Straightening a warped Hensley and Gibbs 6 cavity

[tazman]

I just got in a 6 cavity Hensley and Gibbs number 50(148 wadcutter) and it has been abused by the previous owner. There are a number of dings and nicks in the mold but the cavities are at least usable. The handles are good.
My problem is the mold blocks are warped. Both ends close but the middle lets light through.
I checked the surfaces to make sure no lead or other lumps were holding the mold open.
I cleaned it with dawn dish soap and a toothbrush to make sure all surfaces were clean and proceeded to cast some 200 boolits with it.
There were no fins on the nose or sides of any of the boolits except for one cavity that had a nick on the base. This little fin pops off when I size the boolits so that doesn't matter. The weight is dead on 148 grains with my alloy(range scrap).
Boolits from the end cavities where the mold closes properly mike out at .358 which is perfect for me. The boolits from the center cavities mike at .360-361.
I can size them and all will probably be well, but I would like to get the center to close so all cavities would drop the same size boolits.

Is there a way to get the mold back to true so the center closes as well as the ends?
I am hoping for a simple solution.
Thanks in advance for your input.
tazman

[nhrifle]

My first try would be to disassemble the blocks, get them screaming hot, clamp them tightly in a vise (preferably a milling vise) and let them cool. Maybe repeat this a couple of times.

[fastfire]

The place where the ding is may have a raised area holding the mold open?
Maybe check with a straight edge while disassembled.

[zuke]

fine grit sandpaper on a smooth,rigid surface.

[tazman]

My first try would be to disassemble the blocks, get them screaming hot, clamp them tightly in a vise (preferably a milling vise) and let them cool. Maybe repeat this a couple of times.

After checking to make sure nothing was holding the blocks apart(nothing was) I tried the vise thing. First off, I don't have the means to heat the mold hot enough to matter. When I put the mold in the vise, I couldn't get enough pressure to flex the mold sides. I have an 8 inch bench vise and I broke it tonight trying to flex the halves of the mold. No joy. The sides of this mold are each 1 inch thick and far too strong for that.

I don't want to grind the surface of the mold flat as that would make the end cavities undersize and ruin the mold for my use.

I am still open for suggestions.

[HeavyMetal]

Brute force is not going to help here as you've found out, LOL!

Never seen a warped mold and because of the issue you had with your vise one can only wonder how they were warped in the first place???

So if this was my mold I'd try the following:

Strip the mold of everything, screws handles sprue plate everything.

Not sure how the alignment pins work on an H&G ben years since I handled one but I think it's a press in set up if it is soak them with a little kroil and press them back into the mold block below the surface level of the cavity face. You may need to make a special tool to prevent damage to the surronding areas but getting the pins out of the way is a must.

Now lay your hands on some extremely fine wet and dry sand paper I'm talking 1500 to 2000 grit! You'll find this at any good auto paint and body supply shop, it's used to wet sand final finishs before buffing out custom paint jobs for that final gloss look.

Now find some marble table top material, a 12x12 piece is the smallest you need here, ands run your hands over the surface area to make sure you have to pock marks or pips sticking up, ya want glass smooth!

Clean the marble piece squeekey clean! Use two sided carpet tape to secure the ends of the sand paper to the marble and then wet it with a lite oil 3 in 1 is as good as any and I've used it a bunch.

Now take each mold block and make exactly Two figure eight patterns on the sand paper with each of them, stop clean them with brake cleaner and see what has change on the face of each mold.

You will not have removed enough metal to change any casting diameters but you will see distinct high spots on the blocks.

This is when you will have to decide on a repair or not! You may find a complete flat surface on both mold halfs! If you do then something you took off the mold was holding it open.

If this is the case put the mold back together one part at a time and hold it up to the light, I'd start by putting the pins back into position, if good add the handles, if good add the sprue plate,

Wish you luck go slow and you may fix it.

Option two is surface grind and lap small cavites back into shape.

Option Three is live with it

[DeanWinchester]

Surface grinding them doesn't need to be done by any jack leg machinist. A good magnetic chuck can and will pull a piece of metal down. When you release the field, it will spring back. It needs to be done on magnetic parallels or indicated in as flat as possible in a precision vice and cleaned up. Once they're clean, I personally would skim the other side parallel but there's no real reason to do it unless you want to put the two halves together in a precision vice and grind the top of the mold smooth again. If I went to that much trouble I'd do the spru plate too.
You'll need to consider vent lines as well. If it takes several thousandths to clean it up, you could wipe out vent lines and make it very stubborn to fill out.
If it requires very much at all, it may not be worth fixing. You may just have to cast with the cavities (if any) that cast a usable boolit and just live with it.

[MtGun44]

I believe I would put a .002 steel shim on each end and push the middle together with
a hydraulic press. If that isn't enough, go to .003 shims on the ends. Eventually you
will find the right spacer and spring it back. It must be supported dead flat on the
back.

Bill