Okamoto Hydraulic Grinder information
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    Default Okamoto Hydraulic Grinder information

    I have gradually been improving the operation of a surface grinder that I purchased a couple of years ago and I'd like to share some of the things that I have learned.

    The grinder is a OKAMOTO Accugar 124N. I purchased it from a large company that bought it new in the mid '80s.
    I bought this grinder without looking at it, the price lead me to believe that something was wrong with it.

    After receiving it, the grinder's automatic operation did not work properly.
    Looking deeper, I determined that the grinder had been manually operated since the mid nineties. The company that owned it used it for support and maintenance only, the mag chuck had never had a true-up grind. No one tried to fix it.

    I diagnosed the problem and found that 2 of the 3 solenoid valves had bad coils. I corrected the problem and now I am questioning the lack of maintenance of the hydraulic system.

    I've learned quite a bit, and I'm ready to assist anyone in the care and upkeep of these grinders.

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    I recently installed a 124n at my shop. The auto downfeed didnt work and I looked closely at the 3 way switch on the control and saw that one of the finger contacts on the rotary switch was cracked off. There are spare fingers on all the rotary switches and I clipped one off and soldered it in place of the cracked one to fix it. Something to look out for on these.

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    Quote Originally Posted by markp View Post
    I recently installed a 124n at my shop. The auto downfeed didnt work and I looked closely at the 3 way switch on the control and saw that one of the finger contacts on the rotary switch was cracked off. There are spare fingers on all the rotary switches and I clipped one off and soldered it in place of the cracked one to fix it. Something to look out for on these.
    Thanks markp, I'll make a note of that.

    I've always heard that these grinders are very good, and I'm sure they are. But I am not impressed with the hydraulic oil tank being used as the base casing of the machine, and there is absolutely no real filtration of the hydraulic fluid, this can lead to a big problem regarding fluid contamination resulting in solenoid valve failure.

    I am looking into adding a high pressure 5-10 micron filter directly after the pump's out put. In the mean time, I epoxied 4 super strong magnets to a 1/2" thick and 8" long aluminum plate and placed it on the floor of the sump(well enough away from the sieve).

    I can see why Okamoto went this route (using base casting as a sump), its does save space, but it should definitely be filtered. Nicco grinders do it right, I think they are out of business, but those grinders are very good.

    I will keep you informed on my progress.

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    Okamoto has advised me to flush the hydraulic sump once a year. The process involves using a gallon of a very expensive flushing oil ($400.00 per 5 gallon pail) for approx 8 hours and immediately flush the system and discard the oil.

    There is at least 25 gallons of Hydraulic fluid (Vactra #1) in the system, at $80.00 per 5 gallon bucket.

    Okamoto's procedure is cost prohibitive. I did follow their advise to drain and clean the sump, but I did reuse the fluid after I filtered it. I also cleaned the solenoid valves just as they recommended in their Okamoto Solenoid Cleaning Procedure PDF.

    My next step is to add a 5-10 micron high pressure filter just before the solenoid valves and add another low pressure "spin-on" to the return line.

    I originally contemplated to just remove the pick-up sieve and replace it with a 5-10 micron spin-on filter and be done with it, but after reading about hydraulic systems this short cut is not advisable, permanent damage to the hydraulic motor may result.

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    When I picked up my okamoto 124n, it was full of oil. I used this parker filtration unit to filter the oil into drums. When I installed, I cleaned the sump, the intake filter and I ran it through the filter system again. Ive got the 25 micron inlet and 10 micron outlet filters installed. Any grinder users out there have an opinion on filtering grinder oil to reuse?
    Attached Thumbnails Attached Thumbnails filter.jpg  

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    Quote Originally Posted by markp View Post
    When I picked up my okamoto 124n, it was full of oil. I used this parker filtration unit to filter the oil into drums. When I installed, I cleaned the sump, the intake filter and I ran it through the filter system again. Ive got the 25 micron inlet and 10 micron outlet filters installed. Any grinder users out there have an opinion on filtering grinder oil to reuse?
    Excellent filtering rig markp,
    So it looks like your not having any issues with removing the sieve and replacing it with the 25 micron. How long have you been running this set-up?

