Re: Wigglers and Tricks

Hi Ballendo,

Thanks for the ideas. I like the palette, however I'm not making
multiple parts at this time. Seems no two setups are the same.

I suspect I may get some slippage in Y if I go either way too far, and
that's not too far on this old Sears/Sherline! I've been watching the
end of the Y lead screw, and it squeaks when I get near the end. It's
new, installed when I CNC-retrofitted the mill. I also notice that the
end "wobbles" a little, too. Bad news. I'm still "assessing" how good
these motors, etc. drive the ways. Z is still a concern to me.

Interesting to find out that there are indeed "bomb sights" for
mill/lathe use. Now if I'd thought of that 20, 30 or so years ago...

Alan

ballendo@... wrote:

>
> Alan,
>
> There are both types.(msg reprinted below)
> I'm pretty sure Joe was speaking of the "line intersection" type.
>
> The second type is used like your "bomb sight", and does indeed have
> a mirror(well, usually a prism) so you can peer in from the side.It's
> placed into the cutter collet/check/etc.(It's AS IF you pulled the
> drawbar out of your mill, got on a ladder and looked thru the bore to
> see. Yes, they do have a set of alignment graticules (designed for
> locating to holes, edges,etc.)
>
> You can find both types in the MSC,ENCO, and other metalworking
> catalogs. The optical center punch is ~50 bucks. The other type is
> more like ~$2-300.
>
> Ballendo
>
> P.S. You have been asking about getting/using a Reference point on
> your sherline. A few thoughts:
>
> You can set up a "pallet" system using tooling plates(this is just a
> fancy name for a sub-bed fixture). Put a semi-permanent round stop in
> one of your t-slots at an appropriate point for the work you do(use a
> metal cylinder,t-nut and 10-32 screw). Now when you fasten one of
> these tooling plates(which has your work mounted to it) be sure to
> place it against the stop(locates in X) and flush with the back of
> the sherline table(or front, locates in Y).
>
> If you make, or buy(Joe, at sherline sells 'em) several of these
> plates, you can easily place parts in known position quickly.
>
> Of course, this assumes your mill drives have not slipped! You said
> you don't have limit/home switches on your s/l mill. NO problem. IMO,
> putting limit switches on a s/l is "gilding the lilly" or making a
> "silk purse from the sows' ear". The s/l typically does not have
> enough force to cause any REAL problems to itself(the reason for
> limit switches)After all, the OTHER reason for limit switches is to
> recover from poor programming, and we don't have to worry about that!
> :-)
>
> So let's use a property of steppers to advantage. DON'T do this with
> servos! Simply drive the mill against a stop(this can be the 10-32
> screws used by s/l for end of travel, or certain length block(s) of
> matal(to get the "home" where you want it). Don't continue to jog
> more than necessary to ensure you are fully AGAINST the stop(s).
> Steppers are not hurt by a stalled condition. step a known distance
> "off" the blocks/endstops and clear the cnc counters. Voila,
> repeatable "home position".
>
> Once you have learned your machines' capabilities and limitations,
> you will be in a better position(pun intended) to assess how often
> you need to ck whether "home" still is!?
>
> '******************************************************************
> Joe,
> An optical center punch? is this to align the spindle or to punch the
> intersection of scribed lines? I started to think there was a
> "periscope" type device that chucked up in the collet, and "peered"
> down
> at the work, giving some sort of alignment gradicule. I wonder if
> something like that would be practical? I have a "bomb site" for an
> old
> HP 7475, etc. plotter; if one could add a mirror at 45deg., and mount
> the whole thing, it might be useful.

Ah, the dreaded advertisements!!!!

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