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View Full Version : Drill press project - single phase motor (re)wiring



sgtpepper
02-04-2010, 01:59 PM
I picked up an old drill press off Craigs. Drill only ran in reverse, so i got it cheap with hopes that I can set it straight.

The original motor was been replaced and wiring completely botched in the process, hense reverse-only operation.

Motor is a 1/4hp KC type General Electric, single phase, capacitor start motor - very old. Currently it's missing a relay and the drum switch. Switch has been replaced by a basic SPST/SPDT light switch.

This would all be OK, except the drill only spins in reverse which is pretty much useless (unless you only use it as a drum sander.)

Plan at the moment is to rewire it back to original forward/backward operation. This means replacing the missing relay and switch. I will be following the info posted on another board:

http://www.practicalmachinist.com/vb/south-bend-lathes/1947-model-9a-128005/index5.html#post579470


- Relay will be 120V rated for 1/3hp or 240V/10A (motor is spec'd at 4.8A 1/4hp)

- Original drum switch is unavailable, instead I plan to use a heavy duty DPDT Carling switch to select direction and a second SPDT Carling to switch AC input.

Will let you know how I get on. Meanwhile feel free to comment. My knowledge of single phase motors is 2 days in the making, so fill me in.

Oh and here are some visuals: http://picasaweb.google.com/ybiteykin/DrillPress#

vpt
02-04-2010, 02:10 PM
Nice looking drill press! Good luck with it! I could never understand how people can abuse the tables like that.

I will be watching about the fwd/rev wiring. My 110v lathe has a drum switch which was wired by a blind kid when I got it. I'm not a complete idiot but I am no pro either when it comes to wiring. So I wired up the drum switch the way I figured it should work (reversing the neutral and hot wire for rev). I found out that doesn't work. lol The motor runs forward in both drum positions.

digger_doug
02-04-2010, 02:13 PM
1. The DPDT switch for reversing, do not use a
"center off" unit. This will shut off the starting winding,
someone else may try to start it in the middle, and burn out
the winding.

2. Re-alize you will not have instant reverse, unlike a
3-phase motor, you'll have to stop the motor, let
it coast to a stop, and then re-start the other direction.

3. Get a foot pedal switch, and wire in series with the
main start/stop switch. That way, when changing bit's
or such things, the main switch negates the function
of the foot pedal switch.

sgtpepper
02-04-2010, 02:49 PM
i'm encouraged by the feedback so far. will see if my abilities can keep up..later today.

yeah i thought at first reversing the leads would do the trick, but after thinking about it (and as you found out) .. that doesnt work. it's AC so it's already changing polarity 60 times / second.

the direction of spin is controlled by the starter coil and capacitor. that starter circuit gives it an initial boost and then disengages letting the primary coil do the work. the position of this capacitor within the starter circuit dictates a CW vs CCW starter boost.

it gets more silly from here.. dynamic braking, instant reverse, things I cant understand yet, etc.

- "no instand-reverse" yep i realize this, np, it'll be spinning in forward 99.9% of the time

- "DPDT" ditto, i had a choice of center-off or on/on, picked the on/on as advised.

- dig the footswitch idea. i just built one for my guitar amp, some leftover parts ... just need a momentary footswitch.

whitis
02-04-2010, 09:38 PM
I will be watching about the fwd/rev wiring. My 110v lathe has a drum switch which was wired by a blind kid when I got it. I'm not a complete idiot but I am no pro either when it comes to wiring. So I wired up the drum switch the way I figured it should work (reversing the neutral and hot wire for rev). I found out that doesn't work. lol The motor runs forward in both drum positions.
To reverse a typical capacitor start single phase induction motor, you have to reverse one winding (typically the start winding), not both. It is the phase of the two windings relative to one another that matters.* For a capacitor run motor, you switch which winding is fed through the capacitor.

J Tiers
02-04-2010, 11:03 PM
I am not sure why you want the relay, unless you have the same type start switch as in that motor shown by Paula in the other thread. Or unless you want drop-out on power loss.