    Replacing 26 gallons of vactra every year is a big undertaking (cost wise). I have read that filtering is the way to go. It is also recommended to filter fresh fluid as well.

    Looks like you got a good handle on this. The hydraulic system on these grinders is perhaps the only thing that can go wrong with them.

    I have a question for you markp, what does the little adjustment knob near (lower left of the wheel head handle) do?

    I used both of the coils from the rear solenoid to replace the bad coils on one of the front solenoids to repair the automatic reciprocating motion. So my wheel head auto function will not work until I purchase those two coils.

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    No, I didnt change the seive inlet filter on the grinder. That needs to be free flowing. Those are the specs on the filters that I have installed in the filtration cart.

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    I would like to correct my previous statement, a flush is recommended every 5 years, not 1 year.

    I tried to attach Okamoto's PDFs, but they are too large.

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    I finally got around to adding a filter to my grinder. I started with a return line filter (10 micron spin on), it was quite easy. I found a line just pass the pump outlet. This line apparently was dumping fluid back into the tank. The pressure wasn't very high, so I assumed that this was the return line. I've been operating the grinder quite a bit now for the last few weeks, everything seems to be ok.

    I then purchased a high pressure (10 micron) Parker filter. I will install it in the next couple of weeks.

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    Quote Originally Posted by markp View Post
    When I picked up my okamoto 124n, it was full of oil. I used this parker filtration unit to filter the oil into drums. When I installed, I cleaned the sump, the intake filter and I ran it through the filter system again. Ive got the 25 micron inlet and 10 micron outlet filters installed. Any grinder users out there have an opinion on filtering grinder oil to reuse?
    Hello:

    The theory is that new hydraulic oil dissolves and collects varnish deposits within the system up until a equilibrium concentration has been reached in the oil. Once a equilibrium has been established the process stops. It is analogous to flushing a boiler containing dissolved mineral deposits with distilled water. The distilled water will remove the minerals until a equilibrium has been established in the flush water.

    Oils can form a solid film when exposed to heat, static electric discharges, oxygen, or dissolved metals that act as catalysts. There are additives included in the oil formulation that slow down the process. Eventually the additives are used up.

    A flushing oil may be needed if the hydraulic system is operated too long without changing the oil. Changing the oil at regular intervals should prevent the need for using a flushing fluid.

    I do not know for certain how much of this is true. There is one oil filtration company that has a website detailing the above argument. They sell a filtration system which they claim will remove the degraded oil products from the oil and allow it to be reused. A replacement additive also needs to be purchased to restore the anti-oxidation chemicals.

    My experience is that the hydraulic spool valves need to be disassembled once they jam from sitting too long. The flushing oil is used in the hope that the spool valves can be freed without disassembly.

    The "old" oil does not seem to be a problem provided that the grinder is used on a weekly basis. If the machine is going to be sitting idle for months a oil change may be needed to prevent the accumulated varnish deposits from jamming the spool valves. The hydraulic pistons do not seem to be sensitive to the presence of old oil. There is a possibility that the o-ring and U-cup seals may become brittle. This may be a result of sitting idle rather than from the contaminated oil.

    The ways on the Okamoto grinder are protected from any grit in the oil by the gravity fed oil system. The oil is pumped to the sump at the top of the column and then filtered by the wool wicks that draw the oil from the sump to the way oil feed lines. The spool valves and hydraulic cylinders are exposed to the grit in the oil.

    The other major problem is rust. All used oil contains water and dissolved oxygen. New oil contains additives that form a film on metallic surfaces that will slow down the oxidation of the exposed metal. The additive is eventually used up. Once this happens rust will form and jam the valves if the grinder is left idle. The solution is either to change the oil or use the grinder weekly to prevent the rust film from building up. The flushing fluid will not remove rust.

