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
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?
Yes. The first refill I went to great pains to get as much air out as
The piston will run end to end freely with no oil and with oil and
But not when full of oil.
What is the trick to these things?
I searched the net and this group, but found little info.
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.
Q2: Is that similar to your saw?
Q3: Did it ever work properly? What happened just before it started
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
Q7: Did you fill with real hydraulic jack oil of the proper viscosity or
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.
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
what makes it work.
The difference in top to bottom volumes is the trick.