[cowanrg]

It's actually pretty big. It's a 55x100x21. I just thought I read somewhere that rubber seals typically had a lower RPM range.

But yeah, it's a big bearing, so not many in that size have an RPM range beyond ~6k.

[mactec54]

It's actually pretty big. It's a 55x100x21. I just thought I read somewhere that rubber seals typically had a lower RPM range.

But yeah, it's a big bearing, so not many in that size have an RPM range beyond ~6k.

Yes that is a big Bearing # 6211, that would cost a lot to get that size for high speed, but they are available

So you could make a housing to fit in the 100mm hole,& fit a smaller Bearing to suit your spindle shaft, you don't need that big bearing anymore, that was to support the gear drive in the gearbox

[cowanrg]

That's what I was thinking. I might be able to use the bottom bearing, which is a lot smaller. I can just do a flanged insert that presses down into the bore from the top, has a lip to keep it from going down further, and then an inner lip where the smaller bearing sits.

[mactec54]

cowanrg

That's correct for the insert, Just a slide to light press is all it needs,you can always use some loctite if not tight enough, but your bearing, it can be the same size/dimensions as the bottom, but not the same AC type, it will have to be a regular deep grove ball bearing plus 2RS, the bearing needs to fit also the spindle

[cowanrg]

I meant the same as 207 in the diagram, the smaller of the two top bearings. I think the spline is a strange diameter, so I need to check if a bearing exists with that ID, but most likely I'll need to make an insert for that too. Thanks for the help.

[mactec54]

cowanrg

Yes the spline most likely is odd size/diameter, that bearing 6207-2RS 35x72x17 is good for 9,800 RPM grease filled,you could go with a smaller Bearing if there is enough room still, to put/make a bushing for the spline, the smaller the bearing the higher the RPM will be, for a grease filled standard Bearing

[cowanrg]

Cool. I'll see what I can come up with. Thanks for the help.

[cowanrg]

OK, I came up with a model.

Instead of doing a round spacer that fits into the 100mm bore, I decided to do something a bit differently:



The bearing is a 6907. It's 35mm ID, 55mm OD, and 10mm wide. There are two custom pieces. The flanged bearing spacer has an OD of 35mm, and an ID of 24.5mm (the outer bore of the spindle splines). This will support the spindle on the inner bore of the bearing. Then there is the outer plate. It doesn't rely on the original bore of the bearing, but bolts to the top of the head, which allows for some adjustment. I'm very hesitant to trust the alignment of the stock bore.

Also, the 6907 is a relatively inexpensive bearing. I can get a nice Nachi or NSK for ~$20 shipped. Thoughts?

[mactec54]

cowanrg

Looks good, just make sure you add the seals, Bearing # 6907-2RS is ordered like this, as it needs to be sealed

[cowanrg]

Yep, I was looking at either ZZ or RS. ZZ appears to be metal seals, RS seems to be rubber sealed, correct? Should I be looking for rubber or metal seals?

[mactec54]

Yep, I was looking at either ZZ or RS. ZZ appears to be metal seals, RS seems to be rubber sealed, correct? Should I be looking for rubber or metal seals?

Never ZZ this is not totally sealed they are only referred to as shielded

The 2RS rubber shielded are steel under the molded rubber seal

[cowanrg]

Ah, OK that makes sense. Shielded versus sealed.

[cowanrg]

FINALLY!

I made the parts from comment 28 and they work. I now have a working spindle, woohoo!

I made a video of the whole thing (trying my hand at video editing), here it is:

https://youtu.be/Od5YJonPSsQ

[handlewanker]

Hi, as you were "reinventing" the top bearing layout you could have opted to have two smaller deep groove sealed radials as they are taking the whole side loading from the belt drive and having the bore insert in the form of a cup with the two bearings floating axially in it.

The top bearing(s) in any spindle only serves to align the spindle axially and in your case also resist the belt pull.......it(they) will be the first to wear out

In a simple spindle layout they sometimes for economy and simplicity opt to have only two angular contacts, with one at the top and bottom and use a nut on the top of the spindle to add some preload/adjustment etc.....not a good layout as the thermal expansion and contraction plays havoc with the bearings.

You are right in the spline having an odd OD as a spline only fits on the sides of the keys never on the top or bottom of the grooves.

This is the same as for a keyway in a bore....always clear on the top of the key, but tight on the sides to resist hammering the key way out of shape with load reversal.

If you measure the OD of the spline you'll probably find it's about .010" under a standard size.
Ian.

[mactec54]

Hi, as you were "reinventing" the top bearing layout you could have opted to have two smaller deep groove sealed radials as they are taking the whole side loading from the belt drive and having the bore insert in the form of a cup with the two bearings floating axially in it.

Why ( 2 ) Bearings, when ( 1 ) is all it will ever need,He could not of used a smaller Bearing as well, you should read what is in the other posts, what he has done, is a perfect mod to support the top of the spindle for the belt drive conversion

[cowanrg]

Yeah, I'm not sure how two bearings would have helped here. The only thing I was trying to do was support the spindle where the pulley attaches. It ran fine without it though, but it's probably better to have one.

[handlewanker]

Why ( 2 ) Bearings, when ( 1 ) is all it will ever need,He could not of used a smaller Bearing as well, you should read what is in the other posts, what he has done, is a perfect mod to support the top of the spindle for the belt drive conversion

Because Mac.......this is one area where the maximum side loading will occur from the pull of the belt as opposed to just being the top of the spindle support........if the top bearing wears a bit it will impinge on the ability of the spindle to remain rotating concentrically, and the long leverage aspect ratio of a loose top bearing will immediately show on the cutter.......it will also extend the working life of the top bearing(s) in this area where you really don't want to have trouble, especially as he now intends to apply side forces to the spindle.

As I said, you can have a cup type insert to house two bearings......both of the SAME type and size a floating fit in the cup, one on top of the other.........how you misunderstood that I'll not know.......do you want as sketch?

I have a jig borer with a similar type of head and quill layout....... and having a quill I toyed with the idea of replacing it with bearings directly in the quill bore.......now superseded with other preferences.

But.....the jig borer has a separate top bearing housing that carries the driven pulley and that supports the splined spindle too as it moves up and down, and removed any direct side thrust to the spindle.

BTW........it is not a perfect mod, as the spindle top support bearing is now being forced to resist the side loading from the belt........that is extremely bad design in a milling spindle......more akin to a drilling machine design.
Ian.

[cowanrg]

I'm honestly really confused here. What forces do you think the belt will exert on the spindle? Putting my full weight into it, I can't deflect it more than a couple thousandths. the belt has much less tension than that. side load is being supported by AC bearings in the quill portion.

[handlewanker]

BTW........while on the subject of side loading from a belt drive...........I think that the SVM-0 mill that I am buying from Skyfire has this layout in the ISO-20 milling spindle so in my opinion, the bearing layout for that design would need to have definite characteristics that resisted the loading from the belt drive.

Any wear in the top bearing of a spindle will eventually make the spindle run wobbly at the cutter, even if the bottom angular contact bearings are still good...... the quoted collet run out figures would become null and void then.
Ian.

[cowanrg]

The bearing I used is good for a 7150N load, or 1600+ pounds (static). I'm not sure how maybe ~50 pounds of tension from the belt will wear out the bearing...