Milling spindle

[Raymond AndersonParticipant @raymondanderson34407]

Bearings.

[Raymond AndersonParticipant @raymondanderson34407]

Hello all,

Having just bought the book “Spindles” [very good book bt the way] I have decided to make a milling spindle for 1 of my lathes [the Warco gh750 not the DSG] but as I want the spindle to be capable of fairly heavy use I am thinking of using a pair of SKF or FAG spherical roller bearings for the front end and deep groove for the rear The spindle will be made from my favourite machining steel “EN24T” and the housing from EN8. Has anyone any thoughts on the bearing choice? is it overkill or about right? the front bearings would have a bore of 30mm and an outside Ø of 62 at 20mm width [each]

Regards,

Raymond.

[blowlampParticipant @blowlamp]

You could get a pair of 30206 taper-roller bearings in there that would be more rigid than the plain roller bearings you are proposing.

 

What about a quick sketch of your proposed design for us to look at?

 

 

Martin.

Edited By blowlamp on 26/08/2011 16:55:15

[Raymond AndersonParticipant @raymondanderson34407]

Hi Martin,

I did think about taper roller bearings but have been informed that Spherical roller bearings have a greater load capacity than the Taper rollers. I hope to have my final design finished tonight [when I have decided on the bearings]. I will do my final drawings from the 3D solid model [Siemens Solidedge] and hopefully will be able to upload them to the forum.

Regards,

Raymond.

[blowlampParticipant @blowlamp]

Raymond.

Sorry, I wrote plain roller bearings in my last post when I meant to say spherical.

 

The only advantage I can see to the spherical bearings is their self-aligning properties, but that could work also against you if the spindle isn’t absolutely rigid.

 

A pair of lightly pre-loaded taper-roller bearings at the front end of your spindle would form a very stiff assembly – which in itself would probably be overkill

 

I look forward to seeing your drawings when you get them uploaded.

 

 

Martin.

[Raymond AndersonParticipant @raymondanderson34407]

Thanks Martin,

Also could anyone tell me how to upload my drawings [when finished]

As I created a photo album and did a quick sketch but the drawing is very small.

Regards,

Raymond.

[Chris TriceParticipant @christrice43267]

I’ve got the same book and in fact built the Myford nose 2MT spindle using just spherical bearings as per the text. It’s pretty solid. Even the author states that the taper roller spindle is a probably overkill. Based on my one which I’m using on a Super 7, I imagine the bigger one might actually be a hinderance because of its extra bulk for no real advantage.

[blowlampParticipant @blowlamp]

Raymond.

 

I’m assuming the spindle is fully contained by its housing, apart from access to each end of course.

Putting a pair of spherical bearings at the front end of the shaft isn’t going to bring you any benefits in my opinion.

For the whole assembly to work, you’ve got to pre-load the bearings to ensure there isn’t any play.

Looking at your drawing, it seems like you intend to pre-load the spherical bearings against one another and have the back bearing find its own axial position as well as provide support against the tension of the drive belt.

If I’ve got that bit right, then it would appear that you will only be utilising half of each of the spherical bearings rolling elements i.e. those that are pulled into contact through pre-load.
This is the same situation that you would have if you were to use two taper-roller bearings mounted back-to-back.

 

If you increased the spindle size to 35mm you could fit a beefy 32007 bearing @ 35x62x18mm at the front of the shaft to take most of the load and a another taper-roller in the 25mm I/D range (a bit larger if possible) for the back bearing, thus allowing for adjustment of pre-load.

 

Keeping the spindle at a nominal 35mm along its length will keep it rigid and save machining time.

 

Access to the preload adjusment also looks as if it would be more convenient as it would be just under the drive pulley.

 

 

Martin.

 

Edited By blowlamp on 27/08/2011 12:04:07

[Raymond AndersonParticipant @raymondanderson34407]

Hi Martin and Chris.

Chris, I have a bit more room on the lathe that I am building the spindle for than there is on the Myford so hopefully the extra size will be catered for [if not then I will put it in the DSG]

Regards,

 

Martin, I think that I will go for the Taper roller bearings that you mention [32007] and a slightly smaller size at the rear. The reason for reducing the shaft Ø is to enable the front bearings to reach their seats without having to apply any force although I am now thinking of redesigning the spindle to enable me to install the front bearings from the front end.

When I have finalised the design I will upload a bigger [hopefully] finished drawing to my album.

Thanks for the input,

Raymond.

[Raymond AndersonParticipant @raymondanderson34407]

Have finally decided on the bearings which will be

Front end, Pair of Taper rollers 32007 35x62x18 arranged back to back,

Rear end single Taper roller 32006 XQ 30X55X17.

because the spindle nose for ER32 is threaded M40x1.50 I have no choice but to install the front pair from the rear which means that the centre portion of the shaft will have to be reduced to Ø34.75. I will also incorporate radial shaft seals. [simpler than labyrinth type seals]

now that I have that sorted I can produce my drawings and crack on.

Edit, The housing will now be about 80mm square so it may well end up on the DSG

Then will come the motor to drive it I want the motor to be 240 v 3 phase and about 2.2 kw should be fine. It will also be direct drive [no pulleys].

Regards,

Raymond.

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