I have a Dumore model 16-021 drill press*. There is some float between
the 2 pieces of the motor case, with springs to keep things snug. The
fitting of the 2 pieces affects the bearing alignment and the end forces
on them.

To adjustment the fit I've just been running it while turning the screws
and listening. I'm going for the highest, quiet speed. This works, I
guess, but I'm thinking that there has to be a more methodical way.
Does anybody know such a way?

Thanks,
Bob

* - http://www.dumorecorp.com/docs/Serie...nual-parts.pdf

I don't know if there is a particular procedure for alignment of the parts,
but I expect that the springs around the case screws are primarily intended
to keep the field assembly in place, since there are no screws for this
purpose.

My lower case end has wave washers (#5 Flat Spring in the parts
illustration) in the bearing bore, which will place a small (upward) force
against the bottom of the lower bearing.. providing a preload on the ball
bearings (both of 'em).
There is no end play in the spindle, and having the wave washer as it is,
the spindle can't creep upward into the upper housing as the drill is fed
into the workpiece (essentially zero end play).
Wave washers are typically used in motors to allow for expansion of the
armature/rotor materials as heat is generated.

In my model 16, the case screws are just snugged to seat the machined step
of the lower case into the machined step in the edge of the upper housing.

I suppose the motor will run faster with no preload on the bearings, but it
appears that the preload is intentional.

The upper and lower bearings are a slight interference fit in the case
halves, and the firm pressure of the wave washer keeps the spindle/armature
assembly pushed upward, with the outer race of the upper ball bearing seated
in the upper case counterbore.

If your model is running slow, I'd suspect that the lube in the bearings may
be dried out.

When I assemble motors after inspection/cleaning/repairs, I give the case
end or end bells a thump/whack with a chunk-o-wood or plastic screwdriver
handle equivalent, to align the case sections and bearings, which generally
always works very well.

FWIW, any time I remove motor brushes, I keep them separated so I know which
one goes where (left or right) and I make a small scratch mark on the flat
surface that faces up (or the end) so I can replace them in their original
orientation.

--
WB
..........


"Bob Engelhardt" wrote in message
...
I have a Dumore model 16-021 drill press*. There is some float between the
2 pieces of the motor case, with springs to keep things snug. The fitting
of the 2 pieces affects the bearing alignment and the end forces on them.

To adjustment the fit I've just been running it while turning the screws
and listening. I'm going for the highest, quiet speed. This works, I
guess, but I'm thinking that there has to be a more methodical way. Does
anybody know such a way?

Thanks,
Bob

* - http://www.dumorecorp.com/docs/Serie...nual-parts.pdf

On Nov 29, 6:47*pm, Bob Engelhardt wrote:
I have a Dumore model 16-021 drill press*. *There is some float between
the 2 pieces of the motor case, with springs to keep things snug. *The
fitting of the 2 pieces affects the bearing alignment and the end forces
on them.

To adjustment the fit I've just been running it while turning the screws
and listening. *I'm going for the highest, quiet speed. *This works, I
guess, but I'm thinking that there has to be a more methodical way.
Does anybody know such a way?

Thanks,
Bob

* -http://www.dumorecorp.com/docs/Series_16_manual-parts.pdf

I would guess that the factory had a dedicated fixture or procedure
for this. Besides using a tachometer, maybe an ammeter could give a
better indication of your best alignment. (While the Loctite is curing
on the screws.)

I've been a long time replying, but I just got back to the Dumore. (So
many projects, so little time.)

Wild_Bill wrote:
I don't know if there is a particular procedure for alignment of the
parts, but I expect that the springs around the case screws are
primarily intended to keep the field assembly in place, since there are
no screws for this purpose.

Oh yeah, that makes sense. I couldn't figure what they were for & when
it ran slow, except when the screws were loosened, I jumped to the
conclusion that they were adjustments.

...
In my model 16, the case screws are just snugged to seat the machined
step of the lower case into the machined step in the edge of the upper
housing.

That's what I did now.

...
If your model is running slow, I'd suspect that the lube in the bearings
may be dried out.

