Rek-O-Kut ball bearings: optimal material to mitigate divot wear?

monkboughtlunch

Super Member
For the main ball bearing in a Rek O Kut, I've found the ceramic balls can cause a premature divot.

What type of ball did Rek O Kut originally include?
  • Stainless steel
  • Chrome plated?
  • Other?
I'm thinking the optimal material would be a material softer than the turntable platter stem's thrust bearing surface. That way, if something eventually wears down, it's the softer ball bearing and not the platter thrust bearing. A ball is easier to replace. A platter thrust bearing would have to be polished down which would make it shorter each time.

Any ideas on what the turntable platter stem is made from? And would a stainless steel ball or chrome plated ball be softer or harder than the platter's thrust bearing surface?

Additionally, it seems that ball bearings are more precisely made the lower the "grade number." Apparently, the grades range from 2000 to 3. So what is the minimum grade number to achieve optimal results?

Would appreciate any recommended brands / ball bearing model numbers to consider in a ROK table.
 
I just bought a container of 25 grade 25’s for my 3 ROK projects. The brand is Wheels.

We’ll see how it works out.
 
I'm wondering if 316 stainless steel (or softer) is best material to prevent divoting wear in a ROK platter stem.

"Chrome Steel" loose ball bearings, which are very common, seem to be significantly harder than stainless steel.

Grade 10 - AISI 52100 Chrome Steel
Ball Diameter: 4.76mm = 3/16 inch
Material: AISI 52100 Chrome Steel
Min Crush Load: 1370kg
Hardness: 60-67 HRC
Hardness Depth: Through Hardened
Corrosion Resistance: Keep Oiled

Material: 316 Stainless Steel
Min Crush Load: 1370kg
Hardness: 25-39 HRC
Hardness Depth: Through Hardened
Corrosion Resistance: Excellent

metal-comparison-guide.jpg
 
Do you know the steel type used in the ROK spindle? generally spindles are a 3 series (austenitic) stainless, either 304 or 316. 316 differs slightly from 304 in that 2% moly has been added to the alloy to prevent corrosion from various chloride salts. Hardness of steel comes down to % carbon in the alloy "c" is below 1% "C" is above 1% 304 and 316 are "c". Several ways the end of the spindle can be "hardened" The easiest, i think, would be to counter bore the spindle, install a M50 ball in to it and machine it down to a flat surface of high polish. Then use a tungsten carbide ball for the thrust.
 
Do you know the steel type used in the ROK spindle? generally spindles are a 3 series (austenitic) stainless, either 304 or 316. 316 differs slightly from 304 in that 2% moly has been added to the alloy to prevent corrosion from various chloride salts. Hardness of steel comes down to % carbon in the alloy "c" is below 1% "C" is above 1% 304 and 316 are "c". Several ways the end of the spindle can be "hardened" The easiest, i think, would be to counter bore the spindle, install a M50 ball in to it and machine it down to a flat surface of high polish. Then use a tungsten carbide ball for the thrust.

Hi @marcmorin - great question. I will guess that ROK spindles are not 316 stainless steel as my spindle has a big of corrosion despite being well stored and maintained.

So perhaps the ROK spindle is made from 304? Or perhaps even pot metal?

I don't want to modify the spindle -- I want to keep it stock.

So I'm looking to find a loose ball bearing material that is of lesser hardness than the spindle.

That way, the ball bearing will wear over time -- not the spindle thrust surface.

It's much easier to buy a new ball bearing after it wears down than to polish a platter spindle thrust surface (which shaves off metal and makes the spindle shorter).
 
I'm not convinced reducing the ball hardness is going to reduce spindle wear as much as you'd think, it's still a metal-metal contact. As the ball wears it'll release tiny bits of itself into the oil matrix which can act as an abrasive on the spindle. I think getting the finest surface polish possible on both surfaces and going with a bearing that won't break down will do the most good for reducing wear.

But that's just a theory. someone like Marc (apologies for misspelling the name in my email the other day btw) would know better than me.
 
I agree with EngineerNate. Bicycles use similar cup and cone bearings and it's dirt, lack of lube, corrosion, and maladjustment that kill them.

I would think that a chrome plated bearing that is precision manufactured for roundness would work just fine. Keep it lubed and clean and it'll likely run smooth for years.

If anyone here would know it would be @KentTeffeteller. Hopefully he'll chime in.
 
I think one of the main reasons people buy the ceramic bearings is that because of how they're manufactured, they're easier to get in higher specification for both surface finish and roundness.
 
