Boring some chrome shaft

[Kevinb71]

I am in the process of boring some 2" OD Chrome plated hydraulic cylinder shaft. I am using my little 7x12 mini to do this as my 10" lathe is still down. These are to be .500 wide 2" od with a 1.375 internal diameter. The external face will have a seal ride around it, These are some bushings/seals for a steering spindle and will be one on each top and bottom of the spindle and two sides, so four total. My question is in reference to the boring operation that I am doing. The internal diameter was rough and about 1" ID. Using a 3/8' carbide boring bar I have been cutting this out to the 1.375 ID. What is occurring is I get a "chatter" pattern inside the shaft that looks roughly like a acme thread of maybe 8-10 tpi, though not much depth to it. I have tried different speeds and feeds. Using a 256 feed speed works the best. I have tried adjusting my compound and carriage feed/lead screw backlash as much as possible. It didn't really seem to make a difference. I had been taking out about .010 per pass when i first noticed this and then tried incremently less per pass. it doesn't seem to being diminishing. I really have no idea what kind of steel this piston rod is, but other than this it seems to machine well. The interior finish on this is not critical, just really trying to figure out what is going on. After this piece is bored then the plan is to part to .500 length. I have never parted so any thoughts on that with the chrome shaft would be appreciated. Thanks!

 

[aliva]

Just a thought, I did'nt see in your post how much of the 2" shaft you have in the chuck. Could there be too much unsupported stock in your set up? Keep the 2" stock as short as possable to the chuck to increse rigidity, and reduce flex.
If you only need a final lenght of .500" cut a piece 2"-3" in length then chuck it up.
If you can't do this, think about a steady rest.

 

[Kevinb71]

I have approximately 3" in front of the chuck. Boring it to a depth of about 2 1/2" as I want to cut all four bushings (.500 x 4 plus kerf) from the one piece. It was a real challenge for a newbie to get it centered and concentric with my four jaw chuck. Really don't want to rechuck it if i don't have to. I can try a steady rest. Thanks!