How tu build a nut for the shaft of this stepper? Disassembling is not possible.

[atferrari]

My brother asked for help to build a nut moving along the shaft. Has to be a nut not something applying pressure on the groove.

I have disassembled some of these steppers in the past but never got them back in the original condition.

 

[Musicmanager]

Hola AT ..

You do see the 'nuts' appear on Ebay from time to time although I couldn't see any this morning.

It may be easier to replace the whole thing .. viz . https://www.aliexpress.com/item/33002325876.html?

S

 

[atferrari]

Buying anything coming from abroad in this country could end in disappointment and frustration. Has been like that for decades.

That would be the simplest thing. Thanks MM.

 

[JimB]

Hola AT.

I don't know what machining facilities you have available, but consider this:

A pair of "half nuts" which have been bored out to be a close fit to the threaded shaft.
The nuts themselves will be a sliding fit on the shaft, not gripping it in any way.

In one of the nuts, drill a hole which will accept a ball bearing which fits closely into the thread of the shaft, such that half of the ball is in the thread and half in the half nut.

Does this make sense, or should I create a sketch?

JimB


Pair of half nuts ?
JimB and MM ??

 

[atferrari]

Please Jim, a sketch would be better for me.
Gracias.

 

[JimB]

OK lets try this:

With humble apologies to:
Mr Beardmore of RCET
BS308 and it successors.

JimB

 

[JimB]

I am just showing the lower half nut in isometric (?) projection.
The little ball will need to be secured and possibly spring loaded into it little hole.

JimB

 

[atferrari]

Thanks Jim. Quite simple and, I hope, doable for me.
Maybe the most difficult is to get the right diameter bearing ball.

 

[Nigel Goodwin]

Isn't this just a CD/DVD mech?, strip another one to get the part you require.

 

[atferrari]

It comes from floppy drive. No nut, just a teflon piece working on the groove, under the pressure of a spring. Not the needed nut.

 

[MaxHeadRoom78]

Is this an effort to simulate a machine/CNC ball-screw?
If so, and depending on the loading and application, you could possible use a block such as suggested in the DWG, and use two halves with some epoxy/body filler to cast a mold in each side using the screw itself, with suitable grease, it could work.
Thin shim could be used between the halves to control the right pressure/backlash.
e.g.

Max.

 

[atferrari]

Is this an effort to simulate a machine/CNC ball-screw?
If so, and depending on the loading and application, you could possible use a block such as suggested in the DWG, and use two halves with some epoxy/body filler to cast a mold in each side using the screw itself, with suitable grease, it could work.
Thin shim could be used between the halves to control the right pressure/backlash.
e.g.

Max.

Yesterday I did something like that using cold porcelain (the one used for modeling) but after almost 24 hours it has not dried up completely. Maybe because vaseline impregnated each half too much.

Maybe, I have to wait another 24 hrs.

 

[MaxHeadRoom78]

I'm thinking the metalzed epoxy would be more durable and resistant to wear?
Max.

 

[Les Jones]

It is not a normal nut that is used with this thread.

This is a picture from above showing the "nut assembly" You can just see the end of the rod mounted in the plastic molding above the helix. This rod engages with the groove in the helix. You can also see the flat spring that holds the rod in engagement with the groove.

This picture shows a view from underneath using a small mirror. These pictures are of the stepper assembly
show it in a 3.5" floppy drive where it moves the head.

You would have a more suitable stepper assembly from a 5.25" or 8" floppy drive. Even one from an 8" drive would not be very powerful.

Les.

 

[Les Jones]

After re reading the thread I realise that you want to make a normal type of nut, Here is a link to a possible method that has been suggested for making a half nut for a lathe. It could work with the floppy drive thread. I suspect even if you make a normal type of nut there will be too much friction for the stepper motor.

Les.

 

[atferrari]

Thanks for the tips and suggestions. My pieces are slowly drying and it seems that they fit well on the shaft. Anyway, a valid test would be done tomorrow.
Hand tremor and lack of mechanical dexterity, bad combination.