Questions on reconditioning molds

[kevin c]

I got a couple 6 cav aluminum Lees and a 4 cav brass MP mold from a range pal that I'm trying to fix up. A couple questions to those with experience:

The MP has a roll pin as a stop for the sprue plate. I can't access the bottom of the pin to drive it out. Is it actually removable, and if so, how do I do it?

The mold blocks of the same mold don't close completely. After a thorough cleaning I can only see that the pins won't let the faces mate. I've read here that a vice can be used to press the blocks together. Would it help to heat the blocks first? Would that help with the roll pin as well, and with a frozen broken off bolt in the aluminum molds (already drilled out and still won't move with a screw extractor)?

I've sanded the steel sprue plates of other blocks, but can the light alloy (aluminum?) Lee plates be done the same way?

Thanks in advance,

Kevin C

[Old School Big Bore]

The MP's alignment pins are a press fit and can be tapped back and forth to obtain proper closure. Check to see that the blocks haven't been overheated and warped, though. The roll pin can be grasped with a pair of vise grips, or a machine screw tapped & threaded into it and used either to push it out against the bottom of the hole, or with a slide hammer. Just make sure the blocks are padded in whatever's holding them. In my mechanic-ing days I removed and replaced a lot of roll pins from brass, aluminum and cast iron, and it was seldom pretty.
Some Lee molds have LEFT-HAND threads in the sprue pivot screws; you didn't say whether the stuck one is a handle screw, plate stop or plate pivot.
I have reduced ridges adjacent to gouges on the aluminum plates with fine emery cloth on a flat surface, but have never tried to totally resurface one. New plates are available if one is badly damaged.
Ed <><

[kevin c]

Thank you, sir!

The mated brass blocks are flush (no light visible) on top, have an even gap on the bottom pin side, and symmetric wedge shaped gaps on the sides. I can rock the blocks over the pins. The faces look true. I think I'll try a padded vice.

The broken bolt is actually on a different MP mold, so I don't think it is left hand threaded. That oops is on me: I tried to turn out the bolt, forgetting that I had the set screw still in place against a flat filed in the threads - it worked too well.

I had wanted to sand the top of the brass mold but the roll pin is in the way. I might leave it be, as the top of the mold isn't nearly as bad as the others I'm working on.

We shall see.

[Conditor22]

Sometimes you have to sand the top of a mold smooth (I've repaired a few) IF the sprue plate stop pin won't twist out, I cut it off and drill a hole for a roll pin or to tap for a bolt with its head cut off. I dealt with some molds were the tops so bad I had to get the tops machined down a bit. usually, wet-dry sandpaper on glass/tile of other flat surface holding the mold flat will get the top cleaned up. I've also had to do the same thin with the face of some molds that developed a little warp punching the pins back and sanding the face until they are flat again, then I polish the cavities to make them even.

Most sprue plates can be sanded flat using the same method. You can order a replacement 6X sprue plate from Lee paying shipping and handling or buy a steel plate from a VS on this site. I've had a little lunch putting the lee 6x plate in a vice with some spacers on the ends on one side of the plate and in the middle on the other side of the plate to take a bow out.

[country gent]

What we did for blind pins was to use a collet block or chuck and collet to fit the pin. grip the pins protrusion in the collet tight. ( on a roll pin this will actually compress it some) and using small try bars between collet and block pry it off. It may take several times to get it out.

You can tap the inside of the roll pin but, roll pins are spring steel and tough with an interrupted cut so be very careful here.

For moving the pins I set the block on a lead ingot and use a soft punch and hammer to tap in or out.

As to the sprue plates a known true flat surface with various grits of fine wet dry paper works well. use a light oil under paper to hep hold it to plate. sand in a figure 8 pattern dry then with oil and finer grits to desired finish. Even better is a true lapping plate and lapping compounds. This will work with the sprue plates and tops of the blocks. Some bocks have a small bevel on the tops to form a vent line under the plate and may need recut after the blocks are refinished.

[DHDeal]

Careful pushing the stop pin further in on the MP brass mold. It's long enough to not come out of the handle slot. Did that to one I had accidentally (unknowingly is a better word) pushed down. Had to cut it off and finish pushing it out. Ended up threading the hole to the same size as the sprue plate bolt and adding a stop screw. For all intents it works the same as an Accurate Molds sprue plate stop now. Liked it enough that I had it done to 5 other MP Molds. It's quite easy to pull them out and a PITA to push them down....

[kevin c]

Thanks for all the good advice!

I got the blocks on the MP brass mold to mate except for a barely visible hairline gap that may be from lead build up or tinning at the edge of the cavities.

I first put the mold halves together and compressed them in a vise. That worked too well, they seated flush but it took a (soft faced) mallet to get them apart again, and when they did they were still sticky going back together. I ended up compressing the pins directly in the vise.

I'm thinking I'll leave the roll pin alone. I'll clean the bottom of the steel sprue plate and see how the bases cast (I'll need to get those build ups off the mold faces first). The mold still looks pretty bright, maybe it wasn't ever conditioned. I'll try heat cycling it before I use it.

I might replace the Lee sprue plates if they don't do the job. Thanks for reminding me that's a good, easy and better alternative to sanding through the anodizing!

[Jniedbalski]

All the lee molds I have have steel spruce plates. You said yours has aluminum? I have lee molds bought 30 years ago and some three month’s ago all steel

[kevin c]

All my 6 cav Lee molds have light alloy non magnetic sprue plates, and this is what I'm planning on ordering from their site: https://leeprecision.com/spru-plt-ship-custoo.html

[Jniedbalski]

I have 30 plus’s lee molds all steel. But there two cavity. The three six cavity molds I have are steel also but probably 20 years old except one. It’s probably five years old and also steel. When did they start using aluminum on there plate ?

[kevin c]

I just started casting maybe three or four years ago and started by ordering several 6 cavity Lees in different calibers. They all have the aluminum sprue plate, so maybe the switch happened shortly after your order and shortly before mine.