Angular contact bearing set up

[Mcgyver]

I want to make a high speed, light duty milling spindle and am not sure what the best way to set up angular contact bearings is.

Here are two sketches, the top sketch is how my dumore internal grinding spindle - just a reference. the inner races are a light interference fit on the spindle and the spacer is between the inner races

The bottom is how i'm thinking of making it - main difference is the spacer is between the out races.
Both use a threaded endcap into the housing ot load the bearings. The reason for the change is the bottom allows for a bigger dia end to the spindle.

Is this an ok way to arrange a spindle/angular bearings?

Also, any ideas on taking care of thermal expansion??. I know grinding spindles use springs, but don't think that will work as this is milling spindle and could use helical cutters - ie i don't want it moving along its axis.

Thanks very much



[This message has been edited by Mcgyver (edited 09-24-2005).]

[winchman]

oops, I give up

[This message has been edited by winchman (edited 09-24-2005).]

[SGW]

I guess my visualization is deficient here--what keeps the spindle from moving axially?

[Mcgyver]

well odds are its my visualization that's lacking, I tried to include the picture to make the question clearer but for expediencey only drew half the spindle. let me do a more complete drawing and repost
thx

[winchman]

I'm assuming the housing doesn't actually contact the inner race of the left bearing in the lower sketch.

I'm also assuming the blue part is threaded into the housing and has clearance around the spindle.

My third assumption is that there is a similar arrangement on the other end of the assembly, or at least one bearing there.

The blue piece will not preload the bearings. It just holds the outer races in place.

I think you need to turn the bearings around, and put the spacer on the spindle. That way, the blue piece will preload the bearings, and the bearings won't be able to move on the spindle. I hope I've got it right now.

Roger

[J. R. Williams]

Mc
You need to obtain a copy of an old 'New Departure General Catalog' I have one from my old days the 25th edition dated 1961. There is a section on machine tool spindles and different bearing configurations.

JRW

[Leigh]

The main problem is that your second drawing does nothing. The jam nut applies pressure to one outer race, through the spacer to the other outer race and then to the housing. Nowhere do you apply any pressure against the bearing.

For a design like this, draw the force line, starting at the jam nut and ending up at the housing. In the first drawing, this line forms a U, going through the right-hand bearing to the inner race, through the spacer to the inner race of the left-hand bearing, then through the bearing to the housing.

In the second drawing, the force line is straight left from the jam nut to the housing. It never goes through the bearing(s) at all.

------------------
Leigh W3NLB

[Mcgyver]

guys, sorry been busy redrawing this since i first posted - i realized it didn't do much to advance my question without showing both ends - ie how the compressive force was applied!

The top is dumore, the bottom mine. The light blue shape on mine to the right is a nut that screws onto the spindle to compress things.

the burdundy endcaps are threaded to the housing. taper is made up - put it there just to make clear which end was the business end. I'm not sure if this way of setting it is consider good practice and/or what should be done, if anything about expansion

again, apologies for not getting it right the first time, the help is appreciated



[This message has been edited by Mcgyver (edited 09-24-2005).]

[Mcgyver]

ok going insane here, winchman i think your comment crystallized the error. the inner race was in contact with the housing which of course wouldn't work!

so the bottom design is toast, unless i made the bore in the housing bigger and used a sleeve, but that close to what the dumore does and i don't want a sleeve rattleing around at 6k or more. crap.

thanks to all for helping, I think i'll just get some bigger bearings and go with something modelled after the dumor. doesn't have to be very big, just enough to hold cottets from the foredom.

i wish i had that catalogue with spindle designs!

[This message has been edited by Mcgyver (edited 09-24-2005).]

[greywynd]

Ok, I don't know a whole lot about bearings, but I do understand physics and forces (and sometimes machining too)

I may have an idea that might work with your design. Let's number the bearings 1,2,3,4 from left to right. Start at #4. Actually, the burgundy endcap compressing it. Remove the portion that compresses the bearing, let the shoulder on the spindle do that. Now go to bearing #3. Make an undercut in the housing to clear the outer race of bearing #3, this way the inner race is compressed against the housing. I think this should solve the right hand side.

Left side....ok, again, make an undercut to clear the outer race of bearing #2 so that the inner race is against the spindle housing. Next, remove the portion of the burgandy nut that contacts the bearing race, leaving the blue spindle nut against the inner race. Here's where the problem arises, now there's nothing compressing the left hand side. Make the head of your blue nut larger, and add a series of bolt holes (bolt circle), and drill/tap the burgandy nut to match. If done correctly, then you can shim between the two if necessary to allow for heat expansion. By bolting the two together should also make it a 'locking' assembly, preventing it from coming apart. Wish I could post something here to show you clearer.

Try sketching it up, and post it again, maybe someone can help advance this a little furthur for you.

Mark