Fuel & Brake Line Lapping Tool
Mark SimpsonDescription
We’ve all been there: you just bent up a new brake line and installed it, and as soon as you start to bleed the system, you notice a drip at the flare nut fitting. Of course the first step is often to tighten it some more and sometimes that stops it, but other times it continues to drip. So you grab the wrench again and tighten it beyond where you are comfortable tightening it to, only to have it continue to drip. Eventually you round off the flare nut fitting, damage the threads on the flare nut seat, or just give up and cut off the tubing flare and re-flare the connection.
The problem is actually in the flaring process itself. When creating an inverted flare on a brake line, the metal is stretched, shrunken, and inverted, and occasionally ridges develop in the flared fitting. Small deformations in the fitting will smooth out when the fitting is tightened into the seat, but sometimes these ridges are too large or the material is too hard to smooth out during normal tightening. This can be especially true when bending stainless brake lines.
One great solution to this problem is brought to us by the folks at Koul Tools, who manufacture a great tool for lapping the ends of the flare fitting to create a smooth positive seal without the need to over-tighten your fittings. We join Mark Simpson in the shop to test out the Koul Tools P-51B Surseat Flare Lapping Tool. This tool allows you to lap-in flared tubing to eliminate leaks in fuel and brake line joints.
This tool works by removing irregularities in the flare and hones it to a perfect angle to enable the tube to seat with the fitting. It’s not only perfect for your newly flared stainless steel, aluminum, or copper lines, but 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. But don’t wait to discover a leak when bleeding your brakes to use this tool when it makes great sense to use it every time you make a flare fitting to ensure a great seal.
If you've ever just bent up the perfect brake line and suddenly, you get it all hooked up, you tighten up the ends, and it leaks. And then you think, well, the natural reaction is to grab the wrench and tighten it up a little bit more, and test it again. And sometimes it still leaks. So then you go, "Okay, I've really reefed on that flare nut a lot already. I'll wrench on it a little harder." And eventually, either it stops leaking or you're browned off the ends of your flare nut, or you break a fitting or something like that. But there's a easy solution to fix that, and that is a lapping tool, and a lot of guys haven't heard of this. And what it does, is it... Koul Tools makes a great product for doing just this. And it comes, you know, this one here is their P-51B. They also make some smaller ones that are good for underneath the car. And what this does, comes with these fittings, and what it's going to do, it's going to actually lap the inside of this line. And the reason we wanna do that is we wanna make sure we have a good, smooth surface for it to seal against. And this tool has an abrasive. It comes with two tips, a 37 degree and a 45, so you can do both your AN lines or your typical inverted flares. Comes with the adapters, both for the fittings or for the line themselves, which easily just clip onto the line like this. So you can actually do a Baer line, or you can, like, make... I like using the one that actually attaches to my flare nut, because then I can ensure everything is in a line. That clamps on. Now it's just a matter of going in and using the tool to actually lap the end of this line. And what this does, it has an abrasive diamond surface on it that will actually smooth out any imperfections in our flare. And soon as those imperfections are smoothed out, you should be able to get a good, tight seal on that brake line. So, as I said before, if you're having trouble with your brake lines leaking or you get a little dripping outta your brake lines after you finish making up a new set of lines, or if you've just bought a set of lines, try out this tool. I think you're gonna be really impressed at how good a seal you can get. They also make smaller versions for, like, under the car to a specific size. This one is more their universal kit. So, yeah, try it out. You'll be happy.
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