Pre-vent Moulds?

[Cleve Branch]

Are prevent Moulds harder to cast with? Are there special techniques needed or just cast as usual?

[Hickory]

With no response so far, my guess is, most people who viewed this thread are like myself, trying to figure what a prevent mould is.
Could you elaborate.

[btroj]

Prevent mould? Keep stuff dry and you can prevent mould.
As far as casting bullets I too have no idea what a prevent mould is. Care to shed some light?

[wv109323]

I think he is talking about a mold that has no venting for the air to escape when the lead is poured into a cavity.

[Larry Gibson]

Cleave Branch

I've cast with several "pre-vent" moulds over the years, mostly older IDEAL moulds. I've used no "special" techniques other than the moulds needed to be hot and the alloy about 720 - 730 degrees. Oh, I also really was generous with a sprue over pour. The addition of vent lines in moulds many years ago solved a lot of wrinkled bullet and air pocket on the bullet problems.

Larry Gibson

[maxreloader]

Pre-vent molds... like flat surfaces inside, no venting lines machined in. I dont have any so I can't comment.

[Cleve Branch]

Thanks Larry
you are correct about what I was asking
I guess I didn't pay attention to how I typed that in.

[Le Loup Solitaire]

I have a couple of old Winchester molds with non removable blocks and wooden handles and neither has vent lines in/on the blocks. They do not require any higher temperatures and cast well. Both are single cavity and are a bit slower because the sprue cutter has to be tapped from the front of the blocks and being left handed makes it a little harder for me. With the sprue plate properly adjusted there is no problem with venting, fillout or voids. LLS

[geargnasher]

Do a site search for member Onandaga if there's any trace of him left here and include key word 'swirl', as in swirl pour. It's a technique to tilt the mould to one side and pour the stream favoring the "near" side of the sprue hole to create a vortex inside. This directs alloy up the sides of the cavity and air to vent up and out the middle of the sprue hole. Works great and he explained it better than I can.

Gear

[runfiverun]

it's a good technique to use on short fat boolits too.

I have a couple of non vent molds and they cast just fine, sometimes they like to be pressure poured to get perfect fill-out.
but the ones I have pour out very nice boolits.

[runfiverun]

changed your title it might help clear things up.

[geargnasher]

thanks. I waited all day for someone to ask what in the world it was about!

Gear

[bangerjim]

Preventing molds. That's a new one!

Now, since we are talking "VENTED" molds, I have vented and non-vented ones in aluminum and brass. I see very little difference in the quality of the pour......as long as the molds are pre-heated to full casting temperature on a hotplate, the alloy is at the right temp, and I use good casting techniques.

Some claim venting helps prevent wrinkles. I have not really seen that. What I described above is what prevents wrinkles for me.

banger

[barrabruce]

I got one.
Mine likes it hot.
like feel the heat from the handles.
I need to positive poor with a bottom pour ladle to get a good sprue otherwise it will not fill out the plain base edge properly.

If I have troubles it is usually the gap between the sprue plate.
Mine like just a wee bit of gap help vents air I think.
When its hot and running I just need to keep a steady cadence going.
Not particularly fast just keep it well hot.

I go pour bullet
Wait to set and cut sprue
set mould on wood bench to cool.
With over hand and tongs pick up last bullet and place in lube to coat.
Place lube bullet standing on base to cool on greese proof paper.
Drop new bullet and continue on.
I end up with as many lubed bullets I want.
The retained heat melts and keep the lube liquid without being too hot.

barra

[44man]

Takes very little to get air out. Temps control is best to work with. I made most of my own molds and when I started I cut vents in both blocks to find I only need them on one face. Just .002" deep. Mostly less because I swing a fly cutter by hand. Just a scratch.
On top and under the plate I just use the marks from the end mill.
Lee molds never had lines cut and they worked fine.

[krems]

I've cast with both and I couldn't really tell the difference. I make all my molds with vents like 44man above. If given a choice I prefer vents.

[gwpercle]

I have two or three of the old Ideal , no vent line moulds and just cast with them as normal. Nothing special, clean , bring to temperature and cast. I remember reading about scribing a line from a spot that persistently wouldn't fill out , to the outer edge to "vent" the mould. Mine have never required it. Cast up a few and see how it does.
Gary

[.22-10-45]

Just recently cast with newly purchased "Pre-Vent Lined" Ideal 225415 using a Lyman No.2 equalivant alloy. Some of the best cast bullets I have ever cast out of the half dozen 225415 moulds I own. Very round and right at .225 dia. No problems with getting full fill-out. Though I do stone a VERY slight 45 deg. angle on top mating edge of both blocks for air venting under sprue cutter.