The relay otherwise is NOT needed for reversing. The particular system shown is for "instant reverse", essentially by "starting the motor in reverse" when it is already going "forward". It is VERY stressful, and may be productive of loud and unpleasant noises. It requires that specific type of start switch, AND the particular type relay. You do not need it, and it is not even that helpful.

The common ordinary motor is reversible by removing power, reversing the start winding, and re-starting after letting it come to a stop. That should be good enough for most anyone.

It can be done with two switches, which I did on my lathe years ago. it can be done with a regular single-phase OR three-phase drum switch, which I upgraded to later. (I now use the drum switch with 3 phase power).

The picture is a diagram of a single phase reversing setup using a standard 3 phase drum switch. it is for a 230V motor, but the principle is exactly the same for a 120V, if you ignore the extra winding and pretend it is just a piece of wire.

The switch does not break both sides of the line, but that is common , even in Europe. Since the plug is your safety disconnect, there is no safety issue whatsoever.

http://img.photobucket.com/albums/0803/jstanley/drumswhivolt.jpg

BTW, I have a drill press of that type out in the garage......... without the table holes....... Its quality is.... well it makes holes, generally nearly where they are intended......

fredf
02-04-2010, 11:31 PM
The original motor was been replaced and wiring completely botched in the process, hense reverse-only operation.

Motor is a 1/4hp KC type General Electric, single phase, capacitor start motor - very old. Currently it's missing a relay and the drum switch. Switch has been replaced by a basic SPST/SPDT light switch.


I have a Taiwanese ringer for that press, 12 speed. think the motor is at least 1/2 if not 3/4. is NOT reversible. no relay either . . .

I know my motor probably isn't the best, but wonder if 1/4 will be big enough for you

There is a light socket in bottom. There used to be a real cheap double switch (one of the old ones where you hooked different devices together on one yoke) one for the motor, and one for the light. I replaced with a hp rated toggle and a push on / push off switch for the light (avoids confusion) on a blank utility plate, I had to fudge the hole spacing as it wasn't the same as a box

J Tiers
02-05-2010, 12:11 AM
yeah, teh last post reminded me that you mentioned 'original fwd/rev action", which mine certainly never had....... FWD only.

yes, light switch plus motor switch. The light is pretty handy, so I'd suggest it if the socket is still there.

otherwise, don't mess with FWD/REV.... just get it going forward. I misread you to say that you wanted reversing for some specific reason.

Carld
02-05-2010, 12:13 AM
sgtpepper, why do you want to run a drill press in reverse?

digger_doug
02-05-2010, 07:16 AM
sgtpepper, why do you want to run a drill press in reverse?


It's great for tapping. Label the reversing switch "in-out".

"Since the plug is your safety disconnect, there is no safety issue whatsoever. "

Reaching over to remove the plug every time your hands come near the chuck
(like using the key to tighten up or change a drill bit) is a pain.
Flipping the on/off switch (the original one before modification) is easier,
and will be used more often.

EVguru
02-05-2010, 07:37 AM
sgtpepper, why do you want to run a drill press in reverse?

I always used to run the drill press at school in reverse.

The left hand drill bit set at the back of the cupboard was actually sharp, whilst the ordinary set was usually in a very poor state.


Of course, that might have had something to do with the fact that some people wouldn't notice if I left the press in reverse and just try and plough their way through.

sgtpepper
02-05-2010, 08:34 AM
I am not sure why you want the relay, unless you have the same type start switch as in that motor shown by Paula in the other thread. Or unless you want drop-out on power loss.

I dont see the point of the relay in my situation either. In fact I can't even verify if it had a relay from the factory.
Paula's motor looks ALMOST identical, but no way for me to know if mine in fact had the same relay. Although something is definitely missing from the place where the relay would have been. Some home-brew cap came in it's place.

OK ditching the relay, for now.. although .. i do like the dropout on power loss feature. hm..



