Tapping the mould

358156 hp

At large, whereabouts unknown.
I believe the NRA cast book mentions tapping the mould as soon as you fill it. They say it helps the trapped air to come to the top and vent. I don't do it.

I've seen a number of moulds at auction that had evidently been tapped (a lot) on the side of the blocks on the right side with what I presume was a ladle. Some were pretty dinged up, and all of them in the same exact area. I never bid on a single one of them for obvious reasons.
 

Rick

Moderator
Staff member
I believe the NRA cast book mentions tapping the mould as soon as you fill it. They say it helps the trapped air to come to the top and vent. I don't do it.

It's been several years since I've read it but I don't recall that. Given the density of the lead and the very rapidly freezing alloy inside the mold I would chalk this up as an old wives tale. Logic would dictate that if there is trapped air inside the mold whooping on the mold isn't going to free it, the alloy is already frozen or you are casting way, way too hot.
 

Brad

Benevolent Overlord and site owner
Staff member
There is a difference between tapping and banging.

I do hit the handle pivot when opening the mould, it certainly helps the mould open easier and gets bullets to drop free.
 

Ian

Notorious member
It's been several years since I've read it but I don't recall that. Given the density of the lead and the very rapidly freezing alloy inside the mold I would chalk this up as an old wives tale. Logic would dictate that if there is trapped air inside the mold whooping on the mold isn't going to free it, the alloy is already frozen or you are casting way, way too hot.

Haven't you ever poured a few rounds with the sprue plate open on an up-to-temp mould just to see what's going on in there?
 

Rick

Moderator
Staff member
There is a difference between tapping and banging.

I do hit the handle pivot when opening the mould, it certainly helps the mould open easier and gets bullets to drop free.

My post wasn't referring to releasing bullets, it was a reply to trapped air being released. Yes, I sometimes will tap the hinge bolt to release bullets, not air.
 

Brad

Benevolent Overlord and site owner
Staff member
I don't even try to tap to release air. By the time I could do that the sprue is already setting a bit.
 

Rick

Moderator
Staff member
Haven't you ever poured a few rounds with the sprue plate open on an up-to-temp mould just to see what's going on in there?

Um . . . No can't say that I have. If bullets that I am happy with come out no need to see what they look like without bases.
 

fiver

Well-Known Member
I have seen all kinds of stuff rigged up, electric razors, tappers, locking handles, locks on the mold.
I kind of liked the adjustable locking handle idea a consistent squeeze on the handles is a good idea IMO.
I even seen a wheel once where the guy hit a switch and the wheel went around dumping a specified time of alloy at a specified rate.
 

earlmck

Member
Years ago I played with a little tap after filling (single cavity moulds back in those ancient days). Couldn't detect any advantage then; certainly wouldn't do anything now when using a 5 or 6-cavity job.

But I notice several of my multi-cavity moulds make a smaller diameter bullet when I tap before I pour. Couple taps on the handle hinge and I get better diameter consistency. Obviously I am not getting the mould fully closed sometimes without the tap, but is only a couple thousandths so I'm sure I've cast a bunch without noticing.

It's now become a habit of mine to give a couple taps against the bench top before I fill, even with moulds that don't need it.
 

creosote

Well-Known Member
I didn't even think of giving the blocks a nuge to make sure they were closed. Now I know I need more practice. I always seem to make every mistake possible, that's the only way I learn. :confused:
 

VZerone

Active Member
One thing about tapping your mould blocks, depending on how hard the tap is, when the sprue isn't fully solidified you can crack the sprue lose from the bullet base.