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AN3 Bolt hole sizing

Driving '67

Driving '67

Well Known Member
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Hi,

Not questioning the instructions from Vans, just curious about hole sizing for the bolts that attach the rudder on the RV14. The plans tell us to final drill the AN3 holes to #12 drill size (.1890") where the bolt will fit nicely into a 3/16" (.1875") reamed hole. What is the reasoning behind opening up the hole slightly that could introduce play/movement?

Thanks Jim
 
Hi Jim,
I noticed that too. I think they call for a #12 due to manufacturing tolerances on some bolts. However, if you have a 3/16 reamer I see no harm in trying that first, you can always upsize to a 12 if its too tight. In my experiences thus far, I have tried a 3/16 reamer and the bolts ended up being so tight that I was afraid of messing up the threads by forcing it, so I ultimately went with the #12 anyway...
 
An AN3 bolt is spec'd at 0.186 to 0.189 inches diam.

The #12 is specified to clear all bolts, smaller may work but becomes bolt dependent.

Also, drilling/reaming by hand may make your 3/16 hole (0.1875) a little larger anyway, letting a 0.189 bolt fit. :)
 
reaming is good

Anywhere you can, it seems using a reamer is a good idea. Reamers make beautiful, smooth, accurate, round holes. I have read very experienced builders on this forum recommend reaming bolt holes for anything structural. Seems wise.
 
Thanks for the replies. The two bolts I'm using fit nicely into the 3/16" reamed holes so I'll stay with current setup. Might treat myself to #12 reamer on my next tool order.

Cheers Jim
 
rv8ch said:
Anywhere you can, it seems using a reamer is a good idea. Reamers make beautiful, smooth, accurate, round holes. I have read very experienced builders on this forum recommend reaming bolt holes for anything structural. Seems wise.
Click to expand...

Reaming is good and if that's your preference go for it. However literally thousands of flying RVs were built with very little reaming at all. Your RV is not going to self destruct because you didn't ream bolt holes. On my own RV-10 I reamed exactly 2 holes because the plans called for it.
 
If you "want" precision by hand, just get in the habit of measuring the bolt that you're going to put in the hole and ream with a jig clamped in place (often requiring a few hours of machining and simple tool making). Just beware that the tolerances of the hardware is not lost on the original engineer that approved the process.

Build on.
 
Auburntsts said:
Reaming is good and if that's your preference go for it. However literally thousands of flying RVs were built with very little reaming at all. Your RV is not going to self destruct because you didn't ream bolt holes. On my own RV-10 I reamed exactly 2 holes because the plans called for it.
Click to expand...

My thoughts exactly. It's ok to follow the plans.
 
Most of the bolts used are relying on tension rather than shear to do the required job, so there is no need for a perfect fit. just be sure that they are tensioned correctly.
 
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