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Ralph Finch RV-9A Build
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Date: 6-22-2012
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Number of Hours: 4.00
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Manual Reference:
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Brief Description: Started making parts C-621 -622
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Started making the canopy release parts C-621 & C-622. A bit of a tricky business for me:
* steel 4130 alloy
* the two holes must be drilled parallel to each other, through the tube center, at a fairly precise distance from the end and from each other.
* notches must be cut in each end; the plane of the notch perpendicular to the holes, and each end has a different notch width
The holes I did on the drill press, first making sure the axis of the drill bit was perpendicular in two planes to the drill press bed (had to adjust the bed in one axis). Used my tube holder and a block of wood to clamp it, that helped a lot. Starting with a #40 bit, then #30, then #12 final size. Used lots of oil to avoid dulling the bits. I found once one hole was done and deburred, I could fit a brass tube though it to determine its axial direction, ensuring the 2nd hole would be in line.
The notches are a bit trickier. I started one on the band saw, but the cheap saw wouldn't continue in a straight line. So I moved to the vice. First cut with a rotary air cutter, then finished with a hand file to dress and emory paper and #400 sandpaper to finish. The cutter was a bit too big for the narrow notch (1/16") but acceptable; later I found using a hacksaw and enlarging by hand would be better.
For the wider (1/8") notch the file in a reciprocating air tool was good, followed again by hand finishing.
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