The International Cessna^® 170 Association

"A double flare is used on soft aluminum tubing 3/8-inch outside diameter and under, and a single flare on all other tubing." AC43-13.1B, Para. 9-30, B.

Let's not forget we are trying to contain all of about 30 psi at the most. A double flare seems to me to be serious overkill.

Conical seals, AS4824C02, might be a solution if your flared end has a leak. An easier solution would be to heat the flared end of the copper tube until it is glowing red and then immerse it in water to anneal it.

n2582d wrote:"A double flare is used on soft aluminum tubing 3/8-inch outside diameter and under, and a single flare on all other tubing." AC43-13.1B, Para. 9-30, B.

Let's not forget we are trying to contain all of about 30 psi at the most. A double flare seems to me to be serious overkill.

Conical seals, AS4824C02, might be a solution if your flared end has a leak. An easier solution would be to heat the flared end of the copper tube until it is glowing red and then immerse it in water to anneal it.

Thanks Gary. I was assuming that the tubing was cracked but if not annealing may work.

I had a '55 for a while and I replumbed the primer system to both manifolds AND all six cylinders. I did not double flare any of the 1/8th inch copper tubes.
My double flaring tool will not work on double flaring 1/8th inch tubing. There were no leaks.

lowNslow wrote:

gahorn wrote:1/8" copper line must be "double-flared" in order to properly seal.

George, are you sure about this? I have never seen a flaring tool that will double flare 1/8" tubing for AN fittings.

Revisiting this thread I realized I never answered this question.... Here's a 1/8" double flaring tool:
http://imperial-tools.com/products/flaring-tools

George,
As you (but many 170 owners don't) know 45 degree flares, the kind made by the Imperial double-flare tool you linked to, is for automotive applications. AN fittings use 37 degree flares. A moot point perhaps? On my '52 170b the primer lines are all single flare.

It's not a moot point...it's an important one. Yes, aircraft use 37-degree flares....and one reason the double flare is so useful is that it's forgiving of such minor diffs.
My post was primarily to point out that double flare tools are available in 1/8" sizes.