Do all vacuum pumps use the same oil?

Hi everyone. I’ve never owned a vacuum casting machine before. I got lucky and there was an estate sale near me and scored this old but well made vacuum casting machine.

It’s been sitting in an unairconditioned building in florida so the fluid has probably absorbed moisture by now. I need to change it. The fluid looks more like hydraulic fluid in the window than the clear stuff you see in newer pumps. Is this just because it’s so old and has rust or the old fluid was red?
Can I use this clear vacuum pump oil in it? I see the drain plug at bottom and the hole at the top to fill it.

Lastly, it does work and noticed I can get 23 cf/hg on the gauge when I test the vacuum with the bell housing side. Is that enough vacuum for small flasks? (like 2.5 inch by 4 inch)?
What is the purpose of the glass jar that has metal pieces in it? Are the metal pieces in the glass jar a medium to cool down the super heated air during vacuum casting?

The switch is going bad so I’m replacing the rocker switch.

Thanks for any advice on servicing these, I can’t find any information about Kasto Vacs that are this old.

I tried to figure that question out for myself once. I’ve got an old vacuum casting machine from the 1980’s.

When I was trying to figure it out for me, I noticed that Rio Grande only sells one vacuum pump oil. When you look at the Rio Grande vacuum pump oil SDS sheet, it’s just highly refined mineral oil.

For me, I played it safe and bought vacuum pump oil from Rio Grande. I knew that it was at least designed for a jewelry based machine. But based on the SDS though, probably any vacuum pump oil would have been fine.

Otto Frei told me once that an easy test of whether a vacuum pump is working properly on a vacuum investor is to measure out one pint of water. Put it under the bell jar. Turn on the machine. One pint of water should reach a “boil” within two minutes. If it doesn’t then you have problems.

Hope that helps!



Thank you for that info.

Yeah I can’t find any documentation on this thing. I did read that some people use hydraulic fluid and the old timer definitely didn’t have Amazon Prime when he used this thing so he probably put hydraulic fluid in it instead of that clean mineral oil. Guess I’m just going to change it out to the clear universal vacuum fluid we see today. The stuff in this old pump is kind of red, like burnt automatic transmission fluid. Maybe that’s what he used. Or… it’s the traces of rust.

Now I"m kind of worried though. I read that the type of pump oil you use can affect the depth of your vacuum draw. So now I want to confirm if I can what to use.

For example, are the HVAC vacuum pump oils using a different vescosity mineral oil than other rotary vacuum pumps like this old one that I use? The HVAC vacuum pumps only draw 3 to 7 cfm. But my industrial grade old rotary vacuum pump with this huge bell housing must draw much more … so does it need a different oil?

To the best of my knowledge vacuum pumps in those kind of casting machines haven’t made major leaps in the past 50ish years. Since you’re concerned, get a gallon of the Rio Grande vacuum pump oil. That fluid is designed for jewelry vacuum casting machines old and new.

In the old days, all jewelry tool companies (Including Rio Grande) sold vacuum pump flushing oil. I was told that was mineral oil and kerosene. I’m guessing everyone quit selling that because it was hazardous.

To change the oil in your pump. Run the pump for a few minutes. Turn it off. Drain the oil. Refill the pump. Repeat the process until the fluid comes out clear. Since your pump has dirty oil it will probably take 3-4 cycles of running, draining and refilling. That’s why you need a gallon of the fluid. (You’ll have to dispose of the old oil as hazardous waste, but I’m sure you know that.)

You do want to make sure that when you’re done that you put in the proper amount of fluid. Not too much and not too little. You’ve got a viewer on the side of the pump to verify the amount (you show a picture of the fluid level viewer)

You may need to change some of the tubing and rubber seals, but hopefully not.

Pure vacuum (30) is impossible to achieve. 29 on your gauge is what you’re shooting for.

Good luck!!


Thank you! You have been very helpful.

I did what you said and bought a bunch of the modern, clear synthetic vacuum pump oil so I can do a flush and fill a few times. I think I know what happened. I think the old-timer that this estate sale was from used compressor oil which is very dark to begin with. Some people think that compressor oil should work the same since vacuum pumps use the same design but backwards. But they are wrong in one thing. Vacuum pump oil is specifically designed to pull more vacuum if I understand correctly but compressor oil does not.

So I should pull an ever better vacuum with new proper oil, it was already pulling 23 with this incorrect and old fluid. I motor inside looks way better built than any of the new stuff I’ve seen so I hope it serves me well. I got a new switch for it too. The current original switch only works if I push really hard.

Where were these Kasto Vac’s by W & W made? I only see one other that was for sale and it was in Australia. There’s an old W & W jeweler company in Manhattan but I don’t think they made equipment? The motor inside is a well made stand alone motor and then it couples with a vacuum chamber with the oil in a big, solid steel box. Is that how they were all made back in the day instead of the cheap, all in one unit vacuum pumps?

