Re: Bender question (long reply)

John,

Just want to add that the 16mm rail spacing was set by the existing
holes in the blade. The leadscrew spacing was determined by
the "natural" chain length (#25) that was closest to the rail width,
but still larger than, so as not to cause interference.

IOW, there's no idler to tighten up the chain. And no need for one
IMO. As another posted, you always go past and return to your gauge
point. So any chain backlash is of no consequence.

Not sure if it shows in the pics, but the UHMW where the 1/4-20 goes
through is counterdrilled to make the "nuts" shorter. 1/4-20
allthread going through 2 inches of UHMW is/was just too much
friction. The stepper shown is V2: the first was a 5v,1A round body
type common in those days and only 35-50 oz.in.!

Ballendo

P.S. I'd raid old copiers for chain and sprockets before I'd use
timing belts for this... IMO there's a reason thwe commercial units
all use chains; they could easily afford to use timing belts
instead. Chain is far more forgiving in this app..

P.P.S. So much for JCK's claim of being the first to use 1/4-20
allthread for CNC. <G>

--- In CAD_CAM_EDM_DRO@yahoogroups.com, John Dammeyer <johnd@...>
wrote:

>
> Thanks Ballendo. Ingenious! It's so simple.
>
> But why is your minimum sheer size so large (I think you said

1.5")? Can't

> the bracket below be made so that you can chop 0.125" or are there

some

> interference issues.
>