Mold Temp - Pot/Alloy temp

[James W. Miner]

Nice molds Ian and great idea.
I made almost all my own molds and when I put the blocks in the vice to cherry, I skim with an end mill first. Then my plates are cut flat with an end mill and I leave all the marks. Makes good vents but I still break the inner edge.
Some will lap the plate, don't do that, it will never be flat again.

 

[62chevy]

Breaking the edge of the mold taught me a valuable lesson about pot temp. The Coleman stove keep temp at 750 with my 10# pot and my mold got flashing on the base. But the hot plate would only do 660 to 670 and made perfect bases with no flashing.

Ben is the one who gave me the idea to break the edge of the mold.

 

[Mike W1]

Sometimes a few degrees make a difference and it apparently went into an empty crevice in my head and was forgotten. Been doing a little casting lately at 705° for no particular reason and bullets were really sticking in the moulds. Dropped down to 690° and it was hard to believe those were the same ones. Next session gonna drop some more as old notes showed good success at 645° with those same moulds and similar alloy. Seems I need somebody to remind me what I'd already learned. I don't think I have the skills to try breaking the edge, though it sounds like a good idea.

 

[Texas Hillbilly]

http://www.doitpoms.ac.uk/tlplib/phase-diagrams/cooling.php

A pretty simple, easy to digest explanation of liquidus and how to determin it. Not really that critical but nice to know?

Yeah maybe so at some point in time,but it's way off base for a beginner/new caster,I kinda go with the idea that one learns doing something,even if they make a few mistakes along the way,up until a few years ago I heated my molds by setting them up on the pot,until my lead was ready never paid much attention to the temperature,it was ready when it melted and had a purple tint to it,hey not much help ,but that worked for over 45 years,I started making bullets before I could drive
I still like to pour my first bullets into a mold and let it set a couple of minutes to bring the mold up to temperature,before casting a bunch of bullets,remember rejects can be melted again and again.

 

[fiver]

breaking the edge of the mold is nothing more than running a whet stone along the top edges of the mold at a 45* angle.
1-2 swipes is generally enough to make a difference.

 

[James W. Miner]

Just a fine file, give each side a swipe, you will barely see it. If you close the mold you will only have about a .001" line. Just call it a de burr.
I heat my molds to 500° in a little mold oven on a hot plate. It is an electrical box, hinged the cover and cut a hole to fit the molds in. I put a small BBQ thermometer in the top. My lead is set at 750° and first boolits will be perfect. From then on it is only timing, slow for me but I have cast a 20# pot without a reject.
I did not go back so forgive if I repeated.

 

[KHornet]

James, that electrical box sounds like a good idea, may try it.

 

[Rick]

It is a good idea, it's what I use also. I picked one up at the Home Depot that had an open top and one end open that's large enough to cover 5 cav NOE molds. Keeps air currents off the mold & works great.

 

[KHornet]

A day where nothing is learned is a day wasted. My day is not wasted as I have learned about the electrical box. Thanks guys, now will have to get an electrical box like you have Rick!

 

[James W. Miner]

Go to the BBQ section and you will find a wonderful thermometer. Get the small one.
One thing I found with the hot plates is there is a thermal fuse that can blow out. I bypass it.
You actually need water in a pot to keep heat low and a hot plate can fail if too hot. Years and years with a jumper over the fuse has been no problem for me. The fuse is a good safety thing in the house but can blow fast heating a mold. It is under shrink tubing, easy to find. My hot plate was an $8 thing from Wall mart.

 

[Brad]

I bought a junction box years ago but never got around to using it. I use an open coil hot plate and just put the moulds on the coils. I use low heat at first and once the lead starts to melt I increase the heat. My ladle is on the hotplate at the same time.
I have actually had the mould too hot at times. When the first pour takes 5-10 seconds to harden it is too hot.
A mould oven and thermometer makes sense.

 

[Mike W1]

Been there and done that. And I still don't see much sense in the oven part unless you're maybe sitting out in the wind. Even then you're getting most of the heat from the bottom not the sides and the hot plate has more than enough capacity to do that chore. Did use a 1/4" round aluminum plate over the coils for better transfer to the mould bottom even though mine doesn't have open coils. Did plenty of fiddlin' around with a TC in the mould itself and a PID on the hot plate.

