Pressure Gauge

[jim18655]

I have one of the HF 12 ton h frame shop presses. While using it the other day to remove a rusted-in, stuck u-joint I thought it would be nice to have a pressure gauge. Is there any way to add one to the jack?

 

[JimDawson]

Sure, there is always a way to do stuff. In this case you would have to tap into the pressure passage going to the ram. It might be accessible near the check valve or below the pump ram. As long as you have room in there to drill & tap for a 1/8" NPT it should work. I suspect you will need at least a 10,000 psi gauge maybe more, not sure what the max pressure is on a hydraulic jack. Then do a little math and you have tons, tons= ((Pi * (ram diameter/2)^2) * PSI)/2000.

 

[jim18655]

Thanks, after I sent the post I found some youtube videos about adding a gauge and its pretty much like you said. They tapped a hole into the bottom of the pressure piston and did the same calculation.

 

[Foghorn]

It's actually really easy to do. Practice on a garage sale jack. I did mine for my press, but didn't take pics. Dis-assemble the jack. After drilling out a small bore in the side of the base for a 1/8" pipe fitting, I used the second smallest drill in a std index to drill a small passage to under the ram cylinder. Then used a bit one size bigger to drill down from the ram cyl floor to just intersect my drilled passage. Hardest part was the layout to not weaken the jack base. Yes you need a 10K PSI gauge & heavy wall 1/8" pipe fittings. My cheap POS 12 Ton press jack will put out 8500 PSI. If you mess up & really weaken the jack base with the small drilled passages, I doubt that it would fail catastrophically, just crack and leak.

 

[jim18655]

I took the jack apart today and have the holes marked. The HF 12 ton jack has a flat boss on the side opposite the pump that looks like it should take a 1/4" pipe. I found a 10000 psi gauge and 1/4 fittings from a hydraulic supply house. I wanted 1/8 pipe but all the gauges and fittings were 1/4". The ideal set-up would be a short hose but I couldn't find one over 3000 psi. The challenge now is to remove the jack cylinder sleeve. I can't get it loose and I'm afraid I'll crush it with a pipe wrench. It looks pretty thick but I don't feel like taking a chance. I'm thinking about putting the cylinder in a pipe vise and turning the base. The vise should spread the pressure around the cylinder better.
The piston is 1.765" diameter so i should be good with a 10000 psi gauge. The pipe and fittings I saw as the weak link.

 

[jim18655]

So far success. I gave up on removing the cylinder from the jack. I was afraid I would egg it if I put too much pressure on it. I milled the top of the boss flat so I could put a machinist level on the jack to get it square to the center. Next I drilled and tapped the boss for the 1/4" hydraulic fittings. Since I couldn't get the inner cylinder out I planned on using a long bit to reach the bottom of the cylinder for the intersecting holes. I put the jack back in the vise and shimmed it so I could drill the horizontal hole on an angle up toward the center of the cylinder. I centered the drill in the bottom of the hole and measurements showed I needed to drill about an inch deep. I put the bit in the bottom of the hole and set the DRO to zero and started drilling. I was just about to depth when I heard and felt a small pop. The bit chipped a small piece of metal out about center of the cylinder. No need to drill the intersecting hole. The gauge and fittings should be here this week. I'll give it a good cleaning to remove all the chips and it should be good to go.
Calculations for this jack show it should reach 12 tons at about 9800 PSI.