Flare tools and sizes

[COKE]

Hello,
i,m installing an extra tranny oil cooler on my truck,and i using 5/16"  tube and flare fittings but i,m havin leaking troubles.
I have a flare tool with dies for the tube,but i don,t know if it is correct for the flares i,m using(Car radiator and adapters)

I have read around there that the cars flares such as the brake and tranny lines do need 37 deegrees tools and these do not use dies .
So i,m thinkig maybe  the one i own due it has dies is a 45 deegrees tool .
Could be this the trouble?

Other question,
How  do work the -AN sizes?
I,m watching a lot of adapters,but i really do not what it is.

Thanks  is advance.

[John_Kunkel]

Automotive flares are 45°, 37° is used on AN fittings. If the flaring tool you are using is the common automotive type, it is 45°. You can purchase 37° flaring tools from aircraft or hot rod suppliers.

AN sizes are based on tubing outside diameter measured in 1/16 inch increments; #4 AN tubing is 4/16" (1/4) outside diameter, # 6 is 6/16" (3/8) and so on.

[COKE]

Thanks John for that invaluable info.
There is not any place on internet to get that info.At least i have not been able to find it.

I don,t know wich is the trouble.I have used this tool on Brake lines wich have a lot more of pressure than a tranny cooler circuit an never had  leaking troubles.

I have seen Aeroequip sells a caliper and a set of gauges to measure the flare angles,but it is very expensive .

[John_Kunkel]

I have also had trouble with home done tubing flares leaking on brake systems. I can usually get them to seal by way overtightening the nut, once I do that it stops leaking even when later disassembled/reassembled.

It's as though the new flare needs to seat in that particular fitting. I know it shouldn't be that way but...............

[Chatt69chgr]

I have had the same problem with the flare not being exactly true.  You can chuck up a old fitting in the vice and use it to do the initial really hard tightening procedure to get your flare to "true up".  Works even better if you have an old stainless fitting as they are really smooth.