    The return oil line outlet is kept 2 inches below the oil level in the tank to reduce the pickup of water vapor and air. If you operate the grinder with a low oil level rust is more likely to be a problem.


    On older grinders it is possible to upgrade the machine hydraulics to continuous filtration by replacing the hydraulic sump drain plug with a quick disconnect fitting and then running a hose from the fitting to a external pump and filter unit. The oil is then returned to the tank through a modified tank fill cap. The cap is set up to insure that the return line is below the tank oil level.

    The advantage of this system is that the water and abrasive slurry at the bottom of the tank is continuously being removed. The filtration system consists of several stages. There will be a bag or spin on filter to remove grit, That will be followed with a water separation chamber with a automatic drain. The last filter may contain activated carbon or a molecular sieve to remove the degraded oil products.

    Robert
    Last edited by Robert R; 09-22-2018 at 10:03 AM.

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    I just bought an Okamoto Accugar 124N but haven't picked it up yet. I did get to see it under power and it worked great and the surface finish was good. I plan to go thru and clean everything and change the hydraulic oil. The grinder comes with a full set of manuals so I will be reading up on all of the maintenance procedures. I believe that the ways are hydro-static and the hydraulic oil is the only lube. I will invest in new oil but I am interested in the filtering that you are doing. Thanks for the thread and keep us posted. Daryl

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    We filter the oil with a parker external filter cart 1x per year. Then every other year we dump and refill the oil in our machines. we have several 12 x 24 okamotos that run 2 shifts daily and they have been reliable machines when kept clean and maintained.

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    Quote Originally Posted by markp View Post
    When I picked up my okamoto 124n, it was full of oil. I used this parker filtration unit to filter the oil into drums. When I installed, I cleaned the sump, the intake filter and I ran it through the filter system again. Ive got the 25 micron inlet and 10 micron outlet filters installed. Any grinder users out there have an opinion on filtering grinder oil to reuse?
    We use a filter cart like this to filter the oil on the hydraulic units on our Mattison grinders. As long as hyd oil stays clean and not overheated it can last a long time. we like to stay on the safe side and just like the okamoto grinders, filter 1x per year and change out ever other year. It may seem expensive but vs the alternative of machine downtime and repairs it is pretty cheap insurance.

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    Quote Originally Posted by cash View Post
    We use a filter cart like this to filter the oil on the hydraulic units on our Mattison grinders. As long as hyd oil stays clean and not overheated it can last a long time. we like to stay on the safe side and just like the okamoto grinders, filter 1x per year and change out ever other year. It may seem expensive but vs the alternative of machine downtime and repairs it is pretty cheap insurance.
    I like your thinking on this Cash. If machine owners read and performed the maintenance schedule that comes with every machine, most of them would run trouble free, especially with regards to changing oils. I have been rebuilding a lot of rotary actuators on CNC lathes, and most companies have never changed the hydraulic oil in years. Then I explain how the bearings are lubricated in the actuators and hydraulic pumps.

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    Quote Originally Posted by Other Brother View Post
    I like your thinking on this Cash. If machine owners read and performed the maintenance schedule that comes with every machine, most of them would run trouble free, especially with regards to changing oils. I have been rebuilding a lot of rotary actuators on CNC lathes, and most companies have never changed the hydraulic oil in years. Then I explain how the bearings are lubricated in the actuators and hydraulic pumps.
    Case Closed.

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    Quote Originally Posted by otrlt View Post
    I finally got around to adding a filter to my grinder. I started with a return line filter (10 micron spin on), it was quite easy. I found a line just pass the pump outlet. This line apparently was dumping fluid back into the tank. The pressure wasn't very high, so I assumed that this was the return line. I've been operating the grinder quite a bit now for the last few weeks, everything seems to be ok.
    I recently added a spin-on filter to the return line of my Studer RHU-450 grinder. Some pictures are here: Studer RHU 450 from the 1960s

    This made a big difference to appearance of the hydraulic oil. Now, when I look in the sump, it's absolutely transparent (though tinged with color). I can see everything inside. Before, it was cloudy.

