DIYbanter - View Single Post - FA: Dumore Tool Post Grinder Inserts, K.O. Lee Index Disc and other metalworking items on Ebay

In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[snip]
Right -- but that should not make any difference. Perhaps the
difference in the motor bearings is because only the pulley end of the
motor experiences side loads, while both ends of the spindle do.

Or -- the bearings *may* be identical. :-)

I haven't had the motor apart, so have no opinion.

And while I have had my motor apart -- the bearing at the pulley
end did not want to come out of the housing, and I did not want to try
too hard while I was working on other things.

I assume it is designed to allow removal at least.

It may depend on what you call "removable". Certainly the ones
which started this thread were designed to screw into a hollow spindle
with a taper, based on the photos. (Hmm ... has that auction
closed, yet? :-)

I think that the hollow spindle is a later design.

O.K. But the manual does show that for this model at least, the
same spindle is used for both larger wheels and smaller mounted ones
--
with a screw-on single-sized collet adaptor.

Yes. It appears to be the earlier design. The hollow spindle design
allows one to change the business end without disassembling the
grinder.

Right -- but you can change the business end with the screw-on
"chuck" just as easily.

True, but replacing the whole spindle is faster, and works even for
holes smaller than the spindle diameter. Quick change seems to be the
issue.

That depends on what you call "the whole spindle". If you mean
from the pulley to the stone mount, I would suggest that the "chuck"
(really a single-size collet" which screws onto the arbor in place of
the normal stone and its end plates (and possible centering adaptors as
well -- as is the case with my stones)) is quicker to screw onto the end
of the spindle than changing the *whole* spindle, involving removing the
pulley, both bearing caps, spacers, and bearings, withdrawing the
spindle, and replacing it with a different spindle with all of the
bearings and such (risking exposing the bearings to grit in the process)
is much more trouble prone than screwing on the "chuck".

I meant the conical thing to which the stone is attached.

The "chuck" is designed to accept stones with 1/8" shanks, and
there were several in the case with the grinder (but no chuck -- so I
just finished making a replacement as close to the original as I could
manage). A couple of those stones even were as large as 1-3/4", and the
shank was closer to 3/16" or maybe even 1/4", stepping down to 1/8"
(actually, slightly oversized at 0.126"). Those last ones would not fit
into the reamed hole in the chuck-in-progress, but once I slit it with
two slits at right angles, the stresses opened it enough so those
stones dropped right in.

The one real advantage which I can see to the design implied by
the screw-in ends for the hollow spindles is that a stone can stay
mounted on its arbor, and will not need to be re-trued when it is
re-mounted, if the stone has little enough wear.

I think that's the reason to do it this way. The assembly with bearings
and pulleys seems quite expensive, ~$1,000. I assume (hope) that the
removable part is cheaper. But I don't know that I understand their
pricing structure.

And -- I think that I'll also make a support collar so it will
be easy to restore to the proper height each time, since this is the
only lathe which I expect to use it on. It seems a bit too big for the
little Emco-Maier Compact-5/CNC -- a 5" swing machine. :-)

Right. Now, Ill have to get a big enough lathe.

O.K. Good luck with that. I've been known to collect
accessories when I could, in hopes of acquiring a machine with which
they could be used later.

But did you inherit a tool that caused lathe acquisition?

The thing is that most flashlamps use external trigger -- a wire
wrapped around the outside of the envelope. This one, however, has
internal trigger electrodes, and may operate with a much lower trigger
voltage.

I think that the trigger is 4KV, but such things are far from critical.
I recently built a special-purpose strobe (for illuminating a coil
winder in motion), and couldn't initially get the right parts, using a
trigger transformer that was too weak for the right flashtube, and a
flashtube that required more trigger voltage than the correct tube, the
net deficit being (2:1)(6:4)= 3:1.

It worked anyway, albeit with the occasional misfire. When I rewired it
to double the trigger voltage, the misfires went away. This is with new
tubes. The problems will occur later, as things age. (I now have the
correct flashtube.) This uses an ordinary cheap flashtube, and runs at
up to about 40 Hz (2,400 rpm).

A bigger issue is how fast the tube deionizes. If it isn't fast enough,
one cannot flash the tube fast enough, as it stops flashing and instead
remains always on. Deionization time is mostly determined by flash tube
design.

This may be one of the reasons for the internal trigger
electrodes, and the extra volume (of unionized xenon) to quickly replace
the ionized stuff.

Exactly. It's the nearby masses of metal that does the job.

If it does not deionize quickly enough, and the capacitor
charging current is high enough, it will indeed remain on full time.
Part of the problem is the deionization time, part is the voltage to
which the tube discharges the capacitor.

Edgerton's book "Flash, Strobe" goes into the details of how the
Strobotac and allied devices work.

I have a question in at Perkin-Elmer asking if the FX-6A is still made,
and if not what is it's replacement (perhaps Series 1100), and what they
cost. We shall see.

O.K. Good luck.

So far, no response.

The only other current auction is # 7607451350 -- one of the
older ones, with a less bright flash lamp, and (IIRC) a much lower speed
limit. None of the photos are from an orientation to show the
"soupbowl" reflector -- which may suggest problems with it. Normally, I
would expect, even from the views show, the bulge of the large crystal
to be visible. Since it is not -- it may be broken. And while it
*looks* like a GR unit from the views given -- it may not be by GR --
they say "Electric Brazing" -- which may have been a secondary
contract manufacturer during wartime or something similar.

I saw that one. Never heard of the company.

Nor did I. But it looks like one of the wartime unknowns which
got contracts to make a product known to come from a larger company --
simply because they could not turn them out in the quantities needed.
I've seen Tektronix scope clones made under such contracts -- they
looked almost identical to the Tektronix, other than the maker's name.

Yes. Don't know how good a job they did.

Sam Goldwasser has published a circuit for a three-range strobe that
goes to 6,000 flashes per second. Search for "strobex.pdf". This
circuit could achieve 25,000 fpm with the right tube, and some circuit
adjustments.

O.K. Part of the problem, of course, is stability of the
timebase. A really good one could be made with a crystal oscillator, a
bunch of counter chips and comparators -- load in a count (period, not
frequency) and it would be very stable. Even the nice little GR
Strobotac which I have drifts for the first minute or so. And that one
is solid state. The older (soupbowl) one takes longer to stabilize, and
it is run from tubes.

Yes. The strobe I built is triggered by an optical encoder on the
winder's main axle, so the image stands absolutely still as the rotation
rate is varied.

I can understand ditching the repair parts after 50 years, but how much
trouble would it have been to scan and post the old manuals? These old
units are quite well made, and so will always be with us.

They used to make them available -- for free. (At least the one
for the drill grinder was free.) They seem to have tossed all of the
old parts and manuals now.

Annoying.

Indeed so.

[ ... ]

But -- I'm not going to complain when he didn't have to do this
at all. I'm just passing on thanks.

True enough. If he wishes, he can email to me, and I will post the
files for him. I have no 30K limit. He can email to me, and I will
post the files. The email address above is real.

As you already know -- he has scanned them to a higher
resolution, and put them in his private web space.

I got it; looks good.

Joe Gwinn