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View Full Version : another project - poshin' up an old drill press



metalmagpie
01-05-2016, 12:53 AM
For many of you this will be old hat. But there are lots of pictures to keep you from getting too bored. :-)

Enjoy, and let me know what you think.

metalmagpie

http://www.nwnative.us/Grant/shop%20articles/drillPress20

vpt
01-05-2016, 09:17 AM
Looks very nice!

A couple thoughts, after balancing the motor assembly you then drilled holes and moved the set screw for the pulley, did you fill in the original hole to keep balance? Second thought, I am not sure how much force was needed to press the spindle and bearings into the housing but normally any time you press, pound, or drive any bearing you are supposed to only push on the mating race. In the picture it would have been the outer race of the bearing that should have been driven. Not sure if you are aware (if you are sorry for my assuming) that if you press on the race that is not being driven you risk dimpling the races/balls.

Tony
01-05-2016, 09:39 AM
nice!!

Doozer
01-05-2016, 11:03 AM
The hub where the 3 handles are threaded into is cast hollow.
Rethreading the holes is only a temporary fix.
I had a similar drill press, and thought it best to braze the handles
into the hub. This eliminates any chance of thread looseness working
and wallowing out the fit. These drill presses are classic for loose
handles.
The more conventional method of applying balance weight to an
armature, is to add appropriately sized washer(s) to the little zinc
tits cast circumferentially on the armature. The tits are then peened
to secure the washer(s). Also the tits can be broken off to take
weight away from the opposite side. This is how the factory adds
balance weight to the armature.
But after all that work, you might still have a single-phase motor that
hums and buzzes, something naturally inherent with single-phase motors.
This is not from balance, but from the ripple of 60Hz power. It tends to
resonate in the laminations of the motor. Motors of lesser quality do not
fix the laminations as securely, and the motor makes excessive noise.
It is rare that you find smooth single-phase motor. If I find one, I hold
on to it, and save it for a machine tool application where it might fit.

--Doozer

metalmagpie
01-05-2016, 12:46 PM
The hub where the 3 handles are threaded into is cast hollow.
Rethreading the holes is only a temporary fix.
I had a similar drill press, and thought it best to braze the handles
into the hub. This eliminates any chance of thread looseness working
and wallowing out the fit. These drill presses are classic for loose
handles.

Wow, the things you learn. The thread inserts seemed to go in pretty tightly. Maybe I should have put thread locker on as well. Anyway, sure brazing would work but there are times I can think of when I'd want to remove one handle temporarily (like when I've got a wide ell rod in the chuck for tramming the table, for example). Brazing seems so permanent!


The more conventional method of applying balance weight to an
armature, is to add appropriately sized washer(s) to the little zinc
tits cast circumferentially on the armature. The tits are then peened
to secure the washer(s). Also the tits can be broken off to take
weight away from the opposite side. This is how the factory adds
balance weight to the armature.

That makes sense. However, the balancing shop also balances big rotary fan blades, turbine blades, and other things like that. The two-part epoxy is their method, not mine. And they are a long-standing business in industrial South Seattle.

Not to mention that any balance job done by the factory was cursory at best. If you look again at that enormous hunk of metallized epoxy, then try to imagine how many little washers you'd have to trap for an equivalent weight, it doesn't seem possible to me even if you did cut off all the rivet heads on the other side. Plus, aren't those rivets how the laminations are held together? Not sure I'd want to go cutting those away.


But after all that work, you might still have a single-phase motor that
hums and buzzes, something naturally inherent with single-phase motors.
This is not from balance, but from the ripple of 60Hz power. It tends to
resonate in the laminations of the motor. Motors of lesser quality do not
fix the laminations as securely, and the motor makes excessive noise.
It is rare that you find smooth single-phase motor. If I find one, I hold
on to it, and save it for a machine tool application where it might fit.

I too have heard a lot of small motors buzz when they run. This motor was no paragon of virtue when I started but it doesn't seem to have any loose lamination noise. Mostly what I hear now is the fan blowing air. As far as saving the motor for an application where it might fit, to me this *is* that application.

There was one thing I didn't mention about tearing down and reassembling the motor. On the back (fan) end of the motor, there is a centrifugal switch clamped to the shaft. Before I removed that switch, I carefully measured and wrote down the distance the shaft sticks out of the switch mechanism so I could put it back the same way.

metalmagpie

metalmagpie
01-05-2016, 12:50 PM
Looks very nice!

Thanks!


