View Full Version : Frozen tail stock clamps HiT 18S

09-26-2013, 12:56 PM
They hydraulic tailstock clamps seem to be frozen solid. The tail body moves OK, but it won't lock in position. The tail spindle slowly pushes it back until I get a limit alarm and the program stops. I have been putting a clamp in the way behind the tail body to keep it from moving, but I would like to get the pistons working. I can't turn the pistons using the big hex on top. I have used breaker bars and even an impact wrench.
I am afraid to apply much more force since I could open a hydraulics leak.
I have started looking for a tail stock from a scrap machine.
Any suggestions are appreciated.
Regards, Ray

09-26-2013, 03:12 PM
There is a hydraulic solenoid that directs pressure to the two clamps under the tail body.This locks the body when in use.(The hoses are in the rear.)
If you have the manual,you can check the wiring schematic to test it.
You are correct to be careful about messing with the hex nuts.That can cause a leak.

09-27-2013, 05:53 AM
I checked the hydraulics and they are working. I cracked the fitting and observed leakage going on and off when it should. The pistons are really frozen!
If I set the left tailbody stop all the way to the left and run the tail body full to the left, it binds before it hits the stop. A sharp hit on the piston tops with a brass drift frees it enough to return under power. So, I think the pistons may be actually be moving up and down a very very tiny bit, but I cannot rotate them for any kind of adjustment, which is moot if they can't lock up anyway.
Regards, Ray

07-10-2014, 05:30 AM
Just an update for y'all. I was turning a barrel blank using the tailstock and live center and all of a sudden got some terrific chatter. It looked like a diamond knurl. I observed the tailstock lifting slightly when it engaged the work and realized that something had loosened up. So, I gathered up the courage to pull the thing out of the machine. It wasn't any good the way it was.

Hydraulic lines, lube line and 12 limit switch wires were disconnected. It was a pleasure to disconnect the chain drive that moves the tailstock forward and back, just two allen screws.

Using a 3/4" brass rod, I drove the pistons back and fourth until they were loose enough that the impact wrench could turn them and unscrew them from the bottom clamp pieces.

With the pistons out, I was very surprised to see that the only rust was on the piston itself, and only above the top o-ring. The cylinders were nice and smooth. The pistons were cleaned up, new o-rings fitted and the beast was re-assembled.

Then next day Ruby assisted me in putting it back in the machine. Took all morning to get all the re-connections finished, but it was well worth it. Now the tail stock functions like it is supposed to.

Regards, Ray