Pressure gauge on shop press not returning to zero

[forhire]

I have a Jet HP35A 35-Ton shop press. Works great except the gauge keeps creeping up. It never returns to zero when done. At present it reads 12 tons when it should read zero. It's been slowing climbing over the years. Is there a way to repair the gauge or do I need to replace it?

I looked up the part in the manual (HP35A-23B) and Jet wants $269 for the gauge.

I'm certain I can put a standard hydraulic gauge on there and with some math figure out how many tons is on the cylinder based on the bore diameter. I believe the bore is 6". At 2500 psi the cylinder would be pushing 70,000 lbs. That sounds like the right range.

I really prefer a stock style gauge in tons. Does anyone know where I can source a gauge with a scale in tons?

[Boostinjdm]

I've read somewhere that people were taking an off the shelf gauge and printing their own face for it.

[forhire]

I've read somewhere that people were taking an off the shelf gauge and printing their own face for it.

I thought about that. A 0-3000 range is only about $50. The trick is finding one that can be disassembled and re-scaled. Most I've seen on the net look like they're using a rolled edge, rendering them un-openable. :(

[turk]

write on the face with a sharpee maybe

[Matt_Maguire]

Hi forhire, I took a look at the jet manual and couldn't find any system pressures.

I'll take a guess that the bore is near 6" as you think (from the parts breakdown in the owner manual, last page). What you worry about is if the relief circuit in the press gets messed up. If you go over design pressure things start to break.

If you have a hydraulic repair and hose shop close they can tell you what psi series yours has, and you can go from there.

All my Enerpac, OTC and Porto-Power are 10,000psi (old style stuff) and when I need one I just get a 10,000psi guage. These things can really work a guage to death when they load/break over and over.

(edit) If you go out and look for used or surplus, the oil filled guages look and feel nice but they are not intended for this type of system

Matt

[rlitman]

I looked up the part in the manual (HP35A-23B) and Jet wants $269 for the gauge.

For that kind of money, you can get a seriously high quality digital gauge.

I'd call the guys here:
http://www.ssitechnologies.com/PDF/Application%20Notes/PS_AN4_MediaGauge_MG-9V_ProductOverview.pdf
and ask if a gauge can be programmed to match the scale you need.

OR, the cheap answer is to pull the glass on your gauge, pull off the hand, and push it back on, pointing to zero. The hub of the hand fits over the shaft much like a morse taper, with nothing but friction to turn it. You can't force the hand back, but you can "reset" it. It won't be factory accurate, but it may be close enough. What has happened, is the tube inside the gauge has deformed (kind of like a spring relaxing after years of use).

[Billdacat]

I have fabricated meter scales utilizing AutoCad and “transparency” film. I don’t know if it is still availble or if new copiers are capable of printing on the film. When was the last time you saw someone use an overhead projector???
:cool:

[gordon stephenson]

Can you not take it to a high pressure gauge repair shop and have it tested and re-calibrated?

[Stack of Dimes]

You can't simply rewrite your own scale on a gauge that's inaccurate! It's like adding / subtracting time from a clock that's running slow due to low batteries, it'll ALWAYS be inaccurate regardless of where you write your 'new numbers'. The calibration is set to be where the tube is bent inside referenced to zero. If the tube is broken and pre-bent the zero cannot be accurately reset because it wasn't made that way.

Have it fixed right or replace it.

A gauge doesn't care what it's hooked up to as long as the pressure range is correct and the system is compatible with the internals. Getting a liquid-filled gauge won't really add much benefit to you as they are intended for needle vibration dampening- which you won't have. Jet might require a metric thread, just be wary of that. Otherwise any gauge will do.

Is the scale in 'tons' really relevant to you, or are you just curious how much force you are putting on things to move them. I'd think the latter is correct?

[forhire]

Thanks everyone for all the ideas.

write on the face with a sharpee maybe

If I get a PSI only gauge then I guess that would be an easy enough method. 2500 psi = 35 ton. Good and cheap.

