Re: Wigglers and Tricks

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.