Mold Hard to Open

[buyobuyo]

Recently, my MP 359-125-HP mold has started sticking when I try to open it. The front alignment pin farthest from the mold handle pivot is where it is sticking. The rear alignment pin near the handle pivot separates just fine. To get the mold to open, you either have to yank to handles open with some force or pump the handles like a bellows until it decides to open.

The only thing that I can figure is that either the front alignment pin has moved out somehow or a burr has developed in the hole the alignment pin seats in. I tried setting back the pin in it's hole using a brass rod and a hammer, but I couldn't get it to budge. If I stick a cotton swab in the hole the pin seats in nothing is snagging hairs, so there isn't an obvious burr.

Finally, the front of the mold doesn't close completely unless you squeeze the handles tight. Then it closes and you can't see light through the mold. Once the mold is closed tight it doesn't spring open.

Any help would be appreciated. The mold worked fine when I got it a couple of years ago.

[462]

It could be mould-to-handle misalignment. Are you using the same set of handles, as you did a couple years ago?

[buyobuyo]

Yes. I'm using the same set of handles. However, if I turn the blocks around on the handles, the problem follows the alignment pin.

[Dale53]

I am a great believer in Bullshop's Sprue Plate lube. I regularly lube my pins. This can help a good deal.

I have seen moulds slammed shut repeatedly to the point that a burr is raised around the pin hole. This can also cause sticking. Careful work with a needle file can clean it up an allow it return to previous condition.

FWIW
Dale53

[buyobuyo]

I use the sprue plate lube that Mihec sends with the molds. Maybe it is a burr, but if it is there it doesn't catch fibers off a cotton swab going in either direction.

[Dale53]

Mihec's lube is fine.

Check to be sure that the handles are not binding where they are attached to the mould. Misalignment there can sometimes be a problem.

FWIW
Dale53

[btroj]

Those pins need to be kept lubricated. I find a little lube makes the sticking go away.

[buyobuyo]

Where/what exactly should I be looking for when checking the handles for binding/misalignment?

[btroj]

Is there a lead buildup in the slots for the handles? Anything keeping each block from ovine freely on the handle?

I would also get some Bullplate or similar lube on those alignment pins. Makes a huge difference with exactly what you are talking aout.

[buyobuyo]

No buildup in the handle slots or on the handles. I use the sprue lube that came with the mold. I also have some bullplate and randy's zip lube.

I just put some more lube on the offending pin and that seems to have smoothed it quite a bit. Seems I just needed more lube than what I was using. I'll make sure to lube more often too.

[btroj]

I find it helpful to add some anytime the mould doesn't want to open easily. Long as it stay out of the cavities it is hard to we too much.

[MtGun44]

Maybe the pin has moved a bit in the block, if it extends out too far it will tend
to bind. This happens with Lyman molds and there you
just tap the pin (ball really) back into the block a hair with a punch and small hammer.

Bill

[Rattlesnake Charlie]

I have had this happen on several different molds. Lubing the alignment pins has always corrected the problem. I use both MiHec's and Bull Shop's with success. One drop per pin.

[MtGun44]

Charlie,

I think a whole drop is pretty extravagant. A very slightly dampened Q-tip rubbed on them
has always been enough for me.

As a side note - I have a place in Forbes park just above La Veta, over the ridge. Have
looked out over the countryside and seen La Veta from the ridgeline many times, climbed
Western Spanish Peak a few summers ago, and been through La Veta a few times. Pretty
country and the rock fins are pretty interesting formations.

Bill

[buyobuyo]

Maybe the pin has moved a bit in the block, if it extends out too far it will tend
to bind. This happens with Lyman molds and there you
just tap the pin (ball really) back into the block a hair with a punch and small hammer.

Bill

The pin having moved was my first thought, but I wasn't able to get it to budge. If I have time tomorrow or wednesday, I'll fire up the pot and give it a whirl with extra lube on the pins.

[a.squibload]

Having same problem with a couple of NOE HP molds, hired a safecracker,
no help. Very frustrating, can't develop a casting rythm, fighting to open
and close the molds takes time, molds cool off, etc. Wiggling the blocks
seems to help but heats up the gloves.
I'm sure it's mechanical, alignment pins. Maybe they stick out too much?

Will try again, extra Bullplate maybe, have been using it very sparingly.
A friend (who is not a caster) suggested graphite, any problems with graphite
on hot molds?

[Iron Mike Golf]

Do the blocks stick if you put them together OFF the handles?

I'd try that and then. if they stick that way, I'd flip one block and see which (the pin or the socket) is causing the problem.

[buyobuyo]

In my case, yes. The blocks stick even when not on the handles.

[Mal Paso]

The alignment pins have moved out and need to be reset. On mine it was the male and a tap with a brass hammer reset it. The body of the pins and the female steel inserts should be below the block surface by the same amount maybe.03". It may be the light tapping on the handles or maybe the mold not opening evenly but they seem to need resetting every 5 - 7,000 boolits.

I've reset them twice now. I did it with the mold warm as brass expands faster than steel. An arbor press would be better but a brass drift and a few taps of a hammer strait down with the mold well supported on a block of wood.

[buyobuyo]

Setting back the pins with the mold warm is a good idea. I tried that with the mold cold and couldn't get it to budge using a brass rod and hammer. I'll give that I try next time I'm casting.

[Mal Paso]

It gets better: I had my mold apart to write that blurb and noticed one of the pins was a little high so I heated that half and reset the pin. When I put them back together neither pin would fit it's hole hole. Miha's tolerance is so tight a Hot Pin would Not Fit in a Cold Hole. Heated both halves together and they fit great.

Edit: That may be how the pins "walk out" is that the fit is so close that if the mold opens at a slight angle, it tugs on the pins a little. Repeat 1500 times......