Hi forhire, I took a look at the jet manual and couldn't find any system pressures.

Thanks Matt, I estimated the bore. I'll measure it today. I was thinking 6" also. The relief works fine :laugh:

For that kind of money, you can get a seriously high quality digital gauge.


I looked at these digital ones. I'll email them today and see if I can program it for my scale. I doubt I can crack the one I have... if I could I would have already re-set it :p

I have fabricated meter scales utilizing AutoCad and “transparency” film. I don’t know if it is still availble or if new copiers are capable of printing on the film. When was the last time you saw someone use an overhead projector???
:cool:

Now sticking the scale on the outside... didn't think of that. That's better than the sharpie.

Can you not take it to a high pressure gauge repair shop and have it tested and re-calibrated?

Send it out for repair? All joking aside I hadn't thought about it. I just assumed it was sealed and non-repairable. I'll see if that do-able.

You can't simply rewrite your own scale on a gauge that's inaccurate! It's like adding / subtracting time from a clock that's running slow due to low batteries, it'll ALWAYS be inaccurate regardless of where you write your 'new numbers'. The calibration is set to be where the tube is bent inside referenced to zero. If the tube is broken and pre-bent the zero cannot be accurately reset because it wasn't made that way.

Have it fixed right or replace it.

A gauge doesn't care what it's hooked up to as long as the pressure range is correct and the system is compatible with the internals. Getting a liquid-filled gauge won't really add much benefit to you as they are intended for needle vibration dampening- which you won't have. Jet might require a metric thread, just be wary of that. Otherwise any gauge will do.

Is the scale in 'tons' really relevant to you, or are you just curious how much force you are putting on things to move them. I'd think the latter is correct?

I suspect the gauge is worn out like Matt mentioned. I wasn't going to write a new scale on the old gauge but rather re-scale one new psi gauge. I press a lot of captive nuts in multiple insert fixtures. I know how many tons each insert requires. I'm sure I can change my thinking for psi vs tons. Good call on the metric thread... I'll check that today.

[AndyA]

You can't simply rewrite your own scale on a gauge that's inaccurate!

I think the suggestion was to relabel a new psi scale guage to read out pounds of force from the cylinder.

I'm also curious why an oil-filled gauge wouldn't be an improvement. I would have bought an oil-filled as a replacement thinking the damping of the oil might help the gauge better survive rapid pressure changes.

[Stack of Dimes]

I'm also curious why an oil-filled gauge wouldn't be an improvement. I would have bought an oil-filled as a replacement thinking the damping of the oil might help the gauge better survive rapid pressure changes.

How rapid are you capable of relieving pressures on a press? The flow of fluid from 10,000 to 0 on a 6" bore isn't anywhere near bad enough to require a dampening. It's more intended to dampen rapid needle bounce and provide accurate needle reads.

[Matt_Maguire]

I think the suggestion was to relabel a new psi scale guage to read out pounds of force from the cylinder.

I'm also curious why an oil-filled gauge wouldn't be an improvement. I would have bought an oil-filled as a replacement thinking the damping of the oil might help the gauge better survive rapid pressure changes.

Hi Andy,

When "H" frame presses load there is some deformation in the press itself. Then when you press something that causes "stick/slip" the hydraulic circuit goes from whatever pressure it's at to a much lower pressure instantly as the stuck whatever slides quickly.

Then when the intermal spring is trying to pull the needle back - the oil in the guage acts the same as if you had your finger on the needle keeping it from moving.

If you watch the needle on smaller presses when they are going "pop - pop - pop" it moves so fast it's just a blur.

Matt

[denrep]

Who needs a gauge?

