Hi,

One small comment on the machining is that it is counter intuitive. Think of doing big slow cuts, if things start to get hot go deeper on the cuts. If you go for shallow cuts you will end up with bits of burning powder.

Tim

Alf,

I agree with Graeme on the size of the tapping drill i.e 5.2mm, if you have difficulty

tapping titanium you could try using 2 stage taps.

As an aside you can also electron beam weld titanium, but it would be very expensive

Colin.

Collin, I would suggest using a larger size tapping drill, and cutting thethread in one go, to cut in two stages invites work hardening on the first cut, and difficulties with the second tap. Just my small expiriance when tapping stainless steel, similar problem when using a die on stainless and trying to take it down in stages. Ian S C

Surely the "super hot steam" won't be hotter than petrol vapour burning with air? Why not use aluminium alloy for the block with inserted liners made of steel or meehanite? It sounds from everyone's experience above that titanium will be an absolute b***h to machine with no end of opportunities for things to go wrong.

Thanks Colin, Its good to get the info from someone who knows, I'm teaching myself, and finding out how as I go.

If weight is so important, is the motor for an aeroplane? Ian S C

have machined a lot of Titanium in my time, mostly grade5, and on serious machines, would not recommend it as a material for engine blocks and Ti-Ti rubbing is an absolute no-no.

Have recently cut plate with an angle grinder, the fire aspect that was mentioned earlier was not an issue. In fact it cut better when the plate glowed red…….the sparks are ridiculously hot though and burnt a hole in my trousers and jacket……

Tapping is a nightmare unless you use cobalt style taps and drill at least Ø5.3mm for M6. Work hardening is not an issue but heat transfer is. Titanuim absorbs heat slowly so your cutting action will cause the immediate area to swell and expand and will "grab" your tool with a heart-stopping squeal. Don't try to force it – instead, go and make a cuppa and by the time you return it will be loose enough to retract…….then get another tap……

If you burn a drill out in the metal you are stuffed. The work hardening mentioned earlier is akin to a chilled casting. Cut low revs, feed hard and plenty of lube, pecking every 2-3 seconds maximum.

Have fun………

Trevor

It would be interesting to know why the weights so critical is it for an aircraft? Something like HH Groves steam driven aircraft.

As a user of high temperature steam (engine steam feed pipe glowing) and always having to keep weight down due to regulations could there be an alternative to titanium to reduce machining problems.

There are ceramic coatings on aluminium pistons on one fullsize flash steam engine I know of and maybe other applications it can be applied to.

Experimenting is great when it all comes together.

Paul

Years ago, I was an apprentice machining huge Ti forgings for the engine beams of VC10 aircraft on Droop and Rein hydro copy mills. The forgings were about 8 feet long by 4 feet deep. The cutters were all nitrided HSS and cut using plenty of soluble oil. Machine setters set up the feed and speed of the cutters and as apprentices, we 'rode' the mill, and read our books / playboy mags and LISTENED to the cut as it proceeded. When the sound changed, we stopped the cut and called the machine setter for a new cutter. If we left it, the cutting sound changed to a 'squeak', then either the 2inch diameter cutter snapped, or the forging got pushed away from its mounting jig. In either case, it was hell to pay. The 'damaged' area had to be ground out (removing the work hardened area) before the cut could be resumed. This may have taken a day or so to recover the cut. My experience was that you spent as much time sharpening cutters and setting up as machining.

I tried to make some light-weight piston heads for a match target air rifle I was tuning, turning the outside and screw-cutting no problem, last job was to drill and tap an 8mm hole in the centre. No chance, the drill just heated up and that was that. Work hardened. Is it possible to anneal a titanium part that has work hardened like this?