Brake Line Flaring Tools. Materials, Fittings and Detailed Discussion

Note the Tool Marks on the upper line, made by the low-end bubble-flare tool.  The lower tube was a prefab tube purchased at an auto-parts store.  Incidentally, I believe this lower tube is SAE buble-flared, and upper is an ISO bubble flare (or 'mushroom' flare).  Note the upper tube flare diameter is below the tolerance for minimum size.

This is the simple, inexpensive style of tool used to make that top-most flare above.  It results in unacceptable tool marks and burrs on the shoulder of the tube.

This is the bore of the flaring tool - the part that grips the tubing and leaves the teeth marks.  These bores appear to be formed with regular threading tools and there seems to be very little blunting of the sharp threads in the bores - thus the teeth marks.

I purchased the bubble flare tool from Ultrapro just recently at $160 (same style of tool available elsewhere for $50 - such as from Summit Racing).  It does 4 different sizes of ISO bubble flares - so I tried it out and don't like it - two reasons:
1. It marrs the brake line on the shoulder.  The grips on the flaring tool cause this marring, which is basically grip marks, biting into the tubing (right through the finish).  Marks resemble your leg or arm after being bitten by a dog or alligator -see pic.  This encourages corrosion in the area where the tube was gripped by the tool.  I feel the teeth marks are due to the very short length over which the line is held.  The grip length is 11.85mm for the 4.75mm line and 11.3mm for the other line sizes of 6, 8, and 10mm.  This short grip length probably necessitates the use of gripping teeth in the clamp interior surfaces.  The simply formed die shapes are only threaded holes sliced in half.  The threads don't seem to be blunted at all.  The whole thing is chrome plated.
There is another tool offered by Fedhill which you can find here:  http://store.fedhillusa.com/475mmdin.aspx. 
And their FAQ's for brake line service is pretty good:
http://store.fedhillusa.com/technicalhelphowtopdfs.aspx
Similar tool by BrakeQuip:
My favorite tool is the Mastercool style (expensive, but comparable to the ones above), which is very slim and can be operated anywhere, including deep in the body of the vehicle or machinery.  The Fed Hill and BrakeQuip tools are efficient, but are designed for use on a bench (heavy and bulky, and intended to be mounted).


These tools use dies which have a much longer, plain-bore gripping area, so marring of the line's finish will be much diminished or eliminated.  You can see in the pics I took the prefab lines seem to have no marring on the shoulder at all - I imagine this is a result of using dies like the ones from Fedhill.  Actually looking closely at he prefab line, one can see very slight flattening of high spots on the tubing, and very minute marring just behind the bubble - but it is really much, much better than the results from the Ultrapro tool.  It also seems the prefab tool has been lathe-finished or grinder-finished on the front face of the bubble (the mating face), which has a small step from the plain finish of the shaped steel to the clean/polished mating surface - so I expect that the prefab lines are using a forming and maching process, not just a forming process.  Note that the marring from the Ultrapro tool will not be seen by someone inspecting the finished brake line installation since the shoulder fitting will hide the teeth-marks.  I suppose this area can be protected from corrossion with some thick grease applied during assy - but avoid getting any grease inside the brake line!

2. The bubble for the standard (euro-auto) 4.75mm ISO bubble flare is not a great shape, size, and profile.  The bubble that comes on the pre-fabricated lines is 7.2mm diameter (measured with my digital caliper).  The bubble resulting from the Ultrapro tool is 6.44mm diameter.  The depth of the bubble is also reduced from the pre-fab standard, from 3.1mm to about 2.25mm.  Also, the transition from shoulder to bubble is sharp - the pre-fab line has a more gentle transition from shoulder to bubble.

Lines:
4 types, with prices in Cdn Dollars, as of Oct. 2010, Toronto, 4.75mm line:
Interesting web page discussing pros and cons of brake lines:
http://www.austinhealeywood.com/brakestory.html.  Note they too, have no stainless tube nuts, despite their strong promotion of the copper-nickel lines.  They do discuss the downside of brass tube nuts.  In short, avoid the stainless line - it is too hard and can damage the softer seats in the valves and unions.
1. Satin-Coated Steel (probably electroless zinc plating)  $15.95/25ft
2. Polymer-Coated Steel - $33.95/25ft coil
3. Copper (alloyed with nickel) - $80/25ft coil
Stainless - available on-line - I have to check the prices for this still, but at first it seems more expensive than the copper line.
The dimensions for these 3/16" lines appears to be 0.188"OD x 0.028" thick wall.
I have also found HVAC suppliers provide 3/16" copper line at much lower prices (1/2 or less) of the copper-nickel lines used in brake systems.  I tried to determine the material properties for these cheaper lines and they seem to use material resulting in working pressures of about 1100psi, whereas the copper-nickel lines have working pressures of about 1590psi.

Nuts:
Nuts appear to be M10 x 1.0mm for our european Mercedes and Audi vehicles.  Hopefully one installs stainless or brass nuts when using copper or stainless lines.  I've looked and despite the availability of stainless and copper brake lines, all the nuts I can find are steel!  So far I've found no stainless or corrosion-proof brake line nuts......nuts!

I purchased the 4.75mm ISO Bubble flare die from Fed Hill and their Cunifer Line. - Will report on the results. - I was annoyed that they charged $23.50 Shipping and $10 handling on top - For shipping to Toronto - Unfair!