Gaugeless press pressure guide:
2 tons - Press bed settles to contact at all points.
4 tons - Pump motor settles into a heavy drone.
5 tons - Oil film no longer visible as ram is being wiped clean by pressurized seal.
10 tons - Slight crazing of work-piece's paint becomes noticeable.
15 tons - Pump motor slows to a healthy growl.
20 tons - Coworkers stop production to observe press operation.
30 tons - Dog leaves press area.
40 tons - Coworkers cower partially behind nearest heavy object.
50 tons - Push tool begins a slight deformation at contact point.
60 tons - Pump motor emits a slight squealing sound.
70 tons - Coworkers no longer visible.
80 tons - Coworker cautiously extends arm while wielding video camera.
90 tons - Workpiece support's surface mill scale begins to deform.
100 tons - Workpiece seems to have vanished in sonic flight.
90 tons - Press leaps from floor.
80 tons - Vulgar obscenity slowly uttered by an observing coworker.
50 tons - Heavy laughter from other coworkers.
25 tons - Dog joins in with playful bark.
20 tons - Press crashes back to floor.
15 tons - Second echoing sound, seemingly an "aftershock" emits from office area.
10 tons - Press bed lands with a third crash.
5 tons - Wall-plaster dust begins to permeate shop.
1 ton - Enraged Boss Man exits office with workpiece in hand.
0 ton - Workpiece picks up second sonic flight, aimed directly towards press operator. Pieces seem no further separated than at 2-ton start.

[daddy]

denrep, that is great!

LMAO! I've been one of the co'workers hiding around the corner and shaking my head.

"I don't think that's a good idea, lumpy." "Seriously. Let it off man."



"BANG!"

[denrep]

There are a few pressure points where the operator's involuntary self-preservation reflexes can be observed, but those vary from operator to operator and thus are difficult to pinpoint. :laugh:

[forhire]

Then when the intermal spring is trying to pull the needle back - the oil in the guage acts the same as if you had your finger on the needle keeping it from moving.

Matt, I suspect that's what happened to the original one. It's oil filled :(

Before reading your post I went ahead and ordered a new one today. I suspect it will be oil filled also. I'm not the only one using the press and with the gauge so out of whack it was causing some user issues. Scrapping parts on the final operation becomes expensive quick.

It would have cost about $150 to have the gauge repaired plus down time.

Denrep. Your list was spot on. :eek:

[Matt_Maguire]

That sux forhire,

Maybe if they designed the press to use that guage it has some internal accumulator/dampener in the hyd. circuit? So it may just be a fluke.

Matt

[Matt_Maguire]

Who needs a gauge?

Gaugeless press pressure guide:
2 tons - Press bed settles to contact at all points.
4 tons - Pump motor settles into a heavy drone.
(snip)
40 tons - Coworkers cower partially behind nearest heavy object.
(snip)
90 tons - Press leaps from floor.
(snip) 0 ton - Workpiece picks up second sonic flight, aimed directly towards press operator. Pieces seem no further separated than at 2-ton start.

:laugh::laugh::laugh::laugh: Yer killin' me denrep!

Although in the world of presses the 1st one below is a toy, it's the largest I ever got to play with (from a sales brochure years back).

The second is a handy little puller that got lots of use. We had to weld the feet back on it at least once a year!

I had to include the first pic with "Junior" (VP Local 360 IAM), everyone else in the shop wore blue uniforms. Junior could work all day dressed well, with perfect hair, and put out a crap ton of work while looking fresh as a daisy! Some of the hands hated him, I just got a kick out of the guy. Looked like a gangster (perfect for a union VP).:laugh::laugh:

Matt

(edit) didn't mean to hijack forhire, I guess it has some press content!

[forhire]

I finally replaced the gauge on the press. My original order directly thru JET was cancelled for some reason and I didn't bother re-ordering. A few weeks ago I had to order some other parts for the press and decided to replace the gauge. I ended up getting the parts through ereplacementparts.com as their price was the same as JET without all the handling and shipping fees. The new gauge is working great. Hopefully the gauge will last a long time.