W&W is a jewelry tool manufacturer in Taiwan. They still exist. They don’t sell to the public. They only sell through resellers. Yes, those old vacuum casters are like tanks. They last forever!

I forgot to say, since W&W is a manufacturer, that sells to resellers the same tool may have different names on it depending on who sells it. For example that’s how companies like Sears, Costco, Home Depot etc work. Someone else makes the product, but it’s branded as a Sears tool, etc. I’ve never heard of Kasto Vac, but that doesn’t mean anything, because other companies sold that same tool with a different name.

Another example is at work we have an old kiln that was made by W&W, but it is sold as a Rio Grande branded kiln.

Have fun with your new toy!


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Thanks! Yeah apparently, the only other W & W vacuum casting machine I’ve seen online is an old similar one from Australia. Anyways, wish me luck, I will install the switch and drain and fill the old compressor oil out today. It was already pulling 23 on the gauge with the bad compressor oil so this will be fun to see what it can do.

I was just seeing on Youtube that many people trying to buy Kaya Cast machines are getting fake ones.
The only thing I do like about the new vacuum casting machines like from Rio Grande is that they seem to have a removable top to access everything.

You were right. I’m already pulling 28 with the first oil change. These things are amazing. The motor doesn’t even get hot. The new switch helps too as it starts every time now.

The only annoying thing is the thing is so old that both the bell housing release knob and then the main selector switch on the right that turns the vacuum from bell housing to casting side is worn completely away so I have to figure out by feel where the selections are and then make some new labels.

But man, you can tell they don’t build them like this anymore. (well, I’m sure large commercial grade ones are better but not for what I paid for this thing).

It’s super heavy too, I hate moving it around and can’t wait to find it’s permanent home. I think it’s like 110 pounds maybe 120.

I need your help or advice one more time please. So the good news is that I am getting 29 when I vacuum the bell housing side. But, when I switch to the casting side, I don’t seem to be getting much vacuum when I put my finger over the hole. I noticed that the tubes for that side go to this weird glass chamber. It has an in and an out and it’s full of what looks like steel media? I assume it’s to trap any metals that come in or it’s to cool off the super heated air that is being sucked in from 900 degree flasks? My guess is that either the weird red seal of the glass jar has failed and/or the tubing but what do you think I can bypass this weird glass jar? Is there a filter I can buy and put new tubing on this side? Also, when my vacuum pump goes to full 29 vacuum, about half the time after I turn off the machine, it spins in reverse. I guess that’s not really an issue but wonder if the clutch system of this coupler is failing.

Geez you’ve got me. I have no idea? I’ve got an old Per Cast vacuum caster. It doesn’t have anything like that in there.

Let’s see if anyone else has any suggestions for you. You’ve got me stumped with that glass contraption!


Thanks, but whatever it is, I should just replaced it with a modern filter or contraption?
Do you recommend one or is so simple I should build one?

I bet I could easily make my own filter with steel or stainless steel screen and brass tubing. I’m assuming the steel media in the glass jar was simply to stop/trap pieces of investment.

And should I do anything about how I hear the motor unwind (spin backwards) after I shut off the motor if I pull a full 29 vacuum? (It doesn’t always spin backwards after shut offs but seems to about half the time when at full vacuum before shutoff).

It must have to do with the disengaging and the engaging of the coupler in the middle. It probably needs adjustment after these 30 or so years.

All I know is these cast iron vacuum chambers coupled with a 1/2 horse power motor are BAD ASS. I didn’t expect with 30 year old tubes and motor I’d get 29.

Hi Rick,
Following your journey with the casting machine with interest. I had something like this once, but it was stolen during one of my moves. The castle gear connecting the motor and compressor was the giveaway for my recall…as far as the filter, I would keep it. Just remove the old red stopper and measure the tubing the goes in the hole and the outer diameter of the stopper and buy a black rubber replacement. Amazon has them with holes in various sizes, Home Depot has stoppers without holes, but you can drill a slightly undersized hole in a solid stopper and make it work. About six bucks should do it, and I didn’t even try ebay for a lower price! I’ll bet it will work fine. Also, as I remember, I was boiling water at 72 degrees in three minutes with 27 vacuum, so if you are pulling 29, you are probably going to be able to boil water in under a minute, which is fine, since your limiting factor is going to be the seal at the bell jar or in some other part of the system.

The heat pump people replaced my outside unit the other day and they had a nearly silent Milwaukee battery operated vac pump…they pumped my system down to under 1000 microns of Hg, which is about equal to 29.88 inches hg-V! That unit does 5 CFM and costs about $850 at Home Depot. You don’t need to go down to microns, so consult some old jewelry texts or our old jewelry friends here on criteria…I think it was Jeff who said boiling in about 2 minutes at 72 degrees is the standard…let us know how it goes. I have an older 5 CFM unit somewhere and two DIY vac pumps made with old auto A/C compressors pulling from the “suck” side with a garden variety 1/4 HP motor. I guess I need to divest soon after I figure out which of these still work! -royjohn


Thank you for how the seal the this old red stopper better. The bell Housing side pulls the full 29 vacuum but not on the casting side so yeah, I suspect the red stopper or the thin copper tubing inside the glass is the problem.

