Pressure Casting-Grizzly Paint Pot Conversion

I've been using this paint pot from Harbor Freight for casting
Paint Pressure Tank - 2-1/2 Gallon


The poor design of the clamps made it difficult to seal it air tight. I had to tighten the bolts with a wrench, which caused severe damage to the lid.




The clamps and bolts are cast metal which eventually became deformed, they no longer turn without a wrench. The thought of using it any more is just too scary.

While searching the web for info on this pot I found this horror story. The guy made an unsafe modification to the lid, and was operating at 90psi! but it still gave me the willies.Catastrophic pressure pot failure...my wife almost became a widow! - International Association of Penturners

My search also turned up this post, which got me thinking about the Grizzly pot.
Resin Addict Forum ? View topic - CA Technologies - Pressure Pot : A Review
H6329 2-1/2 gal. Paint Tank w/ Gauges

So I got one last week.


It needs the same mods as the HF pot to get it ready for casting, plus a couple more. First I removed the siphon tube with a torch and pliers.


The Grizzly pot also has a paint mixer installed in the lid, which I also removed.


This unfortunately left a huge hole through the lid.




I got a 5/8 bolt, washers and nut to seal it.


I removed the mixer fitting and reattached it with silicone gasket compound.








I applied the gasket to the bolt threads, and to the back of the washers.


Here it is with a gauge and ball valve attached. I used a valve from the plumbing dept., it feels more substantial than the air tool valves.


The Grizzly clamps are much better than the HF. They won't damage the lid, and the large wing nuts can be tightened by hand.


I tested it out at my usual 60psi, but it had a slow leak. It lost 15psi over three hours.


So I added the regulator that came with it. By setting the regulator to my desired pressure, I can leave the air supply attached and it keeps it topped off.


If I bleed pressure from the safety valve, it will go back to 60psi once the valve closes. After three hours it was still right where I left it.

This pot is much more heavy duty than the HF, the lid alone weighs as much as the whole HF! I now have a great pressure casting rig, for about $170 total for the pot and extra parts. Not too bad

Very nice set-up. Not a bad price either considering it was only 70 more than my HF.Would have been nice to accomodate slightly larger molds. Once my HF gives up the ghost, I might make that switch. Is the bottom of the pot flat?I lose a lot more than 15 in several hours, more like 30. I've been using SC300 though, so just holding for a couple of minutes and it's good. Sucks for molds though when you need to hold for a few hours. I just stay close and keep an eye on it, adding as needed. I've found though, about 40 psi is all I need. I guess 60 gives you that comfort factor though.And as for the guy blowing his, it says right on the pot a max of 80 psi. Yeah you might have bit of wiggle room under ideal conditions, but the slightest thing and...

No the bottom is rounded. I'll make an insert like the one in the Resin Addict post above.

I'm sure the pots can handle 90psi, it's just the bad lid design on the HF that worries me. The Grizzly says max pressure is 45psi, but that's based on the needs of spray painting. The safety valve on my HF would blow at about 40, but the Grizzly went up to 60 no problem. I don't know what the Grizzly valve is set for, but I replaced it with a 70.

I never got to try out the HF regulator to maintain pressure, it was a piece of crap that leaked so I through it out. A good regulator would solve the pressure drop but the bad clamps were the real problem. I use pressure for molds as well, and it's nice to know it will hold pressure for 24 hours or more if needed.

wow, thanks so much for posting this. I previously had a HF 2.5 gallon pot and it's just not big enough and it has the rounded bottom which is just a pain. So I just purchased the California Air tools 5 gallon pot and it's pretty much the same one you got here. Although mine has to my delight a flat bottom. I got it here for decent price I think. Rakuten.com - 5 Gallon Pressure Pot $267 free shipping. But to my surprise it had the mixer in the middle and I had no idea what I was going to do with it. Fortunately I found this post. Very excited now and looking to make bigger casts.

Thanks a bunch!

You're very welcome! That looks like the Grizzly 5 gallon pot H8226 20 Liter Auto Mixing Paint Tank which has an even larger mixing apparatus.

Hmm, yours has a flat bottom? I wonder if the Grizzly 5g does too? I should have gotten that one!

robn1 said:

You're very welcome! That looks like the Grizzly 5 gallon pot H8226 20 Liter Auto Mixing Paint Tank which has an even larger mixing apparatus.

Hmm, yours has a flat bottom? I wonder if the Grizzly 5g does too? I should have gotten that one!

Click to expand...

206 after shipping?? dang, and I thought I found a good deal :-(
and there's even a Grizzly showroom just a couple hours north of here

oh well, it'll be there for the next purchase

I read that thread on penturners. The lid says 80 PSI Max. That means 80 PSI Max. It doesn't mean "Epoxy or hot glue bits of metal to the lid, monkey around with the pop off valve and crank it up to 95 PSI."

What are these guys doing? Forcing Alumilite resin into chunks of wood to make it stronger for turning pen parts? Vacuum might work better for that because it would pull the air out of the wood and the resin should move into the vacancy.

If they want to beef up the lid to make it better able to withstand use within its rated capacity they should have a heavy steel ring machined to fit over the edge of the lid as a way to better distribute the clamping force.

If you're having to crank the bolts so tight they're denting the lid, STOP. Discard the pot and don't use so bleeping much pressure in its replacement.

I have one HF pot, which I run at 60 PSI. I hand tighten the clamps then hook up the hose. It doesn't need the clamps wrenched down, but it has a slow leak so I just leave the hose connected with the ball valve cracked open.

I have another very similar pot from Northern Tool. It usually leaks so I use a wrench and tighten just till it quits leaking. I should remove the gasket and use one of my larger pots to pressure cast a silicone gasket in its place.

