Linear Bearings provide any rotation or purely linear?

[raynerd]

Hello, I was hoping someone could give me some advice.

I`m making a small dividing head and the spindle has a 16mm hardened shaft. It is going to be a really tiny thing for a small machine and I`ve just found out that 16mm is not a standard ID for a ball bearing race!! However, I have found a linear bearing on ebay and not only that, in a housing as well...for the value of the bearing and the materials of the block, it seems great value however would be totally useless if it provides only linear motion and no rotation!!

http://www.ebay.co.uk/itm/CNC-Router-SC16UU-linear-ball-bearing-16mm-XYZ-table-/280803647994?pt=LH_DefaultDomain_15&hash=item416133a1fa

I don`t know how these work. If they are rollers then I guess it`ll be useless as it`ll only allow the spindle to slide along the bearing which would be useless as I don`t want it to do this....however, if they are ball bearings then it`ll provide rotation as well and I`m guessing it would work OK.

Any idea and sorry for the thick questions if there is something I`m missing more obvious!

[Swarfing]

Chris that will not i'm afraid as it is linear only, you can get 16mm bearings http://simplybearings.co.uk/shop/product_info.php?products_id=2744

But if you go that route then you will not have a shoulder on your spindle. Don't be afraid to have a go at try to use the lathe on that hardened shaft. It will probably only be case hardened and if you tool is sharp and you take it slow with plenty of coolant it will cut

[75Plus]

Chris, bearing # 6202/16 is 16mm ID and 35mm OD. X 11mm wide. # 6203/16 is the same ID but a is 40mm OD. and 12mm wide. Both are available on Ebay on this side of the pond. You may find them over there as well.

Joe

[Fergus OMore]

Why ANY sort of bearing?
Why use a solid spindle? Well, that is the way that I am interpreting it.

Ask the question- how long do plain cast iron bearings last with an unhardened spindle? For instance, the ones that ran in lathes -with motors belting them around.

Just the odd daft  question( or three).

Regards

F O'M

[raynerd]

Sorry F O M but I don`t really understand any of your questions or the point you are making!

Chris

[raynerd]

Just re-read it... are you trying to say as others have already suggested to me, just run it without bearings. To be honest, this was my original plan which is why someone kindly sent me the cast iron blocks.

Chris

[Fergus OMore]

Chris,
            I'm not JUST saying run it without bearings but questioning why you are going to use a hardened spindle.

I have a couple of DH's etc -without bearings. No problems.
However, I questioned why you wanted a hardened spindle. My stuff follows a pattern of creative thought( not me but the designers)
My Vertex came with a blank face plate and a three jaw chuck that had a Myford thread( which is suitable for me) but it came with a decent through bore and a No2 MT bore.  So I can:-
1. Fit Myford collets( Imperial)
2. Fit a No2 MT boring head, which bores but also does ball handles
3. Fit ER25 collets ( Metric really)
4. The Myford nose takes all the Myford goodies
5. The ER25's take my end mills and slot drills-- but go on the Clarkson for re-grinding

Re=grinding? Well, the Vertex also 'tips' into a 90 degree plane to act as a rotary table but does the 3 and 15 degree lands
Miner and I were prattling about 4 facet grinding as well.

Ok, it is getting a wee bit heady but the division plates on the George Thomas go onto the Myford headstock.
And of course, I have the micro adjustment to do damned near anything with holes.

Enough , eh? Well, enough for a dizzy old fart who was kicked out of school at 14 without a qualification.

Cheers

F O'M

[Lew_Merrick_PE]

Chris,

1) Most round shaft linear bearings will work as rotary bearings -- just not all that well.  The balls won't circulate as they will for linear action which means that dirt becomes more problematic as does lubrication.

2) Why not just a bronze bushing for your dividing head?  It isn't as if you have high speed rotation or loads that will exceed the compressive strength of bronze.  In point of fact, a longitudinal (internal, not reaching the ends) groove (something that can be freehanded with a rotary cutting tool) can act to distribute lubrication to your pivot axis.  The advantage of this is that the wear will take place in the (replaceable) bushing.

???

[Pete.]

My dividing head is just a plain old shaft running on cast iron. I don't know how old it is but I'd guess at least 40 years. Has a pinch bolt to hold it once it's set.

[DaveH]

Chris,
 It says ball bearing so it will be fine for what you want.

I really don't see why I should answer your question when it ships "world wide" except South Africa 

When you buy it ask the miserable bar steward why not to South Africa

Go for it Chris
 
DaveH

[raynerd]

Thanks for all the advice!

I just wanted to clear a few things up. I`m adapting a straight shaft ER16 collet chuck as a spindle so it already has a hardened ground shaft when purchased.  Fergus - I`m not choosing to use hardened steel, it just has a hardened steel shaft.

I`m going to go with some bushes for two reasons. The chuck is coming from china and so it`ll take a month or so to arrive. I have purchased already some bushes from a UK supplier which will allow me to get on with making the assembly and then I can just slide in the collet chuck when it arrives. Pete, I would actually just go with cast iron bore as we originally discussed but for the reason of simply getting on with it, I`m going to use the bushes as they will arrive tomorrow.