Sprue Dimple

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SgtDog0311
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Sprue Dimple

Post by SgtDog0311 » Sun Jan 01, 2017 4:27 pm

Anyone done any testing to see if a sprue dimple like this throws a bullet off-balance or not. This particular mold cuts it better than others but still leaves a raised dimple. Others pull lead and leave a debit. I think those sprue plates must have a square shoulder causing more of a tearing or plowing effect. Sometimes I drag my bullet a across a file to remove the raised portion and wonder if it is important or not. The debits I just examine for how centered they are. The debits are more frustrating. But in either case thought opinions based on experience and testing group size would be useful.
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Brent
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Re: Sprue Dimple

Post by Brent » Sun Jan 01, 2017 6:41 pm

I doubt anyone could prove that they matter, but let the sprue cool for another beat or two and I bet they cut cleaner.
I'm not from here, I just live here.

Deadeye Bly
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Re: Sprue Dimple

Post by Deadeye Bly » Sun Jan 01, 2017 7:06 pm

Your sprue plate is too loose. Tighten it up some and as Brent says, let the mold cool a bit longer. It could be that the cutting edge is not sharp enough. Countersink it a little deeper and stone the surface that contacts the mold to remove any burrs. That should help the appearance of the bullets. You will need to determine if it makes any difference in accuracy.

Premod70
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Re: Sprue Dimple

Post by Premod70 » Mon Jan 02, 2017 8:32 am

Usually when I see the divots it is a sign the lead is too hot or more so the mold. The hot mold can be cured by adding more time between the pours, good luck.

SgtDog0311
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Re: Sprue Dimple

Post by SgtDog0311 » Mon Jan 02, 2017 9:43 am

Appreciate the input. Figured as much testing as I see done on the forums there'd be some who has controlled for that and I still bet someone has. Last week I did my own little test with and without paper over primer and was interested in the result, the only completely consistent thing being that the velocity was lower in four different loads with paper. Go figure. And here, as alluded to, the difficulty may be in my shooting disclosing enough difference in group sized to get a true reading on whether a slight dimple, well-centered, would have any bearing on stability or not. I know treating them with a file (carefully) adds considerable time.

The dimples are a little exaggerated by the photo. The sprue on that particular mold is pretty snug as is. I'll give tightening a try but as-is it has considerable tension between the surfaces. Much more and it would be hard to open with a gloved hand. I'll see if I can get a better happy medium. And I'll experiment with a longer wait time. I usually watch for that last color-change as heat draws down into the puddle.

For debit-tearing I have tried changing temps with longer cadence but a couple of my Accurates don't seem to respond in either direction. I believe the profile must be blunt with considerable shoulder but I've been a hesitant to increase the depth for lack of control or knowing in how far and fear of ruining the sprue. Any tips on how it ought to be tackled... you use something to hone or something to cut? Understand about ensuring it's deburred on the underside.

SgtDog0311
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Re: Sprue Dimple

Post by SgtDog0311 » Mon Jan 02, 2017 9:54 am

Premod70 wroteCOLONUsually when I see the divots it is a sign the lead is too hot or more so the mold. The hot mold can be cured by adding more time between the pours, good luck.
Sounds reasonable too Premod70, especially since my Accurates are all aluminum and the temp control on my Lee pot is not very effective. I'll pay more attention there and slow down regardless of how I might modify the sprue orifice.

Plainbase
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Re: Sprue Dimple

Post by Plainbase » Mon Jan 02, 2017 1:11 pm

I don't think you have to do anything to the sprue plate and it should not be tight to the mold. You just need to slow down and give more time before opening the mold. Best thing is to cast with two molds and alternate between them which keeps your mold from overheating and a gives a good solid base to cut and will actually give you a higher production rate.
Plainbase

Kurt
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Re: Sprue Dimple

Post by Kurt » Mon Jan 02, 2017 2:00 pm

Hard bullets tend to tear the sprue, especially if using some WW.
A couple things you might try. Take the plate off and figure it on a sheet of 220 emery over a smooth countertop or plate glass. This will take off the uneven high spots from the underside of the plate.
I use a very tight plate that takes a firm push to cut the sprue. I use a 1" dowel about 8-10" long with a dimple in the end so it don't slip off the plate and I use it with downward pressure on the plate and the mould resting on the pot edge and push it to cut the sprue. This cuts the sprue not tear it.
A loose plate will give you weight variances and it will smear the plate and the top of the block if you cut the sprue to soon, then you will have an overflow that leaves a fin over the base edge.
I like to coat the top and bottom of the mould block with Rapine mould preb and also the top of the plate so the cut sprue releases and let it dry when it heats up before closing the plate over the block so the prep don't get into the cavity..
just my way :)

SgtDog0311
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Re: Sprue Dimple

Post by SgtDog0311 » Mon Jan 02, 2017 4:58 pm

Thanks for the suggestions.

