Alloy Temperature

[Jim22]

The casting session went much smoother today. I just got delivery of the lead thermometer I ordered from Rotometals. Used it for the first time today. I am using a Lee bottom pour 10 lb pot. I preheated the alloy with the same thermostat setting I have been using. I just left the pointer at 12 O'clock the way it was set at the factory. That's a reading of about 5 1/2 on my machine. Once the alloy was hot I dropped in the thermometer. It told me the alloy was at 950 degrees F. No wonder the mould blocks have been getting so hot. The boolits were heavily frosted and the sprues were taking a long time to freeze. As I cast boolits I started turning down the thermometer. Finall wound up at a reading of three which gave me an alloy temp of about 750 deg. F.. Sprues solidified quicker and I didn't have to stop casting every few minutes to let the blocks cool.

What experience have others had? I'm using an alloy of 90-5-5. I tried to top up the alloy but the pot's recovery time is also now much longer. Should I turn up the thermostat before adding cold alloy?

[Hossfly]

I cast at 750’ with a PID hooked up to my Lee 4-20 bottom pour pot. With a smaller pot say 10# if just add 2# ingot at room temperature its going to take some time to recover, if you add an ingot that’s been preheated by hot plate or just setting on top of your pot not so long for recovery.

[ryanmattes]

I've worked topping off into my casting cadence on my 10lb pot. I generally keep either small, ~.5lb muffin ingots or throwback bullets near the pot for topping off.

You know the drill, pour wait for the sprue to freeze, and then count.

I cut the sprue onto the table in front of the pot, drop the slugs on a towel (or into a bucket of water), and then pour again.

While I'm counting I have some time, so if there are more than 3 sprues in front of me, I put the coolest ones back in the pot (the most recent 2 cuts are usually too hot to pick up). If I'm air cooling I push the cooler slugs over into columns of the same number, so I can count at a glance. And I'll throw a few throwback bullets back into the pot. If I can drop 4 255 grain bullets in for every 4 I drop out, I'm only ever a couple sprues lower than I started.

I vary which things I do by what needs to be done, sprues stacking up, piles of dropped slugs that need to be lined up, pot's getting a little low, etc.

It gives me something to do while I'm waiting to cut the sprue, and since I'm constantly feeding the pot small amounts of alloy, the temperature stays fairly consistent. The less alloy in the pot, the wider the swings, so keeping it full helps it stay more consistent.

It swings a little bit more when I use ingots, but not like dropping in a 2lb ingot, which would be 20% of the total pot weight that needed to heat up.

When I'm done, I pour off what's in the pot into a mini-muffin pan, which gives me 7-9 oz ingots. They're small enough that I can put 4 in the bottom of the pot, fill the gaps with throwback slugs, and then do layers like that till I reach the top. That reduces the amount of empty airspace and speeds up the initial melt.

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[Jim22]

Thanks. My casting sessions will get better and better using some of your tips. Maybe the best is draining the pot at the end of the session. I have a Lee ingot mould. It throws about 1# and half lb. ingots. Also allows me to use a different alloy if I want. I have some number stamps that I use to mark ingots. 90-5-5 or whatever. I can use them to help keep ingots identified. When the temp was up over 900 degrees the cold alloy melted pretty fast. Now not so much. I will also try preheating ingots before adding them. So far I have been dropping bullets into water but don't think I need to do that for everything. I also have some 95-5 alloy that I am going to try in my Marlin 1894 .357. It will not push 158 gr. boolits past 1800 fps.

[Ed_Shot]

My pistol/revolver alloy is 3-2-95. I use a pid with a Lee 4-20 pot. I keep a record of the temp each mold likes to produce perfect 'dull' unfrosted boolits. Generally my Lyman 2 cav molds perform well @ 675 degrees and the Lyman 4 cav's @ 700*. My Accurate, NOE, Arsenal and Lee aluminum molds generally require hotter temps (710* ~ 725*). When I start casting I empty the pot to a 1" depth and then recharge the pot with the sprue and extra muffin ingots and take a break while the pot reheats.....it's a hobby not a job.

[Mk42gunner]

I haven't used my thermometer in years. Admittedly I am still using the same alloy that I first set the temp on my pot with, which I don't remember off the top of my head.

A number of members here, the only one that comes to mind is gearnasher, recommended casting about fifty degrees (F) above the liquidous state of your alloy.

I tried it, it worked for me with my version of wheel weight alloy.

I also use angle iron ingots that are from 8-10 inches long. This allows me to lay them across the top of the pot to preheat.

Robert

[lightman]

Most of my molds cast well at 725º. At that temp I can adjust my casting speed to get good bullets.

[bangerjim]

I let the boolits "talk" to me when hitting the water pan. If very little sizzle, alloy is under temp. If the keep sizzling in the water, alloy is too hot. Temp? Just the right one to get good drops! The dial setting on the Lee 4-20 is somewhere around 6-6.5 for ball-park reference.

I always heat my feed ingots to around 15-20°F (guesstimate, using an IR gun shooting on a flat black washer) below liquidous so they melt almost instantly when plopped in the pot, keeping the casting temp very constant.

I learned long ago to rely on my sizzle method and forget worrying about mold temps.

Practice makes perfect.........well almost!!!


banger

[GregLaROCHE]

I guess if you are changing alloys frequently, you may want to empty your pot completely when done casting, but I find it much faster to heat up a cold pot 1/4 full, than an empty one where the ingots have much less surface area touching the pot.

