[technomage]

From what I have seen there is NO SOURCE for bargain 1/2" ID Angular Contact Bearings ! I have asked if anyone knew of any, all links that were provided ended up with Metric sized bearings. I hope you have better luck I resigned myself to banded thrust bearing/radial bearing combo:devious:
hopefully someone will make me eat these words ?

[NC Cams]

Paragraph 3 in the link posted in post #16 above says MOST of the difference but not the "why".

Simply put:

A/C's absorb axial and radial loads into two vectors via pure ROLLING friction.

Tapers, take the radial loads in line contact ROLLING friction but they absorbe SOME of the axial thrust via RUBBING friction of the roller ends against the flanges.

This is why there is typically less friction and heat generated in A/C's than tapers, especially when/if you run them in a highly preloaded state.

If you want stiff bearings, you need high preloads - this takes any internal deflection out or the bearing as loading is applied. You can preload tapers BUT you''ll pay dearly with high friction.

Want poof? Check the rotating torque of a 500 lb preloeaded ball screw support bearings versus that of a comparably sized and preloaded rear axle pinion bearing - you can turn the AC with your hand but you'll need a pry bar to turn the pinioin.

Otherwise, the article in post 16 gives an adequate layman's explanation as to why tapers are used in place of A/C's and vice versa.

From an accuracy and speed standpoint, A/C's have pretty much universally usurped tapers in the machine tool industry. Why? They've learned that you can cut faster/better with a light fast spindle cuts as opposed to deep heavy ones - the more cutting edges you can put across/thru the material the faster you can remove it, pretty much regardless of all else.

When you start to run bearings at high speeds, simple internal friction of tapers ultimately detracts from the bearing's ability to run/survive at speed.

Why no small sizes? You need a angled raceway to run the ball againts and it is phyically possible to make an A/C only so small. Besides, when you need to absorb that much thrust at so small a size, needle bearings package even easier and cheaper or there isn't enought deman to warrant the creation of something that small/special.

[Geof]

....From an accuracy and speed standpoint, A/C's have pretty much universally usurped tapers in the machine tool industry. Why? They've learned that you can cut faster/better with a light fast spindle cuts as opposed to deep heavy ones - the more cutting edges you can put across/thru the material the faster you can remove it, pretty much regardless of all else....

It was really the development of carbides (and ceramics) that can be run very fast taking small cuts that removed the need for spindles that could handle the brute force of driving a large HSS tool at a slow speed with a very deep cut at a heavy feed.

[RICHARD ZASTROW]

technomage, I suppose you already know or have now discovered antifriction bearings are almost all metric with a few exceptions. I looked thru every catalog I have and couldn't find any 1/2" AC bearings either. I did find some 1/8", 3/16" & 1/4" in a Barden catalog (C-20) in the instrument bearing (angular contact) section p.26/27 if that helps any.

[JMcDonald]

For the spindle for my mill I am using a .56" ID (15mm) thrust bearing, ushing against a 1"OD x .5"ID shaft. The shaft has a through-bolt going through it to hold the chuck in place. The top of the through-bolt is centered in a 1/2"ID bearing. The shaft that the through-bolt goes through is pressed into a 1"ID bearing.

Here is a diagram I made when I first came up with the idea. That is not the final design, but it is pretty close (some dimensions and materials changed). I did is so I wouldnt forget, heh.



*edit*

Arg, saving the images in paint really screws up their alignment for some reason!

[NC Cams]

This thread does as much to demonstrate the creativity that exists in the hobby as much as any.

The thread also shows that tapers will clearly "WORK" as axial thrust bearings. And for the cost, they are perhaps the most affordable and most wide range as far as size and capacity.

They are NOT necessarily the optimum for low friction under axial thrust, however, and this is due to the way thrust is absorbed. Some of the thrust is clearly absorbed via sliding/rubbing of the ends of the rollers against the flanges. Yes, some thrust is taken via rolling of the rollers but some is taken via thrust/rubbing.

THis is where A/C balls prove superior - at least in regard to friction. Rolling friction is ALWAYS lower than sliding friction. Hence for a given package size, a ball A/C will/should have less friction, especially under high or give preload, than a taper. The tape would have more capacity and be stiffer buy you'd pay for it in size, friction and probably save in cost.

As is the case, it pretty much works down to a packaging versus cost issue. Package what you can find or fit, buy what you can afford, live with what compromises you choose.

[neilw20]

Take a look at
http://www.airbearingtechnology.com

[jason003]

I think there are a lot of factors to consider when choosing a bearing. space, load, speed, rigidity, easy mounting, bearing life, arrangement...

Generally speaking, ball bearings rotate faster, roller bearings can take more loads than ball bearings.

Here's one that describes bearing selection, you can refer to it for a rough outline.
https://www.coolenbearings.com/tech/...rocedure-guide