Re: [CAD_CAM_EDM_DRO] Re: Couplings

I would tend to dis-agree here. There are a vast number of units out
here that use the type pictured in the auction. mine ( a FIREBALL V90
router) uses brass ones.
It seems to me that if there is a danger of the lead screw mis-aligned
so much that it might break the stepper motor shaft, then something is
very wrong and should be fixed. My unit has worked 100's of hours with
out a problem.

OLD BOB

Andrew Werby wrote:

>
> "Alfredo Sola" alfredo@... <mailto:alfredo%40sola.es> alfredosola
> wrote: Good day Johann et
> al, Following your advice on couplings, I found this. It's Chinese but
> looks pretty decent:
> <http://cgi.ebay.de/3x-Kupplung-Drehstarre-fuer-Schrittmotor-1-4-NEU_W0QQitemZ160382401978QQcmdZViewItemQQptZMotoren_Getriebe?hash=item2557893dba#ht_3281wt_912
> <http://cgi.ebay.de/3x-Kupplung-Drehstarre-fuer-Schrittmotor-1-4-NEU_W0QQitemZ160382401978QQcmdZViewItemQQptZMotoren_Getriebe?hash=item2557893dba#ht_3281wt_912>>
>
> Also the price can't be beaten at 9,90 euros for 3 units! what do you
> think?
>
> Hi Alfredo;
>
> If those are meant to couple a motor to a leadscrew, I don't think much
> of them. Unless your alignment is absolutely perfect, a solid coupling
> like that can break the end off your motor, or the stem off your
> leadscrew. What you want for a situation like that is some kind of
> flexible coupling, which will allow for some imprecision in the
> positioning of the two shafts being joined. There are several basic
> designs for this sort of thing; such as the "Lovejoy" type, which has a
> pronged head for each shaft and a rubber "spider" that fits in between
> them, or one that has a helical slot cut in the middle, which acts like
> a spring, or one that has metal ends but a solid rubber center portion.
> The Taig mills I sell have metal cylinders on the end of the motors and
> leadscrews, which are bored with four facing holes with stiff nylon
> tubes making the connection. Any of these solutions would be better
> than what you're looking at on Ebay.
>
> Also, the simple set-screw attachment will tend to give you problems
> over time. A better design is the clamp-type connection, which uses a
> screw to compress the split end of the coupling over the shaft. This is
> less likely to loosen, and if it does, it won't make a gouge in your
> shaft that makes the coupling very difficult to remove. Yes, you can
> save some money going with those cheap solid couplings, but you'd be
> setting yourself up for losing a lot more down the line, not to mention
> the frustration factor of ruining parts and having to tear your machine
> apart to repair it and wait for parts to arrive before you can get back
> to work. I'm not sure who sells couplings in Europe, but I'm sure you
> can find some like this:
>
> http://www.anaheimautomation.com/products/coupling/flexible-coupling.php?tID=114&pt=t&cID=32
> <http://www.anaheimautomation.com/products/coupling/flexible-coupling.php?tID=114&pt=t&cID=32>
>
> Good luck;
>
> Andrew Werby
> www.computersculpture.com
>
>