Changing the motor in Drill press

Hi Jeff. Thanks for your input. Some wise advice there . However my situation is that I operate in a single car garage and there is absolutely maxed out with no space for any metal working machines . So, I intend to build a large shed in the back yard ( kids are growing up fast) and make that into a metal working shop. Currently I don’t have the budget for that , given the cost of timber have soared . That’s why I am planning to make this drill press modification. Well, enthusiasm may die down and I may revert to following your advice . Let’s see ! 😖

I rnostly agree with Jeff’s post. I like VFD operation - soft start, etc - and would not hesitate changing a motor (at the right cost) - particularly if the single phase motor presented any problem.

I entirely agree with the point that s drill press is not a suitable alternative to a proper milling machine. Anyone claiming a drill press/pillar drill is good for milling is misleading those that might take that advice.

Any 3 jaw ‘Jacobs type’ chuck is inadequate to securely hold millinng cutters when side forces are involved. The cutter is quite likely to loosen, be drawn into the work, etc. Jacobs type chucks are (sensibly) only used, with a mill, for drilling and threading jobs. Chuck jaws are hardened and only grip on three points (milling cuttes are hard surfaces, too, unlike drill-bit shanks.

Further a drill is designed for axial, not radial, loading - the spindle bearings are neither of adequate size nor type, for milling forces, particularly while cutting metals.

There is no drawbar facility to hold chucks or cutters in place - the drive is likely by friction, which will cease if the taper is loosened by oscillating side forces encountered with side-cutting.

The quill is likely of lighter design than one for a properly designed mill, so accuracy will be poor and wear will be hastened.

Apart from the above, go ahead, if you decide to ignore the advice.🙂

One other little extra that you can have with VFD's is a braking resistor which makes for instant stop when turned off or when any of the safety microswitches are tripped.

I can only echo the warnings from several others about the unsuitability of a modified drill press for metal milling. Innacurate, and possibly dangerous. You admit to being a newcomer to 'metal bashing' so I would heed advice from experienced people.

I understand your interest and enthusiasm plus the space / budget constraints (been there - done that - got the tee shirt), but realism must prevail. Obviously you are at total liberty to do what you wish but, as others have noted ,this approach will most probably end in dissapointmment, money down the drain.

You might also consider -do I want a mill anyway? Most of started with a lathe (which is usually easy to use for milling anyway with basic accesories) tool bits are cheap and you can do a lot with a basic set, specially if a beginner. Perhaps look at one of the really small mini lathes (secondhand?) which perhaps you could mount on a moveable base to suit your cramped garage? Just a thought!

There have been a few mentions in this thread regarding the unsuitability of a drilling machine for milling purposes.

The OP made no mention of wanting to use the drill for milling purposes, he just asked a straightforward question about changing a motor. I think that all that is happening now is that the OP will get more and more confused.

Ian P

I vote for Plan A. The problem with the relay is it's unnecessary (I think), and adds a potential source of trouble. Either the relay fails, stopping the VFD, or the contacts stick, failing to stop the VFD in an emergency. I see relays as useful for providing isolation, not needed here, and/or, allowing small switches to operate a big switch that has to manage a lot of power. VFD control switching is electronic, typically 12 or 5V at a few milliamperes, making relays superfluous.

A point about jargon may help. Folk with a background in signal switching mostly call these devices "relays". Those with a background in power switching usually call them "contactors".

The hard part of setting up a VFD is usually configuring it, rather than the wiring. Inside the box is a mass of sophisticated functionality, which the user can use to adjust dozens of factors like logic sense and voltages, whether or not a pendant is used. They can also be parametrised to adjust soft-start characteristics, optimised to suit a particular motor, or support advance motor control features. Manuals can run to hundreds of pages of gobbledygook. Most are configured with a plug-in calculator like device, others with a computer interface.

When VFDs first appeared, they were high-end devices sold to industry, who either had them pre-programmed to a specification, or sent someone on a training course. The manuals at this stage were for expert reference, not simple How To Guides. The full manual of a VFD is still intimidating, but the good news is that most ordinary VFDs now work out of the box. They come sensibly pre-configured, and are likely to 'just work'. And if tweaks are necessary, they're likely to be straightforward, and explained in a much simplified get you started guide.

There's a high chance of success, only risk being forced into the deep manual because the defaults are unsuitable. One fairly common problem is the chap who accidentally changes an important setting due to inexperience, and can only fix it by understanding a difficult manual! Another is buying second-hand and finding nothing works because the previous owner specially configured it, and there's no manual. Last case is buying a sooper-dooper high-end VFD, and discovering it assumes installers are fully trained, must be configured from scratch, and the manual is an inch thick...

Dave

Indeed The op states WOOD. Admittedly it's not often we get someone from the dark side posting, but even I know that a basic milling machine for wood is called a router and commonly spins a lot faster than our milling cutters.

Andrew,

On picking your belt speed try to keep the motor speed fairly close to the plated 50hz speed as the motor fan is not very effective at significantly lower speeds. You may also need more power for large forstner type bits or hole saws if you.

Ay up Dave, in my day relays frequently controlled contactors and a timers was a small lead screw slowly pulled down by an energised coil, but retarded via a paddle in container to give the timing. No of that electron stuff. John

To be fair to many who have responded, they tried to be helpful to someone admitting to be a bit of an engineering novice. Perhaps the wording originally was confusing as I quite clearly read the drift to be ' I'm into woodworking and have kit, but am interested in getting into engineering and I want to modify my drill..... ' so understandably some confusion might have occured, if so, apologies.

I appreciate all your inputs and learning a lot as I prod along.

Andrew.

Hi Dave, one question , what happens in case of power failure during operation. When the power comes back, will the VFD power the motor from the pre power failure setup. Or, should VFD be switched on again to run the motor?

Thanks

Andrew

My VFD's are mostly as your plan A but instead of a (two position) F/R switch, I have a toggle switch with a centre off position (so no need for stop/start buttons) On the drilling machine I can reach easily the switch with the same hand holding the downfeed lever.

I use the drill for tapping threads (M2 to M14) and the ability to reverse is a godsend.

I can also reach the speed control potentiometer (to which I have fitted a very extended pointer (just a long grubscrew actually) which means I can change speed by fingertip without having to grip the knob.

I strongly suggest that you fit a remote potentiometer rather than using the up/down buttons on the VFD itself which in my experience carry out their intended purpose but are nowhere near as ergonomic as a potentiometer.

Ian P

P.S. I'm sure Dave will answer, but VFD's are usually set up so that the motor will not restart after cutting the mains power .

Edited By Ian P on 10/01/2023 15:13:23

Andrew, its not really a conundrum. I cannot say all, but most VFDs act in a No-Volt method.

Some can be programmed to restart the motor after power fail but by default most do not 'read' the switch positions at power up so even if the RUN switch is closed tha motor will not start. (until the switch is cycled off first)

Ian P

Edited By Ian P on 10/01/2023 16:02:03

Posted by Ian P on 09/01/2023 22:03:26:

Hopper, how can a grubscrew bearing on the bottom of a keyway recess damage the shaft?

Ian P

This is my solution to grubscrews and keyways. The key was milled down to me just below the shaft OD and the grubscrews were screwed in tight when the pulley was aligned. Then the key was removed, using thesmall threaded hole to jack it out of the keyway and holes made for the tips of the grubscrewsin line with the witness marks. No damage to the shaft and plenty of security.