Point Form Cutters

[wywindsor]

LMK a price when you have it figured out.

Thanks for the info.

[Willbird]

Another option, I made this cutter (one on the left) up out of 3/8" Hi-Roc solid carbide 2 flute drills (right one) using the wire EDM to cut the profile and put the primary clearance in at the same time.

They are made a few thousands of an inch smaller than the actual diameter required, allowing for final lapping and polishing after heat treating.

RRR

Attachment 311837

Yep that is another nice way of going about it . We had two wire EDM and a several sinker EDM at that past job too.

Bill

[IllinoisCoyoteHunter]

My 2 options for boring bars. The Sandvik tool on the left will go in a .205 bore and is going to be my first choice. The tool on the right is an Internal Tool bar that I’ve modified the tip a bit. It will go in a .220 bore, which cuts it kinda close. I can always grind some relief on it if needed to get it in a smaller bore.

[Willbird]

I just saw a video where a cna machine was profiling something like the bearing journal on a wheel hub. The insert used had a very large radius, say 1/2" radius and then a perhaps .045 final nose radius. The cnc rocked that whole 1/2" radius along the bearing journal, then profiled the corner with the nose radius. Pretty interesting way of spreading the wear out on an insert.

That had me picturing a solid carbide boring bar purpose made to single point bore something like a point form cavity....

It would start to look a lot like your right hand boring bar if it was rotated 180 degrees clockwise.

Good excuse to do a little cad doodling, nanocad is a free cad program that behaves almost exactly like autocad. I drew a 375 bullet here with a .125 ejection pin and a simple radius for ogive. left .03" clearance on right side...coolant flush from the back end would be nice to make this work. I just took iphone pictures of screen, would look nicer exported to pdf for sure. Hope it expresses the idea tho. The bar might work with just a 90 degree flute cut into it to leave it stiff ? I used a .015 nose radius in this drawing.

[IllinoisCoyoteHunter]

I like the way you think. A bar like this could easily be created. But, some issues one might run into is with the shank being such a small diameter, the bearing surface diameter (main bullet diameter) would probably have quite a bit of taper. Not a huge issue because you can program the taper out on a cnc machine. Another issue would be surface finish. It would more than likely cut it, but the chatter would most likely be tremendous. That’s a skinny bar hanging waaaaay out there lol. Single pointing down to an ejection hole, in rifle bullets, is basically impossible unless you want to tack on days of polishing lol.

For example, say we’re talking about a simple 55 grain .224 6S bullet. Let’s just say we are only interested in making 55 grainers and nothing much heavier. That bullet, after Core seat, measures about .700 long. So this means that the .224” section of your PF die needs to be at least .700 long to support the entire bullet before point forming. So you’ve got the .700 plus the length of the ogive, which is about .370”. So overall depth to the ejection hole is just under 1.100”. That’s a tall order for a boring bar lol.

Thanks for providing the drawing. Lots of thinking outside the box. This is a fun topic, but unfortunately there’s no such thing as a free lunch. If it was easy everybody would do it, right lol.

[Cap'n Morgan]

Actually, I'm sure Willbird's concept would work. 1.1" depth should not be a problem - a company like Horn Tooling make mini boring bars at 6 x dia. as a standard.

If the tool was designed for finishing a pre-drilled hole, it could be made for maximum stiffness. A small nose radius (.001") would minimize the risk of chatter.
I'm almost tempted to give it a try, even though I don't do any swaging (except .284 bullets to .277)

[IllinoisCoyoteHunter]

You would definitely have to use a form tool to cut 99% of the profile and then come back with the single point tool and run a couple finish passes. 6xD on a sub .250 bore is nuts to me. My Sandvik bar will go in a .204 bore but only .825 deep. That’s a little over 4xD. Sandvik has some pretty awesome engineers.

Cap N Morgan I think you should definitely roll up your sleeves and get after it!! Lol.

[kenton]

There are a lot of company that make micro boring bars. These are a few I have used, there are many more.

https://www.maritool.com/Cutting-Too..._82/index.html

https://www.maritool.com/Cutting-Too..._83/index.html

https://www.micro100.com/products/tu...e-boring-tools

https://www.mcmaster.com/products/la...g-lathe-tools/


I know Harvey Tool makes custom tooling as well. If you tell them what you want to do they might be able to tell you how they could best make tooling for your job.

https://www.harveytool.com/

[IllinoisCoyoteHunter]

Yeah there’s definitely no shortage of options for micro boring bars. But you’ve got to be aware that just because they can stick out that far doesn’t mean that they will actually cut well sticking out that far. There’s tons of variables, with the material being the biggest variable.

