2 Piece Point Form Die… Feasible?

Warning: Long post

Ok so I posted some pics of this already in another thread but I figured I’d post a new thread to get some thoughts on the subject. So I’ve been thinking about trying to make a 2 piece PF die. The die would be composed of 2 parts, the main body and the ogive/threaded piece. So from a manufacturing standpoint, making the main body section would be simply. It’s basically a through hole, honed to the exact diameter you wish. It would also have 3 clearance holes that are c-bored for 8-32 SHCS. The bottom face that mates up to the ogive piece would be ground after heat treat to ensure that the bore and face are perfectly perpendicular. And of course the bore would be honed after heat treat too. Here is a pic of the main body.

Attachment 312184

Next would be the ogive part. It would be cut with a form tool and finished with a boring bar. Polishing the ogive will be much easier with the access you’d have. To get the ogive just right and meet up precisely with the main body diameter, I plan on boring a short section, maybe .03-.05 long just before the ogive starts, to make sure my cutter is cutting at the correct diamter, as it’s very difficult to measure the diameter at the beigining of a radius. Then once satisfied the ogive is correct, the .03 to .05 section will be faced off, leaving maybe .003 for a finish grind after heat treat to ensure perfect perpendicularity. Drill and tap 3 8-32 holes. Here’s a pic of the lower ogive/threaded section.

Attachment 312185

So, then all that has to be done is align the upper and lower half. I’ll take a gage pin that is a snug slip fit in the main body and turn the profile of The ogive on one end. Then screw the bottom section into the press, and insert the alignment pin in the main body and line up the bolt holes and carefully tighten them down while the pin remains in the main body locating the 2 halves.

So a couple of my thoughts/questions:

If a system like this works, using the main body and switching the ogive section would be super simple, and possibly cost effective.

From a manufacturing standpoint, one may think that this process is far more complicated. I can’t answer that. But, I do know that with the complexity and skill of manufacturing a good PF broken down into these operations I feel that guys that don’t do it day in and day out could make good PF dies. As far as high volume manufacturing, I feel this method would allow for much faster and easier production.

Also, could the main body of the PF die realistically be used for the core seat process?? Obviously you’d need a different threaded base piece.

Thanks for taking the time to read this long post. I’m not trying to reinvent the wheel, just trying to address some of the hardships with making these pesky PF dies. Let me know your thoughts. Thanks!

Personally to me the core seat die would be the easiest to make really. Even the person without a sunnen hone (almost all of us) can lap the hole straight enough that the working portion will be perfect.

I think I could make a "snap" or small shoulder to align the two halves of the die myself.

I suppose you will quickly find out if the tensile strength of the 3 bolts is enough.

My first try at a point form worked far better just swaging lead than I ever thought it would, and I did not even polish anything, just used a D reamer in 12L14 to see what happened.
Kinda dusty from sitting around.
I made the D reamer and die on a whim, it is far far from perfect.
https://i.imgur.com/5fcsFkr.jpg

At the time I was borrowing a friends core swage die so I had cores at hand. The lead extruded up the ejection hole super easy. Yep lead not a jacketed bullet for sure :-). For sure I was using 12L14 not something like A2. This bullet is a .458. If I recall right I step turned the ogive of the reamer in .05" dia increments and then blended it with a file, then polished, milled in half, and heat treated with a torch, I used O1.

Yeah the through dies (Core swage and core seat) are pretty easy to make.

Tensile strength on each bolt is about 850#. So as long as there isn’t over 2500# trying to pull the 2 pieces apart it should be ok. I could always add more bolts too lol. I would imagine the only force those bolts should feel is the friction upon bullet ejection. BUT, I’m not sure if the actually point forming pressure would produce some funky equal and opposite upward forces on the main body. That would be a question for someone smarter than me lol.

What you are talking about is roughly in concept how Vickery set up his form dies. It works very well and properly made gives perfect alignment. In practice if there is even the slightest line between the body and point section of the dies you simply run the formed bullet back through the body die and it vanishes.

