Rebuild of a lee 4 20 melting pot

Kevin Stenberg

Well-Known Member
I am in the process of rebuilding this old pot. I ordered and have the new valve stem and a new valve. I am wondering if one of the members with a lathe can make the profile of the valve stem and valve more uniform. So hopefully i don't get another dripomatik.
For anyone that has not had to work on one of the old style 4 20's. When ordering parts for an old pot fix. All parts are interchangeable. If you have to get a new valve stem you also have to get the assemble on the exterior of the pot that holds the stem in place. Or you can just tap the old assembly for the threads on the new stem (which the old stem did not have)
 

Ian

Notorious member
The spout will skate a file, no lathing it.

Lap in the pintle with fine valve grinding compound, don't run your alloy above 725⁰ unless it is pure lead, don't let any sprues or ingots touch the bottom, and don't do anything else to put trash or dross down there and it won't drip.
 

Joshua

Taco Aficionado/Salish Sea Pirate/Part-Time Dragon
Ian beat me too it. I believe folks chuck these up in a drill motor when lapping the seat and stem with valve grinding compound.
 

Tomme boy

Well-Known Member
Lapping the rod make a HUGE difference. Spin it with a drill in the seat. Do it a couple times to make sure it is seated well.
 

Jeff H

NW Ohio
Whatever yo do, don't enlarge the hole in the spout. I have two pots I have to run at half volume because I've enlarged the holes over time by less than careful cleaning and a full pot is too much pressure ("inches of lead column") for the larger orifice and the deluge overcomes my smaller mouds' ability to vent at that rate.

I vote for lapping with valve grinding compound and keeping junk out of the pot.
 

Ian

Notorious member
@Jeff H , you can remove the spout, put it on an anvil, and peen the orifice to close it down some. It takes a remarkable amount of beating to move any metal, I think it's made of sintered pixie dust or some such. Anyway, it works...only problem is slow fill on the last third, but the temps are difficult to control well that far down anyway.
 

Kevin Stenberg

Well-Known Member
Ok i will turn the stem in the spout. For uniformity.
Second question. Lee does not. use any kind of seal when attatching the spout under their melting pot. But i was wondering if it wouldn't help to have some kind of high temp gasket sealer between the spout and the pot bottom? The top of the spout is a flat flair of less than a 1/16" wide which rests directly on the inside of the pot. And a nut is screwed on the outside of the spout under the pot to keep the spout tight to the pot. I was considering using some kind of sealer because of so little area of contact.
 

Jeff H

NW Ohio
@Jeff H , you can remove the spout, put it on an anvil, and peen the orifice to close it down some. It takes a remarkable amount of beating to move any metal, I think it's made of sintered pixie dust or some such. Anyway, it works...only problem is slow fill on the last third, but the temps are difficult to control well that far down anyway.
Thanks, Ian. I want to try something when I get time and wasn't sure/haven't studied the anatomy yet. Tried to talk to a LEE engineer and he got (can't say that here) with me and I decided to go it on my own. One thing that really irritates me is when someone doesn't listen to the actual question and makes up their mind they already know what you're going to say. First not so good interaction with LEE ever.

Maybe when the snow flies and things settle down, I can tear one apart.
 

Ian

Notorious member
Must have been the "engineer" I spoke with at Lee Precision a few years ago about the shellholder slot being milled a touch too shallow in the ram head of my breand-new Classic Turret press. He kept explaining over and over again how to adjust the nut on the top of the auto-index rod to make the die head line up and I kept explaining how the T-slot cutter was either flexing or not programmed to cut deep enough for the shell holder to seat all the way to the center of the ram. He finally said "You'll just have to send it to us and let US decide whether it's defective or not". I said "Then send me a prepaid shipping label" "Oh no! You have to pay shipping." "*click*". Five minutes with a Dremel tool fixed it. I was hoping they'd take an interest in a manufacturing defect which was going to cause them a lot of grief if not caught and fixed, but apparently not. Oh well.
 

L Ross

Well-Known Member
Must have been the "engineer" I spoke with at Lee Precision a few years ago about the shellholder slot being milled a touch too shallow in the ram head of my breand-new Classic Turret press. He kept explaining over and over again how to adjust the nut on the top of the auto-index rod to make the die head line up and I kept explaining how the T-slot cutter was either flexing or not programmed to cut deep enough for the shell holder to seat all the way to the center of the ram. He finally said "You'll just have to send it to us and let US decide whether it's defective or not". I said "Then send me a prepaid shipping label" "Oh no! You have to pay shipping." "*click*". Five minutes with a Dremel tool fixed it. I was hoping they'd take an interest in a manufacturing defect which was going to cause them a lot of grief if not caught and fixed, but apparently not. Oh well.
Just how often does a company run across a customer that actually knows more about machining and manufacturing than the tech does? Three quarters of the time the customer speaks in terms of "doohickeys" and "widgets". Ian, if you had actually talked to a machinist at Lee the response would more likely have been, "Whoa, no kidding?" "Hey thanks."
 