I used a ceramic ball with proper oil and it was quickly creating a divot in the platter stem. So I am concluding hardness does have an impact if the thrust bearing spindle surface is a softer material.

On the other hand, I've seen well used ROKs with virtually no divot in the platter stem. I assume that is a combination of a softer metal ball bearing and proper lubricant/cleaning over time. The question is: what material (and hardness) was used to make the ball bearing that ROK supplied with their tables?
 
Hi @marcmorin - great question. I will guess that ROK spindles are not 316 stainless steel as my spindle has a big of corrosion despite being well stored and maintained.

So perhaps the ROK spindle is made from 304? Or perhaps even pot metal?

I don't want to modify the spindle -- I want to keep it stock.

So I'm looking to find a loose ball bearing material that is of lesser hardness than the spindle.

That way, the ball bearing will wear over time -- not the spindle thrust surface.

It's much easier to buy a new ball bearing after it wears down than to polish a platter spindle thrust surface (which shaves off metal and makes the spindle shorter).

304 corrodes in a chlorine environment, 316 not so much. for your spindle to have corrosion on it, A: there were chlorine salts added to the oil, B: it's neither 304 or 316. C: it's a low grade 4 series Is it magnetic?

The lowest grade steel bearing ball will be harder than most regular steels, and certainly anything in the 3 series. regardless of fit and finish on a ceramic ball, they don't fair well with most metals.

Tungsten Carbide will probably be your best bet as a ball material, and you should finish your spindle end to at least 1 micron finish. Use no polishing compounds, as they can impregnate the grain boundary in the spindle and release abrasives later. No teflon additive oils
 
304 corrodes in a chlorine environment, 316 not so much. for your spindle to have corrosion on it, A: there were chlorine salts added to the oil, B: it's neither 304 or 316. C: it's a low grade 4 series Is it magnetic?

The lowest grade steel bearing ball will be harder than most regular steels, and certainly anything in the 3 series. regardless of fit and finish on a ceramic ball, they don't fair well with most metals.

Tungsten Carbide will probably be your best bet as a ball material, and you should finish your spindle end to at least 1 micron finish. Use no polishing compounds, as they can impregnate the grain boundary in the spindle and release abrasives later. No teflon additive oils
Moly disulfide grease on the thrust point?
 
How deep a divot over how many hours with what diameter ball? Are we talking .010 divot after 2000hrs? 3000 hrs? 10,000? If it's enough to be an area of concern

why not go to a slightly smaller ball and glue a thin piece of Delrin stock to the end of the spindle to take the wear?
 
304 corrodes in a chlorine environment, 316 not so much. for your spindle to have corrosion on it, A: there were chlorine salts added to the oil, B: it's neither 304 or 316. C: it's a low grade 4 series Is it magnetic?

The lowest grade steel bearing ball will be harder than most regular steels, and certainly anything in the 3 series. regardless of fit and finish on a ceramic ball, they don't fair well with most metals.

Tungsten Carbide will probably be your best bet as a ball material, and you should finish your spindle end to at least 1 micron finish. Use no polishing compounds, as they can impregnate the grain boundary in the spindle and release abrasives later. No teflon additive oils

Table was new old stock. But an open box item. No divot when acquired. Only oil used was SAE 20 3-in-1 blue label. Tried a ceramic ball and noticed divot wear starting after very low hours (probably about 30 hours).

Doesn't Tungsten have a higher hardness than Ceramic?

Do we know what material the ball was that ROK used? I'm thinking that material is the safest bet as ROK vetted that material back in the day.
 
How deep a divot over how many hours with what diameter ball? Are we talking .010 divot after 2000hrs? 3000 hrs? 10,000? If it's enough to be an area of concern

why not go to a slightly smaller ball and glue a thin piece of Delrin stock to the end of the spindle to take the wear?

I want to keep it stock. No delrin modifications. 30 hours and noticed ceramic divot starting.
 
I want to keep it stock. No delrin modifications. 30 hours and noticed ceramic divot starting.

Fair enough.

I used Mobil1 5w-30 in mine for a year with a ceramic ball and then sold it. I never noticed any platter dropping but I didn't check for divots after changing the bearing. It had a small divot in the end of the spindle when I got it.

I'll see if I can get the new owner to check.
 
I'm wondering if they all develop a divot during initial break in and the only reason you're seeing it develop like this is that you snagged NOS table that had never been run in.

Are there any confirmed examples of well loved tables of the same model that don't have the divot?
 
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