[machinebob]

I have a 1999 LB-15, there are two chuck pressure nobs, last few days ive been haveing problems. my chuck is crushing my parts, even after i turn it down, I'll run about 5 parts, then it starts to crush again, turn it down, again 5 more parts, and it crushes again.......?

[neilw20]

Does that use a mechanical knob to adjust pressure?
Is the knob position creeping?
I remember adjusting on an Okuma, and had no problem. I wondered how it worked though, having to push it in to read the pressure.
After reading the pressure is it staying the same as you had set to?

[machinebob]

The pressure gauge stays the same, another question is what is the other knob next to it for, it does'nt have a gauge.

[neilw20]

On the LC?? I had a look at the rear of the other day....
There is a knob you turn to select chuck pressure or tailstock pressure and you push in to read the pressure.

Near the rear of the valve, towards the center of the machine there are 2 knobs on the solenoids, One for the chuck and one for the tailstock. Follow the hoses to figure which one, or read the manual.
You hold in the pressure reading knob while you adjust the pressure.
Can't remember if the chuck has to be in closed position while adjusting, because I suspect when open there is no pressure.

It is quite possible the knobs can turn with vibration and get out of adjustment.

I never had a problem because there was a hose pressing against the knobs, and I just left it there, so vibration could not muck it up.

I often adjusted both to suit a job, and they never drifted.
It is possible the hydraulics is low on oil, and the pressure varies as a bit of air cycles it's way through. Pump would make funny noises when air going through. Top up the tank to the design level.

[Armando6887]

The pressure gauge stays the same, another question is what is the other knob next to it for, it does'nt have a gauge.

[neilw20]

Please take a few photos.

[underthetire]

Standard lb's the second one was for tailstock pressure. Using the stock 8" kitigawa chuck? Signs of the chuck being worn out. The hard jaws get loose and start spreading at rpm, once the spindle stops they spring back somewhat and crush thin wall parts.

[DouglasR]

On my LB15 there are two knobs as well as a large rotary dial next to the gauge. The rotary dial switches between tail stock, chuck pressure, spindle brake and system pressure.

The knob CLOSEST to the rotary dial adjusts the pressure. The other knob is for system pressure and should be LEFT ON FULL PRESSURE AND NOT ADJUSTED.

Set the rotary dial to "CHUCK", and push it in - the needle on the gauge will now register pressure. Set the knob to somewhere around 200 psi, give or take. Release the rotary dial and you're good to go.

While you're at it, turn the rotary dial to system pressure and make sure it's up around 500 or so - if there's no "SYSTEM" setting, put it to "BRAKE". Check the tailstock setting, it should be around 80.