I did look with a magnifier at the sprue I suspected of having a shoulder and there was none. So I'll make use of the suggestions and see how I fair employing them. Downward pressure sounds like a good idea. Thanks! I learn something every time I cast.

Brent
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Re: Sprue Dimple

Post by Brent » Mon Jan 02, 2017 6:44 pm

FWIW, I turn my sprue plate open with my hand, protected by a leather welding glove. It gives good control, much like Kurt method.
I'm not from here, I just live here.

Kurt
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Re: Sprue Dimple

Post by Kurt » Mon Jan 02, 2017 7:49 pm

Brent gloves just don't work for me, even in the winter when I was still a working plumber. :)

Actually the holes in the sprue plate for me the way I cast should be a lot smaller then what they use. Buffalo Arms uses a .165" hole that is just about as large as I would ever want for casting. Some mould makers make a much larger sprue plate hole. I use a .100" hole with best results. They make a very clean cut with out tearing a divot and the base is filled with a sharp edge as well the bullet is properly filled.
I have had moulds come with a hole larger then what Steve Brooks uses and if you don't give the bullet below the plate set a little longer then when the sprue grays it would actually pull the base of the bullet away fro the mould wall. Just because the puddle turns gray the bullet below is still like soft butter.
The mould below is one of the moulds I use with a hundred thousands diameter hole and it casts a very good bullet with 750 degree 1/16 alloy.

ImageIMG_2914 by Kurt, on Flickr

Premod70
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Re: Sprue Dimple

Post by Premod70 » Mon Jan 02, 2017 8:14 pm

SgtDog0311 wroteCOLON
Premod70 wroteCOLONUsually when I see the divots it is a sign the lead is too hot or more so the mold. The hot mold can be cured by adding more time between the pours, good luck.
Sounds reasonable too Premod70, especially since my Accurates are all aluminum and the temp control on my Lee pot is not very effective. I'll pay more attention there and slow down regardless of how I might modify the sprue orifice.
I've found that when the bullets become frosty appearing the mold is too hot. Slowing the time between when the bullets are removed and the next pour will give a shiny finish, a flat bullet base and in my opinion a smaller variance in bullet weight and rejects.

SgtDog0311
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Re: Sprue Dimple

Post by SgtDog0311 » Tue Jan 03, 2017 10:57 am

Thanks Again Gents.

From my thermometer reading I need to drop temp from what is posted here and the readings I was getting Saturday. Saturday I cast with a few molds and had finning in vent lines even when I couldn't find any obstructions or see daylight. Started to think I was running so hot that alloy was trying to follow the venting. But bullets remained shiny with no crystallization on the surface so I didn't suspect that heat till I was about finished. Did it with two of the four I was casting with. I'm not so good with cadence and the like yet as to be comfortable casting with more than one mold at a time. Interesting how when I first started I didn't have much trouble at all, probably because if a bullet fell out then I thought I was doing pretty good. Now that I've casted for a little while either more discerning and either discover new issues I missed before or am more critical of what I'm turning out.

And I'll give a little more time after the gray fades as well.

I use a glove right now but if I can't keep downward pressure sufficient to improve the dimple (raised sprue) with my hand then I'll try the dowel. I was kind of excited about the switch from a knocker to a glove but fiddling with the bullet after casting has got to go.

Kurt, that picture of yours is exactly what I'm striving for. btw, do you scrounge trays for your bullets from the range. I've been digging in trash cans at the pistol ranges of late :wink: Would like to cast several thousand before Spring and that adds up to a lot of trays?

Kurt
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Re: Sprue Dimple

Post by Kurt » Tue Jan 03, 2017 7:33 pm

Sgt.
Yes I get them at the range. Seems like nobody reloads on our range. But that is good, I find things I use :)
I finished my .45's today. That gap is now full. When I get more lead I will add to the .44's.
ImageIMG_2913 by Kurt, on Flickr

SgtDog0311
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Re: Sprue Dimple

Post by SgtDog0311 » Wed Jan 04, 2017 9:45 am

Kurt, you inspired me to drive out and dig through the trash cans yesterday. Too cold and windy for anything else. I got a Walmart bag full for storage. I don't cast anywhere near your quantities but I'd like to cast up about 3500 bullets in various calibers over the winter. Wouldn't get you a start but that will last me for the matches I hope to attend. I'm about half way there for the 38-50.

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