$675-No Way-Hydraulics Guru Needed

catmadni · Jun 18, 2007

It seems I bent the spool valve for the loader boom slightly.

I take the loader on/off frequently and I banged the bottom of the spool cap against the frame. Kubota won't sell me just the spool without the whole valve. $675

Has anyone ever machined it right again witout spending the big dough?

techman · Jun 18, 2007

You do not want to machine it, it will increase leakage and reduce effectiveness. Trying to straingten it is a 1 in a million shot as well. Spool to housing clearances are generally about 20-30 microns (1000 microns to a mm).

Best bet is to see who's valve it is. Many Kubotas use Husco. Call the mfg. and see if you can get a replacement spool for the valve. If not you should be able to get the complete valve for about 1/2 of Kubota's price.

paul

JerryG · Jun 19, 2007

You will have to shell out the money for a complete new valve. There is really no way to straighten it and make it work right. Like Paul said, most Kubota valves are make by Husco. That is also a dead end. Several members have tried to get parts from Husco. They have always been told that they have to go to Kubota. Husco isn't the only company that has that policy. A couple of years ago, I needed the detent assembly for a valve. The company only sold in the U.S. to my machine manufacture and they wouldn't sell me the parts. I was lucky because I was able to wind my own spring and smoothed out the damage on the other part so that everything would work.

rbargeron · Jun 19, 2007

catmadni said:
It seems I bent the spool valve for the loader boom slightly.

Straightening MAY be possible if it really is a SLIGHT bend. Is the valve spool stuck now? Or does it just move hard? If you know exactly what direction the damaging force came from, you MIGHT be able to reverse the effect with a careful setup. Can you get the spool out? If so roll it on a flat surface with a bright light to see the bend. If it's stuck, you may damage the body taking it out. But there is a chance you could be successful. As Tecman says its a long shot, but think of the bragging rights !!

I think one reason the spool isn't sold separately could be they are "match fit" to the actual valve body bore - manufacturing tolerances are allowed to float (lower cost) and parts are selected for best fit at assembly. As always, prompt cheerful refund if info is bogus

Dusty · Jun 19, 2007

I would suggest taking it to a machine shop that might be able to straighten it or machine you a new part. I would be hesitant to do anything on my own concerning the valve except replacement. A good machinist will know exactly how and where to put the pressure to straighten it. For $675, it is worth a try at least.. Dusty...

catmadni · Jun 19, 2007

Thanks guys, I appreciate the advice.

Sounds like Husco is a dead end. The spool is not jammed in the block. I have had it all apart. I rolled it on a flat surface. To the naked eye it looks perfectly straight, however I can't see those small tolerances.

My brother in law is a machinists. He said he will spin it on a lathe for me and read it. Even he is pesimistic though.

The valve still operates, but it is jammed just enough that the loaded spring is not enough for it to return to closed.

I think I can pin point the direction of the blow it took.

I'm dropping it off to his shop tonight. Thanks again.

rdsaustintx · Jun 20, 2007

I worked in a hydraulic valve plant at Bendix in a past life. The spool/sleeves are matched sets. Tolerances are unfrigginbelievable (like techman says). No way to make them interchangeable.

They loaded the spool/sleeve on a test bench, ran it, pulled it apart and kissed the spool with tiny grinders over and over. When measuring bores and OD's they would soak both parts in alcohol first to make sure they were the same temperature and no oil film interfered.

They were aircraft servos, so probably a little more critical than ours, but you get the idea...

Russell in Texas

PS: Bendix tried busting the machinist union. No valves came out of that plant for the next six months.

catmadni · Jun 20, 2007

Russell,

I am leaarning each day about the tolerances you talk about. I brought it to my brother in law, the machinist last night, and as soon as he looked at it he said I was in trouble.

He said first off its not just turned on a lathe, its grinded, probably to 1/1000". Although he said the only shot I have is to let him turn it on his lathe, mic it, I guessed that meant measuring the various diameters along the spool with a micrometer.

Then, if he finds that its is within a couple of 1000ths, he will machine it down in the appropriate area with special abrasive.

He thinks it will work, but I may lose performace from the valve by exceeding the tolerences as oil bleeds across the spool.

I trust him. He is a smart guy. He has never worked on these, and does not know much about them, but what have I got to lose. I'm screwed anyway.

catmadni · Jun 21, 2007

He did it!!

He miced the spool and it was bent approx 75 microns at the very tip from 0.00, about 4 cm along the shaft.

He turned it and removed about 30 microns, which was enough to aloow the throw of the spool.

Disaster averted and a lesson learned. If you are a frequent remover of the quick attach boom, don't do it so quick, that you are not watching if the stands are securly stationed at the right height and clear of that low spool cap.

Thanks for everyone's input and guidance.