Simpliest method to reverse a precision 3 phase table top drill press for tapping ?

Milacron · Feb 20, 2017

In other words does the choice come down to either a crude manual lever switch like a Bridgeport mill.... or go whole hog with reversing lock out magnetic contactors like an Alzmetall drill with foot pedal switch ?

Or is there a simplier method these days...perhaps involving a VFD for example ? I think the drill is only 1 hp (with Reeves type vari disc for RPM changes) Has no. 2 MT spindle so changing from drill to QC tap chuck would be easy enough.

(and please resist the obvious alternatives, like a reversing tapping head)

JST · Feb 20, 2017

For purely electrical means of reversing, It likely does not matter much, aside from the time taken to do the reversal, which in the spirit of answering only the question, I am ignoring.

If the switch can take it, use the switch. 1HP doesn't need a motor starter if the motor has an overload in it.

A VFD would need to be able to essentially plug reverse the unit, which is usually beyond the current capacity of a matched VFD. You likely could not use a ramp down and ramp up. DC braking might do it, followed by ramp up in reverse, but it is tough on the motor. Of course, plug reversing is also.

jim rozen · Feb 21, 2017

Many folks use a vfd for this. Foot pedal is the fwd/rev control, and a toggle switch is the run control.

Get the spindle running in forward with the toggle switch, when you finish tapping you either take your
foot off the pedal or put it on the pedal to reverse, depending on your preference. Easy to wire either way.

The ramp down/ramp up needs to be set appropriately of course. I tap so seldom I just use the foot pedal as
on/off, and the toggle switch as fwd/reverse. Tap down to where I want, take my foot off the pedal. Flip the
switch and hit the pedal again to power back out.

Monarchist · Feb 21, 2017

Milacron said:
In other words does the choice come down to either a crude manual lever switch like a Bridgeport mill.... or go whole hog with reversing lock out magnetic contactors like an Alzmetall drill with foot pedal switch ?

Presuming 'instant' is of the essence, DPDT contact form foot pedal if you don't mind running full voltage there, otherwise a relay/contactor.

Disregarding what happened to threaded-spindle mounted chucks, 3/4 HP 3-P SB and Logan lathes were 'instant' reversed by students all the time, HS shop. 'Thump", belt chirp, done.
Classical 3-button FWD-OFF-REV Allen-Bradley on a conduit, so, yes, contactors.

One of a 3-P motor's nicest features, reversing can be IMNSHO.

Pretty hard to do a contactor Dee Cee reverse that fast. Have to force the magnetic fields to collapse, which takes longer than 3-P AC reversing unless using FORCED field reversing.

Either a DC Drive or VFD have ramp rate minimums that are slower yet than raw reversing, so No Joy with a conventional VFD, either.

See JST or jraef for a more suitable VFD suggestion. Above my pay grade.

ewlsey · Feb 21, 2017

My Victoria (English made) drill press has both a reversing contactor and a big clunky switch. It seems to be original, so who knows why they used a contactor and a current rated switch.

The nice thing on a Bridgeport is the hand brake. I always stop the tap with the brake and then reverse the motor.

Matt Matt · Feb 21, 2017

On some more modern drill presses they have 5 position switch. Halfway between forward and stop they have clutch brake. The same goes for rivers to stop. Some of the more modern MAS drill presses, if you do not use this option, you will sit in timeout well the overload cools. So, throwing it from forward to reverse there's two positions that will apply the break. It's up to you if you use it. In smaller drill presses in the one horse power range a VFD could be set up this way. But in the end, knowing your drill is key. Without a break sometimes I just coast in to depth.

I have broken my fair share of taps in blind holes.

rklopp · Feb 21, 2017

I have my old delta drill set up with a VFD for reversing. I get FWD/REV, braking, variable speed, and motor protection all in one device. The VFD is in its own encosure, and it is controlled by a control station with red and green pushbutton pilot devices for on/off, a rotary pilot device for FWD/REV, and a 10k pot for speed. All of the devices are 22-mm WEG brand, and the box is heavy duty plastic. All came from Factorymation as a set. They sell a metal box version, but the plastic is not your grandma's plastic, not cheesy at all.

POAx · Feb 22, 2017

I have installed an "OMRON" VFD, in a separate box, on my drill press. I have an "on-off-on" switch on the front for forward stop and reverse and also a potentiometer for rpm. The plan I have had (not fulfilled yet) is to add two push button switches, in the end of the feed lever. One button upside the handle, for the forefinger and one on the bottom side of the handle for the thumb. So by pushing the lever down with the forefinger activating the button, the spindle is rotating forward. When pushing the feed lever back up, the thumb activates the reverse button on the down side of the handle. The drill press works so good with a VFD. On low rpm, suitable for threading, the spindle stops within one turn, the same way each time, in both directions. Perfect for safe and quick threading, even for blind holes.
Some day I will fulfill this mod but I am very satisfied and happy as it is now.

Peter from Holland · Feb 22, 2017

The best setup for a drill I worked with was a dubble footswitch in a single housing
One for forward One for reverse Why was it the best?
Because you could stop the drill without using your hands
With the footswitch you simly let go if the drill bites the material that you forgot to clamp

Peter

jim rozen · Feb 22, 2017

"I have broken my fair share of taps in blind holes. "

This is really hard to do with a (transgression ->) Procunier tapping head.

JST · Feb 22, 2017

The problem with tapping is obviously that you do break things if the tap goes in too many turns. So you do not want any sort of ramp-down to a stop, you want a stop NOW. VFDs don't like that, they probably will overcurrent if the ramp to stop is really short.

If you have an option parameter for DC injection, that tends to be a quick stop, but not faster than a plug reverse..

Plug reversing with a switch is the fastest, probably no more than a turn or two to stop. Hard to beat that with a VFD, so the added expense and complexity of a VFD instead of a switch is not easy to justify.

rklopp · Feb 23, 2017

JST said:
Plug reversing with a switch is the fastest, probably no more than a turn or two to stop. Hard to beat that with a VFD, so the added expense and complexity of a VFD instead of a switch is not easy to justify.

It all depends on whether you already have motor protection and variable speed. If you need to buy a FWD/REV motor starter, and speed variation is via shifting gears or belts, VFD still comes out justified in my mind. VFDs are so cheap nowadays, they're hard not to justify.

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Simpliest method to reverse a precision 3 phase table top drill press for tapping ?

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