Brass Mold Troubles

[gwpercle]

Hold the mould in front of a small fan to speed the sprue hardening. Another trick is cast with two moulds, fill one, set down to cool while filling the second, set second one down and open the first, it will have cooled by then. Good excuse to buy two moulds....right!
Gary

[Smoke4320]

2024-T4 & 6061-T6 are Aircraft aluminum grade and there are several others

[44man]

Aircraft Aluminum? What is that? Tough as Iron moulds? I think you are shoveling with both hands.

Good stuff, very hard and tough. I worked for an airline and got a huge chunk. Even the sprue plate does not mark it. I believe I have the 7000 series metal. It seems harder then 6061 but might be the higher 6000 series. 7068 aluminium alloy is the strongest commercially available aluminium alloy, and comparable to that of some steels.^[1] 7068-T6511 has typical ultimate tensile strength of 103 ksi (710 MPa) versus a similar product produced from 7075-T6511 that would have a typical ultimate tensile strength of 93 ksi (640 MPa). Typical yield strength for alloy 7068-T6511 is 99 ksi (680 MPa) versus 86 ksi (590 MPa) for a similar product produced from 7075-T6511.^{[citation needed]} Strength allowables for this alloy are provided in Metallic Materials Properties Development.
Sure different then the soft junk lee uses.

[44man]

6061 would make a great mold. The custom mold makers use a good grade of aluminum.

[quasi]

I was not aware 7000 series Aluminum was used in Aircraft. As far as casting with brass moulds or other metals, I find the Bruce B. speed casting method works well. Using a wet cloth or sponge to cool the sprue and or the bottom of the mould works well for me.

[Doc Highwall]

Where I worked in the aircraft we used a lot of 6061-T6 and we also used 7075 along with a lot of other metals.

After I fill the mould cavities I look at the sprue puddle and watch for it to change color showing that it just froze, I then give it a three to four second count before I cut the sprue and squeeze down in the sprue plate while cutting.

[ofreen]

Hold the mould in front of a small fan to speed the sprue hardening. Another trick is cast with two moulds, fill one, set down to cool while filling the second, set second one down and open the first, it will have cooled by then. Good excuse to buy two moulds....right!
Gary

This is an answer. I rarely cast with only one mold. You can move right along without as much problem with overheating.

[GabbyM]

Having machined 7000 series aluminum. I can tell you it is tough to cut to put it mildly.

I like the few brass molds I own. Do end up with frosted bullets some times but so what? I have a fantastic MiHec 30-180-SP-HP.
Pointy bullet hollow points aren't easy to cast. This mold does great. Once the pins get hot enough to allow lead to flow and form up nice. Only takes a couple cast after pre heating on top of my pot.

You do have to be careful with brass a you can get things to hot and solder them together.

A two cavity brass mold is all the weight I care for in a hand cast mold. 4 and 6 cavities I like aluminum to save my wrist.
I use a fan for cooling. Two molds at a time is to much like work.

[Forgetful]

Buy yourself a digital mold thermometer and a pot thermometer and get rid of all the guesswork. I've been having issues with the last aluminum mold I bought, it was dropping fine for the first two sessions. Started up a third session and can't get good fillout with the same alloy and what I thought was the same temperature. Cleaned, re-lubed, tried again, no go. NOE's thermometers are in the mail. Tired of guessing. I haven't had a problem in the past, because I was happy with 90% or 95% efficiency when things are working right.

[Dale53]

I have been casting bullets since 1950. I've even done commercial casting. However, an old dog CAN learn new tricks. Just a few years ago, I read an article by Mike Venturino where he mentioned using a manicurists fan to cool his sprues. I found one at Target (not in the ladies cosmetics but in the fan department) for about $7.00. I later saw one in Walmart. These may be in stores on a seasonal basis but can be had online. Here is one similar to what I have:

http://www.walmart.com/ip/QV-Tools-T...ingMethod=p13n

At any rate, I mounted it about 18" above my casting table. When I pull the mould (bottom cast with an RCBS Promelt) from the furnace the fan blows on the top of the mould. In two to three seconds, the sprue is set - YMMV. I got it to speed up casting. Normally, when the mould is hot enough to properly cast it takes too long for the sprue to set. This allows the best of both worlds. An additional benefit that I discovered is, after you establish a cadence, it maintains proper mould temperature. No overheating, etc.

I have NO problems casting with brass (I have several Mihec brass moulds and LOVE them), aluminum (Mihec and NOE as well as Lee and NEI), or iron (H&G, Lyman, RCBS, and Saeco).

I pre-heat ALL moulds on a hotplate (I bring my moulds up to a predetermined temperature just under casting level - then one or two casts and I am ready to go). My suggestion will keep you from overheating and warping a mould.

The few dollars you spend on a "personal fan" will go a long way to solving time for sprue to set and overheating of moulds from a good casting cadence.

Here's a picture of my set up:



Just a thought or two...

Dale53