VFD recommendations sought

There are a lot of models that will work well for a drill press. I would suggest that you get a model with a display and programming buttons on the unit. Some models do not have a display and are programmed using a serial port. Okay for industry, but not so good for the one person shop.

Dan

A good vendor is automationdirect.com. Fair pricing and good service. Their least expensive unit in your horsepower should be just fine. Just a happy customer.

Karl

First, your drill press has to have a 3-phase motor. VFD's only work with 3-phase motors.

AC tech, Yaskawa, Magnetek, Toshiba, Hitachi, Allen-Bradley, ...... all make small VFDs. Most over 1 HP are listed as requiring 3-phase power, but they really don't. A 50% derating is a good idea, ie. use a 1 HP unit to run a 1/2 Hp motor from single-phase power.

Jon

Indeed, automationdirect.com is a good choice. I have purchased 3 VFD's from them and customer service, tech support and pricing are all very good.

Randy

There are VFDs that are rated for single phase input. Teco brand is one of them, and I have a couple Teco 2HP VFDs running 2HP motors with single phase input. If the VFD is rated 2HP with single phase input, and you want to drive a 2HP motor, I see no reason why you need to spend a lot of extra money buying a bigger VFD.

There is one caveat; Application enginner told me to make sure that the full load current of the motor is less than the max full load current of the VFD. Usually is, but check to make sure.

I also have a 5HP Boston-Fincor VFD. This one is rated 5HP with 3phase input and 2HP with single phase input. It runs a 2HP motor well with single phase input. Never tried anything bigger.

Bottom line is to respect what the manufacture's ratings.

chuck

When you buy your motor (and matching VFD), get it bigger than you would otherwise. 1 hp is good. It might seem large, but as you reduce the speed, you also reduce power. So running at 5 Hz you only have 1/12 the horsepower you have at 60 Hz. 'Cause power is the product of torque and speed. The maximum torque for the motor is fixed (a matter of maximum current), so the power decreases as speed does.

On a drill press that uses step pulleys to reduce speed, this does not happen because torque is increased the same as speed is reduced.

Note that even at 5Hz I have plenty of power to tap. If I tried drilling a large hole at 5 Hz, I would likely trip the VFD's current limiter.

Also, 1 hp is a common, readily available, size for both motor and VFD. Check eBay for motors and/or VFD's.

Bob

Thanks to all who have replied. I will look into all suggestions.

Joe Gwinn

First off -- does your drill press have a three-phase motor? If not, forget the VFD idea, unless you are willing to swap in a three-phase motor.

An alternative, as long as talking about swapping motors, is a DC motor and controller. Those are particularly good at low-speed torque.

Perhaps some details about your drill press would help.

Good Luck, DoN.

No, it's single phase 110 volt 60 Hz.

I did think of that, but needed the comparison.

It's a cute little Delta DP350 12" bench drill press that was on sale for $200 at Rockler, which really serves woodworkers, not metalworkers. I'm guessing that Rockler bought a bunch of DP350s, only to discover that woodworkers don't want T-slot tables on their drill presses, and so put them on sale. A 12" bench drillpress is a bit small for woodworking too, but it's convenient for much of what I make. Although the table could be larger.

The DP350 is variable speed (mechanical, with variable pulleys and a belt), with a claimed minimum speed of 500 rpm, which turns out to be too high for many things, especially countersinking for 1/4-inch flat head cap screws in metal. Lots of squealing and chattering going on unless lots of down pressure is used.

Severance countersinks seem to work better than MA Ford in this application; don't know why. I'm using 6-flute countersinks. The MA Ford countersink also tends to block up with impacted chips when working in aluminum; steel not yet tried. The Severance is polished metal, while the Ford is black oxide. Both are HSS.

All metal cutting operations are done with flood cooling, using Kool Mist 77 in water, which seems to work quite well, although it probably isn't as good a lubricant as oil.

The motor is 120 volts, 6.0 amps, 60 Hz, one phase, 1720 rpm, with one capacitor bump on the housing. The nameplate volts and amps imply 720 watts, which is almost 1 HP, but this is most likely a peak value. Ad materials claim 1/3 HP, which is plausible as a continuous rating. I don't hear any clicking when it starts or stops, so I think it's capacitor-run. I have not had the motor apart.

Given that the DP350 has mechanical variable speed, a slower constant-speed motor could well suffice.

Of course, the solution should not cost more than simply buying another drill press.

Joe Gwinn

....cut....

You will spend more on the VFD and motor that you spent on the drill press. Small surplus DC motors can be had much cheaper.

Put a 1/3-1/2 hp DC motor on it with one of the Minarick controllers one fo the posters here has been selling and you will have something you can control well enough.

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

You may have to paste this onto one line:

A couple of us have done something similar, and it's a lot cheaper than re-motoring... --Glenn Lyford

You're right about that. I already have a 1/3 HP 90 V PMDC motor I got surplus for $20. The mounting is a bit awkward for the drill press though. But possible, as the PMDC motor is far smaller than what's there.

Hmm. This may well not work, because the original motor may have an extra-long shaft that's shaft specially adapted to receive the variable-speed pulley. I'll need to look at this more closely.

Joe Gwinn

[snip]

Now that I think about it, it may not be practical to replace the motor, as its shaft may be long and specially adapted to receive the variable-speed pulley. I'll need to look into this. It's time to oil those pulleys anyway.

It occurs to me that it might be a good option to buy a belt and step pulley drill press, but with a three-phase motor, plus a VFD, to achieve convenient variable speed. This may be cheaper, and somewhat better than the mechanical variable speed approach, especially in speed range. One can always change the belts and pulleys to set the general speed range without great loss of torque. The variable-speed drive drill presses are quite a bit more expensive than non variable speed, and this may pay for the VFD all by itself.

Reaction?

Joe Gwinn

Its not hard to machine a coupler and shaft extention. Might take..what an hour if you were dawdling?

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

I rather like step pully drill presses with a VFD, rather than a variable speed drill press or a VS drill press with inverter for those reasons. Same with a milling machine. Far less complicated, less stuff to need to maintain due to wear and the ability to simply change to a smaller or bigger pulley for maintaining torque at variable tapping or drilling speeds is hard to beat visa vis cost.

Stick a S&D drill bit, 1" or bigger, and the average VFD poops out down there at low rpms, but simply change to the proper pully size, and fine tune your vfd and voila..a hogger. The rest of the time, using the medium pully and the VFD and you have good speed and torque ranges for most drill sizes.

YMMV of course.

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

A local drive repair guy tells me that he can modify a 3 phase VFD to run on single phase. He won't tell me how he does it. Do you have any idea what he does?

stan

1) He might be doing nothing because some VFDs will run an single phase. 2) He Might be replacing the input diodes with bigger diodes 3) He might be adding more filter caps and changing the diodes.

I wouldn't pay for a service unless I knew what he was doing and why it makes the change possible. chuck

He takes the drive, puts it on the shelf, and gives it back in few days along with a bill. Virtually all small to medium sized VFDs will run on single phase. The manufacturers recommend that you derate drives that aren't specifically designed to run on single phase, usually by

1/2 or 1/3, but I'm not convinced that's even necessary for a drive that will see light and intermittent use.

It's possible the drives guy replaces, or adds to, the filter caps in the power supply with larger units to reduce the ripple that increases when running on single phase, but most newer drives are so compact that I'm skeptical you could do that without hanging the caps on the outside.

Ned Simmons