to bring them it size.
The links f the same except for being a different length so were all done as a batch. First some brass was milled down to overall size then drilled, reamed and slots cut as required.
These were then screwed to a waste block and the CNC used to reduce the central section in both width and thickness leaving the rounded and filleted junctions to the ends.
Part 1 here part 2 here part 3 here Part 4 here Part 5 Part 6 Part 7
