Need help with Mihec 452-200 HP Mold

[forcedconvection]

Hi everyone,

I was hoping to get the thoughts of some experienced casters. I just recently got into casting. I really liked the idea of the PID control so I added that within days of getting my Lee Pro 4-20 pot. The lead I am currently using is Lyman #2 purchased from Rotometals and I am fluxing with saw dust.

I then purchased a MP 452-200 HP brass mold and MP Mold Handles. Man, this thing is a work of art. I cleaned the mold with hot water and soap while using a tooth brush. I later cleaned it with a mass air flow sensor cleaner (I would suspect this is very similar to acetone. From what I can tell evaporates almost instantly and seems to leave no residue.) I reassembled the mold with the 5 sided HP pins. I noticed that the pins were very hard to slide in the mold even when lubed. They seemed very much like a friction fit. To make matters worse, it seems that the diameter of the pin is ever so slightly larger than the 2 radii of the mold halves. I figured that maybe at casting temperatures, the different thermal expansion rates of the brass mold and steel pins would solves this issue and may prove that the mold was machined that way on purpose.

Being my first time casting "boolits", I proceeded caustiously and warmed my mold on a griddle (closest thing to a small electric burner I could find at my local walmart). It says it goes up to 400F. I got my pot up to temp (I initally started way to low and of course got wrinkled bullets but I am now around 720F). Ambient temp in my garage is approximately 50F, if that really matters. When casting, I found it still very hard to make the pins slide in the mold. I always had to lightly tap the pins with a small 2x4 block I had lying around to get the boolits out past the lube grove so they could drop. Then the bullets would never drop off the 5 sided pins. I literaly had to pull them off with needle nose pliers every batch. I would also have to push the pins back in place with quite a bit of effort from my gloved hands. Obviously, this is a slow process which is probably letting the mold get too cold. Frustrated, I swapped to the round HP pins. These seemed to slide slightly easier in the mold. When casting with these pins in place, the boolits dropped freely once the pins were slid out past the lube groove with light taps from the 2x4. However, some of these boolits were getting a good amount of the mold split line (I think the proper term is called mold flash/flashing). Also, almost all of the bullets were still lightly wrinkled. I also noticed that there seemed to be a "tit" where the sprue was cut. Do I need to preheat the mold more, do I need hotter lead, do I need to speed up dropping the boolits (I know I need to but am not sure how to with the pin problems), or all of the above.

After finishing up a bad round of boolits, I began to look at my mold (it had a fair amount of time to cool off but still way too hot to hold with a gloved hand for more than a few seconds). I saw significant gaps when holding it to the light (I was holding the mold handles closed tightly). Did I warp my mold? I sure hope not or did I just make a real pretty but very expensive paper weight. Please guys, give this newbie a hand. Looking for constructive criticism, suggestions, anything that would help.

Thanks in advance,

Ryan

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[tomme boy]

You either have lead on the face of the mold or the pins are holding it open. Thats what it looks like to me. Also the mold is too cold by the wrinkled boolit. If you have any graphite spray or molly spray, Spray the pins. that will help to make them drop off the pins. Also, the pins are usually too tight. They screw into the main part. Loosen them just a little. You might have to take the pins out of the mold and polish them to make them slide in the blocks.

Send Miha a PM about this first!

[Dale53]

Ryan;
The first thing to do is to unscrew the pin shafts from the pin (the shafts are threaded) just a touch. This will give you the needed play to allow the mould to line up properly (along with one drop of Bullplate Sprue Plate Lube on the shaft administered on the outside of the mould directly onto the shaft). The pins will now move easily and the mould will fully close.

Pick up a can of spray graphite from your local auto parts store (I had to go to two different stores to find it - Home Depot also carries a similar product. Spray the hollow point pin and let it dry. Do NOT get the graphite spray on anything except the hollow point pin nose. Now, when you open the moulds, the bullets will fall off the pin.

You should now be "Good to Go"...

Good casting to you, my friend.

Dale53

[Max Brand]

^^^^^^ What Dale53 said, you have to loosen the threaded support shafts slightly. I have the same mould and ran into the same problem when new about 20,000 boolits ago. After loosening the shafts the mould should close completely and the pins should move freely.

[Oreo]

Those locating pins need to be loose enough to allow them a little bit of wobble. I turn gently with the tips of my fingers till I feel resistance and then back them off about a quarter turn.

In another thread someone mentioned chasing the locating holes in the mold block with a drill bit and I think thats a terrible idea because it risks your mold. I do like the suggestion above about polishing the locating pins though. If you've got a buffing wheel and can polish off .001" from one row of those pins you wouldn't have any more problems. Since you already have spares on hand damaging one isn't a big deal and your mold is safe.

Also, you can't really close the mold with the hp pins sticking out. The hp pins should fall back to the mold face by gravity alone if you tip the mold on its side. Then close the mold.

[forcedconvection]

Hey guys,

Thank you for all of the suggestions thus far. I know for a fact that the locating pins (thanks for the specific term) are threaded into the HP pin very tight on all of my HP pins, both 5 sided and round. When I get home from work this evening, I will most certainly loosen them and see if that works. As far as leading/tinning of the mold faces, I don't believe I saw any, but I will inspect more closely this evening.

As for contacting Mr. Miha first, I considered it, but as busy as I suspect the man to be, I thought the knowledgeable casters on here might be able to respond more quickly. The intent of this thread is in no way meant to speak poorly of Mr. Miha's work. I wholeheartedly apologize if my post seemed to reflect that.

I will also try the graphite spray on the 5 sided pins to see if that gets them to drop.

As for my temperatures, would you all say that 720F with Lyman #2 and a mold preheated to 400F is not enough. I suspect my "temperature problems" right now are from how slowly I am getting the boolits out of the mold, right? I am just afraid of warping or heavily leading/tinning a mold. Maybe I am afraid to get the mold too hot because I have a NOE 402-180 mold and the instructions included with that mold say not to exceed a mold temperature of 600F. I know aluminum has a very high thermal conductivity compared to steel and higher than brass. Some relative thermal conductivity values: Steel - 43, Brass - 109, Aluminum - 205, and copper (as a reference) - 401. Source: http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html Can somebody give me a generally accepted temperature for brass molds? How about aluminum? I guess while I am asking, how about steel (I may end up with one down the road?

Again guys, thank you so much for the help thus far. Keep it coming

Ryan

[Iron Mike Golf]

Also, take the HP pins out and check for daylight between the block faces at the ends and between cavities. If they are snug at the ends and you have daylight in the middle, you might have one or both blocks warped. If you have daylight at the end(s), too, one or both block alignment pins may not seating fully.

As to temps, yours don't sound too high, though I don't know my mold temps when I cast. I do leave them preheating on a hotplate+saw blade turned up to max for 30 min.

[Oreo]

BEWARE the allen wrench size when loosening the locating pins. The wrench supplied by Miha was the wrong size on my 10mm group buy and would strip out the pin heads. Those locating pins come installed very tight and you need the propper allen wrench (5/64" for mine) to break them loose.

[archmaker]

Also if you are starting out, I would recommend do so with the hollow point. I found I have to mess with the mold more because of the hollow point then without, and what you are wanting to get when started is some experience. Get yourself some good cast flat tip boolits then move onto Hollow point.

It is a lot of fun to see a pile of boolits grow in front of your eyes, and the hollow point tended to slow me down a little in getting there ASAP. :)

I have the mold myself and really do enjoy it, also have one that is 230gr HP and that is one of my favorites.