A lot of This is Incomplete


Hard Brake Pipe Flaring

Figure 1. Moprod pipe flaring tool, cheap but very effective bit of kit.

Figure 2. Snap-On flaring tool, the 3/16" die was missing so I couldn't show a flare done using this tool.
The brake pipe flaring tools usually seen are similar to figure 2, these are fine if you want to do several sizes. But the flares produced are not symmetrical, sometimes they need to be wound on to a hard seat to reform them so they seal and they are a bit more fiddely to use under a car than the tool shown in figure 1. The tool shown in figure 2 cost about £20 the tool in figure 1 £3.50. As supplied the flaring tool comes with another casting that bolts to the 2 blocks, the 2 holes through the two blocks are threaded 5/16 UNF, The other casting is meant as a handle, but I usually use it in a vice and I lost the handle, so I use an old alternator bracket as a handle if I am going to use it in situ.

Figure 3. Moprod tool in action, if possible I use it in a vice.

Figure 4. Tube in flaring tool ready to be flared.
The threaded die has one end formed for single flares and the other end formed to collapse a single flare, figure 7 shows the stages of flaring that corresponds to figures 4, 5 and 6.The groves machined in the threaded die are for pipe-die depth setting. When the single grove is in the position shown in figure 4 the pipe is the correct depth in the die for a single flare; you can still see the groove when the blocks are bolted together. The other end has 2 grooves I just ignore these and collapse the single flared pipe as far as the die will screw in, the single flared pipe is in the position it was left in after being flared

Figure 5. Single flare formed.

Figure 6. Die reversed and flare collapsed, double flare.
A pipe cutter is a good idea if your doing very many brake pipes, I have a Rothenburg pipe cutter its like a miniature plumbers wheel pipe cutter. However I couldn't find it so I had to use a hacksaw. Figure 7 has a sawn piece of pipe a single flare and a double flare. When you cut the pipe try and cut it square, use a file to square and clean the end up, also remove burrs inside the pipe. The pipe used for the single flare in figure 7 looked like the sawn end shown, the double flare still had some burrs in the end of the pipe you can see what's left of them in side the double flare.

Figure 7. The three tube ends, left to right: plain, single flare and double flare
I didn't use any lubricant when doing these flares, they look a bit cleaner when the ends are lubricated with brake fluid. You don't want any traces of oil in your brake system it destroys the type of rubber used in brake seals. Someone asked about Flare nuts and the difference between metric and imperial, the two types are shown in figure 8. On the left are the imperial ones, 3/8 UNF On the right are the metric ones, 10 mm these do come in several different pitches is it 1.25 and 1.0 mm I am not sure and it is very rarely that we ever need the not so common one. I buy these in boxes of several hundred[500?]they cost about a fiver a box, I have no idea how much single flare nuts cost.

Figure 8. left are male and female imperial flare nuts, right are the metric counterparts. Sometimes you will find fittings that look different to these, I think Yank imperial fittings have a much shorter unthreaded bit.

I did have a turret brake pipe tool, it wasn't the one you see in the draper/sealy catalogue's but a rather nice old Churchill thing. It made perfect flares in everything I ever tried in it, including 5/16" stainless steel. Someone wanted to buy it and this tool does the job so well that I said OK. The Snap On tool does the job but not as well as the other tool, under a car flaring steel pipe can be very difficult. Usually a pipe with a male union going into a cylinder will have a single flare, but sometimes a hardened convex seat is in the cylinder, so that a double fare will be needed. So check the old pipe before flaring the pipe.

Something to always remember is to check the pipe union is on the pipe before flaring the pipe, I still forget now and again.


  Cobbled together on the 8th of Febuary 2001

{last modified 8 th feb 2001}