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    Quote Originally Posted by otrlt View Post
    I finally got around to adding a filter to my grinder. I started with a return line filter (10 micron spin on), it was quite easy. I found a line just pass the pump outlet. This line apparently was dumping fluid back into the tank. The pressure wasn't very high, so I assumed that this was the return line. I've been operating the grinder quite a bit now for the last few weeks, everything seems to be ok.
    I recently added a spin-on filter to the return line of my Studer RHU-450 grinder. Some pictures are here: Studer RHU 450 from the 1960s

    This made a big difference to appearance of the hydraulic oil. Now, when I look in the sump, it's absolutely transparent (though tinged with color). I can see everything inside. Before, it was a bit murky or cloudy. Now those small suspended particles are gone, and it looks clear.
    Last edited by ballen; 09-24-2018 at 04:23 AM.

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    I have solved the problem that I was having with my grinder.

    First of all, I did replace all 3 solenoid valves. At first, everything looked good. But then I noticed that the wheel head down feed was not working as it should. I disassembled the down feed assembly and noticed that the splined disk had sharp corners on both sides of it's OD. This condition is a flaw in Okamoto's design of this component. I ground a .05" wide chamfer an both sides of this disk. By doing so, I removed the crushed splines that were in the edges of this disk. After this I diamond filed the few splines that were crushed. I did purchase a new pawl, and assembled completely.

    Even after this repair, I was still having issues with the automatic down feed. I tested the down feed manually (by pulling up the lever) and it worked great.

    What I determined is that the piston that engages the pawl was moving too fast. The valve, (lower left of down feed handle) did not seem to work properly. Even after closing the valve completely, I would still see rapid piston movement. At that point, I knew I had a faulty valve. I disassembled the valve and found a bypass plunger (plastic pin) that was clearly broken. I turned a new one out of Delrin and re assembled.

    The automatic operation of this grinder is working beautifully, but what surprises me is the accuracy of the final automatic movement, when it reaches ("0"), it is stopping within .0002".


    So If you have one of these grinders, check your valve.


    I haven't installed the High Pressure filter yet, but I at least have the return line filter operating.

    I will keep all informed of my progress.

    This is a OKAMOTO 1224N (mid '80's)

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    Quote Originally Posted by otrlt View Post
    Thanks markp, I'll make a note of that.

    I've always heard that these grinders are very good, and I'm sure they are. But I am not impressed with the hydraulic oil tank being used as the base casing of the machine, and there is absolutely no real filtration of the hydraulic fluid, this can lead to a big problem regarding fluid contamination resulting in solenoid valve failure.

    I am looking into adding a high pressure 5-10 micron filter directly after the pump's out put. In the mean time, I epoxied 4 super strong magnets to a 1/2" thick and 8" long aluminum plate and placed it on the floor of the sump(well enough away from the sieve).

    I can see why Okamoto went this route (using base casting as a sump), its does save space, but it should definitely be filtered. Nicco grinders do it right, I think they are out of business, but those grinders are very good.

    I will keep you informed on my progress.
    Hey, I just wanted to let you know the okamotos have steel filters at the bottom attached to the tubing, I didn't catch who said they run without filters but all 6 of our machines have them.

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    Quote Originally Posted by Sjzona View Post
    Hey, I just wanted to let you know the okamotos have steel filters at the bottom attached to the tubing, I didn't catch who said they run without filters but all 6 of our machines have them.
    Hello Sjzona.
    The filter that you are referring to is the pick-up sieve filter, it is only going to protect your hydraulic pump motor. This sieve filter will not protect your solenoid valves. Those valves need at least 10 micron filtering.


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