Hey guys, can someone out there shed some light on how much oil should be put in a Hydraulic Bandsaw downfeed cylinder. This is the kind with the downfeed adjustment valve and the piston has a quick return bypass valve in it. If I fill it slap full with oil it seems to lock up. If I keep some air it's spongy. What's the correct filling setup? RichD, Atlanta
I don't know the answer to your problem but be aware that, because of the volume of the rod itself, the rod end of the cylinder cannot hold as much oil as the other side when the piston is moved from one side to the other. If you fill the system with the rod extended you cannot force the rod in. If you fill it with the rod retracted a vacuum will be created when you extend the rod. I think you need to have an air vent or a chamber to allow for the varying oil capacity.
Q3: Did it ever work properly? What happened just before it started doing this?
Q4: Before topping up the fluid did you flush the system?
Q5: Is the spring that provides downward pressure on the saw frame in place and adjusted properly?
Q6: Does the cylinder lock up in any position when full or does it lock up only if you open the valve as you would when cutting? In other words, when it is full, can you move the piston in one direction but not the other?
Q7: Did you fill with real hydraulic jack oil of the proper viscosity or something thicker?
Q8: When bleeding the system, did you leave the filler cap off, actuating valve open and slowly raised and lowered the saw frame through several (say 10) cycles by hand or until you detected no bubbles in the fluid under the filler?
WAG1: If it really is a Harbor Freight SKU 93507, could you call them and find out what they say: 1-800-444-3353.
WAG2: If the piston locks only when you attempt to 'cut', I would suspect crud in the actuating valve orifice.
WAG3: If the piston locks in both directions, I would suspect crud in both the piston checkvalve and the actuating valve orifice. Air is thin enough to pass through a restriction that would greatly hinder the flow of oil. Alternatively, fluid of too high a viscosity might cause that.
Suggestion1: I would drain the system and re-fill it with solvent that is safe for the seals and valves. I would leave the actuator valve open and cycle the solvent through say 3-5 changes of fresh solvent. Then, I would disassemble the actuator valve and confirm that it opens properly and its orifice is clear and clean. Then I would be tempted to disassemble the piston from the cylinder and see if I could confirm that the checkvalve is working properly. Clean the parts, reassemble, fill and bleed and test once more. That's what I would do.
Nok, Thankyou for the link. The cylinder on that saw is identical to this one. The refill instructions most certainly will leave a little air inside and that's what makes it work. The difference in top to bottom volumes is the trick. Thanks, guys. RichD, Atlanta