Clutch bearing/clutch centre fit?

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DogT said:
Just to add to the bearing thread, I got the bearing, 060750/S, from Old Britts today, 6007 2RS C3 EMQ. EMQ is a Chinese bearing manufacturer. Ella said the unsealed one they had was from UK, but at almost twice the price. I got this one for less than $15. I've seen them on line for around $7 including delivery.
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Suppliers probably make more profit from selling the cheap bearings!

As you said yourself, you've seen them for about $7 yet you paid around double that.
If bearings are bought in even relatively small quantities then the unit cost drops dramatically. For instance, if I bought a single cheap open 6007 from "Bearingboys" http://www.bearingboys.co.uk/ then it would cost £3.94 retail (plus delivery and VAT etc.) however if I were to buy 50, then the unit cost drops to £1.58 - plus I get free delivery - and trade prices would be even less.
If a parts supplier were to buy 50 bearings from AN then I expect they would have to pay full trade price for each, therefore a supplier would probably prefer to sell you a cheap bearing for $15 that cost them around $2 or less to buy, rather than sell you a $30 bearing that cost them $20.
 
Fred called and told me that Andover uses the C2. Getting a bit of conflicting information here. Fred also said he uses the sealed C3 in his belt drives. That may explain that.

Dave
69S
 
L.A.B. said:
If, as ZFD has said previously: "...that all bearing manufacturers now work at the lowest possible tolerance within the norm.," then that could be why AN perhaps specifies a standard clearance bearing now, instead of C2?
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I don't think they do things any differently now than they ever have done them. DIN/ISO standards have always set the norm for tolerances and bearings have always been available in more narrow ranges, just move the decimal point on your check over to the right at least one space and you can have whatever you want. Maybe the reason they don't use a C2 bearing is they will be too tight after they are installed.
My bearing guy told me that more than 90% of the rolling element bearings he sells are C3. The rest are standard, and he couldn't remember the last time he special ordered a C2. The reason is that just about all the bearings he sells get installed with interference fits for the inner race, interference fits for the outer race, or both. Interference causes the inner race to expand and the outer race to shrink. Heat it up and the operating clearance is significantly less than the bearing in the box. Or the other way around, the right bearing installed is too loose in the box? The last time I heard of a specification for a C2 bearing were some main bearings on a certain batch of Combats.
 
rpatton said:
Maybe the reason they don't use a C2 bearing is they will be too tight after they are installed.
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If that was the case, then why would a C2 bearing have been specified originally?


rpatton said:
The reason is that just about all the bearings he sells get installed with interference fits for the inner race, interference fits for the outer race, or both. Interference causes the inner race to expand and the outer race to shrink.
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The clutch bearing is usually no more than a light press fit on both the inner and outer races and may in fact be loose - which was the reason this thread was started.


rpatton said:
Heat it up and the operating clearance is significantly less than the bearing in the box.
Click to expand...

Certainly, one reason for using extra or less clearance would be if there was a marked difference in operating temperature between inner and outer bearing races or because of different rates of expansion from dissimilar "shaft" and "housing" materials, however neither would seem to apply in this instance.


rpatton said:
The last time I heard of a specification for a C2 bearing were some main bearings on a certain batch of Combats.
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Norton Service Release No. 68 October 1971 which deals with the introduction of the revised MRJA.30 or NJ/NF306 (pre-Superblend) roller bearings states that the bearings should be: "2 dot or C2" however a 1 dot bearing is the equivalent of a C2, "2 dot" is normal (CN) clearance.
http://www.nortonownersclub.org/support ... e-releases
 
13th April 1970 drawing for 06-0750 says "one dot" and a later amendment, dated 9th July 1971, says "C2".

However, sorry to repeat myself, and whatever bearing manufacturers may claim, we found in the workshops in recent years tolerances have gone DOWN, probably to the lower end of the DIN scale now that manufacturing techniques allow for more exact manufacture.
Hence the 06-4118 (Superblend) we supply is no longer STD but C3 (higher tolerance), and Triumph 650/750 crankshaft drive side bearing 70-2879 (C2 originally) is no longer used but we (Norton Motors Germany- been dealing in Triumph spares for the last 30-odd years) use 68-0625 (a BSA part# ), same bearing but standard tolerance.

Reason? With the 06-4118 in STD tolerance resp. 70-2879 in tight C2 tolerance the cranks won't turn in the crankcase when the housing has cooled down with the crank installed. This was found by Rudi Kolano, the engine man who has built the engines of my personal bikes for the last 15-20 years, and Mick Hemmings, at about the same time.

Joe
Andover Norton & Norton Motors GmbH, Germany
 
vidar hjelm johansen said:
I just spoke with Nick at Andover Norton.
They use only the standard 6007, not the tight c2
Click to expand...

DogT said:
Fred called and told me that Andover uses the C2.
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So...which clearance bearing does AN currently recommend, C2 or standard?
 
No idea- I (Norton Motors GmbH) just buy them from my favourite Norton Parts Supplier (Andover Norton) without ever bothering to look. Will check what we supply in my 06-0750 parts bin tomorrow. Am home now, no way to check.

They work, that is all I know from personal experience- fitted one to my everyday road Commando http://www.andover-norton.co.uk/SOR.htm and my son fitted one to his http://www.andover-norton.co.uk/Timbike.htm , all within the last couple of years.

Never looked at the thingies- I trust Nick, Keith, and Pete to buy the correct stuff for Andover Norton's parts bins.
 
