Questions about Lever Type Collet Closers

[adbuch]

Hi,

I am considering purchasing a new (or used) 14"-16" engine lathe to fill the gap between my 12" Atlas/Craftsman bench lathe and my Nakamura-Tome Slant 1 CNC turning center. My 12" lathe has a handwheel collet closer (3AT collets) and my Slant 1 has a hydraulic collet closer (16c or 5c with adapter). Most of the lathes I am considering purchasing have (or offer as an option) a 5c lever type collet closer. I have no experience with the lever type collet closers. Here are my questions:

1. It was pointed out to me by the local machine tool dealer that the lever type collet closer allows one to open the collet while the spindle is turning. Under what circumstances would the lathe operator want to do this?

2. Most of the Asian lathes offer a lever type 5c collet closer eitiher as standard equipment or as an option. For example:

http://www.machinetoolonline.com/PM1440HD.html

Some lathe dealers also offer American made lever type collet closers as an upgrade (I was quoted $995 for a JFK model, although I have seen this brand at lower prices). I would like know how the import lever type collet closers really work (or what problems to expect) from someone who has used them (other than a machine tool dealer).

Thanks,
David

www.deserthybrids.com

[Geof]

Originally Posted by adbuch ....1. It was pointed out to me by the local machine tool dealer that the lever type collet closer allows one to open the collet while the spindle is turning. Under what circumstances would the lathe operator want to do this?...

When you are parting off from bar stock and have a bar feeder sometimes it is much quicker to open the collet and let the bar advance against a live stop instead of stopping the spindle. Similarly if you are doing second operation work with a stop inside the collet sometimes it is quicker to load and unload with it spinning; so long as your parts don't have sharp edges.

Regarding quality you need to look at the way in which the lever actuation is transmitted to the rotating parts. Some closers just have cast iron sliders running un a groove; much like the selector forks on a gearbox. These can wear rapidly. Other types have a thrust bearing to take the rotating force.

[adbuch]

Hi Geof,

Thanks for your quick reply. I will keep that in mind (groove vs. thrust bearing) when looking at potential collet closers to purchase.

Thanks,
David

[DJPLAST]

It sounds a little scarry, but as was stated earlier, you can load and unload production jobs without stopping the spindle. I have personal experience with this from about 35 years ago on a Hardinge 2nd op lathe. It worked great! Can have a tendancy to chew up fingers if you don't pay attention though.