How precise are lathes?

[Inertially]

There's so many sections, I don't know where this topic fits O.o

How precise are the usual CNC lathes you'd find in a small machine shop (range?)?
How precise do they get up to?

How precise would a small manual lathe be?

I'm wondering if the benefits of an upgrade in ABEC would matter.
If the bearing seat is manufactured to +- .0005"
Does it make sense to upgrade the bearing where each ABEC grade is a few microns difference.

[MrWild]

This question is like asking how fast do cars go? Well, how fast does a small car go? Hmmm Define small. Define cost. Define use desired.

A "hobby" small lathe is not very accurate due to lack of rigidity. A small tool room lathe is precise to tenths.

A small "Hobby" lathe isn't powerful and you take several light cuts to get anywhere. A good small lathe will let you take a good bite and get done with the job sooner.

Price doesn't mean a thing sometimes. Tormach sells a "CNC conversion" lathe for silly money but it isn't anything more than a 7 x 12 you can buy from Harbor Freight with an inflated price tag. Same weak motor, same limp noodle rigidity.

A used 10" Southbend that has been cared for will out perform a 10" chinese for rigidity and precision. If this is for a shop and you don't want to buy twice, do NOT buy smaller than 9". 10" is pushing it for a benchtop, but is probably the best bang for the buck when shopping for a bench top sized lathe. Anything smaller and affordable new isn't as precise or robust. There are some great used small tool room lathes available on eBay every once in awhile. Steer clear of the All-in-one headaches.

[plasmator]

Would that same advice hold for, say, a Wabeco 2400E?

Only reason I ask is that I have one of these on the way, and I'm wondering what sort of tolerances I should aspire to as an operator.

[Inertially]

Tenths of a what?

It's more like asking, what the speeds are the racecars in NASCAR capable of reaching?

What is common?

[Inertially]

What can be expected out of a machine of this class?
http://www.okuma.com/products/machin...acturn_series/
or
http://www.okuma.com/products/machin...aptain_series/

[plasmator]

Tenths of a what?

In machinists lingo, a "tenth" is one ten-thousandth of an inch (0.0001 inch).

Don't worry, that confuses everyone the first time.

[MrWild]

Originally Posted by Inertially What can be expected out of a machine of this class? http://www.okuma.com/products/machin...acturn_series/ or http://www.okuma.com/products/machin...aptain_series/

A friend claims they will hold .0002 tolerances. I disability retired in 92. To pull tenths like that, we used OD grinders. I don't doubt his word, but the Tool Room I worked at didn't have those type of machining centers. We did pierce and form die work with each Tool Maker taking each job from print to finish. To be honest, I still miss the creativity they allowed us to do that.

[Boots]

As a very skilled Machinist (35 + years), I can make any Lathe cut as Precise as the part needs to be. Even an old belt driven Southbend Lathe can produce high quality parts in the right Machinists' hands. That is what the trade is all about. We get to know the machine and use it accordingly.

[Shane123]

i have ran old mazaks, old mori seikis, harding slants and slant jr's, okuma lb series and crown series, as well as cheaper machines like the romi we have here now. I miss my high end machines, but the place i work for now cannot justify the coins to buy those since we are not heavy production. with that bing said, with the right inserts and programming you can hold tight tolerances, but just like mrwild said, sometimes it doesnt justify trying to hold that tight tolerance on a lathe when a grinder can give you that finish stock size & tight tolerance with great surface finish alot faster and with less headaches. More or less, its all application based, and only you can justify the costs vs rewards on your machine purchasing. In my eyes, i would try to figure out where i want to be in 5 or 10 years in production terms, and base my choice that way. what you skimp on today might hurt you 2 years from now, like it does with my current employer (didnt purchase space saver bar feeder, tool eye, parts catcher), and now every time we run a good size qty of parts, it kicks us in the ass.

[Monkey King]

On My Lathe Project Log, I attach a picture of my lathe spindle after grinding,
http://www.cnczone.com/forums/showthread.php?t=98850
I made spindle by turning, finish by grinding, tolerance less than 0.005mm / 0.0002 inch.
I've done that on manual lathe size 180mmX1000mm
From my experience, precision also depends on operator, not only from machine.

[Shane123]

Originally Posted by Monkey King From my experience, precision also depends on operator, not only from machine.

Correct. Using the correct inserts as well as speed/feed combinations will get him the tolerances he needs, but will they prove to be cost effective? thats the choice he needs to decide .