EngineLabs’ Tool Of The Month: Koul Tools P-51B Surseat Lapping Tool

EngineLabs’ Tool Of The Month: Koul Tools P-51B Surseat Lapping Tool

Let’s face it, anyone who tells you they enjoy flaring hardline is either a masochist or a liar. Ok, maybe there are some people out there who don’t dislike the process as much as your author. The fact is, when it comes to making flares in hardline tubing, it can be incredibly challenging for the average enthusiast, since hardline flares are very unforgiving, and are typically used in applications that are themselves pretty intolerant of mediocre work.

This month’s tool comes to us from the aptly named Koul Tools. Designed to make the challenging task of making perfect hardline flares easier, this easy-to-use widget steps up anyone’s hardline game. The Surseat (pronounced “shure-seat”) P-51B is a recently revised version of the P51 tool we’ve shown you before. Now, its full-frame design, easily swappable lapping heads, and fully retained collets are much more user-friendly while still doing what it was designed to do very effectively.

Here, you can see the color-coded (Blue is 37 degrees, red is 45 degrees) quick-change lapping heads. The steel cones are coated in long-lasting diamond dust abrasive that will last an incredibly long time.

Mating Angles

When it comes to hardlines, there are two major mating-surface angles in use, 37 degrees and 45 degrees. The Surseat P-51B can be considered a “master kit” as it comes with the equipment for both angles. While there are individual kits available for just 45-degree applications (P-45) as well as 37-degree applications (P-37) the P-51B kit adds some additional threaded and flared collets over the two kits.

How the kit works, is that once you determine what flare-angle fittings you’re working with (37-degree is the most common in the engine bay, as that is the angle also used by AN fittings), you’ll select the appropriate lapping head. The lapping heads are made from steel and coated with a highly abrasive, long-lasting diamond-dust abrasive. The 37-degree and 45-degree heads are color-coded and easily interchangeable on the tool’s shaft.

The P-51B kit includes both threaded and clamshell-style collets. The threaded collets are for tight-radius fittings that can’t be moved away from the flare, and the clamshells are for bare flares.

Collets For All

Once you have the correct lapping head installed on the tool, it’s time to mount the tube into the tool via the supplied collets. The kit comes with collets for 3/16-inch to 1/2-inch bare flares (no fittings involved), and for flares in tight spots, where you can’t move the fittings out of the way, threaded collets are provided. Imperial threaded collets come in 3/8-24 and 7/16-24, and the metric collets are threaded for M10 x 1.00, M10 x 1.25, and M12 x 1.00.

Once the appropriate collet is selected and fitted to the line, the hexagonal shape fits into the base of the lapping tool and is secured via a simple sliding wire clip. Once everything is loaded, it’s as simple as lubricating the lapping head with your choice of lubricant (WD-40, cutting oil, machine oil, etc.), pressing the spring-loaded knob, and rotating the lapping head back and forth, similar to lapping a valve.

Here, you can see the new revised frame geometry of the B-model P-51 tool. Besides the full frame, the collet retention mechanism makes life easy.

After a bit of lapping, you should notice a nice register (to use the valve terminology) starting to form on the inside of the flare. That register is the actual mating surface between the hardline and the fitting, so ensuring an even, solid mating is crucial to a leak-free installation, whether it’s fuel, nitrous, transmission, or brake lines. The Surseat flaring tool can take a mediocre to poor flare, and turn it into a perfect one, with minimal effort. Even if you are a master of flaring, lapping your flares can ensure that there are no burrs or ridges on the mating surface of the tube.

On the left, you can see the raw single-flare. While not great, it's not bad, either. On the right, you can see how much the lapping has cleaned up. In fact, this flare could probably use some additional lapping. It's a perfect example of how the P-51B takes a mediocre flare to a solid-sealing one.

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About the author

Greg Acosta

Greg has spent eighteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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