Wing alignment pins^2h

The project for today was the wing alignment pins.

The manual says to use close tolerance bolts, however, the wisdom is to keep them until the moment wings are permanently attached to the airframe. Therefore, I made 16 pins (8 of 7/16" and 8 of 1/4") for alignment/assembly purposes.

I started with the blanks made from O-1 tool steel. The nice thing about O-1 is that you can buy it as drill rods which have a ground surface and also a tolerance of +-0.0005" (half a thousand of an inch). Perfect candidate for the pins.

Then I machined the pin in the lathe. I put a small taper on both sides (~4° degree) of all pins.

I did not use any lubricant while machining (to make cleanup easier). Even without coolant/lubricant, the surface finish on the taper was good enough. However, probably, because of that my insert did not last long.

And the final product.

Not sure if I really need all 16 pins, but I thought that I can use them for keeping everything in perfect alignment while assembling the fuselage.

The only oversight was that I made pins ~3-5/8" long, which is a bit on the short side. If my calculations are correct, the thickness of both sections plus the wing spars is 3-1/8" or about that. The untapered sections of some of the pins turned out to be shorter than that. I think this is still good enough as the center bars are pretty thick.

It worked well. I used a soft mallet to drive the pins and put all 16 of them in the aft section. I checked the holes in the center section bars, and they all look good: no scratches, nothing. Some pins are loose (they won't fall due to gravity, but very little force is required to move them). I can move all the pins with my hands, except for one tight hole.