AN3 Bolt Hole Size ...

[Spike]

I just want a reality check here. An AN3 bolt is actually a 10-32 with required drill size of #12 correct?

-- John

[hngrflyr]

I like to get as close to a zero clearance fit as I can for structural bolt holes. Keep in mind that twist drills generally drill holes slightly oversize. The newer and sharper the drill, the more accurate the holes sizes are. As a practical matter, the size of bolt holes shouldn't make assembly difficult. Good hole alignment and deburring are neccessary for nice work.

Bob S

[captain_john]

Spike,

My Cleaveland chart shows a number 10 clearance hole for a number 10 screw. I seem to recall places on the plans where it tells you to shoot a number 12 for a number 10 screw. I know where you are, because I have been there. I just can't remember where I read it.

To answer your question, Yes.

I have drill bits sized 12, 11 and 10 for this job. I start with the 12 and if everything works well and fitup is good, I stay with it. I usually end up at 11 because the threads and shank fit through nice, but it doesn't bottom out because the head doesn't sit flush when you don't use a washer.

If that is the case, I match drill larger, one size at a time up to size 10 until fit up is good.

The clearance hole size isn't really critical to the strength of the joint. It is the torque of the fastener and HOW it is torqued that matters.

The pinch point between bearing surfaces is where the rubber meets the road.

REMEMBER, do not twist a bolt head or washer unless you have a bearing surface (washer) present. Van usually puts at least one on every bolt fastener callout.

Hope this helps!

CJ

[Spike]

I have drill bits sized 12, 11 and 10 for this job. I start with the 12 and if everything works well and fitup is good, I stay with it. I usually end up at 11 because the threads and shank fit through nice, but it doesn't bottom out because the head doesn't sit flush when you don't use a washer.

If that is the case, I match drill larger, one size at a time up to size 10 until fit up is good.

Why do you find that the be the case. What is preventing the head from sitting up on the bearing surface? Not a clean hole or is the shaft to bole head transition too tapered?

The clearance hole size isn't really critical to the strength of the joint. It is the torque of the fastener and HOW it is torqued that matters.

Hmmm, that just doesnt seem right to me at face value. If that were the case why does Van's use close tolerance bolts on the spars?

REMEMBER, do not twist a bolt head or washer unless you have a bearing surface (washer) present. Van usually puts at least one on every bolt fastener callout.

Hmmm, not sure what you meant by "dont twist" unless you have a washer present. Do you mean make sure the bolt doesnt twist while tightening the nut if you dont have a washer under the head?

[captain_john]

Yah...

The transition from shank to head is larger than number 12. IMO you will create a stress point if you honk on it with that size hole. I want bigger.

If you stick a number 10 drill bit into a 960 washer, it is like throwing a hot dog down a hallway. LOTSA wiggle room!

Close tolerance bolts are another issue. To be honest, I haven't really researched their application and cannot confidently answer any suspicions, assumptions or accusations.

These are not close tolerance fasteners.

Bearing surfaces are there to allow the bolt head or nut to glide on the surface, but not to bind it or gouge the surface of the structure.

Only tighten a fastener AGAINST a bearing surface! Try to keep the non washered side from twisting.

Torque should be measured on the gliding part and the fastener shall be dry, as in NON LUBRICATED and clean.

CJ

[Spike]

Got ya buddy. I think we are on the same page now. I just wasn't sure what you meant but "Dont twist." Two weeks dude!!! Two weeks!!


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[Snap]

hotdog down a hallway.......


you crack me up!!!!
thats is hilarious. I think I will use that.