Titanium's shower of sparks

Wow, Jerry, 1mm wall thickness! Were those parts made from solid stock? Beautiful work!!
 
Bill Kahn said:
I am now playing with titanium. (Well, it is called 6-4 which I think means 6%Al and 4%V). I have noted two interesting features:
  1. On the HF 4x6 bandsaw (with a sensibly good blade) I can cut it. And the "saw dust" (doesn't quite seem to be swarf to me) is different from other metal filings. The filings interlock with each other as they fall to the floor. And they collectively form a loose mat. Move some of it and several inches away it is interlocked and the filings move too. It pulls apart easily, but something surprising and unexpected.
  2. On the mill, on 1" wide bar, 1 mil depth of cut, 1" feed per 10 seconds, with a 3" 5-carbide blade facer at 2500 rpm--whoa! A regular Christmas display of bright white sparks fly everywhere. Beautiful but I stopped the feed pretty quickly--flying fire isn't of much interest in the shop. If I brought it down to 800rpm no fire. Feed slowly enough and the finish is ok (not shiney through). The sparks lasted long enough to land on Ti swarf. No ignition there. The color was much whiter than the slight yellow sparks I get with some steels. And not the brilliant blue-white of burning magnesium.
I am not making anything with the Ti. Just exploring the material.

-Bill
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At 2500RPM you had a surface speed of 2000SFM. That's aluminum speeds. Unsurprisingly, at 800RPM you're down to 600SFM - much more appropriate for Grade 5 Ti. I shoot for slower SFM on my little mill as my tools last longer (at the expense of slower cuts).

Coolant is your friend with Ti. Because it has a very poor thermal conductivity, the heat from the cut doesn't leave with the chips as readily as with other materials. Positive rake tools, no burnishing/rubbing, and coolant. Even an air blast is better than nothing (or using cutting oil).

As you're playing with titanium, remember that it work-hardens easily. A dull drill bit or end mill rubbing on the part will turn the surface rock hard. Whatever you do, make sure you take a chip and don't try to sneak up on final dimension a 'thou or two at a time unless you have really, really sharp tools.
 
So, Jerry, were you a machinist at JPL in your former life? If so, it would be really interesting to hear about the work you did there.
 
mikey said:
So, Jerry, were you a machinist at JPL in your former life? If so, it would be really interesting to hear about the work you did there.
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No, never worked there.
I was a job shop contractor from 1975
until 2006 when I sold my machine shop
and retired.
 
You must have been one hell of a contractor to land a job on the Rovers! Welcome to HM - hope you don't mind if we all pick your brain!

One day, I hope to visit my son in Mountain View and visit the machine shop at the NASA Ames campus.

Happy Holidays, Jerry!
 
Well Mikey , Thanks.

Reality is, there are thousands of shops just in California
That could have done the job.
I felt very fortunate to have the machinery and the
recommendation of engineers I’ve previously worked with.
Happy Holidays
 
I used to run titanium on a peg board automatic turret lathe. We had so many fires we had to keep a extinguisher right at the ready all the time .even if we kept the chips out of the pan. Also every time we used the extinguisher it made a big mess in chip pan. I then took the powder out of extinguisher and filled a coffee can with the powder and then we would take a handful of powder and throw it on the fire. It worked well and we had a lot less mess to clean up.
 
mikey said:
You must have been one hell of a contractor to land a job on the Rovers! Welcome to HM - hope you don't mind if we all pick your brain!

One day, I hope to visit my son in Mountain View and visit the machine shop at the NASA Ames campus.

Happy Holidays, Jerry!
Click to expand...
Mike,
When you make it to Mountain View, make sure to give me a shout. I work in Fremont and live in the East Bay.

Jerry,
Those are great parts. I'm a big fan of e-beam welding. Not cheap to get set up, but once it's dialed in it's fantastic--minimal distortion and fantastic weld quality.
Evan
 
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