 

[Texas Hillbilly]

I like the old coffee can with a hole cut for each handle,I now just l put the old can top onto the hot plate and set the mold on it then put my coffee can over to cover the mold Until it gets hot,,but Most of the time I just go back to heating the mold by pouring a few rejects old habits are hard to break,but with all of the new information one can get nowdays it's something to keep in mind and try.

 

[Rick]

Yeah, an old coffee can, electrical box or nothing at all. It's personal preference and as long as your happy with your results you are certainly doing right for you. There are nearly as many ways of doing things in this hobby as there are people doing it.

 

[James W. Miner]

Just casting a lot of rejects is fine too. Just get up to heat. Once good boolits start you are in the zone. The mold does not need that hot.
The thing with the oven is it also gets the sprue plate hot. Heat is contained instead of just on the bottom.
I went years of putting the mold on the edge of the pot and it helps but you still need to toss some back. A propane torch played over the mold and plate will speed things too, just don't hold in one spot.
Nothing you do is wrong. Soon you will know all it takes for what you do.
I am slow when casting, never cut molten sprues or get in a hurry. I want every boolit perfect. Timing is everything.
I have run 3 two cavity molds at once but 2 are easier. Cast and set the mold on wood, cast the second and cut the first, pour it and put on wood while you cut the second.
The worst thing is to hurry to make more, faster. One good boolit is worth more then 10 rejects.
I get bored to death and want to see dancing girls on my bench. I seen where one guy cast 200# of boolits at one session. WHAT? I would be in the funny farm.

 

[Rick]

Jim is right, sprue plate temp is very important. The last several minutes my mold is in the oven I turn it over and set it on the sprue plate to assure it's up to temp as well as the mold.

200 pounds of alloy cast in a single session? Would be a straight jacket in rubber room for me if I were to try that. Quality is worth far more than quantity any day.

 

[Texas Hillbilly]

I'm most likely the slowest caster on here, I cast with one hand from a wheelchair,no getting in a hurry here

 

[Doug]

The alloy temperature has a very large effect on final bullet diameter, you'll discover this if you ever get into the fourth decimal place when fitting a rifle bullet.

This is where I'm at. Two barrels w/ different diameters and the added difficulty that all my moulds are dropping AT the smaller barrel's groove dia instead of .001" over that. And for the other barrel these will be .001" under groove dia. I'm hoping that temp control will give me what I need w/o resorting to beagling the mold since I use this for two different barrels.

 

[James W. Miner]

I might have mentioned it before but I am not going to look. The thread is up to 7 pages. Water drop WW boolits and let them sit a week before measuring. Avoid measuring fresh boolits.
It may be best with .001 or .002" over groove but I have shot thousands and thousands right at groove size That makes it hard for me to define and in a revolver I shoot .0024" under throats and can't tell a difference if I get closer.
Some things that don't make sense can work and the biggest problems have been boolits UNDER groove.
If you can at least match the groove size, try them.
The right mold temps and aging just might bring get them to fit the larger bore.
I cast all my boolits with the pot at 750° and never fool with it. The cadence takes care of all else.
I have a funny thing and have been the center of jokes. I let the sprues just set, hang my mold down and swing it back and forth. Even that time changes a little each pour, sometimes four swings and another five swings. I cut with a hunk of wood with tiny taps on the plate and if it chunks out with the first tap, I slow a little more. I like to see a bunch of half circles nice and clean at the cut. I don't reject any boolits with a chunked out sprue, just small things that do no harm. I never want a lump on the bottom though. Adjust the plate and use a slight downward tap.
Soon you will not even think and is when you need to read a book while you cast or have dancing girls and a pole on your bench!
I don't enjoy casting or trimming 1000 cases, too darn boring!

 

[Doug]

Thanks James,

Yes, forgot about the aging. No WWs here, just straight lead-tin. Dunno whether water-cooling matters here. But yeah, thought I understood otherwise that cooler temps give largest/heaviest possible drops.