From here someone asked whether this sort of bearing would work in a Cremina. I've split off the discussion to a new thread here:

Upgrading Cremina Lever Roller Bearing

forbeskm wrote:Any comment on the NK 6/12 Needle roller bearing? Fits perfectly with no multiples to mess with. Just wondering about opinions on it.

I'll byte.

I mentioned in my virgin post, I'd get back here. Since I did the 3 times 4mm plus shims, before becoming aware of the NK 6 X 12, and upon reflection, should comment on the difference.

Rich explained his design solution in this thread here.

There are at least two issues with that johnnie-come-lately.

1) It still needs shims to preform as expected, in this application.
2) It's kinda short on needles.

The trouble here, is that there is no friction reducing elegant solution. The Italians didn't blow it. A bushing is not a horrible plan, 'cause this isn't the proper application for either bare roller bearings or the sorta needle bearing either.

It's needs a wheel. The roller bearing is the easiest to turn into wheel. Rich's solution does that.

You need to fix one of the races. The bearings usually see the outer race fixed, in a hub. We don't gotz. So, you fix the inner race with shims about the axle. That axle not moving or not moving much is a good thing, because it's riding in one of the expensive parts, the clevis.

In order for this to have a chance of working better that the bushing, the bearing assembly/wheel width has to be greater than the group thickness at the slot. 12mm is not even close.

It gets more... interesting. While the pull is swinging through an arc, that movement is translated into the desired and undesired movements by the linkage, naturally. The point is the fore and aft or X displacement is not all that great, but it will also have a vertical or Y component on the rear pin.

So if the bearing group is slightly smaller in diameter than the height of the slot in the group, the bearing-turned-wheel runs on the top on the slot on the down stroke and on the bottom of the slot on the up. The third law is still in effect. The same force pushing down on the puck is pushing up through the rear pin to the bearing.

The closer in size to the bore of the bearing the axle is, the greater an area of the arc of the shaft/axle/pin will contact the inner race and distribute the load and thereby wear. As the axle becomes more undersized, the contact area effectively shrinks to a point. Or in this case a line along the inner race.

I don't have a 6 x 12 x 12 like the one shown above, but I got some beans that say the undersized axle pins are only hitting two of those needle when under load. At that point, it may not act much different than the factory bushing. In fact, if properly lubed, there may be less slop with the bushing.

The shimmed stack described in this thread, performs a second, economically more important function. The stack if greater in width than the group, corrals the undesirable movements I alluded to. The Z axis, the dreaded third dimension that confounds the 2D interwebs.

While bottomless filters and scales are observed through the pull, I got more beans that say one's body is adding a twisting moment at the handle and a sideways, Z displacement.

That would be your clevis chaffing away at the previously-nice cast brass group. Two expensive parts.

There's a pretty good chance that most of the missing smoothness in the lever action is the clevis-group bind, due to the greater surface area involved, as opposed to points of contact between the slot, bearings and pin.

One may be trying to feed the wrong end of the horse. (Not that there's anything wrong with that.)

If you want to play the game: Drop your pins, clean off the goo on the side of the group with lighter fluid or Dawn, get it dry and scribble with your trusty MajicMarker. Re-pin, pull. Check back later.

If your MajicMarker drags in the ruts, you've already proved the point. Later any missing Marker is bind.

Same 'ole, same 'ole: Before you do a mod like this, wriggle the tail, and see how much slop you've got. Then riggle again after the change. If it's worse, go for reverse.

I think that I finally understand the initial recommendation of using the three bearings and the shims.... will order the recommended parts to replace the NK 6/12 bearing that I have there now.

To completely eliminate lever slop, some shimming is necessary with the front pin too. On both Europiccolas and Creminas (perhaps not the most recent Creminas), there is a surprising amount of slop in the front of the yoke.

You also may want to consider that this in most cases, could be a solution in search of a problem.

IOW's from a commodity standpoint, they are overbuilt for the amount of use they will probably see in a working society, like the US.

So, the headache with this fix, is that no one has found the correct, for each variation, thin shim.

The only reason to order from McMaster (sorry), is to bundle the wrong sized shims that need to be manipulated, with nicely made bearings. But Rich was right, it's a better solution in any event.

