Another Pressure pot - my ideas

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tool-man

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Steve's excellent library article http://content.penturners.org/articl...ressurepot.pdf was my inspiration for getting and modifying a Harbor Freight paint pot. I have a couple of tips and want to share a couple of modifications that I made:


  1. Notice that the "new" style pot does not have welded connections to the lid. Instead the factory used two-piece fittings on the lid. They screw together from the top and bottom side of the lid. DO NOT REMOVE THESE FITTINGS - there is no need.
  2. As noted in another thread, all fittings on this pot are glued together at the factory with some very tough epoxy-like stuff. Use a propane torch and carefully heat the fitting to be removed. Try to avoid heating the fitting that is directly on the lid. After 30 seconds or so of torch heating the fitting will loosen easily.
  3. The first picture is the top of the lid after removal of unneeded topside fittings. The second is the underside.
  4. The third picture shows my inlet pressure side configuration. The new parts are laid out disconnected to show each type of fitting I used. All threads are 1/4" NPT. Starting at the bottom of the picture is a coupler (which screws into the threaded lid fitting that was left in place) and then a 4 way cross - to the right is a pressure safety valve - on top a dual vacuum and pressure gauge, and to the left a cutoff valve. To the left of the cutoff valve is an air line quick connect fitting.
  5. My vacuum side is not in operation yet so the other hole in the lid is temporarily plugged. Notice that my gauge is a dual function vacuum/pressure gauge and is connected to the pot at all times. It will monitor either vacuum or pressure in the pot without the need to open and close any valves.
  6. I do not have a regulator on the pot because my compressor has its own regulator (most do). I set the regulator to whatever pressure I want in the pot and connect my air hose to the quick connect fitting and open the valve. The desired pressure is achieved pretty quickly - then I close the valve and disconnect my air line. My pot pressure drops about 10 psi overnight. It is a simple matter to reconnect the air hose, open the valve and top off the pressure in the pot.
  7. Picture 4 shows the final assembly. I have pressurized the pot, closed the shut off valve, and disconnected the hose. You can see it is holding at 30 psi.
 

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kirkfranks

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Andy,
Nice set up there. I did mine similar but not quite the same.

If you use the other type quick connect fitting (female?) for you vac line you can leave the plug (vac port plugged) in place and use the same fitting as you use for the pressure. That is how I do mine.
Happy casting.
 

stevers

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Nice job Andy. Simpler can be better. My plan is the all out version. My intent was to get as much control as I could. I wanted to be able to isolate any part of the system I chose to. Also keep in mind, the system I used was dependent on the fact that I had the gauges already. If I would have had the duel gauge, I most likely would have done it differently.
Good job. Good luck with the vacuum side. You'll wounder how you ever did without a PVPot.
 

gomeral

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I know this is a dumb question, but does Harbor Freight ever put these on sale? I want one, I have a lot of the stuff to run one, but I'm trying to purchase some other stuff, too - I was hoping I could pick one up for less than $80. But if I can't...guess I'll still be picking one up. :biggrin:



daniel
 

jskeen

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another suggestion is to call either your local horrible freight store or the catalog if you don't have one, and ask them the price from time to time. I have heard that they either have unadvertised sales, or they will just decide to discount the price from time to time. If you get a quote you like just tell them to either ship it to you or hold it with a note with that price on it till you get there.
 

tool-man

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Andy,
If you use the other type quick connect fitting (female?) for you vac line you can leave the plug (vac port plugged) in place and use the same fitting as you use for the pressure. That is how I do mine.
Happy casting.

Sounds like a good plan to me. Fewer fittings just means less opportunity for places to leak.
 

tool-man

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I know this is a dumb question, but does Harbor Freight ever put these on sale? I want one, I have a lot of the stuff to run one, but I'm trying to purchase some other stuff, too - I was hoping I could pick one up for less than $80. But if I can't...guess I'll still be picking one up. :biggrin:
daniel

Keep an eye on eBay.:bananen_smilies035:
I got my pot from a freight liquidator for $26 including shipping. The regulator fitting was broken but of no consequence to me.
 
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Andy,

Can you post a link to where you purchased the combo gauge? When I was setting my pot up that was the hardest piece to locate. It may go far in helping others.
 
