Question for Collet chuck users.

[Frank_S]

I am in the process of putting together options for a HAAS SL-20 build. One of the main parts I will be machining is 4.000 inches in diameter by 1.100 inch long Aluminum. I would like to grip the O.D. of the part by a minimum of 0.200", 0.400 would be optimum length to grip. I will not be taking heavy cuts. The part will only be finish machined so the cuts are light.

I have been making these parts on an engine lathe with a 3 jaw chuck, however when I get the SL-20, I was think that using a 16C? collet chuck would be advantageous, IE less rotational mass and less wear on the machine in general. I would imagine the collet would be quite accurate, at least as accurate as the chuck? I need to maintain 0.001" concentricity.

I have little experience using large collets such as this which as I said would have to be able to hold a 4.000 aluminum part. Does HAAS offer anything other than a 5C collet chuck option? Are they accurate enough for this type of a job? Would it be an air type collet chuck? I'm used to using a regular old Royal 5C collet closer with a manual actuator arm.
Your comments on this would be greatly appreciated!

[Geof]

A collet to hold 4" will be a large collet and the associated holder and everything I think will be around as heavy as the standard chuck on an SL20.

Use the regular hydraulic chuck with custom machined jaws and you will be able to get your required precision.

[Geof]

A collet to hold 4" will be a large collet and the associated holder and everything I think will be around as heavy as the standard chuck on an SL20.

Use the regular hydraulic chuck with custom machined jaws and you will be able to get your required precision.

[dcoupar]

Hardinge makes 5-C step collets that will hold up to 6" diameter. If your 5-C collet chuck has a threaded end to hold the step chuck, you can do what you're trying to do.

http://www.hardinge.com/usr/pdf/collet/2348F_LR.pdf

[Frank_S]

Thank you for the replies on the subject. I probably will end up using the chuck for that part.

I do make parts that will necessitate using a 5C collet chuck. How much of a pain is it to remove and re-install the hydraulic chuck on the SL-20? Also, what 5C collet closer would you recommend buying for the SL-20?