[video]http://www.youtube.com/watch?v=UWtn_obrQTo[/video]

So here's the bearing that came with my brother's Maney kit. As you can see there's a problem. What's perplexing, as it is for others is that the original bearing was a press fit. Seems odd that the new bearings are different. So the choices are to try a different bearing or get a new clutch center.
 
L.A.B. said:
rpatton said:
Heat it up and the operating clearance is significantly less than the bearing in the box.
Click to expand...
Certainly, one reason for using extra or less clearance would be if there was a marked difference in operating temperature between inner and outer bearing races or because of different rates of expansion from dissimilar "shaft" and "housing" materials, however neither would seem to apply in this instance.
Click to expand...
That would apply if we were talking about a bushing. In this case there is a rolling element, ball bearing, in there that's expanding too. I'm told it is common practice to take into account that bearings close up with heat. Does it really apply to a clutch center bearing? Probably not, they don't get that hot. I don't know why I brought it up.

I think most of the confusion is coming from people not understanding that clearance and tolerance are not the same thing, the terms are not interchangeable. C2 is an undersize clearance and C3 is extra clearance, and no designation at all is standard clearance. IMHO, if you have a clutch center that is a slip fit or a light tap fit in the bearing then it's been machined incorrectly. Personally, I find it amazing that they can machine things in mass production down to tenth's of a thou. Whatever the clearance is inside the bearing, it's nothing compared to a loose fit of the center in the inner race.

Edit: What I meant to say is that whatever the clearance is inside the bearing, it's nothing compared to the problems caused by a loose fit of the center in the inner race.
 
Got my clutch bearing out and it's an FAG 6007. Looks like a CN since there are no other marks. So, I'm just waiting to see what Joe comes up with from his supply at Andover. There is probably 1-2 mm of rocking motion at the outer rim of the clutch basket with the plates out and the chain off. I cannot discern any slop with the hub to the trans shaft splines, and the hub was a press fit in the bearing as well as the bearing into the basket. Not tons of pressure, but no way I could put it in and out without some pressure, certainly not possible by hand. The only slop I can feel is in the bearing itself, I can just feel it with the bearing alone, but put it all together and I can certainly feel it at the basket. May be mostly a moot point because like someone said, when the clutch is engaged, nothing is moving, unless it's slipping, or like hobot says, it may beat itself into a C3 after a while.

Clutch bearing/clutch centre fit?


Dave
69S
 
My clutch basket has a wobble in it too, a good wobble. I replaced the bearing and it reduced it a little. My clutch center would wobble in the bearing, it had play.
So I ordered a center from RGM and am hoping it will be a tight fit in the bearing when I get to buttoning it back up. My bike is completely stripped cuz I got the frame and swing arm straightened. Doing the clutch center was what led me to this whole strip down in the first place.
But from what I heard from Phil @ Fair Spares, it is normal to have some wobble in the basket as the whole basket rides on a shaft the size of a quarter and there is play in the splines that the clutch center rides on too. But when the engine is running and pulling on the tri chain and spinning the basket it pulls everything straight.
So, if the OD of the bearing is tight in the basket and the clutch center is tight in the ID of the bearing then thats all you can do as there will be slop in the splines of the main shaft to clutch center.
Remember that the whole clutch basket assy bolts to, and is pressed tight against, a small circlip which in my opinion is a piss poor design in the first place.

But of course, if the bearing itself like you said is sloppy then that doesn't help either.
 
The C2 and C3 tolerances are intended for the differences between running grease or submerged in oil. The C3 would be looser internally and intended for running in oil in an engine or transmission. Of course an engineer can take advantage of this standard manufacturing practice to select different bearings for the application he chooses.
When I lived in South America we came up with the theory that all the bearing manufacturers sent their seconds to South America because we couldn't get a decent bearing for rebuilds on Hondas. I remember one time buying a new set of NTNs in town that had more clearance than the "worn out" bearings we were taking off of the crankshaft on a Honda 200. Another variation was the ball count. A lot of cheaper bearings will have smaller balls for the same bearing number.
I gave up years ago on bearings made in countries other than Europe or the USA. (I'm sure Canada, Australia and NZ would also be fine but have never seen bearings from there.) I stick to name brands like FAG or SKF and buy from local bearing supply houses where I usually get a better price than a vehicle dealer parts department.
Dan.
 
Got the Andover bearing from OB yesterday. 6007 Z17 Timken Also a ZC mark on it. Been trying to find it in the Timken site, but no luck. Anyone know what the Z17 or ZC means?

Don't know that it's going to make any less wobble on the clutch basket, the slop all seems to be on the hub cente to the mainshaft and the slop in the bearing itself. But like someone said, with the clutch engaged, the bearing is not really doing anything except holding things together.

I got the OB clutch stack shim kit too. See if that makes any difference.

Dave
69S
 
I put the new bearing in today. Lots less wobble due to the bearing, I'd say about 1/10th as much wobble. The clutch hub was a press fit into the inner race, but once all the way in, it was loose, I could push it in and out by 1/8" or so. Put some sleeve retainer in it, now waiting on the clutch shims for install, but I can put the chain and all else back on.

Dave
69S
 
Clutch shims!? Where you get them? Who makes them? My stack is not flush with the splines on the basket. Should it be? I'm about .098" short.
 
Headfullofsnakes said:
Clutch shims!? Where you get them? Who makes them? My stack is not flush with the splines on the basket. Should it be? I'm about .098" short.
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Old Britts sells a kit of various thickness, or you could just try another regular plain plate which is 0.080. It might get you close enough. Remember though if you get the diaphragm over center too far you loose pressure and it may slip. That's what happens to me with a spacer. I just live with having the minimum slop in the clutch rod to adjuster clearance.

Dave
69S
 
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