S

spiritwoodturner

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I know this is a dumb question, but does Harbor Freight ever put these on sale? I want one, I have a lot of the stuff to run one, but I'm trying to purchase some other stuff, too - I was hoping I could pick one up for less than $80. But if I can't...guess I'll still be picking one up. :biggrin:



daniel

Daniel,
I started a thread 2 days ago about getting mine from HF for 50 bucks. Here's the details- http://www.penturners.org/forum/showthread.php?t=42030 . I have no idea if it's still good, but you need to call them directly or go into the store to find out if and when they go on sale-the website only has list price. They're a peculiar company, from a marketing standpoint...

Dale
 
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spiritwoodturner

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Andy,

Can you post a link to where you purchased the combo gauge? When I was setting my pot up that was the hardest piece to locate. It may go far in helping others.

Andy, this guy has good ones for 15 bucks all the time. You can even zero them out for altitude, which for me at 6,000 ft. is nice. Here's the link- http://cgi.ebay.com/100-psi-GLYCERI...emQQ_trksidZp1742.m153.l1262#ebayphotohosting.

I had already decided I didn't need as much valveing as on my first one, but still am very grateful to Steve for getting me started in the right direction!

Dale
 
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tool-man

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Can you post a link to where you purchased the combo gauge? When I was setting my pot up that was the hardest piece to locate. It may go far in helping others.

I got the gauge and fittings from Surplus Center, 1015 West "O" Street, Lincoln, NE 68528. I have ordered from them twice and both times the shipment arrived promptly. They have a varied selection of items - just the thing for those who like to build their own stuff. Also has a printed catalog.
http://www.surpluscenter.com/air.asp

Here are the part numbers and prices (which I think are very reasonable) when I ordered. Since this is a surplus operation I'm sure his stock changes.


  • 455-MM ......... CROSS 1/4" NPTF 3950-04-............ $5.25
  • 455-GG ......... HEX NIPPLE 1/4" NPTM 122 ............. 0.89
  • 21-1583-C ......30-0-60 2.5 LM DRY GAUGE............. 5.95
  • 4-1795-75 ......75 PSI 1/4" NPT SAFETY R............... 4.99
  • 20-1486 .........1/4" NPT BRASS BALL VALV............. 2.99
I have seen individual items such as ball valves and gauges for better prices on eBay, but when you factor in shipping and getting everything at one place, I decided to go with Surplus Center.:wink:
 

kirkfranks

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Originally Posted by kirkfranks
Andy,
If you use the other type quick connect fitting (female?) for you vac line you can leave the plug (vac port plugged) in place and use the same fitting as you use for the pressure. That is how I do mine.
Happy casting.

Sounds like a good plan to me. Fewer fittings just means less opportunity for places to leak.


I just put a couple pictures in my album if it would help you.
 
S

spiritwoodturner

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Kirk, maybe I'm not understanding what you're meaning, but how could you use the same opening in the pot for pressure and vacuum input? I can see how I'll just use 1 two-way gauge on the pressure input side (versus a separate pressure and vacuum gauge), but I'll still need to put the venturi block/valve assembly in the other port. Won't I?

Edumacate me, please!

Dale
 

kirkfranks

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See the pictures in my album if you haven't already.
Basically since you cannot use both pressure and vacuum at the same time you really only need one opening into the pot. It will either suck or blow.:embarrassed:

When I want Vacuum I hook up the Vacuum adapter (HF venturi block) and hook the compressor up to that to draw out the air. When it is at the correct vacuum I close the valve and all is good. Hose and Vacuum adapter can be removed since the valve will hold the Vac.

To create pressure (starting from neutral) just add compressor hose and open valve slowly till reach the correct pressure. Close valve and remove hose since the valve will hold the pressure.

To neutralize from either Vac or Pressure simply open the valve (slowly.)
 
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spiritwoodturner

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Originally Posted by kirkfranks
Andy,
If you use the other type quick connect fitting (female?) for you vac line you can leave the plug (vac port plugged) in place and use the same fitting as you use for the pressure.


Kirk, I get it now! I got confused reading the above, thinking you completely sealed off 1 port and stacked everything into 1 port. I couldn't see how the gauge would work that way. Your removable vacuum block assembly is really clever though. I'm waiting for my second pot this week, have my combo gauge already and will use your setup when it comes.

