ABEC bearing ratings, and what the heck they mean...

[J!m]

ABEC ratings are important on low tolerance devices, such as a tonearm. Designed for machining spindles, the ABEC 7 is really tight. But, there is also the exotic ABEC 9 available for some sizes.

• ABEC 1: 0.0075 mm (0.000295″)
• ABEC 3: 0.0050 mm (0.000197″)
• ABEC 5: 0.0035 mm (0.000138″)
• ABEC 7: 0.0025 mm (0.000098″)
• ABEC 9: 0.0012 mm (0.000047″)

As you can see, even ABEC 1 bearings are pretty good, with tolerance of just under 3 tenths (1/10th of a hair). ABEC 7 is down at 98 millionths, and 9 is at 47 millionths.

Needless to say, ABEC 9 bearings can easily cost 100 times what an ABEC 1 bearing costs. Components are hand-matched based on exact sizing, and that costs money...

 

[8991XJ]

Blueprinted, makes em good.

I got abecs in my roller blades.

 

[J!m]

Up to ABEC 5 can be reasonably priced, particularly in smaller sizes sold in large volume- such as roller blades and skateboard wheel bearings. You sort the billion loose balls by size and the millions of races by size via machine and throw the good matches together.

 

[WOPL Sniffer]

 

[laatsch55]

Jim, what tolerance is really needed? How do you know?

 

[J!m]

Tighter is better. You don’t want bearing “rattle” in an arm. They run dry so no oil to damp…

 

[laatsch55]

Hookay...

 

[Vynuladikt]

The problem is maintaining ZERO free play, by using a slight preload, but not having that cause drag.

 

[J!m]

Yep. Making the arm out of cast iron takes care of that. But, that causes other problems…

 

[laatsch55]

So what amount of bearing play is acceptable?

 

[J!m]

None!

That’s why knife edge bearings are popular. So are ruby (technically, bushings) bearings are also popular. But with the latter, you get a bit of wear due to direct friction.

Ruby is used a lot in watches (sapphire in earlier pocket watches) but the big difference is they are lubricated in watches, and run dry in arms. Also, in a watch, it is a pivot with a shaft going through a hole in the ruby, and a depression that holds less than a drop of oil (the oil well). I do a bit of watch repair and despite this background abandoned jeweled bearings early on.

But, for the vertical bearing, a single point makes a lot of sense. Implementation of it is not as easy with the wires passing through and the desire to have VTA adjustable. I may revisit it because now I have two larger bearings, spread as far apart as I can, with wires passing right down the middle.

I spent most of yesterday just working this part of the arm out. Now I just need to finalize the drawings (dimensions, tolerance, surface finish and material selection) and it’ll be ready for quotations.

This is going to be expensive…

 

[Gibsonian]

Was thinking of taking some of my best vintage arms apart and replacing the bearings with 5's or 7's. Where does one find these high grade balls? And which material is best for tonearms?

 

[Vynuladikt]

I was going to mention jeweled pivots in my earlier post, but like you say they have their issues too.

 

[J!m]

This is a good place to enter the rabbit, er, black hole.

Ball Bearing Supplier - Boca Bearings :: Ceramic Bearing Specialists

 

[borchee]

...enter the rabbit, er, black hole.

Here, a photo of one:

 

[J!m]

sapphire in this pocket watch

ruby in this wristwatch

 

[borchee]

Nice! Not so long ago I saw a couple of videos about oiling the watches - couldn't imagine how important and difficult it is to put the tiny drop of oil just on the right spot. Fascinating stuff.

As you've been talking tonearm-bearings-jewels...and rabbit/black holes, I posted a photo of a tonearm thrust bearing - the one and only physical bearing with this tonearm.

 

[J!m]

MA-505 uses pivots; bronze I think. I only removed this one so as not to disturb the dynamic balance string and spring.

I need to straighten the weight shaft.

 

[J!m]

Oiling watches is an art for sure.

A drop is WAY too much. We use oilers, which are like microscopic coke spoons, of various shape and size depending on how much is needed.

The watch uses two types of oil and two types of grease.

Oil for fast speed, low load
Oil for low speed high load
Grease to reduce wear (winding stems and other parts)
Friction grease for the mainspring barrel wall and sometimes in the canon pinion. This has a specific properties so the mainspring grips the wall of the barrel but will slip to prevent over-winding in automatic wind watches.

There is also a stupid expensive treatment for parts so oil does not migrate from exactly where it is needed.

It is about $150 to purchase tiny amounts of oil for a watch…

 

[borchee]

Just curious - what is the size of the bearings with your arm?