Safetying flop tube fitting

[sblack]

The -4 plans, and I suppose the other models as well, say to safety wire the B-nut of the fuel tank flop tube hose fitting to the bulkhead fitting that it attaches to. It shows that the nut is drilled on one corner for safety wire. Mine isn't. I doubt I have much chance of successfully drilling into a piece of aluminum at a 60 deg angle, not to mention the risk of going through fitting and coming out in the threads on the inside. Any suggestions?

[1001001]

Originally Posted by sblack

The -4 plans, and I suppose the other models as well, say to safety wire the B-nut of the fuel tank flop tube hose fitting to the bulkhead fitting that it attaches to. It shows that the nut is drilled on one corner for safety wire. Mine isn't. I doubt I have much chance of successfully drilling into a piece of aluminum at a 60 deg angle, not to mention the risk of going through fitting and coming out in the threads on the inside. Any suggestions?

If you need to drill a small part at an angle to the surface, you can use an end mill in your drill press to mill a flat at the angle needed. Then center punch, center drill, and then drill with your normal drill bit. Just make sure the part is clamped well and held at the proper angle.

Not sure this would work for the nut you're describing, but if I couldn't buy a nut with the required hole, this is how I'd consider doing it.

[sblack]

Originally Posted by 1001001

If you need to drill a small part at an angle to the surface, you can use an end mill in your drill press to mill a flat at the angle needed. Then center punch, center drill, and then drill with your normal drill bit. Just make sure the part is clamped well and held at the proper angle.

Not sure this would work for the nut you're describing, but if I couldn't buy a nut with the required hole, this is how I'd consider doing it.

The difficulty I see is that we are talking about a .040 hole so that whould be a pretty tiny flat. I suppose one could make a jif, like they have for drilling bolts, but I was all set to close the tank today and did not see this snag coming. I don't have the necessary equipment at the hangar to deal with this.

Does anyone know if these hose fittings are available drilled? It's always something...

[krw5927]

Originally Posted by sblack

The difficulty I see is that we are talking about a .040 hole so that whould be a pretty tiny flat. I suppose one could make a jif, like they have for drilling bolts, but I was all set to close the tank today and did not see this snag coming. I don't have the necessary equipment at the hangar to deal with this.

Sure you do. You take your smallest drill bit that is slightly larger than safety wire (.040 sounds great, though I think I used a 1/16" bit) and chuck it in a nice slow-turning battery powered hand drill. Clamp the fuel fitting nut in a vise, center punch where you want the hole to start, and begin drilling perpendicular to the surface. As soon as the drill bit is deep enough that it won't walk away on you, start increasing the angle (only while drilling). You'll see that before you get very deep at all you will be at the proper angle.

You're right that if you go too deep you will need to buy a new nut. But I did two of these successfully on the first try using this method. Go slowly with both drill speed and pressure, and chances are you'll be fine.

If you want to go the expensive route, you can buy a tool that will help you with this: http://store.wagaero.com/product_inf...oducts_id=1482

But really, try it first. The worst thing you do is ruin a $1 AN818 nut.

[RVTrumpet]

Originally Posted by krw5927

Sure you do. You take your smallest drill bit that is slightly larger than safety wire (.040 sounds great, though I think I used a 1/16" bit) and chuck it in a nice slow-turning battery powered hand drill. Clamp the fuel fitting nut in a vise, center punch where you want the hole to start, and begin drilling perpendicular to the surface. As soon as the drill bit is deep enough that it won't walk away on you, start increasing the angle (only while drilling). You'll see that before you get very deep at all you will be at the proper angle.

That works very well. Be prepared to potentially go through a few bits.

[Dean Pichon]

I drilled the nut on my -4. I started by making a small flat with an end mill and then drilled thru. The tricky part was safety wiring thru the access port

[wirejock]

Probably not the best idea but maybe buy a new flop tube. Mine was drilled.

[greghughespdx]

What Kurt said worked for me. Start perpendicular to the surface, work the angle as you increase depth and be willing to sacrifice a bit or two in the process. Be patient. It works.

[N941WR]

Originally Posted by krw5927

...
If you want to go the expensive route, you can buy a tool that will help you with this: http://store.wagaero.com/product_inf...oducts_id=1482
...

This worked for me. Check with your EAA chapter, someone might have one that you can use.