[kenton]

If your material is a variable you should be buying from better suppliers with more consistent material.

Keep your SFM down, I usually start around 100 in austinetic stainless steel and alloy steel as to keep the harmonics down. Chip loads will probably be .0004-.001 IPR on your finish pass depending on your bar dia and stick out. I also usually set the bar a small amount above center with long boring bar extension to keep the bar from deflecting below center line and taking a bigger cut as it deflects down. There is a potential for cosine error if you set it too far above center line but it is usually negligible as long as you don't set it more than a few thousand's above.

Generally if you contact the tooling manufacturer with your project parameters they will give you recommended speeds, feed, cutting depths, and likely tool heights. They usually know their tools better than I ever will and you can't sell tools that don't preform. At least not more than once.

Edit: I will note that everything I do is a one off so I tend to run stuff on the conservative side, I'm sure they could be run faster but I'd have more time in breaking one tool than I would save in 20 parts. Also roughing out as much material as is reasonable with drills and larger tools is always a time saver but I like to run a single tool finish pass rather than try to blend 2 tools.

[IllinoisCoyoteHunter]

What I meant by material being the biggest variable is that the boring bars we are talking about will cut differently in different materials. I’m not taking about variation in the same type of material. For example your length of effective cut Will be much longer in delrin vs inconel with the same micro boring bar.

[IllinoisCoyoteHunter]

Running 2 tools (form tool and boring bar) and blending the beginning of the ogive to the main diameter is extremely simple, even if you had to G code it. Good CAM software with stock recognition will allow you to tailor your toolpath for a perfect blend with no step.

[Willbird]

Yea they only way to know how it would act is to try it. The tool and die shop I worked at did a lot of medical implant parts made from TI and other exotic stuff. Some of it on Swiss turn machines. The catch there was than a long skinny part had to be turned in one pass, no rough and finish passes allowed because of how the Swiss Turn works

[kenton]

I agree that writing G code to theoretically give you a perfect blend is simple. I also agree that there are a lot of variables in a project like that. Using one tool to finish the whole profile instead of 2 removes a lot of those variables since you have a CNC and don't need a form tool to achieve the correct profile.

But that i just my perspective. I have been wrong before and will be again

I look foward to more updates.

[Cap'n Morgan]

Cap N Morgan I think you should definitely roll up your sleeves and get after it!! Lol.

Over the years I've modified an awful lot of Sandvik-Coromant inserts for special operations (we were their Danish to-go shop for one-off jobs)
I've also designed and made hundreds of special tool holders to suit various jobs were a standard tool holder was less than ideal - or didn't exist.

If I were to make to make a swaging die today, I would probably mill or EDM it, but if lathe turning was the only option, this is what I would try:

The boring bar would be grinded from a 5mm (.200) micro grain carbide and the cutting length is 30mm (1.18")
Notice that the "height" of the boring bar is about .185" - adding considerable to the stiffness in the vertical direction.

The injector hole is .06"

[IllinoisCoyoteHunter]

Love the elliptical shank!! That is one hell of a tool you’ve drawn up there! Willbird and Cap N Morgan you guys are definitely thinking outside the box. There’s so much knowledge and experience on this forum. It’s amazing.

[Willbird]

Even cooler would be to do that tool with a CBN wafer on it that would allow hard turning after heat treat.

[IllinoisCoyoteHunter]

Yeah I looked and Internal Tool has some cbn tipped micro bars. I’ve never micro bored 50+ RC material before so I can’t give any input on it.

[IllinoisCoyoteHunter]

And if we don’t have enough to think about, what about a modular PF die? It would have the main body, finished to bullet diameter, and the ogive machined in a separate piece that bolts to the main body. A fixture (alignment cyclinder) would have to be used to align and bolt them together. Or just a gage pin with the ogive turned on it and used as and alignment pin for bolting together. So if you wanted a 4S or 10s ogive, you could simply swap the “ogive parts”. And this main body could probably realistically be used in the core seat process too.

[Willbird]

Yeah I looked and Internal Tool has some cbn tipped micro bars. I’ve never micro bored 50+ RC material before so I can’t give any input on it.

They did some external turning of die cases that way at a prior employer. Seemed to work well, not as "nice" as grinding but a lot faster.

On the two piece design...I have thought about making reloading dies that way. Making the body taper as a through hole would be a lot easier, then the neck and shoulder could be a separate part. I keep thinking of it as a way to make a full length bushing die by using a normal chambering reamer maybe.