Homebrew PCBs

>A flexible coupling will introduce error as
>the encoder in this example is on the motor shaft

That's why rigid couplings are preferred and being used in this case.

>Coaxial alignment of two shafts is at best an
>approximation irrespective of the machinist's
>savvy or methods.

Have you really looked at your advice and comments?....They're a 
hodge-podge of discrepancies....On one hand you're suggesting that 
one make their own encoder including the disk itself, and now here 
you seem to be critical of shafts aligned within the runout of the 
shafts themselves...Yes, plus or minus one or two thou is an 
approximation...In terms of specifications and tolerances, we live 
in an approximate world....LOL!

--- In Homebrew_PCBs@yahoogroups.com, uhmgawa <uhmgawa@m...> wrote:
> derekhawkins wrote:
> > Use shims and a dial indicator or use a flexible coupling. I 
prefer 
> > proper alignment and rigid couplings. Yeah, machining and metal 
> > working savvy is beneficial.
> 
> A flexible coupling will introduce error as
> the encoder in this example is on the motor shaft
> rather than the lead screw.
> 
> Coaxial alignment of two shafts is at best an
> approximation irrespective of the machinist's
> savvy or methods.
> 
> -- 
> uhmgawa@m...        www.gnu.org