Sprue plate won't release.

[blueline541]

I've been casting for about sixteen years now, and I've never had this problem occur.

I'd been casting for a few hours this morning when one of my molds sort of froze up, and it took a ridiculous amount of effort to break the sprue plate loose. It's a two-cav RCBS .45 mold which I've used without issue for some years now. The sprue plate isn't too tight or too loose, swings properly after finally getting it released, doesn't have any scratches or gouges, and is lubed.

I let it cool off and tried it again, but the problem persists. I'm not new to casting, but I'm new to this problem.

Ideas, recommendations? Thanks.

[Winger Ed.]

The set screw that holds the tension on the sprue plate's screw might have come loose.
I've had it happen and when closing the sprue plate, it'll drag the tension screw along making it be too tight.

It's a deal of something not being broken, ya just need to 'take it apart, and put it back together again'.

[blueline541]

I checked the set screw as soon as the problem began. I'm still stumped.

[gc45]

Winger Ed is right IMO- not much can go wrong and screw tention is often the issue, that and lube.

[Delkal]

Are you casting with a harder alloy than usual? Some can be hard to break open once the lead hardens and cools too much. Once you mold is up to temp don't let the mold rest as long and try and open the sprue plate as soon as the lead solidifies.

[blueline541]

I keep the mold properly lubed with two cycle synthetic oil. The set screw hadn't moved when the problem started. My alloy is the standard WW I've used for years without a problem. And I cast with two molds simultaneously which gives me the perfect rhythm for dropping bullets. This mold was running just fine for a few hours, and then suddenly the sprue plate flat refused to budge after filling the cavities with alloy.

I've cast tens of thousands of bullets, but this is a new one and has me stumped. My method, and this particular mold, have never been a problem until this morning. The sprue plate moves freely and smoothly as soon as the bullets are dropped.

[G W Wade]

Think the best thing to do is just take the sprue plate off and look. I have seen lead get into sprue plate hole and bind. i got in the habit off making the edge od the sprue plate screw head with a small file notch that points at the lock screw so you have a visual alignment reference. just a glance will tell you if it has moved, either tighter or looser. with the plate off you can check if it's warped or just some gunk causing binding. Maybe washer on hold down galled and trying tp tighten plate when rotated Like Winger Ed said" nothing broke but just need to be checked" GW

[country gent]

Take the shoulder bolt out of the sprue plate and look at it and the hole for galling or lead. also look for burrs. This is about the only area that can bind the plate up

[jednorris]

There is all kinds of different mixed metal in wheel weights, could that be your problem?

[dale2242]

It sounds like a hard alloy.
If I am casting with pure Linotype, I can`t break the sprue with my thumb.
I have to tap it with a wooden dowel.

[Bazoo]

Interesting. My first thoughts is that you have a speck of lead between the sprue plate and blocks, near the pivot (in a manner you cannot see it when inspecting) that is intermittently melting and solidifying, and thus, locking the mould tight.

Remove the sprue plate, inspect, and relubricate the pivot with graphite.

[gwpercle]

Zinc in the melt will make the spues Hard - Hard to cut ...
The harder the alloy ... the harder the sprue will be to cut ...
Check your metal .
Gary

[country gent]

Also check the spring washer if it has one they have been known to break and bind

[JonB_in_Glencoe]

I keep the mold properly lubed with two cycle synthetic oil. The set screw hadn't moved when the problem started. My alloy is the standard WW I've used for years without a problem. And I cast with two molds simultaneously which gives me the perfect rhythm for dropping bullets. This mold was running just fine for a few hours, and then suddenly the sprue plate flat refused to budge after filling the cavities with alloy.

I've cast tens of thousands of bullets, but this is a new one and has me stumped. My method, and this particular mold, have never been a problem until this morning. The sprue plate moves freely and smoothly as soon as the bullets are dropped.

From everything you said, especially what I've highlighted...I have to assume your mold is getting colder than usual for some reason, ambient room temp? or breeze? or something else.
.
OR...maybe it's time to completely disassemble the mold, have a looksie, look closely at sprue holes-are they sharp? or dull? or damaged? then give it a thorough cleaning, then try casting again.

[45DUDE]

I had to remove the spring washer on one of mine and replace with a flat washer. Hold the plate up to the light and make sure there is no warp.

[Bazoo]

Zinc in the melt will make the spues Hard - Hard to cut ...
The harder the alloy ... the harder the sprue will be to cut ...
Check your metal .
Gary

I forgot that a small amount of zinc will alloy with lead. Thanks.

[blueline541]

I took it apart, inspected for warps, lead deposits, etc., and I couldn't identify any issues. I put it back together and ran it again Monday. It started off fine just like before and then began seizing up to the point I could barely open the sprue plate. I'm completely stymied at this point.

On the plus side, the NOE mold ran like a champ, and I was able to cast around 2,000 bullets with it.

[Delkal]

You should try some anti seize on the screw and spring. I use this on all of my molds and it does make a difference. I also use it as the lube for the pins and spreading a little on the top of the sprue plate with a q tip then rubbing it all off makes it so the sprues easily fall off.

[gwpercle]

I took it apart, inspected for warps, lead deposits, etc., and I couldn't identify any issues. I put it back together and ran it again Monday. It started off fine just like before and then began seizing up to the point I could barely open the sprue plate. I'm completely stymied at this point.

On the plus side, the NOE mold ran like a champ, and I was able to cast around 2,000 bullets with it.

Lube the Sprue Bolt , Underside of Sprue plate and Top of mould blocks with Permatex Anti-Seize Lubricant ... this stuff will keep the plate from seizing as it heats up and is The Absolute Best stuff for this job ... a little tube of Permatex will last a long time ... you don't need much . I use a Q-Tip to smear a thin-thin coat on the block top and underside of the sprue plate ... less is better !
I lube whenever the sprue plate starts to show any resistance to easy opening ... lube often and cast long !
Gary