New Problem, Lee 6 Cav Sprue Plates

[leadman]

I bought 2 new Lee 6 cavity molds in the last week and a half and both of them left fins on the base of the boolits. I spoke with Andy Lee on the first one and discussed what I wanted to do to fix it.
I had found that the top edge of the molds faces was slightly chamfered so I lapped the top of the mold. This fixed part of the problem but still had flashing on the bases away from the part line.
I took the sprue plate off and tried a known good one off another mold and there was no flashing. So got to looking at the new sp and there was about .020" of upward curvature side to side on the bottom. Andy said there is a slight amount machined in for venting but this was excessive. So I lapped the plate down and got it so there was no flashing when I first started to cast.

As the Sprue plate heated up flashing reappeared on the bases of different boolits. I found that the sprue plate stop bolt is contacting the front edge of the slot in the plate so there is no room for the plate to expand so it warps upward in spots depending on how hot it is.
I used a file to relieve the plate so it doesn't hit the stop bolt and with the little bit I cast after that it seemed to work fine.

So if you have a sprue plate that shows no light, or very little between the plate and the mold block, but does when it is hot check the clearance between the front of the stop bolt and the slot in the sprue plate.

[ultramag]

Thanks for posting your experience. I too experienced this problem on a new Lee 6 cavity mold. I've been working on it for about a week and have done exactly what you did in chasing the problem.

I have been planning on getting a different type of cap screw and replacing the Lee sprue plate stop all together. I had pretty much determined the problem was with that bolt.

Thoughts on replacing that whole assembly?

[leadman]

I'm going to give the mold a more thorough test soon and see if it is fixed. I also polished the sprue stop bolt shoulder and the little collar that hold the sp down. The machining marks on these feel like a file and it was digging into the edges of the slot.
There is someone on here that makes a steel sprue plate that I have been thinking of getting.

[Lights]

I was having the same problem on my 1 week old Lee 356-120TC 6 cavity mold this week. Fins on the bases and raised sprue marks. I was in a hurry to use it before I headed off to work. So I did not get to take a good look at what was going on with it. Thanks for the heads up. I might just make a steel sprue plate for mine.

[Pooch]

Believe it or not the 358-125-RF two cavity that I bought did the same.

[JonB_in_Glencoe]

I've had a few Lee 6-cav molds where the sprue plate would warp. I never thought about the bolt stop being an issue. I replaced them with steel "aftermarket" sprue plates and the problem was solved.

I'm glad to read this thread, next time I have this issue with a factory sprue plate, I'll be investigating the stop bolt/sprue plate contact, and "fix" that potential problem first.
Thanks,
Jon

[ultramag]

This did end up being what was wrong with mine as well. I filed some more relief in the slot in the sprue plate as the OP suggested, heated the mold up, and then cast about 250 bullets quick and easy like. I never had a good run with it previously and you could just feel it was working like it should.

A replacement steel sprue plate is interesting if the price is not too over the top.

[JonB_in_Glencoe]

A replacement steel sprue plate is interesting if the price is not too over the top.

Mine were from a "one-time" run group buy about a year ago...$25 each, I bought 5.

[gunoil]

Do this to lee molds or they will trouble you:


Drill and tap, then add lil' set screw and drop one piece of lead shot in before tightening set screw. This way you vertical bolts will stay where you adjust them.

You need a single-eye hot plate from walmart, dont set your mold on 700 degree pot to warm it up.

You have to add a steel sproo plate somehow. I got one from mihec and lil' machine work its great.

[leadman]

gunoil, I haven't had any problems with the sprue plate stop bolt coming loose. There is a bellville (wave) washer and a sliding collar on a lee stop bolt to keep tension on the plate so an adjustable stop bolt is not necessary.

[leadman]

Spoke with Andy Lee today and he is doing to investigate this issue.

[gunoil]

Leadman, your a pro, beginners have trouble with this and this is a great mod for any mold. All do it except for lee. Newbies are rougher on molds than you. I was, I better now. I disagree.