Thanks so much,
Dale
 

titan2

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spiritwoodturner

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Kirk, once I got started on my new second pot, I totally got it. Thanks so much for the spark! I ended up with a plug in the second port, I DID stack everything in one port. The only change I made was I ditched the popoff and added the regulator. For me, the popoff is a weak point. I have my compressor set at 80 lbs., the regulator set at 70, and I NEVER move away one inch while filling my pot. Some say, "What if the regulator fails?". Well, what if the popoff fails, either by going off too soon or worse, too late?

The best and really ONLY perfect failsafe is to sit there for the 5 seconds it takes to fill it, then shut it off, then disconnect the source. I could have used the other port for the popoff, but figured it's one more leak source. Anyway, the entire bill at Home Depot was 17 bucks, versus about 75 the first time! I got my pot this time for 50 bucks, so this was a very cost-effective 2nd pot.

Thanks Kirk,

Dale
 
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spiritwoodturner

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Rob, it doesn't include that. I paid 17 bucks including shipping for the gauge off FeeBay. But I wasn't including that either when I said I paid 75 bucks in hardware for the 1st pot. This one has 1 ball valve versus 4, and WAY less brass!

I like it.

Dale
 

Tn-Steve

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Thanks a bunch. I'm not quite ready to start casting my own blanks, but I've bookmarked this thread, since everything I need to know about building a pressure pot is here.

Good simple design, good directions, and a good source to get all the fittings from.

Thanks,

Steve
 

kirkfranks

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For those of you that have one close by check for an industrial supply house for the pressure/vac gage.
I was able to get mine locally for about $10 - $12 and no shipping (Yes sales tax). I found mine on the first phone call.
MSC supply was better price for the gage at 8 bucks but another 8-10 for the shipping.:mad:

Dale,
Glad I was able to help.:)
 

GouletPens

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Man, I'm kicking myself for not having found this forum before I built my pot. I went off of Stevers design from his tutorial. Granted, the pot works great, but man was it a huge pain to figure out and I have two separate guages for vacuum and pressure. I hardly even use the vacuum now b/c Curtis converted me to Alumilite from PR.....oh well live and learn I guess. :frown:
 

tool-man

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The Harbor Freight paint pot has two ports, one is intended as pressure input and is 1/4" NPT. The other is a paint output (which some modifications use as a vacuum port) and is 3/8" NPT (national pipe thread).

To buy a fitting that is all you really need to know.

But if you need exact dimensions -- this type of thread is tapered so it does not have a fixed diameter. Visit this web site
http://www.webfootcustomcalls.com/temp/NPTThreadSpecstable3.pdf
and you can see an engineering drawing with all of the various thread dimensions. Probably more than you ever wanted to know. :biggrin:
what's the diameter of the vacuum port plug?

Thanks
Manny
 

Manny

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The Harbor Freight paint pot has two ports, one is intended as pressure input and is 1/4" NPT. The other is a paint output (which some modifications use as a vacuum port) and is 3/8" NPT (national pipe thread).

To buy a fitting that is all you really need to know.

But if you need exact dimensions -- this type of thread is tapered so it does not have a fixed diameter. Visit this web site
http://www.webfootcustomcalls.com/temp/NPTThreadSpecstable3.pdf
and you can see an engineering drawing with all of the various thread dimensions. Probably more than you ever wanted to know. :biggrin:


lol 3/8 got it. thanks for da info
 

AceMrFixIt

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Another pressure pot question........

If there is a regulator on the compressor, whats the down side of leaving the hose connected to ensure the psi dosen't drop? Besides the fact the compressor might run once in a while. Just thinkin out loud......Thoughts?????
 

holmqer

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If there is a regulator on the compressor, whats the down side of leaving the hose connected to ensure the psi dosen't drop? Besides the fact the compressor might run once in a while. Just thinkin out loud......Thoughts?????

I leave mine set up this way, I have not gotten around to fixing some small leak so my compressor kicks in every hour when I am keeping the PP under pressure.
 
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spiritwoodturner

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For me, the most foolproof safety feature on my 2 pots is to disconnect the hose from the compressor after filling, no exceptions. It may not seem likely, but if your regulator at the compressor ever failed, and it went higher than the pot could take, KABOOM!

I used to fill Scuba tanks at a friends shop, I respect these things for what they can do. I have a tiny leak in one of my pots, it loses about 6 lbs. overnight. It doesn't affect the casting, so it's not worth the risk for me. If a pot's losing 30 lbs. overnight, that's not holding pressure, and I'd fix it before moving forward.

