Live center/ dead center

[jocat54]

Well here's my newbie question of the day, I know what a live and dead center is. Why would one use a dead center instead of a live center?
I just can'r come up with a good reason in my newbie mind.

 

[pdentrem]

In normal use the dead center would be used in the spindle as it turns with the work, such as when using a lathe dog. The live center is usually used in the tail stock. You can use a dead center in the tail stock, just be sure to lube the center hole in the part and check the tension from time to time as the part will change length as it heats up from turning it. If wanting a live center, you can spend little or a lot. You are buying precision, less run out, with the pricier centers.

 

[jocat54]

In normal use the dead center would be used in the spindle as it turns with the work, such as when using a lathe dog. The live center is usually used in the tail stock. You can use a dead center in the tail stock, just be sure to lube the center hole in the part and check the tension from time to time as the part will change length as it heats up from turning it. If wanting a live center, you can spend little or a lot. You are buying precision, less run out, with the pricier centers.

Thanks, That makes sense to me now--just didn't think of the center being used in the spindle.

 

[doco]

This is the same way that one would not go gather a "f a g g i t" of sticks anymore.

While we are in the anal retentive mode it would be "f a g g o t" of sticks.

 

[Tony Wells]

I'm not going to get into the discussion about terminology. I see it as a change in the vernacular and accept it. Part of the question was the use of dead centers. In any event, there will always be runout, no matter how small, and sometimes there is need for absolutely the least possible. Once common application where this is so is in OD grinding. It is standard to use a dead (non rotating) center in both ends of the work. This gives as rigid and true support as possible for the work. Of course, OD grinding is done at relatively slow spindle speeds, so there is no appreciable friction created heat. The center is lubricated with a grease that won't dissolve easily in the coolant. Of course, the drive end of the work is supported on a center that rotates with the work, so no lubrication is required.

Not mentioned, but associated use of non-rotating centers is the half center. This is used in the tailstock of a lathe, with the missing half of the center facing the front, operator side of the lathe. This allows a facing operation to cut the entire face, down to the edge of the center hole. Half centers are not used on the drive end of the work.