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Old 10-26-2022, 11:52 AM
bshawco bshawco is offline
Join Date: May 2021
Location: Near Durango, CO
Posts: 38
Default Adequate Flare?

I'm trying to flare 3/8" fuel lines using the Imperial 2-piece flaring tool & a couple drops of oil. I've practice at least 20 flares, and I think I must be doing something wrong.

I've watched several videos, followed the VAF threads as well as the instructions that come with the tool and section 5 of the KAI. I've tried cranking on the tool both lightly and as hard as I can. I've tried starting with the end of the tubing flush with the top of tool and with it slightly above it.

Attached below are photos of my best flare next to a T.S. Flightlines flare (on the right), and I'm obviously not getting as much of a "neck" on my flares. The last photo is my flare with a sleeve.

My questions are whether my flares are likely to be adequate or not. If not, any tips would be appreciated. I'm also wondering if I just need to break down and buy the Rolo-Flare tool which is the alternative flaring tool carried by Aircraft Spruce.
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-Brad Shaw.
Mancos, CO.
RV-12iS (Finished Wings)
VAF Donation Made June 2022

Last edited by bshawco : 11-15-2022 at 05:09 PM.
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Old 10-26-2022, 01:05 PM
Ralph Inkster Ralph Inkster is offline
Join Date: Feb 2008
Location: Calgary, Alberta
Posts: 1,962

Confirm that the Imperial tool is a 37 degree flare type.
Other than setting the tube a bit deeper in the tool so the 'neck' ends up same outside diameter as the blue sleeve, should be good.
built a few RVs, rebuilt a few more, hot rodded more, & maintained/updated a big bunch more
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Old 10-26-2022, 02:51 PM
Desert Rat Desert Rat is offline
Join Date: Aug 2018
Location: Wichita KS
Posts: 1,055

It looks to me like that tube wasn't inserted far enough in the tool. Those circular marks on the exterior of the cone look like it was probably smooshed into the die part of the flaring bar.

You mentioned cranking it down, but typically you don't want to bottom out the cone point in the socket. Certainly if you crank it down like I think you mean, you're weakening that flare where it has a good chance of cracking radially in the transitions back into the unflared portion of the tube.

From the time the cone makes contact with the tube, it should take about 1/2 dozen cranks on the handle to create a proper flare and that should happen before the flare cone starts to crush the flare into the chamfer on the flaring bar. If it doesn't, then you likely didn't have it inserted far enough.
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Old 10-26-2022, 03:36 PM
Waiex-guy Waiex-guy is offline
Join Date: Oct 2012
Location: Rocky Point, NY
Posts: 67

The directions for the tool suggest that the tube should stick out of the bar to approximately the same thickness as the foot of the flaring tool (the part with the crank in it. That foot is something more than 1/4”. In other words, the tube sticks “way out” of the bar and the flaring action never gets close to the bar. With my tool I have found that 3/8 tubing is best flared with seven half turns of the handle from the first contact.
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Old 10-26-2022, 04:14 PM
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Rick_A Rick_A is offline
Join Date: Oct 2005
Location: Jacksonville, FL
Posts: 1,632
Default Check out these instructions

I have the same tool. If you go to the Imperial website you will see a number of manuals.

The one I have is the 500 series and even though the description of the manuals says 45 deg the instructions are the same as the 37 deg model.
Rick Aronow,
Flying 7A Slider;
Jacksonville, FL
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Old 10-26-2022, 04:51 PM
TS Flightlines TS Flightlines is offline
Join Date: Apr 2010
Location: Ridgeland, SC
Posts: 3,139

Typically, the flare should be about 1/2 the width of the flared part of the sleeve. Yep, takes some practice. Extend the tube out from the flare die about .060 and try again. Should be about perfect.

Tom Swearengen, TS Flightlines LLC, AS Flightlines
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Old 10-26-2022, 05:59 PM
bshawco bshawco is offline
Join Date: May 2021
Location: Near Durango, CO
Posts: 38

Thanks for all the tips and suggestions. The 37 deg flair tool I have is the Imperial 437-FB Hi-Duty model.

After more practice today, the best looking flares I've gotten were when I had about 1/4" of tubing above the yoke. The instructions for this model say the top of the tubing should be flush with the top of the yoke. One video suggests the top of the tube be about 1/64" above the top of the yoke. I'm hoping more practice will do the trick.
-Brad Shaw.
Mancos, CO.
RV-12iS (Finished Wings)
VAF Donation Made June 2022
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Old 10-26-2022, 07:44 PM
DennisRhodes DennisRhodes is offline
Join Date: Jul 2007
Location: Taylorsville, Ga
Posts: 940

Didn't see any mention above , but I have problems similar to some of your pictures if the cut off end to be flared is not reamed out sufficient. Or sometime cut with a set of cutters with too much pressure on the roller at the final rounds of the cut. Some of the pictures looks as if the cut end may have rolled into the flare formation which will make a substandard flare connection and poor seal. Maybe not as much of a flare formation operation as a cut and prep operation.
2022 VAF Supporter
RV9 N908DR
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Old 10-27-2022, 12:27 AM
rapid_ascent rapid_ascent is offline
Join Date: Mar 2008
Location: Dublin, CA
Posts: 1,765

See this thread. The included chart is a good reference to determine if your flare is within acceptable limits.

I have this chart taped to my hangar wall for reference. It takes the guesswork out of it. I'm sure like many other things once you are more experienced then you probably don't need to confirm with the chart.
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Old 10-27-2022, 09:41 AM
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DeltaRomeo DeltaRomeo is offline
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Default Sorry.....couldn't resist

v/r,dr <G>
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