No vent lines!

[jonk]

I have a minie ball mould made by a company called Challenger (anyone ever heard of them?) that looks great- but I could never get it to fill out properly. I finally figured out why- no vent lines! The mould halves are perfectly smooth, and I think that that is a large part of the problem. I never noticed this before- I mean who would think that there wouldn't be ANY?

So... what to do with it? Any reason that I couldn't etch some vent lines in it? A pass or two with a fine edge file should do the job. What do you think?

[beagle]

No reason not to scribe vent lines but be carefil. A carbide machinist's scribe works well for this available at Lowes.

Before you do this, take a stone and bevel the edges at a 45 degree angle at the top of the mould where the bullet base cavity is. Only hit it lightly 3-4 strokes. Enough to see a shiny line when you hold it to the light.

Normally, this will vent a mould sufficiently to allow good casting.

I have many old unvented Ideal moulds and they make darn good bullets and cats easy with this mod.

When I have attempted to vent one by scribing vent lines, seems like I always have an Ah sh_t! in the process./beagle

[leftiye]

Clamp a guide to the blocks and scribe AWAY from the cavities. Biggest problem will be finding small "C" clamps (they're the cheapest ones too!). I may be wrong, but don't be shy about making some grooves (don't get too King Kong about it either though). I've got a mold that is beagled and lapped out from about .310" to .316". so a few thou to let air out shouldn't make whiskers except in special cases.

[Maven]

jonk, Before you scribe vent lines on the block faces, consider this: Neither the early Ideal mold blocks (with integral handles) nor the Thompson/Center roundball & maxiball [aluminum] mold blocks (ca. 1970's - '80's) has vent lines, yet they cast beautifully. Scribing won't hurt things if you're careful, but I think the problem lies elsewhere; e.g., too low a casting temperature for a large, hollow-based projectile in an aluminum (?) mold. Scrub the mold again with your favorite solvent, smoke it with a butane lighter or wooden matches and raise the temp. of your furnace to at least 800 deg. F. (You can reduce it once you get 10 - 15 good bullets.) You may also need to loosen the sprue plate to help venting and use a ladle: Try pouring fast v. slow; with the ladle in contact with the mold v. slightly above it. If none of this helps, by all means add vent lines. Hope this helps!


P.S. Spray on dry graphite lube, e.g., NAPA DGF 123 may work if smoking the cavities doesn't. It certainly will help on the HB pin.

[stocker]

If you are a bottom pour caster, pressure casting by holding the mould tight to the spout fills them out pretty good. I have an old Ideal 7mm spitzer mould with no vents and it is the only way I can get good boolits from it. Add a dollop for a sprue after you take the mould from the spout.

[longbow]

I'm with Maven on this. I have had several moulds with no vent grooves and had no more trouble casting with them than vented moulds. I also make cylindrical push out moulds that are also unvented and work fine.

Having said that, I ladle pour and pretty much always have. I had a bottom pour pot a long time ago and didn't like it. Maybe that makes a difference too.

Certainly adding vent grooves if done properly is likely a good thing but I would be inclined to check out other options first if you haven't already.

Something else that may do the trick and won't harm the mould is to Beagle it (I'm surprised Beagle didn't comment on this one). If you use very thin foil or shim stock at 0.001" to 0.002" you will leave a slight gap without increasing size much at all. I have used aluminum foil in 2 to 3 layers glued on with Permatex silicone blue - my purpose was to enlarge the mould not vent it, but thin foil should allow venting with no other mod to the mould.

And thanks for that idea Beagle it certainly works! I have a lapped and Beagled 314299 that works much better now.

Longbow