18-02 step 2 : Pivot Brackets

[Gagarin737]

I'm making the four A-1206 Pivot Brackets. After drilling 11/32 and tapping with 3/8 x 24 in the part that was left over I found that there was some play after inserting a rod end bearing. After trying it with a 21/64 drill and tapping the fit was much better.
Can someone confirm that there is some play after inserting the rod end bearing?

 

[Mich48041]

I used the 21/64" drill

Drill size Q is the correct size to use according to a tap chart. 11/32" is 0.0117" too big and 21/64" is 0.0039" too small. I used the 21/64" drill bit because that is what my plans said to use. Van's changed the plans to Q or 11/32" in a revision. The tap should not be forced in aluminum because the threads can be stripped out, especially the first few threads. A friend of mine thought that he was tapping a hole. But when he took the tap out, the hole was smooth as if he had drilled it. He had to order new parts.
Joe

 

[Gagarin737]

Thanks for the info!
Which drillsize used your friend?
Tap goes in smooth even with the 21/64.

Joeri.

 

[Tony_T]

Is re-engineering allowed?

I usually cross check the tap drill size with a chart just because and wondered about this 11/32 size also. Thought it might have something to do with the fact that aluminum was the material and not steel. Joe confirms that.
I agree that the 21/64 hole gives a tighter fit, but I drilled 11/32 because that was on my plans...and we are not allowed to change the engineering on this plane.

Tony

 

[Gagarin737]

Good inspector who will see the difference
Thanks for the input Tony.
The pivot and actuation brackets are more work than expected (without a bandsaw).

 

[John 312]

Need to cross check some of the numbers

I usually cross check machining operations with Machinery's Handbook, especially when there is a conflict in the directions. The AEX Tie Down drill and tap on page 13-02 is a similar case, where step 5 is drill and tap 19/64" holes per Fig 4, and then Fig 4 tells you to drill a 5/16" hole for a 3/8-16 tap. The hole size limit for a 3/8-16 thread x 1" deep is suppose to be .318-.325, which is in the 'O' drill size range. The 5/16" drill size (.3125) is considered a undersized hole which will make tapping the hole harder, and the 19/64" hole (.2969) would be even worse. While I did the A-1206 both ways (21/64" and Q), and yes I did build 8 of them, I figured I only get one shot at the brackets on the Spar and they better be right the first time.

I am not sure how much leeway is allowed between the directions and E-LSA compliance, but I have found a few minor problems with the instructions and proceeded with the logical fix anyway (page 16-02, step 1 to drill #31 holes and machine countersink. Problem is the #30 countersink pilot will not fit a #31 hole, and a #31 drill bit is not listed in the tool list, but I have one in my drill index. Solution, drill a #30 hole and machine countersink.)

 

[Gagarin737]

Van's changed the #31 drill to #30 in revision 2 while the MS24693S10 is not as wide. If I could do it over I would do it with the #31 drill. Countersinking can be done with a countersink tool, the heads of the screws are quite small.
Thanks for the input!

 

[Gagarin737]

18-02 step 1

18-02 step 1 wants you to make a 3/16 hole in the bracket. I don't have a 3/16 drill (not in the tool list). #12 o.k? (Time for the U.S. to go metric )