New caster questions

[Ring3]

I'm just getting started casting my own bullets. Lyman, YouTube and this site are my mentors. Don't know anyone local to ask for advise. I have a Lee 20# bottom pour pot. Casting with 50/50 ww/soft with 2%tin. Mould is a New Lee 6 cavity 358-105. A Lyman probe thermometer is used in the pot.

My first attempt made about 400. About half were culled because of rounded driving bands and cratered spruce cuts. The rest I powder coated, sized and shot. They shot ok.

Second attempt was worse. Culled most same as above problems except bullet spruce cuts were worse. Either cratered or raised nubs.

Read the "Leementing" thread and did the procedure. Also adjusted the Sprue plate bolt.

Third attempt getting same results. Bullets dropping free mostly but the rounded driving band persisted and cratered sprue cuts. Cranked the heat up to 850 in the pot and heated the mould longer. Bullets now had nice driving bands. They stubbornly stuck in the mould requiring tapping handle bolt. The cratered sprue cuts remain. I also notice more finning on each bullet.

Ive included a picture which hopefully helps describe what I'm typing.

What can can be done about the cratering of my sprue cuts? Is it an issue? Is some finning normal?

I should note the sprue plate isn't flat. Using a flat piece of glass and 600 sandpaper only the outer edges of the plate were abraded. Also I'm casting in my shed with windows, doors open. Temp is 20-35 degrees, no draft.
http://i689.photobucket.com/albums/vv259/ring33/IMG_1259_zpslakaadkv.jpg

[boho]

I am by no means an authority, I have only cast a few thousand bullets. In my limited experience, 850 is too hot a pot. I usually run at 725-750. I preheat my mold on a single burner hot plate on medium, i focus on a hot mold. I found that I would get sprue cut craters if I cut too late and my bullets cooled too much. I always get small craters with lee molds. If I get finning in this temp range it is usually a dirty mold face.

[runfiverun]

your killing yourself here.
what is happening is your opening the sprue plate at different times.
which is throwing your mold temperature off.

the trick is to keep the mold in a consistent temp range and to cut the sprue in a consistent time frame after filling the mold.
you use the time frame for cutting the sprue to adjust your mold temp.
if your smearing the lead it's too soon.
if your fighting the plate to open the mold and have high sprue bumps your waiting too long.
sometimes you need to cut the sprue and count 1-2 more seconds before dumping the boolits out of the mold.
or you need to pour a bigger sprue to keep the base a bit hotter a second longer.

notice I have said nothing about the pot temp.
once you have the mold at a consistent pour count cut and it seems you need to wait another count longer to cut the sprue then you turn the pot temp down about 20-f.

[wv109323]

If not filling out mold is too cold. Lead temp should be 700 or so. The craters is caused by cutting the sprue too quick. Sprue needs to be solid to eliminate the craters. Finning is mold is not closed, lead in alignment pins or lead stuck to mold halves.

[runfiverun]

or your thumb is on the sprue handle.

[gwpercle]

It's hard to keep things at a constant , proper casting temperature when it's 20 to 35 degrees in your shed. An experienced caster could , maybe , do OK but you're trying to learn.
Aluminum moulds are tricky to keep at the proper temperature , they loose heat fast.
I know you would do much better if the temperature was at least above 45 , things are cooling down to quickly and running the pot at 850 isn't solving the problem. 725 to 750 should be all you need.
If the sprue plate is warped , replace it or sand it flat. The plate and block tops must be flat and level or you will have problems. The little chunks being torn out of the sprue holes usually happen when the metal hasn't cooled enough. The nubs usually happen when the sprue plate is not flat or too loose or warped , it rides up and doesn't shear the sprue off flat with the base .
Don't get discouraged...we all have gone through this , it just takes some practice.
Gary

[Ring3]

Thanks for all the responses and ideas. I got a lot to learn. A bit discouraged but I'm stubborn and will figure it out. Shot 300+ of those ugly ones at steel plates yesterday. They worked ok.

Might swap out sprue plates with a new 45 mould I just got. The one I'm using isn't perfectly flat. Will also watch temps and cadence more closely.

Rob

[runfiverun]

almost every 6 cav sprue plate I have seen is not really warped nor really sharp.
but they generally have a little roll in them one way or the other.