A couple thoughts, after balancing the motor assembly you then drilled holes and moved the set screw for the pulley, did you fill in the original hole to keep balance?

I probably didn't write the sequence of events down correctly. The additional set screw hole was there when the rotor went to the balancing shop.


Second thought, I am not sure how much force was needed to press the spindle and bearings into the housing but normally any time you press, pound, or drive any bearing you are supposed to only push on the mating race. In the picture it would have been the outer race of the bearing that should have been driven.

Mea culpa. I did find that a short piece of 2" pipe was just about the right length to bear on the 6206 bearing outer races. In my defense, it wasn't that hard of a press. You're completely right.

metalmagpie

J Tiers
01-05-2016, 01:19 PM
...Not to mention that any balance job done by the factory was cursory at best. If you look again at that enormous hunk of metallized epoxy, then try to imagine how many little washers you'd have to trap for an equivalent weight, it doesn't seem possible to me even if you did cut off all the rivet heads on the other side. Plus, aren't those rivets how the laminations are held together? Not sure I'd want to go cutting those away. ...

Not really. The laminations are held by the cast aluminum alloy on the rotor. Those "tits" are just cast alloy material sticking out, they are not rivets.

As for the balancing, the epoxy is so close to the shaft it takes a lot of it. The washers you would add would be almost to the outer edge, so their contribution to balance is a lot more per each. And the washers are more dense. Same ratio if you snip them off, but I prefer adding washers, it's less permanent in case more action is needed.

lakeside53
01-05-2016, 01:31 PM
I had a 3hp 3 phase motor precision balanced by the same place as MM 4-5 years ago. I watched the entire process. The first thing they did was take off all the old balance washers. I asked about it... they said.. "haven't used those for years" (they are a "one off" balancing company, not a motor manf). This balance is 2 plane both ends and the tiniest adjustment make a big deference in the results. A lot of my epoxy was "outboard" tucked under where the washer originally went. The computer tells them the approximate weight and distance to place, and while it's still soft they push it around and to the center for fine adjustments.

Mine was very close to G2.5 and is smooth as silk up to 7000rpm (or so) for my step pulley BP ;) "Typical" rotors from the good manfs are balanced to G6.3 which is usually sufficient.

If needed, a Dremel with a coarse carving bit is what's used to remove the old epoxy.

mattthemuppet
01-05-2016, 03:29 PM
beautiful work, that must be a joy to use! How much did the rotor balancing cost?

Ian B
01-05-2016, 04:23 PM
That big glob of epoxy doesn't look right to me - imagine if someone balanced the alloy wheels on your car like that!


For the rest, lovely rebuild. How come the table isn't full of holes, like most other used drills?

RichR
01-05-2016, 04:34 PM
For the rest, lovely rebuild. How come the table isn't full of holes, like most other used drills?

Because he hasn't gotten around to drilling them yet.

Beautiful job metalmagpie, loved the write up.

metalmagpie
01-05-2016, 05:33 PM
How much did the rotor balancing cost?

About $160. Probably about the same as a top quality 1hp motor from Baldor or Leeson once you factor in their discount which generally starts at 50%.

Appreciate your comments, Matt.

metalmagpie

mattthemuppet
01-05-2016, 08:38 PM
that's a fair amount, but at least you're guaranteed it's as smooth as it's going to be vs. getting a new one. Cheaper than 3ph and a VFD too.

I'm working up to installing a treadmill motor and tach on my Walker Turner drill press as speed changes are a pain and there's a huge hole in the speeds (nothing from 900 to 3000rpm). Can't wait :)

sasquatch
01-05-2016, 09:07 PM
Thanks for the interesting thread. Nice pics, looks great!

mickeyf
01-05-2016, 10:55 PM
Very nice!


there are times I can think of when I'd want to remove one handle temporarily

I have had to do this many, many times on my (admittedly smaller) drill press, to position some odd thing correctly. No, don't braze. Better to re-tap every few years if you really need to.

wierdscience
01-05-2016, 11:09 PM
Nice job,I think that's the first time I have had a look at how a real balancing machine is set up.

Tundra Twin Track
01-05-2016, 11:23 PM
Nice job ,I have similar machine in General line 22" with 4MT it runs smooth.

vpt
01-06-2016, 08:54 AM
Very nice!



I have had to do this many, many times on my (admittedly smaller) drill press, to position some odd thing correctly. No, don't braze. Better to re-tap every few years if you really need to.



I as well have had to remove one or more of mine for odd parts sticking out the side of the drill. More than a few times this has happened as well.