Reversing drill press

Hi Everyone,
I am thinking about making my drill press reversible, so I could use it for drilling out broken bolts with left handed drill bits.
It is the cheap department store drill press. The motor, if I am correct, is a single phase induction motor, with centrifugal switch for startup. I am also thinking about just disconnecting the startup capacitor, and starting it in the reverse direction by hand, and then applying power. Any comments welcome.
Thanks, Peter -- Peter E. Orban National Research Council of Canada e-mail: snipped-for-privacy@nrc.ca
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I'd get another motor. Too much fussing and what would happen if it gets left on without " hand starting"
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On Wed, 30 Jun 2004 13:16:02 GMT, "Tom Gardner"
......and in reply I say!:
remove ns from my header address to reply via email
chnchncchhnchn!
You could just threaten to shot up the shop...

ASK! They must be good!
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Peter E. Orban wrote:

If there's a diagram and push-on connectors allowing you to set the motor up for either rotation, then it won't take rocket science to figure out how to wire up a DPDT toggle switch to satisfy your desires.
If not, then I agree with what the previous poster said, it's probably too much trouble, combined with a risk of trashing it, to take the motor apart to gain access to both ends of the starting winding if they are not clearly visible already. But it's your motor...
I certainly wouldn't go with the "hand job" for starting, that's too far out even for me, and should be reserved for emergencies only. <G>
Jeff
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On Wed, 30 Jun 2004 10:07:22 -0400, Jeff Wisnia
......and in reply I say!:
remove ns from my header address to reply via email
It was only a little hole, so I started it myself....

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Standing on the ceiling?
For stability you need braces.
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It's easy to reverse single-phase motors. There was a decent article in HSM about it and I once took the time to type it up. It's old-style ASCII art but reasonably readable: http://www.metalwebnews.com/howto/elec-mtr/elec-mtr.html
This is best done with a proper drum switch. If you can't find a wire which works mechanically with the right number of connectors in it, you may have to pull wires through plastic tubing or use conduit.
Grant
Peter E. Orban wrote:

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I wired my Leeson 3/4hp motor for reverse on my SB10K lathe. Then one day my son switched it into reverse and the centrifical switch stuck. I pulled it out. Put in a new motor. Same exact problem. Put the old motor back in. Anyway, this particular motor isn't happy about running in reverse.
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"Peter E. Orban" snipped-for-privacy@nrc.ca writes:

Peter, If you could somehow get it to work, I sure wouldn't recommend hand-starting a motor to get it to spin in reverse. At a standstill, an electric motor has virtually no internal resistance, depending upon how the field and armature windings are configured, wire size, wire length, etc. At best, the internal resistance is minimal at full stall (start-up). Therefore, while the motor would be sitting there with power applied and waiting for you to hand-start it, it'd be drawing near if not full current from the supply into what'd be virtually a short-circuit. If you don't start it spinning immediately (i.e., within milliseconds), then at best you'd blow a fuse or trip a breaker in the power supply, and at worst your motor would self-destruct within a few secondw. It also could be a serious fire hazard.
Not a good idea at all.
Scotty
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Have you considered using a crossed belt? You might have to use a slightly longer belt, and I'm not recommending it for continuous service, but I think it would beat hand starting.
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slightly
think
You beat me to it Leo. Agreed, a crossed belt should work especially if not for long periods of use. It can be a bit of a hassle but guaranteed to work and as safe as normal.
John
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Almost all capacitor start ac motors are reversible. You need to get a drum reversing switch to do it right. The starting capacitor is connected in series with a starting winding in the motor and the starting switch which is applied accross the line to generate a phase shifted current. If you switch that network 180 degrees, the motor will run the other direction.
John Lovallo

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On Wed, 30 Jun 2004 08:34:38 -0400, "Peter E. Orban"

Can you remove the motor and rotate it 180 degrees before remounting?
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Switching red and black wires will reverse some 120 volt motors. I use a cross type 4-way house lighting switch on mine to do it, wired to switch the relationship between the two wires at the motor. The motor will not reverse until the centrifugal switch drops out, so you will not have instant reverse. Run either direction, cut off power switch, wait for the click, then the additional added switch can be used to reverse the motor for you. Switch the power switch back on to run. To clarify, you will have 2 switches... One for power, and the other solely to provide reverse. Make sure your chuck isn't a screw on type, or you might get a surprise trying to run in reverse.
RJ
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On Wed, 30 Jun 2004 08:34:38 -0400, "Peter E. Orban"

Couldn't you just get a longer Vee belt and make a figure 8 out of it before hooking it over the drive pulleys? Sure, they'd rub a bit where they cross over, but if you are careful with the length, you could make it so that you drop/gain one pulley size to prevent rubbing. This way (if it works?) it's a simple task to convert between standard and reverse?
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Peter,
All you need to do is reverse both the wires on the start winding, this puts the capacitor feed and return onto the opposite lead of the winding from where it was before....
This can be easily be done with a AB bulletin 800T 2 position rotary switch having a dpdt contact block, or equivalent.
Beware, the motor must come to an ( almost ) full stop before it can be restarted in the reverse direction, as the centrifugal switch first needs to close, reconnecting the capacitor into the circuit.
--

SVL



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Some good replys, the only thing I can add is that if you do end up starting it by hand, spin it before you turn it on, and have your hand well clear before you hit the go button. I've seen a 2.2 kV motor started with a steel bar that way, and they had been doing it for fifty years before I seen it without incident.
Just swapping the leads to the start winding will reverse it for you. Back a long way, when I was an apprentice, one of the tradesmen, who was a pain, was using a single phase drill press. When he went for a smoke, we reversed the drill on him. Took him a while to figure it out!! Live entertainment!
regards
John
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On Fri, 2 Jul 2004 19:35:45 +1000, "john johnson"
......and in reply I say!:
remove ns from my header address to reply via email He would have come back for a bit of smoke as well....

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Hi Everyone,
I would like to thank everyone for their comments, pointers to information, and notes by e-mail!
I also appreciate all the warnings about hand starting a motor, I meant it more like a theoretical possibility than a practical solution...
On the other hand, I checked out my drill press on the weekend, and the motor has a table with detailed instructions on how to wire it up for CW, CCW, 120V, and 230V operation.
The moral of the story is that I should have looked before I asked the question.
Thanks, Peter -- Peter E. Orban National Research Council of Canada e-mail: snipped-for-privacy@nrc.ca
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Kind of falls under the same principal as "RTFM" doesn't it. I set up a cheap drill press to reverse several years ago. 110V, cap start, instructions read something like----For CCW rotation move wire X from point A to point B. Did it with a SPDT toggle switch. A and B to the outside terminals, X to the center. Using a drum switch gains you nothing. They work great in a situation that will instant reverse, such as a mill or lathe. With the drill press, you will have to turn off the main switch, wait for it to slow enough for the centrifugal points to drop out, flip the reverse switch, and turn it back on at the main switch. Quicker than it sounds.
Bill
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