Pilot bearing fit

a 6203 is 17mm Bore 40mm OD 12mm Width.

17mm bore =.66929"

What is the diameter of the shaft? A dial caliper will be accurate enough, unless you have a micrometer.
 
Mart said:
The pilot bearing is a standard metric bearing with a 17mm bore. The bearings will be sized to a very tight tolerance. If the input shaft does not slip in, as the input is new I would suspect it is not sized correctly. Do you have another shaft you could try the bearing on? Or do you have a means of measuring the shaft accurately?

I would agree with the suggestion above that the input could be polished. If you have access to a lathe the task would be much simplified.

Mart.
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I'm in the bearing business as a sales engineer for a major manufacturer.
You would think pilot bearings are more accurate and harder to align and
less tolerant of mis-alignment. Not always the case though.
Although not a flathead application, I recently battled reinstalling a
transmission using a pilot bushing (NOS and miked), where it previously
had been installed using a pilot bearing. It was a major PITA to slide that trans in place. I ended up making two studs for the bottom two transmission
mounting holes to guide the trans in place. Didn't need that kind of accuracy when I did the trans last time (when the pilot bearing was in the crank).
 
hulleywoodworking's comments make sense to me, as his points logicaly describe how a bearing functions. The OD of the bearing is a press fit in the flywheel, and the pilot shaft needs to be tight enough to allow the center of the bearing rotate. If the pilot turns in the center of the bearing, it will wear the nose of the pilot shaft. This quandary is why I have always used oilite bushings. I will polish the pilot shaft, and see how it feels. Henry must have had a good reason for using ball bearings there.
 
Which brand of bearings are made in the USA? So far I have three different brands of(203) made off shore.
 
At the place I work, we use pretty well exclusively SKF bearings. These are a quality world famous brand of bearings. Interesting that the packaging always states country of manufacture. I've seen and used SKF bearings from Sweden [obviously], and all sorts of countries including China and India! Doesn't seem right- Chinese made SKF bearings. But, never seen USA manufactured SKF's!
As coop stated; 6203 series is probably about the most commonly used bearing globally.
 
To add to what John Hulley has written; as he says, engineering practice dictates that one surface is a press fit, whereas the other is a slip fit. The rule is; if the housing is fixed and the spindle rotates, the press fit will be on the spindle.
Conversely, if the spindle is fixed, and the housing rotates, the press fit is in the housing.
Think he front hubs on your Ford; the bearings are a press fit in the hub [which rotate], and a slip fit over the stub axle.
Whereas, in the transmission, the shafts turn, consequently the press fit of the bearings is on the shafts, and the bearings are a slip fit into the housing.
 
B-O-B said:
Which brand of bearings are made in the USA? So far I have three different brands of(203) made off shore.
Click to expand...

High quality 6203's are from Japan. Many of the rollers around those sizes
are as well. ABECs too. (NSK, Nachi, NTN, etc.)
I work for NTN (Osaka), our US headquarters is in Mount Prospect IL.
A number of years ago we purchased most of the old Federal Mogul manufacturing facilities back East (Elgin IL, Macomb IL, Hamilton AL, etc.)
when FM decided to cease US production and source EVERYTHING offshore.
We build our stuff in those old facilities, under the BCA & Bower trade-names, since we bought rights those too.
We are one of the only bearing manufacturers in the US. Most of our automotive hub line is produced in Elgin. (OE and aftermarket)
Timken, Schaeffler/INA, *** also does some production here in the USA as
well. Much of their stuff is sourced globally however.
 
I know I'm not going to change any minds with this post but I look at this pilot bearing versus bushing from a different perspective. Some of the helicopters I've worked on over the years have a lot of rotating ball bearings. There are also oscillating ball bearings but that is another story. The shelf life on the synthetic grease the manufacturer calls out is 4-years. As a safety factor, we have to reservice and inspect these bearings every 24-months. Some bearings make there life and some don't and that mostly is affected by the environment the helicopter is operated and stored in. Bearings will corrode when the grease gets displaced and moisture gets in through condensation or even trips through the car wash by owner/operators that don't like grease all over the place. They even corrode between the inner race ID and the shaft sometimes and that would be affected by a loose fit on the shaft.

For a pilot bearing, the thing only spins when the clutch is disengaged or when there is clutch slippage. If a person drives on the highway a lot, the bearing won't rotate as much as when the car is driven short distances like when just cruising around town. The bushing was thrown into the mix when mechanics complained about the bearings getting stuck on the pilot stub and the motor won't come away from the transmission during maintenance. The bushing is more forgiving in this case and its phosphor bronze make up (somewhat porous) allows it to absorb some lubricant when heated in a pan with some lube. Most folks don't even lubricate the bushing

My own opinion is that the ball bearing should be serviced at some scheduled interval that will allow it to remain in serviceable condition but that schedule depends on how the car is operated. The bushing should also be lubricated at some interval and the same conditions apply to it as the bearing. Folks that don't drive a lot can run a bushing and not worry as much about service at 10-years like a ball bearing and that's why the bushings are out there. When you replace the clutch or throw out then the pilot (either type) should also be replaced and the new part well lubricated. Apple and an orange.
 
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Rotorwrench, I totally agree with your comments, and thank you for your input. I come to the conclusion that the bushing is the superior solution. Failure of either, to me anyway, would favor the bushing over the ball bearing. The failure of a ball bearing will have more troublesome consequences, IMHO.
 
Years ago I attended a seminar on bearings. The thing I took away from that class was that the quality control for common bearings is 10% failure. Bearings used in aircraft are subject to more stringent quality control and also higher price, much higher price. The 203 bearing in rotor wrench's chopper must meet greater tolerance standards than ford generators.
Bruce
 
Pretty sure all the French military motors have bushings. That must mean something.

Mart.
 
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A Hughes tech rep once told me that the bearings we were using on the helicopters were rounder than the same bearing used in industry. I loved the guy (tech rep) to death God rest him but I found out later from the manufacturer that the statement by cmbrucew is pretty close on this. The bearings are mainly just inspected and tested more per unit for tolerance and machining accuracy than their industrial counterparts. The balls aren't any rounder than the industrial ones but they are checked more often during manufacture to insure a closer tolerance. Most of the bearing assemblies are serialized now for tracking in case of premature failure and most also have life limitations that range from 200-hours to 3000-hours depending on design and type of service intended. These are bearings that rotate the whole time that the helicopter is turning the blades so they get a good work out.

The pilot bearing (ball type) likely doesn't work near as hard as the average rotating bearing but they do tend to stay in service for a lot longer by date and obviously there is no easy way to service them to insure proper function.The clutch makes dust and the linings & friction surfaces generate heat so it's not the easiest environment for a small bearing to live in.
 
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