Advice for angelar contactbearings

I have a lathe with 2 worn angelar contact bearings (7013AC/P4)
The old ones have a 25 dgr contactangle
It is the bearings for a V-belt pully which rotates freely on the spindle (That is for the high/low speed part on the spindle)
Why they use a high precision bearing there I don't know
But a V belt pully gives a radial load So would a 15 dgr contact angle be better or not
I can buy those (7013CD/P4A)for about a quorter of the price as the others
Any insights

Peter from Holland

But a V belt pully gives a radial load So would a 15 dgr contact angle be better or not

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As there is almost no side load, I see no need for the big contact angle.
They have chosen P4, because it runs smoother. But the difference should not be worth the money, considering the pulley is almost decoupled from the spindle.


Nick

I wouldn't worry too much either, after all a vee pulley & belt is not a high precision drive.

FWIW ;- I suspect they fitted high precision because they were used elsewhere, and saved inventry........... think about it,......... at what they were paying it was a lot cheaper than putting the wrong - uns in

My Boley 5LZ has a similar headstock pulley arrangement and is fitted with a pair of 7013 P5's.

Phil

peterve said:

I have a lathe with 2 worn angelar contact bearings (7013AC/P4)
The old ones have a 25 dgr contactangle
It is the bearings for a V-belt pully which rotates freely on the spindle (That is for the high/low speed part on the spindle)
Why they use a high precision bearing there I don't know
But a V belt pully gives a radial load So would a 15 dgr contact angle be better or not
I can buy those (7013CD/P4A)for about a quorter of the price as the others
Any insights

Peter from Holland

Click to expand...

On my lathe the headstock pulley assembly is either direct drive to the spindle, via a dog clutch or via helical gears to give a 1:4 reduction. With the reduction engaged the minimum rpm is 28 and the motor is 2 kw. I think therefore with helical gears there will be considerable axial thrust on the pulley bearings, hence angular contact.

Phil

For your application, I wouldn't hesitate to use the 15 degree angular contact bearings. I don't know why they would use 25 degree bearings, in a pulley where the load really has no thrust component.

I make machine tools and frankly SOMETIMES I use different angles simply because I have them in stock, OR I got 25 degree bearings at a great price. every machine in my line calls out 15 degree contact angles, but in the drive of my right angle heads where I feel there is thrust, I use 25 degree bearings if I have them. You can certainly go the other way.

Will he not have an axial thrust component if the pulley drives a helical gear.

Phil

Brian@VersaMil said:

For your application, I wouldn't hesitate to use the 15 degree angular contact bearings. I don't know why they would use 25 degree bearings, in a pulley where the load really has no thrust component.

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I agree with a lot that has already been said, but not all of it.

With getting 15-25 years of service out of the original why would you consider changing the bearing to a lesser one.

With the potential for failure and customer having to to do rebuilds more often and customers loss of the machines production.

Then generally not being happy with a machine because of down time because you chose to save a few Euro's on the cost of a bearing is not good.

My .05

Regards
DD

deckeldoctor said:

I agree with a lot that has already been said, but not all of it.

With getting 15-25 years of service out of the original why would you consider changing the bearing to a lesser one.

With the potential for failure and customer having to to do rebuilds more often and customers loss of the machines production.

Then generally not being happy with a machine because of down time because you chose to save a few Euro's on the cost of a bearing is not good.

My .05

Regards
DD

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My question in fact was if the 15dgr bearing was a better choice for a application with little or no thrust I believe it is
Is there any reasson to believe it is a worst choise
The spindlebearings are the same so that is why they probbably used the 25dgr bearings Less stock
BTW I have seen a lot of design/construction mistakes on all kind of machines in my career and did a lott of improvements on them

Peter from Holland

peterve said:

My question in fact was if the 15dgr bearing was a better choice for a application with little or no thrust I believe it is
Is there any reasson to believe it is a worst choise
The spindlebearings are the same so that is why they probbably used the 25dgr bearings Less stock
BTW I have seen a lot of design/construction mistakes on all kind of machines in my career and did a lott of improvements on them

Peter from Holland

Click to expand...

Are'nt angular contact brgs sposed to be mounted in PAIRS and preloaded ? so as to remove end play?
If your shaft mounting and brg mounting is set up to do that, then the angular brgs are ok, as long as you know how to set up the preload...

Otherwize maybe your better off with plain ball brgs...

Gary E said:

Are'nt angular contact brgs sposed to be mounted in PAIRS and preloaded ? so as to remove end play?
If your shaft mounting and brg mounting is set up to do that, then the angular brgs are ok, as long as you know how to set up the preload...

Otherwize maybe your better off with plain ball brgs...

Click to expand...

Yes 2 bearings in a O configuration I know
Furthermore if I take a universal SKF bearing witch is marked with "GA" (like in 7013CDGA/P4A) the preload is correct if the spacers on the inner race and outer race are exactly the same
Now if I buy these 7013CD/P4A I have to grind those spacers for correct preload

Peter from Holland

Reading some of the above replies, I think some people don't realize the spindle bearing pairs that ARE angular contact bearings, are available in two pressure angles. 15 degrees and 25 degrees. Both of these angles are used in angular contact bearings. There's also 40 degree angular contact bearings, that tend not to be sold in pairs. The bearing companies nomenclature for bearings is somewhat cryptic until you understand the letters and number. In Fafnir bearings the 15 degree bearings are the 2MM series and the 25 degree bearings are the 3MM series.

Both 15 degree and 25 degree bearings can take both axial and thrust loads. In a machine as an example a drill press, the loads are mainly thrust, so a 25 degree angle would be more suitable. In a purely axial load like a pulley driving vee belts a 15 degree set would make more sense. But in the real world there's a combination of thrust and axial loads. A Pulley that is driving a gear set has BOTH axial and thrust loads. The gears want to push themselves out of mesh. So it's a judgement call whether it's more radial or axial forces. A deep groove bearing also has the ability to handle thrust and radial loads. In some applications, it's more than adequate at a substantial savings. These days when spindle bearing pairs of this size are selling in the five hundred dollar range, analysing the use and substituting different bearings is simply a judgement call. I make right angle heads that originally used angular contact spindle bearing pairs, and now I use deep groove bearings. If you want to reach a certain price to sell machines for, you CAN'T use bearings that cost fifty times more money, to get an extra year or two of service. Thirty years ago, there didn't seem to be the huge difference in price between spindle bearing pairs and deep groove bearings. Using angular contact bearings was simply good insurance.

I bought the 7013CD/P4A


Peter from holland