newbie questions about hydraulic chucks / collets / boring jaws...

[dsmdude]

We are getting ready for the arival of our first cnc lathe, a Haas HL-1. An area i'm a little confused on is the work holding options. I did the Haas factory training on Friday and the instructor basicly told me that I would be reuqired to bore the jaws of the chuck to the diameter of the stock I am working with. We will be working a lot with 12"-16" lengths of 1" to 2" diameter solid pieces of aluminum and steel. Do I need to bore the jaws every time we switch out diameters? or would a collet chuck be a better option? I'm pretty sure the lathe has an 8" KITAGAWA hydraulic chuck. It just seems like a lot of work to constantly bore the chucks everytime you switch out a job, is there a better way or can some one kind of explain the different options out there. I'm only familiar with our smaller manual lathe that uses a regular manual closing chuck. Thank you in advance for all help!

[Geof]

You do not have to bore the jaws, universal hard jaws are available for the Kitagawa chuck and these can be adjusted to clamp any diameter up to the draw tube maximum; they are also reversible for chucking larger diameter flanges and such like.

The limitation with these jaws is that they may have a bit of runout and because they are hard truing them up is a grinding operation and is not practical sometimes.

When you want to hold bar stock to within a thou or a bit better boring a set of soft jaws is the way to go, but you do not need to keep on re-boring, you have a set for each diameter you use.

After boring the jaws are numbered so they always go back on the same jaw base in the chuck and if they are replaced in the same position in the serrations they will repeat to better than a thou.

[oriondad]

You should not need to rebore your jaws, as long as you know where they were located on the base jaw. However, you should have enough sets of top jaws to accomodate all your rounds you will be turning. So, if you have 1 size of steel, 1.625", then you bore your jaws to hold that diameter. When done, take the jaws off, mark them as 1.625 dia. and store them for when you get that diameter again. You should NOT need to re-bore them.

[dsmdude]

Cool, I researched the hard jaws and it seems like the way for us to go. The tollerances we will be machining to are pretty easy (prob .005 at most). Also, the major diameter of the part will usually be the rough OD of the stock. Thanks again guys for all your help!