Petrol & Powder

Well-Known Member
Full disclosure – I have and use a Lee 4-20 pot. I also have some other Lee products.

Expense (or lack of) is a major factor when dealing with Lee products. I’m not rich and cost factors into my purchasing decisions. That being said, one does not buy a Lee product to get a good device, one buys a Lee product to get a good enough device.

The 4-20 pot is an engineering exercise to hit a price point. It is serviceable but that design is dominated by low cost, not quality.

The spout and valve rod can be lapped to greatly improve the operation of the valve. This is probably one of the best “bang for your buck” improvements that can be made to the 4-20.

The shoulder bolt (more accurately called a sheet metal screw with an unthread shank) that controls the travel of the handle is another point of failure. The extruded aluminum channel that the threads engage (or strip out of) can be tightened to improve this connection.

I added a longer power cord to mine because I hate extension cords and only needed about 4 more feet.

The good news is the 4-20 pot is a simple device and most of the parts are cheap and readily available. So, it can be repaired as needed and it isn’t difficult to repair.

Someday I will replace my Lee pot with a higher quality pot, but for now, it does what it is called upon to do.
 

MW65

Wetside, Oregon
Ok i will turn the stem in the spout. For uniformity.
Second question. Lee does not. use any kind of seal when attatching the spout under their melting pot. But i was wondering if it wouldn't help to have some kind of high temp gasket sealer between the spout and the pot bottom? The top of the spout is a flat flair of less than a 1/16" wide which rests directly on the inside of the pot. And a nut is screwed on the outside of the spout under the pot to keep the spout tight to the pot. I was considering using some kind of sealer because of so little area of contact.
Sounds like it's kinda like a flare... so it does have a metal to metal seal once the nut is tightened up. Silicone based gasket material will get eaten up after a while (above 500f), and may migrate into the melt. Unless you have a leak at the flared seat there, I wouldn't mess with it.
 

Ian

Notorious member
Molten lead isn't water. It won't leak if reasonably snug and the mating surfaces aren't damaged.

I had the channel for the shoulder screws strip on mine. The screws worked loose and I didn't notice until the threads were "wallered out". Took the pot apart, reinstalled the screws, and peened the aluminum channel back around the screws to re-form and tighten the threads. Reinstalled with stove gasket cement (water glass) and haven't had a problem since.
 

bruce381

Active Member
thread swerve here I had a drum of NA silicate and gave it to a friend back when Barry or Bush? wanted to get all the older cars off the road and they dumped "water Glass" in to the cooling system or maybe was crankcase anyway to have it go sieze it up.
then I guess the busted gas guzzlers were turned in for a few grand to help make us buy newer more gas friendly cars or someting like that.
Buddy was happy to get a 55 gallon drum tho I do not remember why I had it?
 
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JonB

Halcyon member
Ordering Lee parts:
I have a spare "used" Lee 4-20 pot...it's a long story...but the short version is, when I got it, it needed some major cleaning and my hamfisted cleaning technique opened up the orfice too much, wrong drill bit. Now, it works well with Pure lead casting large PB conicals and RB. But I figured I should replace the spout at some point. When I ordered a spout in the before times, I also ordered ever part Lee offers for free (just pay shipping), and when I replace the spout, I plan on doing a full rework of it. I also ordered some free spare parts for the Lee pro-disk powder measure at the same time. Shipping ending up being about $21, but I got a big box full of parts.
Just sharing my thoughts on this...
 

Joshua

Taco Aficionado/Salish Sea Pirate/Part-Time Dragon
Ordering Lee parts:
I have a spare "used" Lee 4-20 pot...it's a long story...but the short version is, when I got it, it needed some major cleaning and my hamfisted cleaning technique opened up the orfice too much, wrong drill bit. Now, it works well with Pure lead casting large PB conicals and RB. But I figured I should replace the spout at some point. When I ordered a spout in the before times, I also ordered ever part Lee offers for free (just pay shipping), and when I replace the spout, I plan on doing a full rework of it. I also ordered some free spare parts for the Lee pro-disk powder measure at the same time. Shipping ending up being about $21, but I got a big box full of parts.
Just sharing my thoughts on this...

Get your order in early with Lee. By the end of the tax year they won’t do business with you directly if your state forces them to collect sales tax. Once they hit their annual limit and then stop selling.
 

JonB

Halcyon member
Get your order in early with Lee. By the end of the tax year they won’t do business with you directly if your state forces them to collect sales tax. Once they hit their annual limit and then stop selling.
Interesting, I did not know that. I am reasonably sure MN is one of those States.
Good info for others, as for me, I am set for a couple Lee rebuild projects that may or may not get done this winter.