Lathe advice...

[WilliamD]

I am currently retrofitting my IH mill for CNC. I want to get a lathe to compliment it. At first, I want to use the lathe to turn down the ends of the ballscrews I need. I see that this has a "bore" of 1 7/16", does that mean I can pass the 3/4" ballscrew threw it and machine the end? I'm sure I would have to find some way to support the other end, I just need to know if that's what it's for. It would be a year down the road, but I'd also retrofit the lathe for CNC also. But any opinions or advice on this lathe would be greatly appreciated!

[HuFlungDung]

Yes, spindle bore is a very important feature of a lathe. The larger it is, the more convenient it can be for many kinds of work. Larger bores tend to have lower top rpm limits, because the bearings are larger, but in the size range you are talking about, this would not even become an issue.

A rear mounted 3 jaw chuck is handy to have on the outboard end of the spindle. On my Summit lathes, with 4.125" spindle bore, I made special backplates to clamp onto a section of the spindle that projects out the rear side of the headstock, then mounted a chuck on there.

The added weight of two chucks takes a bit more horsepower to ramp up, but the benefit of working on longer pieces of stock without resorting to a steady rest is worth it.

Still, there is a practical limit to the overhanging length of material hanging out the back end of your lathe. I suppose about a 12:1 length to diameter ratio works well enough for moderate spindle speeds and straight stock. Think safety: stay clear of the rear side of the spindle, keep people and obstacles away, in case you have an accident. The stock will bend to a right angle and flail (or kill) anything (anyone) that it hits.

I had an employee forget this with a 3/4" rod about 3 feet long hanging out the back end. It severely beat up a toolbox before he could stop it.

Another time, a fellow had a piece of 1.5" stock hanging out about 6 feet. It started out straight enough (so he says) but as harmonic vibration built up, that bar started to bend mightily. It rocked the entire machine off the floor pads. That is a 6000 lb machine.

[WilliamD]

WOW! Thanks for the input, and warning. I definetly wouldn't do it very much, because I could definetly see that it would be potentially dangerous. But I'm thrilled to know that's how it works! Other than those ballscrews, the most it'd ever do is a 20" barrel. Only about 10 inches of it would be stick out anyway. Definetly weird to see 6 feet of stock hanging out the back end of a lathe!

[Mcgyver]

HuFlung, neat idea on the outboard 3jaw. There are few thing as terrifying as when you think you've gone too far and length of steel bar is turn itself into a giant weed whacker. I've seen it start once or twice but managed to kill it in time - 1.5" whipping around! jeez that'll kill a regular man. You definitely want to err on the side of caution. William 1) "that's all i will ever do with it" - famous last words, and 2) even if it does stick out 6', its only dangerous at a certain speed. Even at 6', if you run it a 50 rpm with the stock resting on something, its not going to get out of control - maybe not a solution for production, but for a one-of its fine

[WilliamD]

"Famous last words..." It's true, I thought the same thing about the CNC mill, but ideas just keep coming I'd never thought of prior to the CNC. I love this hobby. I'm thinking of getting into starting my own machine shop, but time will tell. Would anyone give a yea or nea on this lathe though? It definetly fits my size requirements, and then some. I don't think 2 HP is underpowered, but I guess that all depends. I just don't know if this is the kind of lathe that will hold .001" over 12 inches or not.