[jsheerin]

Yeah, you need some thrust bearings in there somewhere. It could be back to back deep groove bearings, it could be a single radial bearing like you have with flat thrust bearings, but I would be worried about the setup as you have it now.

[Harpye]

Hmmm you have a 1 m long thread made from steel ?

you have a parallel basement made from Aluminium?

You want to use just and only axial bearings both ends to fix the thread in between?
A) B)
Expansion coefficient of Aluminium 23.5*10-6/K
means that a 1m long Alu - bar is changing its absolute length about 0.000235m by 10 K delta on ambient Temperature
Expansion coefficient of steel 11.5*10-6/K so the thread is changing its length by 0.000115m on same ambient temperature delta

= > effective expansion delta would be about 0.12mm for that Temperaturechange ( I hope, I took the right coefficient from the web - if not I beg your pardon)

An Axial bearing would get about 0.12mm axial play -> but the radial play would be factors larger so the thread without radial support - in anyway would loose the coaxial position ( if not supported radial) within both bearing rings .... what would decrease the bearing life time cycle to rather 0 ( however you would have to additionally install a radial bearing - which could be your skater bearing if it would be designed in properly

c) applying thrust from both sides will bend the thread so proper function and performance will be away - stick, slip and wear out will rule ...

( hope I understood you right ... see picture below...)


=> A) and B) are the reason to work with a fix side bearing and a loose side bearing to keep the distance between the fixations in both direction as short as possible not to deal with temperature and expansion in that way... Different expansions become critical when the thread is getting loose as shown above or the tension caused by expansion effects is forcing the bearing to damage by pressing the balls together ...

[Drools]

Thanks for all the replies everyone. I think I understand what you are saying Harpye.
I think my setup just might be able to use a setup similar to Gerry's without too many modifications. I could thread the 1/4" ends of my screws and use a 1/4" ID bearing? I just happen to have several 1/4" ID bearings like the ones in the pictures. If I were to thread the ends how much material would I loose? I still need to use the 1/4" couplers I have.
I want to do this with as little modification to the existing setup as possible. Ideas on how to do this are welcome.
Thanks for the help everyone.

[ger21]

Mine are on the other end of the screws. On the motor end, I have a single bearing like you.

[Drools]

Thanks Gerry, but would it work on the motor end? I have lots of material to work with on this end and little on the other.

[Harpye]

in principle a fix side bearing on the other spindle end works but

A) what is an ID bearing?


if it is a radial one your spindle has axial play and so would affect and damage the motor bering due to axial load !

if it is a radial one and it is mounted on the Motor side it would have thesame effect..

the motor bearings are under tension so they are not allowed to have play --- so while the single thread bearing is in play the coupling has to have also EASY axial play ( even when engaged to cut what is impossible to specify duet to friction / surface roughness and wearout over the life time cycle)

using two radial bearings you have the possibility to work without play for light loads but .. assembly would need rather high tec tools not to kill the bearings by tightening the nut which pulls them toogether too hard

BUt light loads mean that you motor and thread transmission could easily damage the bearings for example by a hard engagement in the working plate - one time more force applied than specified in the datasheet the bearing races are pitted by the balls..... this means damage and possible blocking ...

[Harpye]

Some approach to fix your problem - But that is all not the best - If I were you I would catch another piece of thread to make it right!!

[Harpye]

In my case - I'd still recommend the right bearing for the right app - I use the 7200 10x30 x9 diagonals and my machine has still no issues even when cutting this...

THe part above is fine plainned Alu

- the knife below is 1.28.42 Chrome Vanadin tooling steel