The upper wings attach to the cabane struts, and the lower wings attach to "L" shaped brackets on the sides of the fuselage. The 5/16" bolts run through the spars from top to bottom. You could drill these by hand, good luck. Fortunately I have a ShopSmith and it is perfect for drilling these holes using the Horizontal Drill Press.
As with the other bolt holes the first step is to get everything aligned and positioned. Drilling is the easy part.
The headstock rails are back down to their horizontal positon and the table is back in the normal, flat, position. I'm using the long drill bit again to align things. Use a back light to level the table to the drill bit. As you adjust the table "zero stop" you can look at the light coming through the gap under the drill to see when the table is aligned to the bit.
I discovered the center section of the table is slightly lower than the outer sections. We'll drill with the spar resting on the outer section.
Next square the fence to the the drill bit. It has adjustment screws, which is why I love the Shopsmith. Everything on it is adjustable.
I put in a 1/4" drill and used 1 1/8" of gauge blocks to position the stop for the end of the spar. My wife was a die maker. This gets the center of the hole 1 1/4" from the end of the spar. When the root rib is installed the hole will be 1 1/2" from the end of the wing.
Double check with the vernier.
The height of the table was set to 5/8" with a 1/2" gauge block under the 1/4" drill. Check with the center punch to see that the height is correct.
I drilled past 1/2 way from each side of my test piece.
A piece of threaded rod went right through the hole.
I'm going to drill all the way through with the long 5/16" drill bit. To make sure it starts out nicely centered on the 1/4" hole, I'm using a shorter bit for about 1/2". Then I finished the through hole with the long bit. There is a backing block to make sure I don't drill into the fence.
The last step is to open the hole a few thousandths with a "P" size bit ( 0.323" ). I use an "F" bit ( 0.257" ) on 1/4" holes, and a "V" bit ( 0.377" ) on 3/8" holes. The bolts fit easier and come out easier if needed some day.
A perfect hole. How cool is that?
Time to go drill the spars.
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