a mould fit for a mother in law!Help!

[Qc pistolero]

I have been casting since the late 70's.I have moulds from Lee,Lyman,Saeco,NEI,Ideal(these are oldies but goodies).I know that each and every one of them has its own specificities but there is one that has a temper worse than an enraged mother in law!It is a 358091Lyman4 cavities plain base wadcutter.

When I cast at normal temperature(yes I have a thermometer)of 775*F,the nose doesn't fill up correctly.I get aproximatly 50%reject.When I jack up the temp.to 850*F,the nose fills up nice but the bases have some kind of a dent right on the edge(as if I would have made a scratch with my thumbnail right on the side of the base).But I must say that in this second scenario,my rejects go down to aprox 35%(still way too high).

I have tried casting with ww, 50/50WW/pure lead and ww mixed with aprox 5%lyno;result still the same.I'd really like to find out what is going on here because
A)that bullet really is accurate
B)maybe I can apply the cure to my mother in law....but that's another problem!

Anybody has ever encountered that problem?

[Doc Highwall]

I would guess that air is being trapped in the mould cavity.

I would first check to make sure all the vent lines are not blocked. Then I would check that the sprue plate fits nice and flat and swings freely when the mould is up to temperature.

[462]

The ill-formed noses are caused by the mould not being at its optimum casting temperature. Pre-heat the mould.

The scratches may be caused by rough edges around the bottoms of the fill holes. A Q-Tip will tell if that's the case.

[Qc pistolero]

I would guess that air is being trapped in the mould cavity.

I would first check to make sure all the vent lines are not blocked. Then I would check that the sprue plate fits nice and flat and swings freely when the mould is up to temperature.

Sprue plate is ok.
But as you stated,the vent lines might not be.Since my reject% is about 35% and my mould is a 4 banger(1 out of 4 would be 25%; getting close,it just might be that one of the cavity has got a plugged up vent line and a second cavity with a partial clog up).Thanks Doc.I'll check that out under a magnifying lamp.

[Qc pistolero]

The ill-formed noses are caused by the mould not being at its optimum casting temperature. Pre-heat the mould.

The scratches may be caused by rough edges around the bottoms of the fill holes. A Q-Tip will tell if that's the case.

Sorry,I should have stated that I pre-heat my moulds(hot plate next to the furnace).As soon as I jacked up the temperature to 850*F,the nose filling problem disappeared....and that is just when the base problem appeared.

Really am scratching my scalp about that one!

[runfiverun]

i'd have to go look at mine to be sure, but airc these have a bevel on the base.
you might just be able to pour some bigger sprues and get the plate hotter.
i run my 4 cav closer to 675 alloy temp.
so the venting of the plate might have something to do with it.
if it's one cavity continously then i'd look at that cavity's venting, either under the plate or along the top edge of the mold.

[Dale53]

You're not going to like my suggestion but I would be willing to make a small wager that if you add 2% tin to your mix the problem will go away. Tin helps greater by reducing the surface tension of the melt allowing better fill out. I would cast no hotter than 700-725 degrees and 675 may work better.

FWIW
Dale53

[rmatchell]

I also have the same mold in 4 cavity with the same problem. Ill have to check the vent lines next time I go out.

[Qc pistolero]

Nope,mine doesn't have a bevel base.It is flat.

It is a 4 banger and I've tried 4 separate large and small sprues/or 1 single large sprue for all 4 holes.
I'll check the venting of the plate(you might have something here)since I don't have any problem with the base at 775* but at higher temp the problem appears.Does the plate thickens or lenghtens(or both)under heat expansion?

[Qc pistolero]

I've tried adding Lyno(aprox 5%)ihope that the tin in the stuff would help cure the problem.
But I'll follow your suggestion and go buy some tin and try it out.

Thanks Dale53.

QC Pistolero

[Qc pistolero]

Please RMATCHELL let me know how it comes out.I am starting a new business and it might be a few weeks before I have time to cast a few more.

Hey guys,this site is great;lots of helpfull people!

QC Pistolero

[bruce381]

is the base hitting the other mold side as the boolits drop? sometimes my boolits have a "dent" and it is due to me not rotating the mold over enough and as the boolits fall they hit the other mold halve.

[longbow]

Here is another vote for venting but... I am going to suggest that not only you clean up the vent lines (or check to see if they need cleaning) but also to put a VERY small bevel at the top edges of the mating mould faces under the sprue plate. I use my diamond hone to just break the edge a bit. I have found this to sole fill out problems for me.

Ben does a good job of describing his method of tuning a Lyman mould which includes the bevel:

http://castboolits.gunloads.com/showthread.php?126129-Lyman-Mold-quot-Tune-Up-quot

Longbow

[40Super]

I put that bevel on almost all of my molds, it has helped in all cases. a few thou is all that is needed. Casting temp is not needed to be that high. I cast around 675F, Tin is needed to fix nose fillout. The Lino isn't a good source to add for tin, it adds more antimony and takes away any benefit of the tin that's in it.

[Larry Gibson]

Venting
Adding tin (adding lino also adds a disproportionate amount of antimony and induces another problem insteand of silving the fillout problem) using pure tin or solder such as 50/50.

The above problems are adequately addressed. However there is one other potential problem; pouring. If using a bottom pour open the spout to allow the alloy to get into the mould quicker berfore cooling. Keep the sprue plate close (within 1/2" or so of the spout) when pouring. Let a small amout of alloy (small squirt will do) run out of the spout imediately before putting the mould under the spout to allow the spout to "preheat" before each fill of the mould. Allow a generous sprue to build (even if it runs off the side) over each hole before moving to the next hole.

If ladle pouring swirl the ladle down through the alloy to fill with the max temp alloy. Use the horizontal/vertical twist method filling each cavity independently. Allow a good sprue to form over each cavity hole.

Using the 4 cavity mould alone will vastly speed up production. Speeding up or short cutting the actual casting prodcedure can reduce production by excessive rejection rates with poor quality bullets produced.

Larry Gibson

[youngda9]

Don't stop the flow of lead between pours, turn up the flow, cast fast and keep that mold hot. Leave a decent sprue.

[mdi]

I have a mold that just won't produce more than 50% keepers when used with a bottom pour pot. But, when I use my Lyman ladle, I'm up to 99% keepers. Same lead temp., actually same pot of lead at the same time. Perhaps if you tried the other pouring method it'll help (if you bottom pour, try a ladle, or if you ladle, try bottom pour). Works for me...

[miner49r]

I am new to casting and I am still working out all the bugs. Are you bottom pouring? I am finding that pressure casting is working for me. (knock on wood)

[40Super]

Yup, pressure casting has helped me with 2 different hp molds that were troublesome to get full fillout.

[rmatchell]

I found mine needed cleaned. results were better still need to work on it though