Do alignment pins ever swell during use?

[tnlonghunter]

I've got a Lyman .410 Snover single cavity mold I bought used (ebay). Before use, I cleaned it with brake cleaner and a nylon brush, and it appeared to mate/close perfectly with no gaps. During my first use, it began to stop closing cleanly. I could feel the pins sticking when opening it, and the top and bottom would rock/pivot on the center.

I scraped away any visible lead with a chopstick while it was still hot, and cleaned it again after it was cool. It closes better, but still not like it did before. I checked the surfaces with a precision straight-edge, and they appeared perfectly flat. Whether I have the mold on the handles or not, with or without the sprue plate attached, it still rocks a little with a small gap visible when help up to the light.

While I can't feel the pins sticking anymore, that is still the area where it pivots. Hence my question: is it possible that the pins could swell from the heat during use? Before I do something like try to relieve the inside of the pin-holes or some, I thought I'd ask if y’all have any ideas.

[JonB_in_Glencoe]

You likely have some other mechanical problem. If your problem was pins swelling when heated, then every Lyman mold would have that same problem.
If there is something inside the pin receptacles, like a burr, you could try "polishing" them, but I surely wouldn't relieve any metal from them.

[Mk42gunner]

The pin might be protruding too far. It doesn't take very many thousandths of an inch for it to cause rocking.

Robert

[tnlonghunter]

The pin might be protruding too far. It doesn't take very many thousandths of an inch for it to cause rocking.

Robert

In the case of this particular mold, the receptical holes go all the way through the mold, so I know the pins aren't bottoming out, but I wonder if the inner diameter of the hole is ever so slightly too small for the base of the pins.

[MT Gianni]

In theory yes, all pins swell when heated, as do the holes. At normal mold temps the amount is insignificant.

[Winger Ed.]

I'd do a super good/aggressive job of cleaning the pins and inside of the holes with something like blue jean cloth & solvent
before I did anything violent to the mold.

[beshears]

Pins pushed out to far

[georgerkahn]

After the cleaning you do -- which is great -- let the mould totally dry and "paint" as much as you can with a used Sharpie. New ones apply too much black, which is why a used one seems to work better. After Sharpie-application work the mould, and any spots rubbing will have the Sharpie-black either scratched or rubbed off. Perhaps not the most "scientific" solution, but I had a mould with a similar malady, and this provided me the solution. (Bion, one pin was bent a teeny tad -- just enough to bind)
geo

[JSnover]

Make sure it has had enough time to warm up. I've had molds that get a little 'sticky' and then loosen up after a bit. Mold blocks don't always expand at the same rate. Larger molds (like the size of a truck tire) actually don't have round holes for the alignment pins, they have slots to allow for uneven expansion.

[country gent]

I doubt the problem is expansion as the complete mould expands with the heat. the bigger a part the more expansion to it. This is figured in to the blocks finished dimensions. Look st the blocks for rub marks or bright spots. the sharpie is a big help seeing this. Lipstick also is a good spotting agent. Best is dykem 109 blue but its hard to find and since it never dies can make a real mess.

I would add to check the handles hinge point and legs, here expansion will snug them some.

One thing to try is a piece of small angle iron. (1/8 x 1 x 1 about 6" long) set this gap down on a flat surface Lightly set the mould on it when opening and closing. This provides a "pre" alignment for the blocks.

[DocSavage]

Had the same problem with an RCBS mold alignment pins were seated a bit deep couple of taps with a brass hammer set the pins back allowing the mold to open and close frrely.

[Larry Gibson]

Not having the right handles for the mould can also cause this problem. Each half should wobble freely on it's handle "prong" when open and the blocks when closed should also have some movement on the handles.

[45DUDE]

Also if you decide to adjust it do it cold. Take it off the handles and hold together. I have used a flat punch. It just needs to not <wiggle>Pretty easy. Make sure the handles frames are straight.

[jsizemore]

What kind of lube are you using on the pins. Silver or copper anti-sieze works.

[gwpercle]

In the case of this particular mold, the receptical holes go all the way through the mold, so I know the pins aren't bottoming out, but I wonder if the inner diameter of the hole is ever so slightly too small for the base of the pins.

If one of the pins has moved out ...ever so slightly ... it will keep the mould from closing ... it has nothing to do with bottoming out in the hole ... it is simply sticking out too far and gets crosswise in the hole . (Hard to explain) It may be one or it may be both pins . Usually it's just one pin is sticking out farther than the other ... carefully tap the pin back into place , protect the pin from peening with a small wood or nylon block and get both pins to protrude the same amount .
Gary

[JSnover]

If one of the pins has moved out ...ever so slightly ... it will keep the mould from closing ... it has nothing to do with bottoming out in the hole ... it is simply sticking out too far and gets crosswise in the hole . (Hard to explain) It may be one or it may be both pins . Usually it's just one pin is sticking out farther than the other ... carefully tap the pin back into place , protect the pin from peening with a small wood or nylon block and get both pins to protrude the same amount .
Gary

I've run into this with other equipment.
What you're describing is the fact that since the mold blocks are closing on an arc, the pins can't be entering the holes in a straight line.
That's why they make the pins so short, and why the ends ought to be rounded or tapered at least a little bit so they don't have a square shoulder to bind up on.

[gwpercle]

I've run into this with other equipment.
What you're describing is the fact that since the mold blocks are closing on an arc, the pins can't be entering the holes in a straight line.
That's why they make the pins so short, and why the ends ought to be rounded or tapered at least a little bit so they don't have a square shoulder to bind up on.

Per-sactly... Thanks for explaining it for me ... I couldn't figure out how to explain the ...pins closing in an arch ... part , thats exactly what happens ... pin too long ...Arch is too short and it gets in a bind and the mould wont close completely ...

That's easier done than said ... Thanks
Gary

[45DUDE]

I have a couple of single hole Lyman's and they have short handles. I agree with post 12. I had to whack the pins back a tad yesterday on a 44 Lyman mold single cavity. It worked so good I did a 10 pound pot. Man--That took a while. The whole football game.

[Cap'n Morgan]

I gave up on separate pins when making my own molds. They always seem to come lose at some point, or causing the mold halves to bind when opening.
Instead, I CNC mill the blanks with tapered pins/holes as an integrated part of the mold. It takes a small bit of fiddling to hit the point where the halves will close perfectly without any play, but then it's smooth sailing for the rest of the batch.

[45DUDE]

I gave up on separate pins when making my own molds. They always seem to come lose at some point, or causing the mold halves to bind when opening.
Instead, I CNC mill the blanks with tapered pins/holes as an integrated part of the mold. It takes a small bit of fiddling to hit the point where the halves will close perfectly without any play, but then it's smooth sailing for the rest of the batch.

That almost looks too good to be real. SOLID GOLD. I like it.