lathe your own molds

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geotndtwine

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Hi, I have seen videos of guys turnings dies on a lathe and making their own molds. I know the time it takes is a lot, but hey casting can eat up a lot of time too. Just wondering if anyone out there on CGN has ever tried. Would love to hear how the experience was, good, bad, or still thinking about doing it. Pictures would be great too.

Thanks.
Kevin
 
I have opened up the lube grooves on a 459 diameter mold to 465 so that it would throw larger diameter bullets. the big thing is to make sure the set up is square and absolutely centered. I tried a damaged mold before attempting the mold I wanted to open up. It takes lots of set up time and lots of patience with a finger micrometer to check out internal run out. I found the mold blocks were very square to their axis but my chuck jaws had a slight taper. Just enough to throw things awry inside on the closest grove to the bullet nose. I had to start all over again and wrap the molds with thicker brass shims where they grabbed each side. It worked though but it took me all day and I had a headache by the time I was finished. I also had to grind up a special internal tool that was identical to the groove profile.

When molds are made in the machine shops, they are made with rotary bits called "cherries." From the videos I have seen, each side of the mold block is held in place by jaws/jigs on a mill table and adjusted closer together on the cherry until they are clamped tightly together. They are being bathed in a constant flow of cutting fluid as well. Very heavy, solid machines that have zero play or runout.
 
w ww.accuratemolds.com.
These molds all have CNC machined cavities, no cherries used. Just got one, beautiful piece of machining. By using CNC, every mold can be made to exact order, no need for thousands of cherries.
As mentioned, the setup to bore a cavity from solid, or alter an original mold would be the hardest part. The cavity has to be exactly centered in the blocks, and the final machining has to be done accurately with a tiny boring tool, working blind with dimensions controlled with dials or a dial indicator.
 
Years ago when I tinkered with air guns I made a pellet mold for a .45 cal gun that I had built. The gun is long gone, due to the fact that I could not get enough power out of it, but I still have the mold. As you see in the photos there are no lube groves, none were needed for this application, but it could be easily done.

Strange that this subject should come up now as I was just thinking yesterday about making a mold for my recently acquired .577 Snider.

 
I modified an old Lee mold to make a bullet for my Snider (0.588" groove diameter). I drilled out an old Lee Mold (I used a 9mm double mold) with a 37/64" drill (0.578"). I then tapped the mold a 5/8" (0.625") NC bottoming tap. This created sharply pointed grooves to a 0.625" depth in the mold, which translate into bullets with 0.578" grooves and a 0.625" O/D. I sized them to 0.590", which was not difficult.

The bullet had a "spiral" lube groove which held enough lube for the low pressures I employed.
 
Andy said:
I modified an old Lee mold to make a bullet for my Snider (0.588" groove diameter). I drilled out an old Lee Mold (I used a 9mm double mold) with a 37/64" drill (0.578"). I then tapped the mold a 5/8" (0.625") NC bottoming tap. This created sharply pointed grooves to a 0.625" depth in the mold, which translate into bullets with 0.578" grooves and a 0.625" O/D. I sized them to 0.590", which was not difficult.

The bullet had a "spiral" lube groove which held enough lube for the low pressures I employed.
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Very creative, Andy! The small grooves would be ideal for tumble lubing with Alox. Do you have a picture of this bullet?
 
Gun5tuff said:
Very creative, Andy! The small grooves would be ideal for tumble lubing with Alox. Do you have a picture of this bullet?
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I don't have a picture of the bullet, only the mold. I used an old Lee mold, a drill and a tap.

Mold_Side_View_zpsdq7257ap.jpg
 
Roalco said:
Yeah, me too... Just shows they have no idea...
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Just shows that they are interested, and have a few things to learn. That is all.

If they stick it out, they may well be the guy that teaches you something interesting and useful. :)

Yeah, it grates a bit too, for me, when the person does not know that the processes are called turning, facing, boring, treppaning, drilling, etc. But if we learned, they can too. First they gotta have a reason to bother.

Cheers
Trev
 
I turned this cherry up on my lathe yesterday. I cut it to .333" and then finished it by hand with emery cloth and finally fine sand paper to a finished size of .331". I then cut it in half and heat treated it to make it hard.




I used a damaged lee mold as the donor mold and it seemed to cut very well.


Bullets dropped at .331 and I'm going to size them to .330"

I fired 5 as cast last night and they stabilized which is more then I can say for the previous attempts with lighter slugs.

They aren't super smooth but they are very concentric. I plan to lap the mold to smooth it out which will give me some extra size on the bullets. I can always size them down as needed.





Not bad for a first try.
 
Tinman204 said:
I turned this cherry up on my lathe yesterday. I cut it to .333" and then finished it by hand with emery cloth and finally fine sand paper to a finished size of .331". I then cut it in half and heat treated it to make it hard.




I used a damaged lee mold as the donor mold and it seemed to cut very well.


Bullets dropped at .331 and I'm going to size them to .330"

I fired 5 as cast last night and they stabilized which is more then I can say for the previous attempts with lighter slugs.

They aren't super smooth but they are very concentric. I plan to lap the mold to smooth it out which will give me some extra size on the bullets. I can always size them down as needed.





Not bad for a first try.
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Nice! Can you post a pic of the completed cherry? I'd like to see how it's cut (in half).
 
LeroyvdH said:
Looks pretty good to me.. I ain't no machinist don't know where to start.. This is a very interesting thread
Leroy
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Me either I'm a tinsmith lol.



There's a picture of the cutter. I cut it from drill rod and then heat treated it. It stayed sharp so I'm guessing I half assed did it right.
 
That is great Tinman. That was what I was thinking about doing using an old lee mold. I was wondering how you center the cherry on the old mold. I have had many ideas but if you have a great Idea I would love to hear it. Thanks.
 
Papaclaude said:
Could you make moulds with a milling machine?
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Yeah. CNC is easiest, as you drop the custom cutter into the hole, do a a lap around, then center the cutter up and withdraw it from the cavity.

The next choice is to use a rotary table and rotate the mold around the axis of the table, to create the cavity. Both methods rely on being able to source or produce a cutter that has the correct profile, but has a diameter smaller than the core diameter of the cavity, so it can be inserted and withdrawn without touching the sides.You WILL have to be on your game as far as centering up the rotary table under the head, as well as having the head trammed to near perfection.

With a self centering vise (both jaws move away and toward a fixed center point as they are adjusted) you can close the mold blanks up on a full size cherry or cutter to produce a mold too. It will take no small amount of trial and error to sort out where the exact center of the vise is, as the screws on the ones I have seen were pretty much non-precision. Flood coolant to wash the chips away is going to be almost a requirement too. And patience. Open, close, open, close, rinsing the chips the whole time.

There are ways and means of generating radii using a boring tool and a boring head, but they are pretty convoluted for the end result desired. Like as not, not practical.

Cheers
Trev
 
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