[toolsy]

We have to make a whole bunch of custom prototype collets with some strange features of them that are not normal to standard collets. But they basically are just ER collets between ER 11 and ER16 sizes (so they are pretty small).

We would like the runout of the collets to be 0.0005" or less. We are looking into getting a new lathe for these parts and lots of other parts we need to make.

I just went to IMTS and looked at both swiss lathes and conventional lathes with live tools, a Y axis, and a subspindle with a full c-axis. Both machines are around 42mm bar stock size. Both are basically the same price.

The swiss machines hold lots and lots of tools but it looks like there are major clearance issues with tools that aren't short/stub length. Plus, being forced to use oil for a coolant means every part needs to be de-oiled (major headache) and then there are disposal costs. I'm not really stressed about having using ground bar stock. We use ground stock a lot now with our conventional lathes to get better tolerances. Programming looks pretty interesting but we can figure it out.

The conventional lathes seem pretty straightforward. However, we currently use Hardinge 3J collet on our lathes and they aren't great. We often get tolerance runout issues of 0.001" or even 0.002". The Hardinge people tell us we need one of the new quick change Flex Rubber Collet Chucks for better repeatability. I am skeptical that it is just marketing BS or does the flat contact patch on the Flex Collets really make a difference? I still see chips getting in there to throw things off. We can hold the parts less than an inch away from the collet chuck when we turn the OD and bore the ID.

So my question is.... will we get significantly better runout with the swiss lathe vs the conventional lathe on a short part? Or does the swiss only offer a benefit for really long parts.

It is pretty confusing.

[g-code_junkie]

Just my personal opinion but the swiss style have a guide bushing that will help you achieve the tolerances you are trying to hold instead of just the collet system alone.
Hope that helps

[hacdlux]

swiss machines are not necessarily the best for roundness or concentricity. if you want to get your concentricity up bore your collets true to center line. i had to make some .078 pins before i had my swiss, i ripped them out of 7/16 stock in on pass just like you would in a swiss on an 8" chuck lathe, and those came out truer than the swiss turns out. on jobs where i need high concentricity on my swiss we break out the chucker kit. other tricks for fixed head acuracy include not pulling parts for transfer and running shorter bars to reduce vibration and deflection

[OMS2010]

Some newer model swiss machines(Stars, Citizens, and Tsugamis) now come with an option to remove the guide bushing unit to run the machine just like a lathe....so you can test runout in both instances on the same machine!

[ygorek]

Reducer should be placed, and the error will be removed.