Re: rigid coupling, stepper to leadscrew

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Tony Jeffree <tony@...> wrote:

> DO NOT assume that steppers are capable of handling end loads. All
>of the ones I have dealt with are not - their shafts are generally
>biased to the front by a spring washer at the back of the motor. If
>the end load is comparable to the spring force, the motor shaft/rotor
>will simply get pushed 1-2mm back into the motor housing.

Thanks Tony, that settles that! It makes me wonder what the guy
selling item 330005256358 on ebay is up to.

> That would work fine - as would a pair of back to back ball races.

I spent some time looking at bearings last night and I think I am
going for a 10mm ID needle roller, the type with an insert, this is
only 12mm long and 17mm OD, the smaller OD makes it easier for me (the
workshop at work is closed and I am not fully tooled up on my Emco
mill). This will be held partly by the casting once suitably bored
and partly by a 6mm thick plate. On either side of this assembly I
will add a axial needle roller bearing, these are only 2mm thick and
seem to be cheaper and have better specs in terms of speed and load
than the normal thrust bearings available. I'll thread the end of the
screw for a thin retaining nut and then turn it down for an oldham
coupling.

The alternative would be one thrust bearing and one conventional
bearing, there is no room for two conventional bearings unless the
whole thing is taken out of the casting, even then they tend to have
very large ODs and be quite thick when they have a 10mmID.

Graham