I would probably make a male/female step on the dies to keep them aligned - more work, I know, but it would do away with the alignment pin and the dies will not shift, no matter what.

Any upward pressure will be between the point die and the punch. Three bolts are more than enough.

My only concern with a step is it moving during heat treat and possibly losing that perfect snug slip fit.

Quote:

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Originally Posted by IllinoisCoyoteHunter

My only concern with a step is it moving during heat treat and possibly losing that perfect snug slip fit.

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One thing I have thought about in regards to stuff like this is making sure to do a stress relief prior to any close tolerance machining. Some "movement" during heat treat IMHO is actually just due to the stress relief inherent to the heat and soak involved.

They had wire edm machines at one past job, the process will really reveal the stress present in a steel part when you see that the portion cut off by wire EDM curls up like a potato chip.

The original Rock Chuck Bullet Swage was a system like that. The body former was a smooth straight hole in a 7/8”x14tpi rod, partial-threaded at the top for a capstan piece that held the point forming section.

The core and jacket was pressed into the assembly with a punch in the ram of the reloading press. When the point was fully formed (determined by taking the capstan off, inspecting, putting it back on, and screwing the assembly further in), the capstan was removed and a longer punch put in the ram to push the formed bullet out the top of the lower section.

The slight ring on the bullet from the two-piece setup could be ironed out with a second push through the cylindrical lower die.

Fred Huntington dropped the Rock Chuck Bullet Swage from his growing list of reloading products because the heat treatment of the parts would sometimes move the cavities out of alignment, giving the diemaker extra work to hone them back into line. This might enlarge the bullet beyond what the customer wanted, making it necessary to start over.

As Huntington put it, “There was no money in them.” He shortened his company name to RCBS and concentrated thereafter on every other reloading appurtenance except bullet swage dies.

Hollywood also had a two-piece swaging set where the cylindrical part was on the ram and the point former on the die station. I think the bullet was ejected from the bottom part by the downstroke of the Senior reloading press.

There may be better steels now that don’t change dimension after heat treating. And, for a one-off for home use, your design is certainly worth a try, although bullets from RCBS and Hollywood two-piece dies eventually lost out in the benchrest matches to those made by the dies offered today. I wouldn’t think, though, that the bottom section would do for core seating. The seating die would need a smaller diameter so the core assembly would slip into the forming dies.

Glad to see you are finding it far far easier when actually trying things than the complex scenario you envisioned before undertaking the tasks. I don't even mind that you denigrated my work.

There was no denigration of your work. I was just stating facts. When I first watched your videos I thought it was very clever. But as a machinist, I see some possible shortcomings to this method. I actually applaud your patience and steady hand doing all that grinding lol.

What I’d like to do is break down each element of the PF die and absolutely perfect it. I want the bore to be dead nuts the entire length(size and no out of round), I want the ogive to have no out of roundness and line up perfectly to the centerline of the main body. The centerlines of both halves need to be perfectly in line with each other. To do all that in basically a blind hole after the die has been hardened can be done but it’s not easy, as we all know.

Hard part is done. Whew!

Attachment 312974

Attachment 312975

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Nice :-).

Bill

Point form die, 1/2 of it. Polished up and ready for grind. I still have to make the mating straight-walled portion and heat treat and hone it.

Attachment 313649

Core swage and core seat dies ready for final hone.

Attachment 313650

Wow ICH, great work. That is amazing to us non-machinist types, at least it is amazing to me. I don't know if it would be helpful to know or not, but in addition to RCBS, another company found the 2 part PF die viable as a manufacturing option also. Not nearly as sophisticated as your idea, but the same general principle.

Here is a diagram of the Hollywood Gun Shop 2 part point form die from an old print ad.

Attachment 326122

Here is a pic of the actual die set in 308 caliber.

Attachment 326123