Upon finally doing my due diligence I'll proffer a 'however':

It turns out, other than instrument bearings, the 6 x 12 x 4 has a normal life, as the standard upgrade for Japanese RC car axle smoothness. In the hobby shops they're about 2 bucks a piece. On-line a bag of 10 for that many dollars.

Now there are some neat ones, but many have plastic dust shields, so that's why the McMaster deal is a safe one.

The idea with the thin shims is that you can build out to the proper width... for you. Think of these as hand-made sorta. They vary a bit.

BUT... if you are trying to grow a 12mm width to something over 13mm, the 6mm brass washers in the Hillman boxes at Ace... may work for you. And at a nominal 10mm OD they won't need to be turned/ground down.

You may not be able to get one between each bearing and then one on each end, which is why the nod in the general case is still Rich's plan.

But it may not matter, depending on the machine.

It's cheap, not bad looking, and readily available.

Thank you Mark. That helps as I can just drive and pick those up locally at the Hobby Shop and ACE.

What I had missed from Rich's approach was the making of a wheel that rotates inside the group head... with the 6x12x12 and no shims, I was only providing the bearing for the pin and doing nothing to preserve the group head... the group head is what we are trying to protect from wear.

With the pressure profile kit, I no longer have the same pin in the front... so all I can do is protect the group head with this mod... will do so over the weekend.

Yes.

And the fine point, since the Needle Bearing In Name Only (NBINO) is running a carrier, and under 9 euros and from the globalonists, I bet that cage is something special like a stamping.

It's probably going to deflect under the vertical load, since that's not at all what it's intended use is, which will probably stall the rotation.

ie: my previous comment regarding the not so bad lubed original bushing. Me thinks that's why it was a bushing all along. And the futility of gaining a nice smooth raceway in the elongated brass slot.

So, if anyone is dealing with a WTF moment and just wanted to do something positive, 3 - 6 x 12 x 4 race car bearings from the hobby shop makes lot's of sense/cents.

And they got 'em in ceramic, which matters not for this app, but has a certain ring to it.

Renovator wrote:...And they got 'em in ceramic, which matters not for this app, but has a certain ring to it.

I like your sense of humor. I will leave the ceramic ones to crush in the Helor 101 grinder... lol

There is another variable to consider, which is that some of the brass pins people have made themselves (to swap out for the crappy steel with e-clip types that come stock with these machines) can be (or possibly have been?) made in a lightly larger OD such that they would engage with any of these various bearing alternatives people have been exploring. For example, I was able to determine that the one I purchased for my Cremina was a one-way by removing it, placing the brass pin through it, and turning the pin in both directions while holding the bearing. It moves freely in one direction, but locks up the other way. That tells me there is enough contact between the pin and the bearing that it is in fact acting as a wheel, albeit not exactly in the manner we had hoped.

There is also the possibility that I've completely misunderstood your post.

That is the more important point, I think; and the earlier posts did start there.

The pin properly fitting the clevis would be the first step, and why 1/4" brass was fashioned to those machines' nominal 6mm clevis bore.

Then worry with the bearing/wheel. That's the priority but the (new word) achievability is problematic. It's tough to get custom bored insignificant bearings .

So staying with the idiomatic; the reason the bearing gets replaced is the same reason the dog... because you can.

In the thread, the idea of custom binding posts emerges, and I personally think they're sweet.

Within this year, they become more readily available, but since they being applied in a questionable sequence, they can be the wrong size for specific machines. Mine are.

Mine are about 3 thousandths smaller in diameter than my 35 year old pins. And they are too long and really should be ground to proper length . (Lots easier than making longer, so we'll take it.)

And they really aren't designed to be snugged down, they're really binding posts or longish Chicago Screws. Depending on your POV. (Yeah, got it... baby soft jaws... but really.)

So the availability(, dog can,) raises it's head again, and in order to match the chrome ACAP, undersized stainless gets the call for the pins.

(In your best Rick Perry... or Will Smith...) Ooops.

Ya know what we call that extra .003" ? ... a running start. Every pull down, every raise up... and every friggin' half pump, both ways.

In closing... just because you can, doesn't mean you should.