Re: Step resolution question, dividing head

Jan,

I've seen some small rotary tables, where they've removed the handles,
and driven them with steppers. Always direct, so I'd have to agree with
you there. 720K, not that's a LOT of steps! Sounds like it must have
been a compound drive (two worms?). That's past me!

I think John's got it worked out now, lotsa steps with the "micro
stepper", we'll see! I hope he posts pix when he's done.

Alan KM6VV

JanRwl@... wrote:

>
> Alan:
>
> I am only a hobbiest when it comes to "being a machine-shop", but I did some
> stepper-driver electronics for a "professional" machine-shop 15 years back,
> and they attached a size-34 stepper to a "dividing head", but as I recall,
> they put the motor "in place of" the handwheel/crank the dividing-head CAME
> with, and it had something like a 10-turn-per-degree ratio, as I recall.
> That is, one had to turn the crank 10 turns to get ONE degree out of the
> chuck on the head. In other words, to make exactly one turn of the
> dividing-head, the stepper had to step 720,000 steps. Or something like
> that. I didn't keep the info, as it was a "one-timer" for that one firm, and
> they went away with the "whole thing", so no point in keeping such details
> (they did the "hardware work", anyway).
>
> I admit I have no clue if "store-bought" dividing-heads have handwheels,
> ratios, gears, nor what; or, if some are made "to order", or whatever. I see
> talk of pulleys and timing-belts (toothed belts) in this group, and that
> makes me wonder, HOW tight folks expect to MAKE that, cause the
> "tensioning-up" when starting/reversing would equal a step or several, it
> seems to me! Tight gears, maybe, but a rubber belt, even with "teeth"???
> Nah... Direct-drive! Or, tightly-loaded Berg cable-chain stuff. (No
> backlash kinda stuff. Expensive, but "right"!)
>
> Hmmm... Will be interesting to continue reading comments on this
> thread...
>
> Jan Rowland, Troll