Neither of those pots have the constant bleed type of regulator. You only want to use that type of regulator on a pot that will hold pressure, with the ball valve between the regulator and pot.

Even if you have an output regulator on your compressor NEVER EVER put pressure in a pot without a regulator on the pot. If the compressor regulator fails you could quickly overpressure the pot and if the pop off valve doesn't open you'll have a very bad day.

That's why you must have a gauge directly showing the pressure in the pot. That's the one to watch, with a hand on the valve handle in case it goes over the pressure you want in the pot.

Pressure pots are like resins. Follow the directions and they work. Don't follow them and you'll have a mess.

Brilliant thread. The information on this forum is just fantastic.

I have a HF pot too, I use it for Vacuum & Pressure,
I made a custom silicone seal, there is absolutely NO leak, and it holds 80PSI well.
I also sealed the Holes with urethane

At least I'm casting under 50-60PSI only & I only hand tight the bolts !

click to enlarge:

custom silicone joint


custom "round fit" silicone joint for vacuum

I'm contributing to the resurrection of this thread .. I began looking at tanks for my molds and casting .. and now, there's a 20L Grizzly tank but it says that it goes to 25-30 PSI.

Can any of the expert here comment on this thing?

This thread is talking about this:
http://grizzly.com/products/2-1-2-ga...w-Gauges/H6329

I'm talking about this model that is currently 137$ CAD with free shipping on Amazon.ca!
http://grizzly.com/products/20-Liter-Auto-Mixing-Paint-Tank/H8226

Another note, is it better to have something like this?
http://www.amazon.ca/gp/product/B00JWQLU48/

I really can't advise on the 5 gallon tank since I don't have it. I almost got it but the size difference isn't as much as it seems. Yes it's twice the volume but it's a little taller and a little wider, so I didn't think the extra volume would really be usable. Plus the larger mixing apparatus may be more difficult to remove.

As for pressure these tanks look identical to the casting tanks that cost much more, I do believe these are the same base tanks. The Grizzly manuals state maximum pressure as 45psi for the 2.5 and 50psi for the 5. I use my 2.5 at 60psi regularly and I have had no issues with it. I intend to get another one.

I need to find one of these in Germany!

I've found some in the UK, but still, shipping is prohibitive due to the weight.

Any tips for finding one in Germany, at at least what they are called in German?

Farbdrucktopf, drucktopf, farbtopf results in no hits and I'm still researching the right name.

I can't say what they are called in Germany. But there must be suppliers for spray painting equipment, most pressure casting is done with tanks made for spray painting.

robn1,
Thanks for the input!

Could you tell me the inside diameter of your 2.5 gallon? Basically, I'd love to be able to fit my HIC panel mold in there and it's about 14" wide.

Also, The 2.5 gallon on Amazon is 195$ while the 5 gallon is 137$ .. I mean it's cheaper to go bigger .. would you just do it? I guess in the end, it'll depend on the inside diameter!

Bigturc said:

robn1,
Thanks for the input!

Could you tell me the inside diameter of your 2.5 gallon? Basically, I'd love to be able to fit my HIC panel mold in there and it's about 14" wide.

Also, The 2.5 gallon on Amazon is 195$ while the 5 gallon is 137$ .. I mean it's cheaper to go bigger .. would you just do it? I guess in the end, it'll depend on the inside diameter!

Click to expand...

I know that the more inside mass you have, the stronger of a compressor you need. The way to get around this when you have a big pot is to put something in there, like a block of clay, stones or anything solid to displace the air when you're not filling it the whole way.

I just saw a video on youtube where the girst had a pressure pot on the side .. so that gave her the whole height for her mold .. that's clever!! Never would have thought of this .. will probably fix my width issue .. I guess it's as safe as using it standing!

I've been exchanging PMs with another member who was suggesting doing a plug for the bottom or filling with sand .. not sure about that latter .. but I can definitely see a series of plugs to fill it depending on the mold you're using!

Even the large mixing apparatus can be easily eliminated by removing the large bolt that the mixer goes through and replacing it with a solid bolt without the paddle mixing arm going through it.
I believe the solid bolt is a factory part you should be able to get from the manufacturer. I've modified a couple pots this way.


I can't believe the guy in the story from the first post said he was going to try to straighten the lid to keep using it after the accident. Sounds like a Darwin Award in the making!

Thanks Duncanator, I've just emailed Grizzly about this and I'll see what they can come up with!

Yeah Bigturc I think you could lay it on its side just fine. You may have to make a little support braket to level it to since it has the casters on the bottom. You also would need to build a shelf to put your mold on, but that would help with some of the volume of air in there so it would be dual purpose. Like I said I wish I could make sense of their quoted measurements. I have messed around with both but just can't remember the dimensions. I know the five gallon isn't much taller but is a lot wider. I believe you might be able to put your mold horizontally in there no problem as is.

Bigturc said:

I just saw a video on youtube where the girst had a pressure pot on the side .. so that gave her the whole height for her mold .. that's clever!! Never would have thought of this .. will probably fix my width issue .. I guess it's as safe as using it standing!

I've been exchanging PMs with another member who was suggesting doing a plug for the bottom or filling with sand .. not sure about that latter .. but I can definitely see a series of plugs to fill it depending on the mold you're using!

Click to expand...

I saw that same video, very smart and will solve my problem is needing a long flat pot for my one long part. From the measurements I've found the 2.5 (10L) gallon pots are about 24cm tall and 24cm wide (about 9.5 inches).

The 5 gallon ones (20l) run in the area of 31cm tall and wide (12.3Lx12.5W in inches).

For me, I actually don't know if this size is big enough for one long piece...

Maybe this will just have to be a single piece that I do not pressure cast.