The Grades of Titanium We Use

6AL-4V is an alloy containing 6% aluminium, 4% vanadium, and 90% titanium. 6/4 is mostly used for the machined parts as it's very hard to make into seamless tubes, currently the only tubes made from 6/4 are welded and seamed, UK company Reynolds having ceased production of this material. To make 6/4 tube sheets of titanium are formed into the desired shape and then the seams are welded, there is some doubt the strength of such tubes, we believe its far better to use seamless cold drawn 3AL 2.5V tubes as they have no inherent stress risers.
All of our dropouts, cable stops and head tubes are CNC machined from 6AL-4V titanium billet as the alloy is very easily machined and is extremely strong.
6AL-4V typically has an ultimate tensile strength of  1050 MPA and is 8% stiffer than 3AL-2.5V whilst being approximately 1% lighter.

3AL-2.5V An alloy consisting of 3% aluminium, 2.5% vanadium, and 94.5% pure titanium. Also known as grade 9, is easily formable, excellent corrosion resistance and superb fatigue life make 3AL-2.5V the most used titanium when making an Enigma frame.  All of our frame tubes are 3AL 2.5V which are seamless and cold drawn and in some cases double butted. Double butted tubes have variable wall thicknesses, usually thicker at both ends for strength and ease of welding and thinner in the middle of the tube to save weight in a less stressed area. The only downside of butted tubes is their high price as they are harder to produce than plain gauge.
3AL-2.5V typically has an ultimate tensile strength of 900 MPA

Tubing

Not content with using standard off the shelf tubing, at Enigma we have designed our own range of tubes and profiles, using EST, Enigma Shape Technology. By subtly ovalizing and tapering tubes in crucial areas we are able to reduce weight, increase power transfer whilst bring better levels of comfort, no easy accomplishment.
We have many different shapes, diameters and weights of titanium tubes; these are selected for any given purpose. For instance smaller frames are given a more flexible and lighter tube set, a larger frame is given stiffer tubes to build out too much flex.
We use both plain gauge and double butted tubes, depending on a frames price point and intended purpose, butting is very costly but does reduce a frames weight whilst increasing comfort slightly.
Plain gauge means the wall thickness of the tube is constant, typically only .89mm thick.
Double butted tubes have variable wall thicknesses, usually thicker at both ends for strength and ease of welding and thinner in the middle of the tube to save weight in a less stressed area. Another benefit of double butted tubes is the fact that they can bring increases in comfort levels too, they are more costly to produce however.