bridgeport motor bearing clearance

Does anyone know what the correct clearance is for the bearings in the motor of the bridgeport 2j head. I know the size, but as the bearings do not seem to be original, i just want to check the clearance.

I suspect that as nobody has answered this question that the question itself is not understood. Whereabouts does the clearance that you are asking about supposedly exist?

If you are able to clarify the question I won't be able to answer it myself, but someone else may be able to.

Do you mean as is C0 bearings vs C3 with extra internal clearance? Most electric motors use the standard C0 clearance bearings. Not sure about specific Bridgie motors though.

Adding to Hoppers comments...

Depending on how hot and fast the motor was originally designed to run at during continuous use and load, it is more likely to be a C3 clearance. Certain OEMs may have put in C0 as the original bearing clearance, subjecting them to a running-in period, but replacement market is also most likely to suggest C3 clearance to give a run-in feel and avoid failure which could potentially be caused by a C0 clearance bearing being introduced into a worn components assembly.

Ketan at Arc

Exactly, the OP knows what he is talking about but no one else does.

Tony

If in doubt, fit the C3 with extra clearance. A bit of extra clearance never got in the way, as Mr Harley said to Mr Davidson way back when.

(Brainfade, standard clearance bearings are C1, not C0 as above. Usually not marked as anything. Eg standard clearance (C1) will be marked 6203, while the looser clearance will be marked 6203C3).

Edited By Hopper on 04/11/2018 12:29:50

When I put new bearings in my Bridgeport motor 12 or so years ago I was advised by "one who knows" to get bearings specified for motor duties rather than a generic same number C3(?) type. Possibly because a Bridgeport motor is not only installed vertically but also has an unusually long shaft which may mean that loads are higher than an ordinary foot mounted motor.

Cost was maybe a half as much again as bearing supplier generics. How much of the difference was due to being a premium brand and how much due to better specification I know not. Certainly not enough difference to be a major worry and worth it to me as insurance against having to do the job again if the standard bearings couldn't cope. That said ordinary bearing quality has steadily increased over the years due to improved manufacturing methods so the difference may no longer be relevant at that end of the market.

Hauling the motor off a J head vari-speed once in a lifetime is quite enough for me thanks.

Clive.

Edited By Clive Foster on 04/11/2018 13:20:01

Hi Hopper,

Your original thought was correct, 6203 as standard is C0 clearance. Unfortunately, C1 and C2 are tighter than C0 and C3 and C4 are looser than C0. I know, no logic in terminology, but that’s the way it is.

Ketan at Arc.

Clive,

‘The One Who Knows’ was told by the bearing technical sales engineer that he needed to fit an EMQ quality/grade bearing. It’s meaning within the bearing manufacturers operations meant - check the applications load/heat/speed under continuous operation and supply the standard C0 or C3 clearance bearing and fill the bearing up with appropriate HT grease, Mark the packaging as EMQ, look at the buyer and charge what you can get away with 🙂

Ketan at Arc

Thanks for the replies. The top end of the head was making noise when i was running the machine. I hate noisy machinery. But know for certain the rest of the bearings in the head are fine. The plastic bushes in the pulley's, which are the usual source of noise on vari heads, are perfect, so the motor is the main suspect as far as i can tell. As bearings have a hard life and are relatively cheap to replace, i will replace them.

But knowing to go for cn or c3 is what i was wondering. There are also specific bearings designed for electric motors, so that is another option.

Ronan,

Don’t worry too much.

If there is no printed information about the motor parts available, look at the seals or shields on the bearing. They will probably have the necessary marks on them to guide you. Also check what is the max speed of your motor.

Ketan at Arc

Ketan

In all fairness my "one who knows" had advised using normal, albeit premium brand, bearings of the appropriate class in other motor duties. Which is why I sat up and took notice when he said I should use proper EMQ ones in the Bridgeport motor. Dunno about the "charge what you like" issue but objectively the extra £ compared to bearing factor generic of same number wasn't great. Quite happy to pay a bit more when I don't know enough to evaluate whether or not a more economical alternative is long term OK for my use.

Clive

Edited By Clive Foster on 04/11/2018 17:57:55

Clive,

Okay, I understand where you are coming from. 🙂

Ketan at Arc

Have you changed the bearing in the top housing at the top of the spindle? They have a short life and get rattly.