Brittle spru

[gjemba]

I was pouring an unknown alloy this morning and am concerned. What happened is the spru on my 6 banger just breaks and looks chrystalized. (Don't dis me if that is spelled wrong.) This is and the boolits are very frosted. I know I was pouring a little too cool because I checked with my new thermometer so I upped the temp. Some of the spru off-fall can be broken easily with one bend and others hold together or it just breaks when it hits the. I bet is is an alloy with very little lead in it.

[GP100man]

No the mold is too hot & your cuttin before the lead solidifies al the way !

Or alot of antimony ??? But I`ve never experinced too much antimony !!!!

I `ve cast twice with the 6banger now & the biggest difference I can see is managing the heat once it gets hot !!!

So you may be dealing with semi-molten lead ????

I just put a big sponge on the grocery list so I can cool the 6banger `bout every 4th cast.

[JonB_in_Glencoe]

Some of the spru off-fall can be broken easily with one bend and others hold together or it just breaks when it hits the.

I think the alloy must be quite hard...Like Linotype or even harder.

[lwknight]

A hardball ( 2-6-92 )mix will have a brittle sprue.
You get frosty when the mold is really good and hot like maybe getting too hot.
What you describe sounds pretty normal.

[gjemba]

Thanks guys. I may have been rushing the mold. I will keep a sponge handy and cool it.

[fecmech]

Timing is everything in spru cutting. On my Lee 6 cavs I pour, wait for the spru to suck in and turn the mold over and touch the spru to a wet rag then cut. The time on the wet rag(less than a second) and the time between cutting the spru can mean the difference between a nice easy but clean cut or a really difficult cut. If I hold it on the rag longer or add 3 or 4 seconds more till I cut can double the effort to cut the spru. Play around with the timing, not so fast that you smear lead but not so long that the lead has hardened a lot.

[fredj338]

Frosty is always too hot. Slow down, reduce the alloy temp a bit or both. Having a small fan near you to run the mold under will help. I don;t like the idea of water cooling, sems like warping is possible, especially w/ the cheap Lee alum & thin sprue plates.

[Roundnoser]

Frosty is always too hot. Slow down, reduce the alloy temp a bit or both. Having a small fan near you to run the mold under will help. I don;t like the idea of water cooling, sems like warping is possible, especially w/ the cheap Lee alum & thin sprue plates.

Yep! Thats what I do. I have a small fan blowing cool air over my 6 cavity mold. In the time it takes me to pick up the sprue from the previous pour and place it back in the pot, its cool enough to cut the sprue and drop the bullets.

Once you get the timing down, it goes really nice and fast (until the pot gets low...uggggh!).

[reloader28]

Not all of mine need cooling, but when they do, I use a damp rag. It only takes 1 second to cool a mold just a touch. Longer that that seems to get too cold.

I've also had bad luck doing it with beagaled molds. The steam seems to really screw with the tape. I had to replace the tape every 15-20 minutes.

[wallenba]

My six cavs do that sometimes. I then leave the mold halves open for a bout 10-15 seconds between dropping and pouring to cool off a bit, and slow down a bit too.