How to prevent torn bases...?

[DEVERS454]

What is the best technique to prevent torn or ripped bases on freshly cast boolits?

[hiram]

This is what I do.

Use a countersink BY HAND (may require a little pressure) and turn it in the sprue hole. Do not use it in a drill press, hand drill, or cordless because you might open the hole faster than a blink of your eye. This happens to throw a burr on the underside of the sprue plate(the top of the mold). I then take a fine, flat india stone and stone off the burr. If you run your fingertip across the bottom of the sprue plate, you can probably feel a sharper edge.

[fourarmed]

This happens to me when I am casting very hot and very fast. I have adopted a method called around here the "Bruce B". (Where is he, by the way? Haven't seen his name here in a while.) I use a metal pie pan half full of water with an old terry washcloth folded in it. As soon as the sprue puddle crystallizes, I press the sprue plate against the wet cloth for 2 to 3 seconds. This cools the sprue enough that it cuts instead of tearing.

[DEVERS454]

So, let it cool first a bit, then seperate... correct?

I'll also double check the sprue holes to make sure they are sharp.

Thanks for the tips!!!

[FISH4BUGS]

So, let it cool first a bit, then seperate... correct?

I'll also double check the sprue holes to make sure they are sharp.

Thanks for the tips!!!
That idea with the wet towel (the BruceB speedcasting) is one of the best tips I have ever gotten about casting, and it has upped my production a by fair amount. The smearing you are encountering is simply because the lead hasn't had time to harden quite yet (at least that's my guess - I can't think what else it could be). It is all a balancing act between lead temperature, mould temperature, pouring speed, and cooling speed.

[Dale53]

I have had MUCH better bases when I started using my hand and just twisting the sprue plate to cut the sprue. Requires welding gloves or equivalent to avoid burning your hand, of course. I do NOT strike my sprue plates with ANYTHING.

Dale53

[montana_charlie]

I have had MUCH better bases when I started using my hand and just twisting the sprue plate to cut the sprue.
I saw you mention this in an earlier thread (I think it was you) and started turning the sprue plate by hand. Since my plate tension is very light, I like this MUCH better than whacking it.
Now, except for the occasional 'sticky' bullet, my knocker is just decoration on the bench.
CM

[Dutch4122]

I do NOT strike my sprue plates with ANYTHING.

Dale53

Same here. Cutting the sprue by hand gives me a much better "feel" for how fast the alloy is cooling after a couple of cycles.

[Bucks Owin]

What is the best technique to prevent torn or ripped bases on freshly cast boolits?

Do you mean "smears"? If so, you're cutting off the sprue too soon. Let it harden a little longer...

Dennis

[Nrut]

"smears"(on spure plate & top of mold) and ripped bases are two different problems....to stop smearing you can use the BruceB method mentioned above or use Bullshops "Bullplate" and cast at a lower temp.....I have used both methods and they work....ripped bases is a problem that I have with a few molds and I suspect that that is due to a dull spure plate as mentioned above also (thanks hiram).....so I better get off my ass and sharpen the buggers.....:)

[DEVERS454]

By letting the 6 cavity block cool a bit by sitting it on a wet rag (on the sprue side first, then the bottom) the boolits cool off enough so that I don't have torn bases.

The cavity nearest the sprue plate anchor bolt is the most likely to tear. (least amount of shearing force is applied there.

I also adjusted the tension on the bolts and sprayed the bottom of the plate and the top of the block with graphite...

100% success.

[Newtire]

I have had MUCH better bases when I started using my hand and just twisting the sprue plate to cut the sprue. Requires welding gloves or equivalent to avoid burning your hand, of course. I do NOT strike my sprue plates with ANYTHING.

Dale53
Just to add my vote on the subject...I too am a "born again" squeeze the sprue plate with the gloved hand guy now. No more hitting the sprue plate for me. Haven't tried a 4-cavity yet though!

[Wayne Smith]

To sharpen the sprue holes all you have to do is hone the back side of the plate, just as you would to remove the burrs. This removes or reduces the possibility of taking to much with the countersink. Be sure you hone the entire back of the plate, not jhust where the holes are.