BTW, I have a drill press of that type out in the garage......... without the table holes....... Its quality is.... well it makes holes, generally nearly where they are intended......

I kind of like the holes... looks like the surface of the moon.
as far as precision, not too worried. no high expectations since i paid 50 bux for it.




There is a light socket in bottom.
Yeah, I just realized that this morning when i went down to take some pictures.
Will definitely be retro-ing a light in there..somehow.





sgtpepper, why do you want to run a drill press in reverse?
..in case I decide to move to Australia.. ? :D

J Tiers
02-05-2010, 08:42 AM
Reaching over to remove the plug every time your hands come near the chuck
(like using the key to tighten up or change a drill bit) is a pain.
Flipping the on/off switch (the original one before modification) is easier,
and will be used more often.

SAY WHAT?

What on earth would suggest you should do THAT? "whenever your hands come near the chuck"...????? Eh?

Are you under the impression that I suggest no power switch? Because if so I might suggest you re-read the post.

The original switch on most of those DPS that I have seen, in common with virtually all such switches, breaks ONE side of the line..... This is what the 3 phase drum switch does when wired single phase.

When the electrical circuit is open, EITHER WAY, the motor isn't turning, there is no power. I can certainly appreciate safety, but that is "out there".

My comment on the safety disconnect was from the standpoint of ensuring the electricity is disconnected when working on the wiring....... In place of a disconnect switch on the wall which would be used for machines wired a permanent connection and no plug.

And since the original switch does the same thing as the drum switch, I guess you will have to pull the plug anyway..... if you want to be extra super-duper safe. Now I have so far never found the switch to become mysteriously turned on when I was in a different part of the shop, but maybe you do.

Are you sure you shouldn't shut off the main breaker when you replace a bulb or plug in a lamp..........................?

Don't go to a regular machine shop, many of the machines keep the motor on at all times, and disconnect the spindle with a mere mechanical clutch......... "incredibly unsafe", I suppose you would say.

sgtpepper
02-05-2010, 08:43 AM
otherwise, don't mess with FWD/REV.... just get it going forward. I misread you to say that you wanted reversing for some specific reason.

yeah, no immediate need for reverse. so maybe i'll keep it simple for now and wire it FWD only plus a light. Light would be key.
maybe add a DPDT for REV operation later if a situation calls for it.

thanks all for the input. hopefully will have some progress to report later tonight. didnt get my hands on it yesterday.

digger_doug
02-05-2010, 08:49 AM
SAY WHAT?

What on earth would suggest you should do THAT?

Because you wrote this:

"The switch does not break both sides of the line, but that is common , even in Europe. Since the plug is your safety disconnect, there is no safety issue whatsoever. "

I took this as you saying that the on/off switch was an unecessary expense
if using a foot switch.

wierdscience
02-05-2010, 08:53 AM
Honestly before I went to all the trouble of wiring it I would dig up a longer belt, put a half twist in it to run forward and try drilling a few holes.

Reason being you will most likely be looking for a bigger motor.1/4HP ain't much even for an old motor which means a 1/2" hole in steel probably won't be doable.

I have a nearly identical machine that's an honest 3/4hp and it's adequate but barely for a 5/8" hole which is what the machine is rated for.Good luck anyway.

J Tiers
02-05-2010, 09:04 AM
Because you wrote this:

"The switch does not break both sides of the line, but that is common , even in Europe. Since the plug is your safety disconnect, there is no safety issue whatsoever. "

I took this as you saying that the on/off switch was an unecessary expense
if using a foot switch.

Ah, but if you take the trouble to look at the diagram, you will easily see that of course tehre is an "off" position....

The usual thing on this board is for several horrified people to see that it is a single-pole "off" switch and instantly start excitedly hyperventilating, saying :"but you MUST break both sides of the line or <insert multi-failure extremely unlikely safety scenario here>".

digger_doug
02-05-2010, 09:24 AM
Ah, but if you take the trouble to look at the diagram, you will easily see that of course tehre is an "off" position....