[AndyC]

Every pot is different, but on my 20-lb Lee pot, the 4-1/2 position on the dial gives me around 760F

[GregLaROCHE]

Every pot is different, but on my 20-lb Lee pot, the 4-1/2 position on the dial gives me around 760F

I find that after a full 20# Lee pot has gotten up to temperature, I have to reduce the setting as the level goes down, unless I am adding new lead.

[fredj338]

I am not sure you can get alloy that hot in a lee pot, maybe 875deg?? I run a Lee 20# with pid set to 750. I try to heat up ingots on the pot edge or a hot plate & add 1-2# to keep the pot running.

[AndyC]

I find that after a full 20# Lee pot has gotten up to temperature, I have to reduce the setting as the level goes down, unless I am adding new lead.

Yes, I have to do the same - nature of the beast.

[Cosmic_Charlie]

700 works for me. Seems to keep the molds about the right temp.

[mvintx]

I've been casting every evening this week, breaking in a SAECO #68 and using my well-worn Lyman 4-cavity molds. They all seem to like at least 750 and still do well at 780 with no frosting. I cast as fast as I can dump the mold. Just for grins I tried casting at 720 this evening...incomplete fillout and uneven bases. Molds are warmed on a hotplate, alloy is 50/50 COWW/PB/2% Sn, running a PID-controlled Lee 4-20.

[8shot]

Anyone have a specific temperature for casting with "brass" MP Molds, more specific 360 cast diameter, hollow point (4 cavity) in the 130 grain range? This will be my primary bullet.

I read that MP recommends pouring the lead off center and not directly into the pour hole?

[fcvan]

'Specific temperature' changes with mold type (aluminum, brass, iron) number of cavities, size/weight of boolit, cadence of casting speed.

I cast for 40 years without a thermometer, only casting by eye. Hotter alloy can give frosty boolits, colder can bring wrinkles. Alloy type changes the required temperature as different alloy has different materials which changes the melt temp.

You can cast hotter alloy if you are running 2 molds, you can cast cooler if you are speed casting from one mold. How do you know? Use your eyes. No wrinkles, but still a rounded base, my be a little cooler. Cast faster or bump up the temperature. Crisp bases, good fill out but the sprue takes a while to frost over (harden) blow on it, if it hardens before your eyes, you are close.

I started casting some years ago by pouring a 2 cavity mold by filling both at the same time. Mold slightly canted, stream slightly above both cavities, alloy swirls into both at the same time. Good fill out, easy to see sprue harden, larger sprue helps keep sprue plate up to temp.

I have steel and aluminum molds mostly 2 cavity, but some 3 and 4. Weights range from 55 grains to 440 grains. Each mold has it's own likes and dislikes. 2 cavity 55 likes hot to keep the steel up to temp. 3 cavity 62 grain aluminum likes speed casting and heat. Both of the little boolit molds are best when only running 1 mold. 125 to 230 I can run 2 at a time. In recent years I just run one mold at a time.

I start my casting session with my pot still full from the last casting session. Lee 10 pound drip-o-matic stopped doing so when I stopped dripping when I started smelting in a separate pot. Cleaning is still required, just not as often. I keep a bent safety pin for a spout pick nut don't need it as much. While I am heating up the pot, I place a tin can lid on top of the pot. I cut out a relief for the operating rod. Mold gets placed on the tin lid, allow and mold are up to temp within 15 minutes.

While casting, I place an ingot or 2 on the pot rim which preheats the alloy before placing into the pot. When I place the next ingot in, I quicken my pace as the alloy is cooler for a couple of minutes. You sprue cooling rate should let you know when you are fully up to temp. My sprues go right back in the pot, using a metal spoon. The boolits are then picked up off the folded towel, visually inspected by rolling side to side, and then placed into a metal bread loaf pan. Simple stuff.

As I said previously, I cast for 40 years without a thermometer. I bought on because it sat on the shelf at the LGS where it had been for at least 20 years. I have know the shop owner since the late 1980s, she said 'you finally going to buy that thing?' I did. When I used it, it merely confirmed what my eyes had always told me, I was right at temperature. I learned to cast from the guy that taught my Dad, we started ladle casting over a briquette fire, later with a SEACO bottom pour. He told Dad and me, 'use your eyes to tell if your temperature is right.'

This isn't rocket science, folks cast over the camp fire or at the hearth using a large spoon, waiting for the lead to liquify. Some guys who had a wrinkled boolit would simply close the mold and remelt in the fire in the mold. Sprue melted, boolit wrinkles were ironed out. They didn't cast a lot, they were generally re casting the boolit reclaimed from the game shot that day.

Lead was heavy and cost money, reusing or reclaiming was just part of the deal. Black powder was sold in a metal container, a container made of sheet lead. Can got opened, contents went into the horn, container went into the stockpile for future boolits. I have 2 molds from 'back in the day' but reproduction molds made of brass are still available, just a little more 'perfect' than an original. I just happened to luck out on the molds I was gifted from a gentleman 50 years ago, he said they were carried west from Georgia when his great grandfather headed toward Texas. Well, he actually gave them to Dad, who passed them to me. Dad doesn't shoot round ball, I do. Sure, old men told whoppers to their grand kids, but generally didn't tend to lie to other men. Honor and honesty still used to mean something during his lifetime, still does to Dad, and he's 81.