Turning very small aluminum rod

I need to take an Al rod and turn it down to make two pieces about 100 thousandths diameter by 350 thousandths long. Tolerances need to be no better than 5 thousandths or so, that part's easy. I have some ~0.5" rod stock to start with.

I'm guessing that if I just turn it down to that diameter it will flex quite a lot and I'll have some problems before I even get to 100 thousandths. Any advice on the best approach on this before I create a lot of scrap?

Or, am I worrying about nothing, it will be easy, and I should quite typing and just get on with it?

 

Using a sharp tool bit you should be fine. Just work close to the chuck to minimize flex. You could support the end with a center, but at only 0.350 long you should be fine. Don't get to greedy with the cut depth.

 

Joe Pi had a video on doing this. The trick is to take one huge cut to your final diameter.
You will need to scrap a couple of pieces to figure out the exact depth of cut to get your desired diameter.
After that just take the cut.
It really works, trying to sneak up on it will just lead to heartache and tapered parts.

 

I turn thin sections in multiple steps to minimize stick out. For example, on that piece I would make it in 4 cuts about .087 long with each going to finished diameter so there would never be more than .087 effective stick out.

 

That is only 3.5 diameters out of the holder, you will have no problem doing this.
I would turn aluminum at 600+ FPM with carbide tooling and 200 SFM for HSS tooling.

 

I tried the Joe Pi method while practicing with a newly ground HSS tool in 12L14. It worked great. Took a light pass and measured with a micrometer. Put that in the DRO and dialed in the cut. Hit the power feed and the cut worked great.

 

I routinely make some nose bushings for Balsa airplanes, 6061 Aluminum, T6, .400 long, .110 diameter with a .048 hole in them. Turret lathe, two passes (two tools,) first pass at .125, second pass at .110. hand feed. I make these a dozen at a time. I have more trouble breaking drills than scrapping pieces because of bad turning.

Oh, I make these from 3/8 rod, leave a .030 thick flange full diameter and cut them off from the rear. There's no saddle, just a fixed crossfeed. All hand feed.

 

At my last position, we needed some 303 stainless .050" in diameter and just over 3" long with an integral boss on one end and M1.25-.25 threads on the opposite end. Other part we needed was a tapered piece .9" long, .090" in diameter at the large end and .020" and the small end, made from Teflon. We contracted the work out to a machine shop in Santa Clara. They made these parts holding sub-thousandths tolerances on a Swiss screw machine starting with 1/4" rod. To see if he could make the Teflon part, he made about 3' of .040" Teflon string.

 

Sherline users do this kind of thing all the time, and 0.100" is not that small. Just keep your stick out minimized, use a sharp HSS tool with a small nose radius and run the lathe as fast as it will go.

 

Thanks for all the advice! I'm going to try tomorrow. I'll probably screw up a few times before I get it right.

Joe Pi had a video on doing this. The trick is to take one huge cut to your final diameter.
You will need to scrap a couple of pieces to figure out the exact depth of cut to get your desired diameter.
After that just take the cut.
It really works, trying to sneak up on it will just lead to heartache and tapered parts.

Exactly what I was concerned about. The small diameter part deflecting and I'll end up cutting a taper.

I tried the Joe Pi method while practicing with a newly ground HSS tool in 12L14. It worked great. Took a light pass and measured with a micrometer. Put that in the DRO and dialed in the cut. Hit the power feed and the cut worked great.

View attachment 280634

Ok, that photo convinced me it can be done, LOL.