12" 200psi Antique Brass Pressure Gauge Repair

While searching ebay for a larger pressure gauge for my mig gas regulator, I came across this antique 12" 200psi all brass ashcroft pressure gauge. $186 later it's out in my shop and I decided to repair it tonight.
Someone had cut the inlet fitting off the back so I drilled it as deep as I dare with a 7/16" bit and tapped it 1/4"npt. I started the threads with a standard tap and finished with one that I've ground to make a bottoming tap.
The male qc is only in there for testing, I'll replace it later with a push lock fitting. The pics are fairly high res so if you want a closer look, click/click/zoom (hold alt key and roll the mouse wheel forward)

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After I finish the interior of my shop this spring, I'll install this gauge on the wall and plumb it into my airlines. I can't decide whether to restore the faceplate and polish the housing or just leave it like it is. What would you do ?

Very cool :)

How's the accuracy check out? I'd assume something like that, especially from that era, can be calibrated? Is there ever a need to? So much stuff these days is disposable and/or generally cheap (I have a pressure gage on a bike pump that every time I bump it over the the garage, the needle 'zeroes' out to a different pressure. Right now, 32psi means zero ... ugh)

It's very close on the pressure and returns to zero. There are adjustments inside if needed.

That is too cool. I kinda like the old patina. Are the white speckles, missing ink or something else? I guess you could re-silkscreen the dial. Or maybe just do some retouching, to keep the old look. Either way it's a great find, and at 12" I bet even I could read it from across the shop. ;)

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Originally Posted by Rambozo

That is too cool. I kinda like the old patina. Are the white speckles, missing ink or something else? I guess you could re-silkscreen the dial. Or maybe just do some retouching, to keep the old look. Either way it's a great find, and at 12" I bet even I could read it from across the shop. ;)

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The speckles are a combination of corrosion and missing paint/ink. The face is steel and has some rust at the bottom on the back side, three screws in the back are the only other steel parts in it.

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Originally Posted by zoama585

While searching ebay for a larger pressure gauge for my mig gas regulator, I came across this antique 12" 200psi all brass ashcroft pressure gauge. $186 later it's out in my shop and I decided to repair it tonight.
Someone had cut the inlet fitting off the back so I drilled it as deep as I dare with a 7/16" bit and tapped it 1/4"npt. I started the threads with a standard tap and finished with one that I've ground to make a bottoming tap.
The male qc is only in there for testing, I'll replace it later with a push lock fitting. The pics are fairly high res so if you want a closer look, click/click/zoom (hold alt key and roll the mouse wheel forward)

Attachment 9420Attachment 9421Attachment 9422Attachment 9423Attachment 9424Attachment 9425Attachment 9426Attachment 9427Attachment 9428Attachment 9429

After I finish the interior of my shop this spring, I'll install this gauge on the wall and plumb it into my airlines. I can't decide whether to restore the faceplate and polish the housing or just leave it like it is. What would you do ?

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That thing just screams "cool"! I would leave it as is and simply calibrate it (if need be). It's a "classic" at this point, so messing with the face might make it worth less in the long run! Maybe put a light coat of wax over the top to keep it from getting worse? Rub lightly so you don't burn through the paint!

Wow, that really is a nice find. If you decide to wax, definitely do so lightly as youngnstudly suggested but maybe only use one that is 100% wax as opposed to a wax / polish.

As it is, I can't touch the face because the paint lets go in tiny flakes. I'm not concerned with the value of it at all so I may get a new face plate that matches the original.

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Originally Posted by zoama585

As it is, I can't touch the face because the paint lets go in tiny flakes. I'm not concerned with the value of it at all so I may get a new face plate that matches the original.

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You can always hit it with some artists' fixative spray to keep it from deteriorating any more.

+1 on the fixative. that will keep any flaking paint in place and give a uniform matte finish (assuming matte fixative, sometimes 'fixatif'). Personally, I'd clean up the outside with 1200 grit or so, but I like shiny things and I know being brass and in a shop setting that it will patina again soon enough. I like watching the change, personally. I occasionally buy old dial indicators on fleabay just to play with :)

Cool.

If you need to adjust it, in teh 5th picture, the screw on the bottom, with teh circumferential slot under it should adjust the zero point.
the screw (s) on the left, on the arm of the bellcrank with the sector gear on it should adjust the ratio.

The bourdon tube will expand with added pressure and Pull the left side "down" in pic 5. that will then cause lever arm on the sector gear to pivot the assembly on the pin on the left, turning the gear and shaft attached to the pointer.

I'm a gauge engineer for Ashcroft Inc, and restore these all the time. It appears as thought you had the bourdon tube/movement assy bright dipped in nitric acid. The only concern here is degradation of the bronze hairspring. Hope it's OK. I would suggest lubricating the gearing interface, and journal points of the movement with a light silicone based fluid. This will extend the life of the movement, and add a little resistance to any vibration or pulsation effects on application. As for the brass case/ring, I always buff them to a high luster. Spraying with a non-yellowing clear acrylic is also recommended. Calibration of these is a little tricky. You have to adjust for both span (0 to full scale accuracy), as well as linerarity (points in between).
The amazing thing about pressure gauge design is that it hasn't really changed since Mr. Ashcroft issued the first US patent back in 1852.

As an aside, we offer free restoration to any Ashcroft pressure gauge. Contact Ashcroft Inc, Stratford Ct (203) 385-0474

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Originally Posted by gaugemaster

I'm a gauge engineer for Ashcroft Inc, and restore these all the time. It appears as thought you had the bourdon tube/movement assy bright dipped in nitric acid. The only concern here is degradation of the bronze hairspring. Hope it's OK. I would suggest lubricating the gearing interface, and journal points of the movement with a light silicone based fluid. This will extend the life of the movement, and add a little resistance to any vibration or pulsation effects on application. As for the brass case/ring, I always buff them to a high luster. Spraying with a non-yellowing clear acrylic is also recommended. Calibration of these is a little tricky. You have to adjust for both span (0 to full scale accuracy), as well as linerarity (points in between).
The amazing thing about pressure gauge design is that it hasn't really changed since Mr. Ashcroft issued the first US patent back in 1852.

As an aside, we offer free restoration to any Ashcroft pressure gauge. Contact Ashcroft Inc, Stratford Ct (203) 385-0474

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I haven't touched the bourdon tube/movement assy, I only drilled and tapped the air inlet. I'll be calling about the restoration. Thank you for the information.