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Surseat Flare Lapping Tools

(13 customer reviews)


  • Surseat P-51B is for 3/16″ to 1/2″ flared tubing with a 37° or 45° angle.
  • Surseat P-45 is for 3/16″ & 1/4″ flared tubing with a 45° angle.
  • Surseat P-37 is for 3/16 & 1/4″ flared tubing with a 37° angle.

* Free shipping on orders over $99 in the continental United States.
* International orders: Please contact us to place an order.

US PATENT 9,943,942 B2

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The Surseat flare lapping tool allows you to lap-in flared tubing to eliminate leaks in fuel and brake line joints. This innovative new tool removes irregularities in the flare and hones it to a perfect angle to enable the tube to seat with the fitting. The Surseat will not only perfect your newly-flared stainless steel, aluminum or copper lines, it can also repair the seal with the fitting of an existing brake or fuel line. It is based on the tried and true practice of lapping engine valves. A diamond dust coated lapping head with a precision 37° or 45° angle literally polishes the flare smooth to perfection. The Surseat is a valuable asset for car builders, automotive repair facilities, and hobbyists.


Surseat P-51B
  • The Surseat P-51B comes with collets for 3/16" to 1/2" tubing.
  • Includes imperial threaded collets for 7/16" x 24 and 3/8" x 24 sizes.
  • Includes metric threaded collets for M10-1, M10-1.25, and M12-1 sizes.
  • Interchangeable 37° and 45° lapping heads snap on to the shaft.
  • Includes a custom case for safe storage.
Surseat P-45
  • The Surseat P-45 is used for 3/16" & 1/4" brake lines with a 45° flare.
  • Includes 3/8" x 24 and 7/16" x 24 collets to screw the fitting into.
  • The collet and tube are secured into the P-45 with a lock spring.
Surseat P-37
  • The Surseat P-37 is used for 3/16" & 1/4" brake lines with a 37° flare.
  • Includes collets to clamp the tube.
  • The collet and tube are secured into the P-37 with a lock spring.


Using the Surseat P-45 & P-37

Screw fitting into collet

1. For the P-45, screw the fitting into the collet.

Clamp collet around tube

2. For the P-37, clamp the collet around the tube.

Secure tube with lock spring

3. Install the collet by sliding the locking spring into the closed position.

Spray lapping head with light lubricant

4. Spray some light lubricant to the lapping head before use.

Rotate lapping head back and forth

5. Rotate lapping head back and forth until a clean seat is formed.

13 reviews for Surseat Flare Lapping Tools

  1. Rich Banz

    This tool is extremely clever design and very simple to us. It takes the imperfections that inevitably come from a flaring tool and finishes them, ensuring a proper seal. In my case I had to re-bend many lines on my car for adding Disc brakes and a Wilwood proportioning valve this meant I had many flares that potentially could leak this Lapping tool just took away all my concerns about slow leaks.
    Good stuff guys keep up the good work.
    What is next in the development timeline?

    • koultools

      Thanks Rich! Next up is a tool that will refinish and repair the conical seal on male fittings.

  2. Russell @ Nerd Rods

    Another winner and time saver from Koul Tools!

    Here at Nerd Rods we have to make brake and fuel lines for out custom chassis. Its time consuming work especially when you need to pressure test each line to make sure that end didn’t split or have some other imperfection from the press on the ferrule face. With this little guy we slap it on make a few quick passes and done! Its been 6 months since we got this tool and 6 months since we’ve had to re-flare a line. Just the materiel we’ve saved has been amazing much less the time in redoing or pressure testing each and every line.

    Thanks again Koul Tools!!! Keep up the killer work. We can’t wait for the your next too we can’t live without and didn’t even know we needed!

