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Is the BLACK WIDOW 20 TON AIR OPERATED HYDRAULIC PRESS Any Good? I assemble, review and mod it.

I needed a hydraulic shop press for many uses.

  • Force testing vs displacement on some rubber samples.

  • Pressing and forming PEM nut threaded inserts into sheet metal

  • Bending sheet metal

  • Pressing in pins. Pushing out pins.

One thing I would like to be able to do is to pull on samples to test to failure. I could find or modify this press with a double acting hydraulic cylinder. The way this hydraulic press is designed, the head with cylinder can be flipped upside down with the cylinder extending upwards. A steel frame can be made to hang down from the cylinder piston, allowing samples to be pulled apart.

I looked at all the 20 ton floor standing hydraulic presses that use a hydraulic cylinder that is independent from the pump and reservoir (does not use a bottle jack).

Selection Criteria

Necessary Requirements

  • Floor standing

  • At least 20 ton capacity

  • Independent cylinder (No bottle jack)

  • Adjustable cylinder head position left/right

  • Air operated in addition to handle/foot operated. Air allows the cylinder to be moved significantly faster.

Would Be Nice

  • Hydraulic cylinder is dual action. It can be retracted with an equal amount of force.

  • If dual action hydraulic cylinder is not available, then it should be possible/easy to flip the cylinder head upside down.


I chose the Black Widow 20 Ton air operated hydraulic press. It appeared well made and reasonably priced. It didn't come with any accessories, but it appears to be the same as models sold by OEMTOOLS and Redline Engineering



  • Very solid and well made frame.

  • The hydraulic components appear to be well made and good quality.

  • The air powered pump works well, especially for rapidly extending the cylinder.

  • The force gauge is large, easy to read and appears to work well. The graduation spacing is small.

THE BAD (Room For Improvement)

NOTE! Although the bad list is longer than the good list, I'm mainly nitpicking on details that could be improved. There's nothing that affects the functionality of the press. Other presses in this price range will have similar issues.

  • The packaging was terrible. The boxes were barely holding together, but fortunately I'm surprised that the more sensitive parts didn't get damaged. Most of the parts are heavy metal, so at those just got scratches and nicks in the paint. The force gauge was close to death, but survived.

  • The instructions don't indicate screw sizes on the diagram. You have to figure that out yourself.

  • The cylinder slides around too easily on the upper beam. It needs some way to lock it in place.

  • The cylinder mounting block hangs down a few mm from the rail, so after contacting the workpiece, you still have to extend a few more pumps before the force begins to be applied. Adding some screws on the top side of the mount above the rail to pull the mounting plate against the bottom of the rail will fix this and the cylinder sliding issue.

  • The pump handle stays in the pump when released, but falls out easily if bumped or the pressure is released. This is dangerous as it can feel and hit you. I get that leaving the handle in place is dangerous because it is long, sticks out far and so it's easy to run into it, but they need to figure out a better solution.

  • The spring clips for the table support pins are goofy. They pop off easy and shoot off, so they will be easy to lose. They should have included extras.

  • The table is loose on the column. It would be nice if it could clamp to the upright legs to prevent the table from moving around as you are using it.


Shop Press Pin Set

I bought the OEM TOOLS Shop Press Pin Set. It's a modular system that allows you to quick change the diameter of the press pin. Also comes with a base with holes for each pin.

Redline sells an identical looking asset for more money. Redline also sells individual pins, so pins can be modified and replaced easily.


Clamp The Cylinder To Prevent It From Sliding

Install a sheet metal plate under the bottom plate, and another over the top beam. Use 3/8 threaded rods to clamp the hydraulic press assembly to the rail. One threaded rod on each side should be enough.

Tabs To Prevent Table From Falling Off Pins When Raising Or Lowering

The table assembly bolts are mounted in a diagonal pattern. This design allows the table to be removed from the frame by lifting up one end, rotating the table vertically until it is free from the legs and can be removed from the frame.

The table is not terribly heavy and can be lifted and held in place while the pins are moved. However it is unwieldy, so holding it steady while you're moving the pins is challenging without help.

The easiest way to raise or lower the table is to tilt it up an angle such that it pivots on top of the pin at the stationary end until the other end reaches the next hole. The risk here is that the end that's sitting on top of the pin slides off the pin, and the table falls if not held properly. Adding some tabs the prevented the table from sliding off the pins would solve this problem.

Add A Foot Pedal Air Valve

It's tricky and slightly dangerous to try to operate the air pressure switch and hold the piece being pressed in place at the same time. A foot pedal operated air valve would make things much easier.

Where to buy Pneumatic Air Foot Valve

Adding A Digital Pressure Gauge

The included gauge is nice, but the resolution is low. Each line is one ton, so it's not a useful measurement gauge for precision use. I found a 10,000 psi digital gauge that displays pressure which can be used to calculate the force applied if the cylinder bore diameter is known. This pressure gauge will provide higher accuracy and resolution.

Buy 10,000 PSI Digital Gauge on Amazon

This gauge has a G1/4 thread, which is 1/4 BSPP (British Standard Pipe Parallel)

The hydraulic press pump outlet is 1/4in NPT female. The first fitting is a 90 degree 1/4in NPT male to male fitting. The hose from the pump to the cylinder has a 1/4in NPT female fitting on the pump side.

In order to attach this pressure gauge, I will need a T piece with 1/4 NPT male inlet to 2 female outlet. A hose with 1/4 NPT male fitting and on the pressure gauge side, a 1/4 NPT fitting with a 1/4 NPT to female G1/4 adapter.

It is difficult to find 1/4in NPT hydraulic fittings that have a 10,000 psi rating. In fact it appears that the thread/pipe hole diameter itself might be a limiting factor to the max pressure.

This company in the UK has 10kpsi rated fittings

These fittings are rated to 15kpsi.

Adding Caster Wheels

The feet have holes in them for bolting the hydraulic press to the ground. I doubt most people will do that, especially if they ever want to move it around. Some shop spaces are dynamic and equipment has to move around depending on the project.

My favorite caster wheels for heavy equipment that also needs to be very solid when stationary are Foot Master leveling casters. I've used these on my Southbend lathe and other shop tools for years. The wheels don't get flat. The rubber feet work great, but the extension/retraction mechanism coul use improvement.

To support the casters, another piece of angle iron will need to be added to the feet. The angle iron should be bolted back to back such that they make a wider platform to attach the caster wheels, and the spine is in the center.


Some hydraulic presses have manual foot pedal pumps, and the concept is pretty simple. The advantage of the foot pumps is a hands free method to apply pressure, that way you can have both hands free to control the part being pressed.

The foot pedal pivots on the side of the frame and a linkage goes up to the hydraulic hand pump. This foot pump could be made from simple sheet metal parts.


How To Pull With a Hydraulic Press

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