I found out by looking at pictures of newer casting machines that we are supposed to release the vacuum before we turn off the machine after a deep vacuum. Because it’s BAD for the motor to spin backwards afterwards. It will create extra heat/charge and it can hurt the motor over time.

I assume even if the electric motor is off they don’t want the motors to spin backwards so now I will be sure to release some of the vacuum before turning off and then it won’t go backwards. I wish I knew this before yesterday but I only let it happen 2 or 3 times.

I’m glad you mentioned about how much time to “boil”. I never had a vacuum machine this powerful before because I too just used a mock-up version. I used a cheap 3 cfm vacuum pump but now that I am boing to use this thing, I’m afraid I might over do it with flasks. Is it okay to go a full 1 to 2 minutes of full 29 vacuum for a small flask if I’m at sea level and it’s around 70 degrees?

Wonder if I just need to go 1 minute for the first flask when I start casting again and go from there. My flasks would only be 2.5 wide by 4 inches high.

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Your instinct was correct. I should try a new rubber stopper because you can see from this photo, it’s the red stopper that has failed. You can see the darker color red and the lighter color red where the stopper has separated from being inside the glass jar. Rubbers usually shrink over time.

The problem is there both an “in” and an “out” so I will have to carefully drill two holes into a new black rubber stopper, then I think I should epoxy glue the stopper in the glass. I should sand/scratch up the inside of the glass so the epoxy has something to hold onto. The actual tubes inside the stopper and the glass are 3/16 thick copper tubing so I don’t have to drill the holes too large luckily I guess.

I hope 2 part epoxy does not destroy the rubber stoppers. Does anyone know if it’s safe to use epoxy on the rubber material that stoppers are made from?

So far, the tubing all looks good.

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If there is vacuum in the bottle there is no need for gluing.
The vacuum in the bottle will hold the stopper in position.

Okay thanks. The only reason I was thinking of epoxy is because there is so much going on. 2 different copper tubes are to be drilled into the the stopper. I agree the stopper will suck itself into the glass jar deeper under vacuum but the two holes that have the copper tubes in them will not cooperate as much. If I epoxy it all together, it will help seal the holes for the copper insert tubes I think.

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I agree with Per-Ove on the decision not to epoxy. Yes, the forces on the stopper will be inward, but also, from my time in organic chem lab years ago, I remember that rubber stoppers were everywhere in distillations, etc. and they never leaked. You will find some stoppers with double holes in them for sale, too, because they are frequently used in the lab. Just be sure that you can just push the tubing with some force into the holes using some vaseline or other inerrt-type grease and the forces of the rubber pushing on the tubing will hold it fine. Think about it and realize that as the stopper pulls in, it squeezes the stopper around the bottom of the tubing, too. You are thinking of vacuum as too powerful…it is only 14.7 lbs/in^2 pushing against no pounds per square inch, while a compressor can push with hundreds of pounds per square inch against the 14.7 of atmospheric pressure…the compressor uses O-rings and metal fittings that compress them and push them against their mating surfaces. I hope this is not clear as mud!

I think we may have discussed this in the archives somewhere, I would suggest you just try and see if you are pulling 27 to 29 inches of mercury with your pump. As far as what you need, it varies with who you ask. I have a book that says the gage should read “from 12 to 20” (?!??) and another that says 27 to 29 (more realistic). Try looking at the instructions here for a unit like yours:
It says you should be able to boil half a glass of water in less than a minute at 70 to 80*F. And that’s about 29 inches, but I wouldn’t be too doctrinaire about that.

I’m following your progress with interest! We haven’t even discussed torches and crucibles and melting furnaces and all that other stuff yet!
Be careful crossing the street (LOL),

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As Royjohn says, use an inert grease like silicone grease, Vaseline what ever inert grease you can get.
Then you can add a zip tie around the bottle between the tubes length wise so you keep it in place when the machine is off.
If you for some reason have a pressure surge it will not pop off but just lift and not break the bottle.
I do not know if it is even possible to have a pressure surge or “flash back” in these machines.

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Yes, the gauge says I’m getting 28/29 on the bell housing side and should be the same when I fix the bad glass filter. The gauge doesn’t go past 30) I think the gauge is accurate because the vacuum is so powerful that it spins the motor backwards after I shut off at full vacuum (which I recently found out is bad for the motor so I need to release the vacuum before turning off the machine).

I’m good with torches and crucibles, I’ve been casting with a crappy little centrifugal casting machine. I use a large Smith torch. Propane and Oxygen tank. A huge Oxygen tank I got second hand.