Anyone up for a blow-by-blow of how this progresses?
I thought so!:lolsign: So here we go:
The bar arrived vey quickly. Man this guy must really be impatient--he sent it Express Mail--as though that would get him his light any quicker.
Problem is that the bar wasn't .75" in diameter (19.05mm) but was really 17.92mm, before any turning down needed to get to a smooth clean surface. What the heck, it's a challenge, isn't it? Back to the drawing board to redesign the light to fit the bar.
Decided to go with a McR-17-XR reflector and will turn it just a smidge to fit into the 16.50mm bore for the lens, reflector and converter module. OK, looked fine on paper, now on to the real world--the basement.
Took forever to saw through the bar using a hacksaw, but that's OK because it was very cold in the basement. Chucked up the 60mm piece in the four-jaw chuck, adjusted it true and then cleaned up the mushroomed end and turned down the diameter until I had a nice clean surface--net diameter 17.84mm. Not a lot of metal left to play with between the lens/reflector bore and the outside of the head--that would mean using a fine thread to avoid cutting too deeply into the wall.
Next up: drill and bore for the lens and reflector space. Never having drilled Ti before, this was all guesswork, especially since I was too dumb to seek the advice of others first. :thumbsdow
Took out a nice new cobalt 10mm drill that I had in stock and went to it. I had not read about suggested SFM, or RPMs for drilling Ti, so I think I went with 800 RPMs. At first I didn't think it was going to go anywhere, but a little more determined feeding got it going. Tough stuff, took a lot of pressure to hand crank the drill into the piece. Noticed a little smoke coming off the surface--definitely getting hot. Backed it off and decided to put a little cutting fluid into the hole to cut down on the friction and reduce the heat.
Stuck the drill back in and went deeper, only to see smoke real soon--the cutting fluid on the outside of the head was being vaporized quickly. Not sure what to do--keep going or back it out? I backed out, let it cool a bit, and started up again. More smoke, real soon. In fact, the outside of the piece was getting discolored. I couldn't tell if it was from the fluid being burned off, or whether the metal was really discoloring.
Oh, well, backed it out again and let it cool for 15 seconds and then back to work. Took a bit of pressure, no fire broke out, but still a bit more smoke--I stopped adding the cutting fluid.
Finally reached my desired depth of 25mm and withdrew the drill bit. Inspection showed no unusual wear and no bonding of any Ti to the bit, a little surprise given all the heat and pressure.
On to boring out the opening to size, from 10mm in diameter up to 16.50mm. Man did that take a while, especially when the best depth of cut was .30mm per bore. You do the math.
At a decent hourly wage, I figure I'm already losing money.
Beaming with pride that things were going well, i.e., it was being machined into some sort of shape and I hadn't started any fires, or broke any tooling, I broke out the threading bar and set it up carefully. Took great pains to make sure it was parallel to the piece and on center.
The first cut was fairly light, .02mm, and it came out just fine. I did put some cutting fluid on it for each pass. Succeeding passes were gradually increased up to .08mm per pass. Suddenly I had a sinking feeling in my stomach--I realized that instead of the .5mm pitch that I wanted to cut, that I had failed to change the gears and was, in fact, cutting 1mm pitch instead.
ARRGH! All that time and energy was now really going up in smoke, since the depth of cut for .5mm pitch was only .52mm versus the 1.08mm for the 1mm pitch. And with only .67mm of metal thickness in which to cut the threads, the 1mm pitch wasn't going to work.
Shut down the lathe, shut off all the lights, and called it a night. :scowl:
Ah, well, it is a learning experience after all.
About an hour later, I realize that all is not lost yet. Fortunately, the 60mm piece still leaves plenty of material to play with axially--I just need to deepen the bore, cut off the mis-sized threads and start threading again--this time at .5mm pitch.
(To be continued.)
OK, you can stop laughing now!