screw thread mounting without machined ends

[Action-KAT]

Is there an alternative fixing method for Acme screw threads that doesn't need them to be machined.
I have found a supplier of threads at a great price but the end machining cost makes them to dear,
so i am trying to find a way to mount them without having to have the ends machined.
any input would be helpful

[LeeWay]

It is doable I think. It may not be a perfect setup, but you can do it.
I use pillow block bearings on my ball screws on the router. My screws are turned down, but if you get a good fitting bearing with an eccentric locking collar, it would work. You would need a larger coupling to the motor also. That part will be the hard one to find. You could drill a hole in the end of the screw and then insert the small shaft of the motor assuming the Acme is large enough. That would be difficult to do without a lathe. If you had a lathe, then you wouldn't need to worry about turning them down though. A minilathe will do acme rod just fine.

[CncLite1]

what size Acme's ?? OD that is

what is driving them ??

[ger21]

This might help.

http://www.cncrouterparts.com/parts.html

[Action-KAT]

Thanks Leeway for your input might be a lot of hassell but a good cost saving.

cnclite1 :- i will be looking at 16mm / 20mm

Thanks gerry that gives me food for thought i will have to have a good look around for parts that will work.

yhanks for all the input

[BEARINGMAN]

Leeway

you sugested eccentric collar bearings (usually Fafnir (now Timken)) but they should only be used for non-reversing loads. What you should use here is Sealmaster($$$$) McGill, or Dodge with the squeeze-lock collars. The eccentric will come loose with the inertia of the reversing load, where the squeeze-lock type grips evenly around the shaft and won't come loose.

[Action-KAT]

Thanks for the feedback bearingman
but i am unsure what these bearings look like if you could pop a link so i know what i am looking for would bw a great help
many thanks for your help

[LeeWay]

Originally Posted by BEARINGMAN Leeway you sugested eccentric collar bearings (usually Fafnir (now Timken)) but they should only be used for non-reversing loads. What you should use here is Sealmaster($$$$) McGill, or Dodge with the squeeze-lock collars. The eccentric will come loose with the inertia of the reversing load, where the squeeze-lock type grips evenly around the shaft and won't come loose.

You are correct of course. No where near optimal and not normally good for CNC. I use a bearing on both ends of my X a=on my router. I locked them both and was getting issues with the lazy end coming loose at the collar. I pulled the collar and used a couple wave washers between the journal and the bearing and I no longer have the collar on the other end loosening up.

On my Y axis, I use the same type bearing, but flange style. The other end of it though is a bronze flanged bushing also with wave washers. These have to be adjusted periodically and are not maint. free, but induce only little play and within my tolerances. For the ease of installation and low initial cost, I feel it was a fair trade off.
I had intended to build new mounts with proper bearings and will likely do that now that I have my mill running, but it's not critical for me right now because it is working so well. The most play I have measured on the router after it was tuned was .008" and that was before I installed the second ball nuts.


Here is a link to pillow blocks. These don't have the eccentric collar and would like work well with a set screw inserted into the screw.

Here are the flanged type I used.


Here are the 4 bolt flange type.

If you have plenty of screw and room, you could mount the flange bearings back to back on a plate with a spring in between and would have a decent setup.



One other thing, since you won't be turning journals on the screws, you can lock these bearings in place on the shafts using a locking nut configuration on both sides. 4 nuts total. Takes some real estate, but works pretty well.

[BEARINGMAN]

Here is a link to an example of one of the units I mentioned. Advise-- SHOP AROUND.
http://www.applied.com/apps/commerce...169&r=0&type=a
To look up sources in the yellow pages, look under POWER TRANSMISSION EQUIPMENT.

[Action-KAT]

Many thanks again for the input guys,
I think leeway has the better option to suit my needs as this will be my first build and cost is at a premium,
that’s why getting the ends turned down is not an option at this stage.
I want to build as cheap as possible but not to cheap as to sacrifice quality, you know the story
thanks again