Ball end mill bits

[Avery Arms]

Will a "ball end" end mill bit make a perfect half sphere when set at the proper depth?

I want to make a super-capacity buckshot mold and would prefer not to make a bit or cherry unless I absolutely have to.


PP

[ANeat]

The ball end mills should cut a good half sphere. I think the trick would be to get the halfs lined up.

Probably if you cut the blocks and did the alignment pins first; and reference off the pins ; you should be able to get really close

[redneckdan]

Best bet is an undersized ball end mill in a CNC machining center. Failing that, a ball end mill of the correct size should suffice.

[halfslow]

The problem is that the ball end mill has a shank the same as the diameter of the ball.

What you need is a cherry. The shank is turned down where it merges with the ball, giving an "almost" perfect sphere.

Wood working ball cutters come this way.
I have never seen a metal cutter made like this, but there may be some out there.

[jhrosier]

Will a "ball end" end mill bit make a perfect half sphere when set at the proper depth?...

Probably "perfect enough" for buckshot.
The quality of the grinding of the ball end mill will be the first limiting factor.
The rigidity of your milling machine will also be a big factor.
It would be best if you could rough out the cavity with a smaller size first, but cut to nearly the correct depth for the finish cutter.
Although they are suposed to be center cutting, the surface speed of the center of a ball end mill is exactly zero. It can only push the metal towards the outer cutting surfaces to be removed. It is hard to explain unless you have experience with these sort of cutters. A very short and ridid cutter will help keep the cutter from shifting location under load.

If you are machining multiple cavities on a typical knee mill. you will want to lock the spindle and use the knee, with a good dial indicator to control the depth.

I recall hearing that someone once made round ball moulds by cutting the cavities a hair undersized and then forcing a ball bearing into the cavity to swage it to the finished size.

If you are actually going to take a stab at this, let me know and I will explain a simple way to align the two halves of your mould.


Jack

[machinisttx]

Depends on how it is used. In plunge cutting, no....especially with smaller diameter tools.

A sphere can be approximated by using circular interpolation in a CNC milling center, and it will be darn close if programmed correctly and the machine is accurate, but it will still not be "perfect". Even a CNC lathe cannot cut a "perfect" sphere.

[Avery Arms]

I only have very basic tools and even less skills, basically a drill press and a grizzly 3 in 1 that I'm slowly teaching myself to use.

Any advice on a bit that would make a half sphere good enough to stack correctly inside a shotgun shell? If they ain't perfect I can put them in a cement mixer with some graphite...


PP

[ETG]

Get a mold from Sharpshooter - less than you will spend on tooling and raw materials - 20 per cast.

[machinisttx]

A drill press(99% of them) most certainly isn't rigid enough for milling work, even plunge cutting. The bearings in them are made for linear loading, not radial. Also, endmills have a very bad habit of pulling out of drill chucks.

I'm pretty sure you can do an adequate job on the 3 in 1(with the ballnose) IF you are careful and take your time.

[ETG]

5/16" Ball endmill $5.88 - shipping ~ $7. 3/4" Aluminum stock 3/4"x2 1/2" x 12" $7.74 - shipping ` $10. Handles - ?????, Hindges - ????. skiesunlimited buckshoot mold $35 + $5. I'm not associated with skiesunlimited but do use his mold.

[Buckshot]

I recall hearing that someone once made round ball moulds by cutting the cavities a hair undersized and then forcing a ball bearing into the cavity to swage it to the finished size. Jack

............I seem to recall that it was Lee did this and they called it hobbing. I thought hobbing had to do with gears, but possibly the term also has to do with 'forming'? Anyway as I remember they'd partially form the cavity in each block half, put a carbide ball in the partial cavities. Then it'd go into a 40 ton press to have the 2 blocks pressed together.

..................Buckshot

[Avery Arms]

Interesting technique with the ball bearings, I have a 10T press and can access a 20T so maybe I can make that work at least with smaller sizes.

I realize that skiesunlimited sells cheap do-it style buckshot molds on ebay but I want to make my own utilizing a sprue plate so I don't have to go through and twist/cut off the pellets. I already have gobs of handles and it won't have hinges so I will only need to buy stock and bits.


PP

[calaloo]

I have made jig molds by drilling undersized holes in two blocks of copper bus bar then pressing in a large industrial vice with a ball bearing in the detents. Leave the ball in the cavity when you drill for the alignment pins. After the pins are in place the hook is pressed into the mold in the same manner. I silver soldered the blocks to a pair of cheap slip joint pliers. Ought to work just fine for a round ball mold. The local Ace Hardware has a nice selection of bearing balls.

[Marvin S]

If you look at the special projects tab I made a shot mold by plunging a 3/16 ball nose mill into Alum. It turned out well with the shot being plenty round. This was done on a Bridgeport.

[trevj]

The technique of sizing using bearings is sometimes called ballizing, or ballsizing, depending who's literature you run across.

There are a couple outfits selling carbide balls, just for such uses. Might be worth a look around the web for, if you are really interested. That gives a few more possible starts for searching for info, anyways.

Dunno why Lee would call the process 'hobbing' , unless they are referring to their initial process of cutting out the unsized holes as that.

There are some pretty neat tools starting to become more common out there. One of interest, is called a lollipop tool, and it is used mainly for stuff like chamfering edges on parts on a CNC machine. They look a lot like a cherry, and maybe could be used as such.

Cheers
Trev

[kywoodwrkr]

If you look at the special projects tab I made a shot mold by plunging a 3/16 ball nose mill into Alum. It turned out well with the shot being plenty round. This was done on a Bridgeport.
I have plans for making some shot moulds in the upcoming year using a similar process.
We have some sheets 4'x8' of 1" thick aluminum for 'projects'.
Have the CNC drawing done, just need the time and endmills.
Currently focusing on CNC lathe operations right now.
Have other mill projects lined up, Dillon 550 25 ACP shellplate and case retainers for same.
More projects than time actually!
We have a Bridgeport and two Haas CNC mills available to learn on.

[Russel Nash]

I have the same exact idea to make a buckshot mould with a sprue plate so you don't have to come back later with wire cutters to snip the "balls" off a central sprue.

Just flip open the sprue plate/cutter and let them buckshots fall into a bucket of water.

I have a plan in mind on how to make the mould halves to get the two hemispheres to line up.

I was planning on it being a gang mould of sorts where ya could drop 10 or more "balls" at one time.

I did look at ball end mills at one point. The fractional inch ball end mills do come kinda close to the buckshot sizes I was looking at.

I bought enough aluminum that I thought I would try making a handful of the moulds and then selling them here on this forum.

Huh... I guess not anymore...(sigh)

[SHORTY 1919 TODD]

I like the suggestions and I have had similar thoughts... I Contacted Lee to see if they would make a batch of Buckshot moulds based off their six cavity blocks with as many as you could fit and they said that their round ball machine can only do single and double molds. It seems as though the natives are restless for a production buckshot mold. I know that I am tired of casting two .311 balls at a time and loading 12 in each shell........

[3006guns]

Just for future reference..........Lee most assuredly DID call the process "hobbing". I remember it quite well from their early mold advertisements. The brief description implied that the two aluminum mold halves were literally squeezed on a hardened form. No mention of pre-drilling the cavity that I can remember, but it does sound logical to remove the bulk of the material first.