  3. Bill Kantos

    I have been double flaring brake lines for street rods for 30 years with great success. My latest project, a 32 Ford Roadster had 6 fittings that I could not get to seal. I kept trying to tighten the fittings, hoping the joint would seal. I don’t know if it’s the quality of brake lines or just me, but I couldn’t get the brake system to not weep. I remember seeing this tool at the Street Rods Nationals, and decided to order one, and see if it would solve my problems. I disassembled the entire brake system and lapped every flare with the Koul Tool P45. I reassembled the brake system and didn’t have a single issue. I will lap every fitting I make from now on just to make sure I get a proper seal on my brake fittings. The tool is easy to use and certainly performs.

  4. Edward Coyer

    I’ve used several of your tools before, and have found all of them to be real time savers!
    I had a master cylinder to brake line leak with my ’55 Chevy that your line lapper resolved. It seems that no matter how carefully I flare the tube, sometimes I still have a leak. It seems that the cause of this is roughness of the flare. Your lapping tool removes this making for a positive, leak free seal.

    Thanks again for saving me time, and trouble!

  5. Michael

    After finally getting back to stalled my 1968 Chevelle project, I got to bleeding the brakes. The lines/cylinders were installed in 2014, the shoes and e-brake just this past month. Using a one-person brake bleeding tool took forever, because system was bone dry. Once fluid appeared at rear-passenger corner, I had my wife (awesome helper) help me the old fashion way, and pump the pedal. Instead of vacuum, it was now pressure, and almost every joint was leaking. I purchased the Surseat P-45, and within two days I was back underneath using it to go over all the flares. After lapping all the flares, the only leak I had left was at the rear flex hose. Once hose was replaced, all leaks were gone. Even though it was the Mini, I still had a couple spots where I had trouble using it, so I had to remove the entire leg of steel tube. If it included a third collet, 1/2″, it would’ve been perfect. Thank you Koul Tools !!

  6. Bob (verified owner)

    Replaced all the steel brake lines in my ’66 Corvair. Although I bought pre-made lines, three of them had pretty rough finishes on the flares. Using the P-45, I was able to clean them up and did not have any leaks. Truly a “Koul Tool”.

  7. Robert Townsend (verified owner)

    Restoring a 62 Corvette Fuelie and the tool came in very handy when replacing the brake lines. Easy to use and would highly recommend it.

  8. Don (verified owner)

    Absolutely as promised. EVERY fitting leaked on my new build due to some garbage line. Saved the day and worth every penny! Thanks!!

    • Koul Tools


  9. andy (verified owner)

    I thought it would be a live saver but still have problem seating the lines at union connections

  10. John – Huntersville NC (verified owner)

    I am restoring a ‘69 Camaro convertible. About half of the fittings on the power disc brake plumbing (all new lines and fittings) leaked with seemingly no resolution. Using my new Surseat P-51 kit cleaned up the problem joints nicely and stopped the leaks! Thank you for a quality American made tool and the EXCELLENT customer service.

  11. Grant from Petaluma, CA (verified owner)

    The Surseat P-45 solved the brake fitting leaks I had been chasing for months on my 1971 Dodge Dart. Reproduction part variances in the new brake lines and distribution block created a situation I never thought I could fix. I used the P-45 on the 3/16″ line fittings into the distribution block and voila – problem solved. Thank you Koul Tools for helping me get my car back on the road.

  12. Allan

    Wonderful company to deal with. Called them from Canada about the 37 degree lapping tool for my 2000 Silverado brake line redo using stainless steel lines. It turns out that the stainless lines in the Dorman kit are flaired 45 degrees even though they are stainless. Dick personally corrected the situation before I bought the wrong kit. Great guy! PS: Thanks for that “additional” tip, Dick!

    • Koul Tools

      Thank you Allan

  13. Pete

    I have used this product on several projects and absolutely love it ! However, my latest misguided adventure has metric fittings. Do you guys have any plans on offering 45* metric collets ?

    • Koul Tools

      Thank you for your comments. Our new P51B coming out in 2022 will have metric collets.

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Surseat P-51B, Surseat P-45, Surseat P-37