Bottom Pour Techniques

[jr545]

Could a few of you die hard bottom pour casters expound on your technique?

I just started trying to use a bottom pour after 20 years of ladle casting and I'm having a rough go.
I tried letting the lead drop about and inch to the mold, then a half inch and then right up against the nozzle which doesn't leave much spue.
I tried all manner of tipping the mold to try and direct the sprue away from the other cavity when holding it just below the nozzle only to have the sprue splash over and cover the other cavity.
Fill out was less than satisfactory with any of the different techniques except holding the sprue plate tight against the nozzle which did give me complete fill on the front driving bands.
I figure I'll just have to work at it and develop what works for me but hearing some pointers might give me some much needed insight.
I cast for 2 hours last night and only ended up with about 75 keepers. :groner:

[fourdollarbill]

If you have a Lee 4-10 pot it is the easiest of them all because the nozzle is angled to you and you can see it well. If you have a Lee 4-20 that is a bit tricky as the nozzle is hidden away too far under the pot.
On both pots I typically pour hotter than normal into a very hot mold leaving a large sprue to cut. On the 4-20 pot I have to sit down and raise the pot onto a tall table so I can just see the tip of the nozzle. I lube the black adjustable ledge to help the mold slide and fill it close and fast.

Maybe try to adjust your lead to pour faster or just make it hotter.

What kind of pot do you have?

[markinalpine]

In addition to any responses you get:
Check out Goat Lips pages: http://castboolits.gunloads.com/showthread.php?t=36726
I hold my six-banger moulds tipped slightly down, away from me, starting at the nearest cavity, and pulling the mould back towards me. I have the pot raised high enough that I don't have to bend over to see the nozzle, and hold the mould about 1/2 to 1 inch below the nozzle.
Mark :coffeecom

[Echo]

Could a few of you die hard bottom pour casters expound on your technique?

I tried all manner of tipping the mold to try and direct the sprue away from the other cavity when holding it just below the nozzle only to have the sprue splash over and cover the other cavity.


You don't mention what kind of furnace, nor what make mold nor mold composition. Dropping an inch between nozzle and cavity should not make problems.

If possible, slow down the flow rate and you will have less of a problem with alloy splashing over into an adjacent cavity. Also, maybe increase your casting temperature - IME, if I am casting rather warmly (~700), and if the mold is up to temperature, then even a little splash over doesn't affect the second cavity's quality.

[jr545]

Sorry, I guess I left out some pertinent info.

The furnace is an old Saeco 24.

The mold is a Lyman 410610 DC/GC

I had the mod up to temp a few times but was fighting small sprues(I ladle cast large sprues that come off when cut) that seemed to weld themselves to the sprue plate.

I tried slowing the flow, upping the flow....I felt like a complete failure.:violin:
I know it'll take some practice but I would have never guessed how much it would take.

I also have trouble walking and chewing gum...

[SharpsShooter]

I set the mould guide to allow the alloy to drop about a half inch, then begin with the cavity nearest the handle cross-bolt. Pour continuously and draw the mold towards yourself. The sprue will generally be one piece for all cavities. This is somewhat handy as you can pick up several at a time to return to the pot. It takes a tiny bit of practice to get the rhythm down pat, but once you do, quality production in large numbers is not difficult. I did over 600 311407's from a 6 cavity mould in an hour and rejected less than 30 boolits. FWIW


SS

[Tazman1602]

You're doing fine. Wife got me a new Lee 4-20 pot for Christmas and I fired it up........................and HATED it. Was having the same issues you are and it just takes some work on technique.

I've got molds that like to have about 1/4-1/2" drop and molds that like to be right up tight to the spout when they pour. When I have them up tight against the spout I always pull it back a little and let the sprue pour to where I have a good, solid sprue plate to cut.

If your having splashing issues make sure your pot and mold are up to temp (sounds like you've already got this one..) but slow down the flow a bit, that seemed to help me.

I still like to pour my biggest single cav (.458's typically) by hand but man I wouldn't give up that bottom pour for anything now that I've got the techniques down to where they work for me.

Keep pouring, it won't take more than two or three thousand rounds back in the pot before you've got it figured out <GRIN>

Art

[HangFireW8]

Could a few of you die hard bottom pour casters expound on your technique?

A few (deep, narrow) molds require pressure and I keep the sprue plate hole hard against the spout.

Most molds need space for the air to get out and I get the best results with the hole barely touching, but some air space to let it breathe a little as I pour.

Leaving the right amount of excess on the sprue is a matter of counting and letting go just as it gets full, letting the lever bounce a bit which will finish off the pour with a little puddle.

I found that large (45's and such) cavities that are close together, pouring in quick succession will cause the first boolit to have a flat breathed-on side near the second boolit. I have to wait for the puddle to fully harden, and a few seconds more, before pouring the second boolit.

-HF

[Le Loup Solitaire]

Different folks do things differently so whatever works for you, go with it. I use a Saeco 24 with 1,2, and 4 cavity molds and they all work fine. In addition to the temp being right, an important factor is the volume of the melt stream. If it is too thick then it is wider than the sprue hole and splashes and or blocks the hole and doesn't let any air get by. You don't need a heavy pour stream to get good bullets. You have to adjust it and experiment. If done well it will also let you pour from a one inch height and allow a generous puddle to form on top of the hole so that the extra sprue can feed the shrinkage and avoid voids in the base of the bullet. You can also pour in a continuous stream and move the mold so that 2 and 4 cavity molds can be filled without too much slop. Its all about adjustment and practice. Holding the mold up tight against the pour spout has never worked for me as it doesn't allow for having extra on top to feed the shrinkage and it often causes spout freeze-up as the blocks draw heat from the spout. Some folks have had success with that method, but I haven't. On sprue plates....the sprue cutter should not be too tight...it should lie flat on top of the blocks but also swing free on its own weight. Not sloppy so that there is up and down play, Air has to escape from the top of the mold and plates that are too tight won't permit that, so incomplete bases and bands will result if air is being trapped. 1%-2% tin in the alloy makes it pour "pourable" and fills out the bullet details better. Cast at a temperature that is just below that which makes frosty bullets....although frost doesn't effect accuracy...but why waste energy. Give the sprues time to harden, don't cut them too soon or you will get smears on the blocks and the underside of the cutter. Flux often and keep your metal clean....if the metal/alloy starts to pour "stringy" then flux,skim and clean it. Practice, adjust, and practice. LLS