The usual thing on this board is for several horrified people to see that it is a single-pole "off" switch and instantly start excitedly hyperventilating, saying :"but you MUST break both sides of the line or <insert multi-failure extremely unlikely safety scenario here>".


Jtiers,
Hold on here just a minute, your last posting marked 1:42 p.m. was not as
it was when I answered it.

I'm not talking about cutting both sides of the line what so ever.

I have run d.p.'s that run all the time, multi spindle ones
that you slide the jig from spindle to spindle.

My point is, using a foot operated switch is nice, free's up both hands,
and doesn't not require a hand to shut off the spindle.

BUT, when changing drill bit's, you can accidentally step on
the switch (even a guarded one) and by simply wiring in
a switch (I ussually use the original one on the d.p.)
an extra level off safety is provided.

Especially in the home shop environment.

Yes, clutched machines are nice, I have several.
But the typical home shop d.p. (a belt changing
unit) is not clutched.

Carld
02-05-2010, 10:50 AM
Hmmm, I didn't know that the machines in Australia run the opposite direction that they do here, that's interesting to know. Maybe some of our Australian members can tell us about that. Maybe they can enlighten us on how they solve the motor problem.

Foot switches are dangerous. They allow your hands to be involved in being on or near the work while your foot can accidentally hit the foot switch. Things seem to collect on and around the foot switches and even the shrouded ones are still dangerous.

As stated, a 3 phase motor is the easiest to reverse without stopping the spindle and single phase motors generally have to be stopped rotating to reverse.

Power tapping with a drill press is a little tricky in that you have to use your hand to stop the chuck and that is dangerous even though we all do it and if you don't stop the chuck in time you'll break a tap.

If you want to power tap on a drill press you should modify a tapping head to chuck it up or make a tapping head to at least instantly release the feeding of the tap with a dog clutch and then reverse the motor and remove the tap.

I realize everyone can't afford a mill or an expensive drill press that could handle power tapping but it's no reason to keep doing something that can break taps or hurt you.

sgtpepper
02-05-2010, 11:10 AM
Hmmm, I didn't know that the machines in Australia run the opposite direction that they do here, that's interesting to know.

sorry i might have mislead you there. (unless that is you're just going along with me, in which case I'm the one misread you.) the australian reference was a bit of a stretch for a joke with a refrence to toilets flushing the opposite direction.

sgtpepper
02-05-2010, 11:26 AM
Honestly before I went to all the trouble of wiring it I would dig up a longer belt, put a half twist in it to run forward and try drilling a few holes.

thought about it.. i would have to remove the middle spindle if i were to try the crossed belt idea. then i would also have to find and purchase said belt.
vs. rewiring which is 0 cost since i have all the parts.

that being said, 1/4hp should be plenty for me as 90% of the time it'll be woodworking with only occasional metalwork. i have access to a full shop if i need major metalwork done.
do i need to be concerned for bringing up woodworking on a Machinist Workshop forum? :) hehe.. if it helps any i built an electric motocycle with my buddy last year, no wood there whatsoever.

Doozer
02-05-2010, 02:44 PM
I have an Atlas drill press with a 1/6 hp GE motor, and it is fine for metal work. Actually I think it is safer, as it limits how much trouble you can get into somewhat. Also, this is a very good quality motor, with minimal single phase humm. My drill press is so quiet, you can barely tell it is running.
--Doozer

Carld
02-05-2010, 03:13 PM
:D sgtpepper, I was just going along with you and started to put the rolling eyes in but figured it would take away from the, Geez, he didn't really believe that did he, effect. Yep, it was all in fun but I was kind of interested in what your going to use it for in reverse except for left hand drills or power tapping.

Is there some special thing you have in mind?

sgtpepper
02-05-2010, 04:13 PM
Is there some special thing you have in mind?

forget reverse. i've given up on it.
now i'm concentrating on making it go up to eleven!

anyway, all this talk and no progress report. who does this n00b think he is...??
i'll try to get it running tonight and report back.