Basic questions about ball end mills

Hi all.

I have some basic questions about ball mills. My VMC4020 is somewhat limited by current standards so I'm just exploring catalogs and these are awfully popular. I've never used them always, I've assumed they were pretty limited to cutting round bottom slots. Now obviously this isn't true, they're the backbone of modern 3D surfacing ops.

What I'm wondering is what are other areas where they excel? Given modern CAM, until you get into tight spots is there an advantage to a ball vs a regular EM with a healthy corner radius?

Do they have any not so obvious tricks up their sleeve?

Thanks, Cole

It's all about ingenuity. There isn't any trade secret that they excel in aside from the obvious.
But if you have an application where a ballnose works better, go for it.

Mtndew said:

It's all about ingenuity. There isn't any trade secret that they excel in aside from the obvious.
But if you have an application where a ballnose works better, go for it.

Click to expand...

Damn. Ok.

Thank you!

Probably the real secret is that just like discount mail order brides; after a while, the novelty wears off and you figure out you don’t really like them very much and only use them when you are desperate and nothing else is available in the right size. Plus, unless they were new when you got them, they’re probably all worn out and have been used for God knows what.

All kidding aside, ball endmill a suffer from the problem of having Zero Surface Feet Per Minute (SFM) at the tip. Therefore, whenever you are cutting towards the middle of the cutter, your surface finish suffers because of smearing and cutter deflection. The larger the radius, the coarser the step over you can take, but only if you have room. For those reasons, I find myself using alternatives to ball ems, such as barrel profiles (steep surface), lens profiles (shallow surfaces) and most frequently, bullnose endmill.

Cole2534 said:

.....
What I'm wondering is what are other areas where they excel? Given modern CAM, until you get into tight spots is there an advantage to a ball vs a regular EM with a healthy corner radius?

Click to expand...

Due to the lack of speed mentioned above at the tip they do not excel at anything other than manual machining where you have no choice.
Radiused end mills can do a lot of the 3-D surfacing work and will run better/ last longer.
Ball nose, despite the poor cutting geometry are easier to program so used very often for die or surfacing as it is kind of a no brainier.
This is good as you provide more jobs for end mill makers or resharp houses.

Drills have the same zero speed center but you can not put an advanced drill tip on a ball nose endmill, won't fit and would leave a tit or flat.
Best if these never see the center used when scalloping or profiling.

They do work better for poking out or sort of drilling out bad or broken insert screws than a regular endmill but you will kill it during this process.
Often on a manual machine you have no choice. No matter the grind or mods, everything is wrong at that tip.
Bob

Ball end mills? Pshaw... Old tech.

We're onto barrel/circle segment cutters these days!

gkoenig said:

Ball end mills? Pshaw... Old tech.

We're onto barrel/circle segment cutters these days!

Click to expand...

I need to look into the barrel cutters. I don't do a lot of 5ax work, but they could definitely be handy.

Mtndew said:

I need to look into the barrel cutters. I don't do a lot of 5ax work, but they could definitely be handy.

Click to expand...

The theory is quite sound, but support in various CAM software is taking a while to come around. I think everyone has it for 5 axis now, but I think it would be neat to see it in 3/+1/+2 axis applications where we can tilt a tricky surface over and get many of the benefits.

You are also limited to Frasia or Emuge for end mills at this point, which gets kinda spendy.

Onsrud also does a few different styles of conical endmills. However, last time I looked it was like 2 week lead time.