Could be, but they're sealed, so they'd have to be replaced. I can live
with the slower speed (14,000 vs. 17,000 spec).

When I assemble motors after inspection/cleaning/repairs, I give the
case end or end bells a thump/whack with a chunk-o-wood or plastic
screwdriver handle equivalent, to align the case sections and bearings,
which generally always works very well.

I used a plastic faced dead blow hammer, so as to not scratch my new
paint G. Didn't make a difference - I think you're right about it
being the bearings.

FWIW, any time I remove motor brushes, I keep them separated so I know
which one goes where (left or right) and I make a small scratch mark on
the flat surface that faces up (or the end) so I can replace them in
their original orientation.

Me too. They'd probably re-seat themselves anyhow, but why not.

Thanks,
Bob

On Mon, 13 Dec 2010 21:06:24 -0500, Bob Engelhardt
wrote:

...
If your model is running slow, I'd suspect that the lube in the bearings
may be dried out.

Could be, but they're sealed, so they'd have to be replaced. I can live
with the slower speed (14,000 vs. 17,000 spec).

Actually..they can have the seals on one side removed, then greased,
then put back in, open side facing the rotor. And if they are metal
shielded..you can put the shield back in if you were gental about
removing it.

Gunner

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Gunner Asch wrote:
Actually..they can have the seals on one side removed, then greased,
then put back in, open side facing the rotor. And if they are metal
shielded..you can put the shield back in if you were gental about
removing it.

Thanks - good to know. I don't think that I'll be doing it on the
Dumore, but I'm sure that there'll be other opportunities.

Bob

The springs around the case screws are the same in an old Dumore flex shaft
motor I have, which looks to be from the 1930s-40s, in that the springs
serve to hold the field assembly in place.

The bearings in my model 16 are shielded as many high speed bearings are,
rather than sealed, which are often used for slower bearings.
You may have noticed that the bearing type is different from ordinary,
flat-sided small ball bearings, although I haven't looked up why these
bearings are constructed differently (but I suppose it's due to the thrust
and preload aspects in this application).

I routinely clean the sides shielded bearings, and apply a drop of
lightweight oil (Pennzbell TO-32 GP oil in a zoom-sout bottle for fractional
HP motor bearings) to the seam on the top side where the shield meets the
inner race, and then manually rotate the bearing while watching the oil work
it's way into the bearing's inner cavity.

This practice rarely has a negative effect on a ball bearing assembly that
is in good mechanical condition, and nearly always improves the bearings'
performance.. but adding a couple of drops of oil can risk carrying a spec
of dirt past the shields, so the pre-cleaning step is important.

--
WB
..........


"Bob Engelhardt" wrote in message
...
I've been a long time replying, but I just got back to the Dumore. (So
many projects, so little time.)

Wild_Bill wrote:
I don't know if there is a particular procedure for alignment of the
parts, but I expect that the springs around the case screws are primarily
intended to keep the field assembly in place, since there are no screws
for this purpose.

Oh yeah, that makes sense. I couldn't figure what they were for & when it
ran slow, except when the screws were loosened, I jumped to the conclusion
that they were adjustments.

...
In my model 16, the case screws are just snugged to seat the machined
step of the lower case into the machined step in the edge of the upper
housing.

That's what I did now.

...
If your model is running slow, I'd suspect that the lube in the bearings
may be dried out.

Could be, but they're sealed, so they'd have to be replaced. I can live
with the slower speed (14,000 vs. 17,000 spec).

When I assemble motors after inspection/cleaning/repairs, I give the case
end or end bells a thump/whack with a chunk-o-wood or plastic screwdriver
handle equivalent, to align the case sections and bearings, which
generally always works very well.

I used a plastic faced dead blow hammer, so as to not scratch my new paint
G. Didn't make a difference - I think you're right about it being the
bearings.

FWIW, any time I remove motor brushes, I keep them separated so I know
which one goes where (left or right) and I make a small scratch mark on
the flat surface that faces up (or the end) so I can replace them in
their original orientation.

Me too. They'd probably re-seat themselves anyhow, but why not.

Thanks,
Bob