That's just me though. Got 2 kids that spend time in the shop with me!

Dale
 

titan2

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Steve's excellent library article http://content.penturners.org/articl...ressurepot.pdf was my inspiration for getting and modifying a Harbor Freight paint pot. I have a couple of tips and want to share a couple of modifications that I made:


  1. The third picture shows my inlet pressure side configuration. The new parts are laid out disconnected to show each type of fitting I used. All threads are 1/4" NPT. Starting at the bottom of the picture is a coupler (which screws into the threaded lid fitting that was left in place) and then a 4 way cross - to the right is a pressure safety valve - on top a dual vacuum and pressure gauge, and to the left a cutoff valve. To the left of the cutoff valve is an air line quick connect fitting.
  2. My vacuum side is not in operation yet so the other hole in the lid is temporarily plugged. Notice that my gauge is a dual function vacuum/pressure gauge and is connected to the pot at all times. It will monitor either vacuum or pressure in the pot without the need to open and close any valves.


Question: Cann't you use the same connector that you use for the pressure side on the vacuum side? You're pulling a vacuum on everything there either way!

Barney
 

ElMostro

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If there is a regulator on the compressor, whats the down side of leaving the hose connected to ensure the psi dosen't drop? Besides the fact the compressor might run once in a while. Just thinkin out loud......Thoughts?????

One down side of leaving the hose connected is that if any fixture on the pot or the gasket fails then the compressor will run continuously even if set to a low PSI…if you are away from home like "my friend" was then that compressor will run for a long time and can damage the compressor. The constant air flow will also build up moister in the tank which may ruin the cast. The best approach is to ensure that the fittings are properly sealed, I have used plumbers putty and it works great.
 
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If there is a regulator on the compressor, whats the down side of leaving the hose connected to ensure the psi dosen't drop? Besides the fact the compressor might run once in a while. Just thinkin out loud......Thoughts?????

Rick,

If you are around to keep an ear out for it no big problem. I do it all the time. My little compressor at the house is a heavy duty service rated oiled compressor.
 

Manny

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60 psi

Question on the gauge here. I noticed..... "after I installed it" :eek:

That it only goes to 60 PSI for pressure.
Is there any need to go higher? WHat are the benifits. Since the working PSI on the pressure pot say 90 and I belive I saw a post that Curtis goes much higher (100?)

What is the gain above 60 and is it worth it?

Does it make a difference for PR or Aluminite?


Thanks, Manny
 
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spiritwoodturner

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One down side of leaving the hose connected is that if any fixture on the pot or the gasket fails then the compressor will run continuously even if set to a low PSI…if you are away from home like "my friend" was then that compressor will run for a long time and can damage the compressor. The constant air flow will also build up moister in the tank which may ruin the cast. The best approach is to ensure that the fittings are properly sealed, I have used plumbers putty and it works great.

First, Eugene, I don't know whether to be depressed or angry you got to go to Roatan while we were in the cold. I hope you had a wonderful trip (voice dripping with sarcasm).

Hey, that's the first time I've heard of plumbers putty for leaks. My little dinky annoying one is coming right out of the face of my regulator on the pot with the large screw, to adjust the pressure. If I ran some PP around that threaded bolt and under the nut would that be OK? It only loses a few lbs. overnight but my compulsive side doesn't like it. I was going to replace the whole regulator but it works, just leaks a touch.

Thanks! Did you see anything cool down there on the bottom?

Dale
 

ElMostro

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First, Eugene, I don't know whether to be depressed or angry you got to go to Roatan while we were in the cold. I hope you had a wonderful trip (voice dripping with sarcasm).

Hey, that's the first time I've heard of plumbers putty for leaks. My little dinky annoying one is coming right out of the face of my regulator on the pot with the large screw, to adjust the pressure. If I ran some PP around that threaded bolt and under the nut would that be OK? It only loses a few lbs. overnight but my compulsive side doesn't like it. I was going to replace the whole regulator but it works, just leaks a touch.

Thanks! Did you see anything cool down there on the bottom?
Dale

Dale, hello. I had a great time at Roatan...thanks for asking.

Anyway, ref the PP. What I do is that when i am in the process of screwing all the fixtures together I apply the putty to the threads instead of the teflon tape. The PP is a bit messier but, for me at least, it seals better than the teflon tape.
 
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