Hi Andrew,

Not quite sure why you would want to do this. I have a floorstanding drilling machine, which I use for everything, wood and metal. It has a middle pulley, giving 16 speeds, just by changing the belts, so where is the gain ?

Just wondering ?

Like Larry I fail to see WHY you want to do this. Belt or gear reduction gives the torque to rotate large drill bits slowly. A VFD powered motor runs the risk of overheating if run too slow. You give us no clue as to what sizes of machine or drills you are intending to use. At a guess I would say 4pole if you must, but I would save my money. Noel.

When you say the middle pulley I assume you mean that the machine has an intermediate shaft with a stepped pulley on it so you can (with some trouble) get more speeds by changing the two belts around? If that's right, I did exactly this on my VMB milling machine when I fitted a 3-phase motor and VFD. Because of the middle pulley the stepped pulleys on motor and spindle were "the same way up" and anyway the motor pulley wouldn't fit on the new motor. So I actually made a bushing to allow the intermediate pulley, which is almost the same size and the same number of stapes as the spindle, to be mounted on the motor. I use a link belt to get the necessary extra length, it has transformed the machine.

Don't go pulling on the thin flanges of a pulley with a gear puller. The all-too-common result is to pull a lump out of the flange, rendering the pulley useless. Better to heat the pulley and slide it off. Or set it in a press with plates supporting the thick body of the pulley, not the thin flanges, and press the shaft out after heating the pulley. A propane torch that fits on one of those disposable small bottles costs less than a new pulley.

And do use a key when reassembling. Driving a grubscrew into the empty keyway could damage the shaft and make it hard/impossible to get the pulley off in future.

Edited By Hopper on 09/01/2023 21:53:56

My advice is to change the motor without disturbing the pulleys if possible. Speed control with a VFD is convenient, and it will much reduce the need for belt changes. But speed controlled motors lose turning power at low rpm, which is bad news when a large diameter drill cuts into some metals,

Belt drive is a useful when that happens because it amplifies torque when speed is reduced. Keeping belt and pulleys gets the best of both worlds. Mostly the drill is speed controlled on a middle belt setting, much reducing the need to move the belt. But if the motor struggles with a big drill, the belt can be changed down to get more torque. The belt also increases power because the motor runs faster, closer to it's comfort zone.

Dave

By chewing up the keyway and raising burrs along the edge of the keyway that can jam the pulley in place. Grub screw bears only on one point on the end which will eventually with stopping and starting and shock loadings wear away the metal at the point of contact, allowing movement that now allows the rounded profile of the threaded screw to start chewing away at the edges of the keyway. A key spreads the load along a long flat surface with no room to move and create wear.

Driving a pulley with grubscrew in a keyway is a bodge that can end up ruining your motor spindle. Stick with the way the engineers designed the machine and use a key. It is there for a reason.

Andrew, when you get a mill in future, you may find the drill press gets used less and less. I would not recommend spending large amounts of money and time remotoring one. Spend your time and money on the mill you need and go forward. By the way, a drill press is not rigid enough for milling, if you had thoughts about that being a purpose for remotoring. Many have tried and failed with that approach (me included, when I was a young man with big ideas, lots of enthusiasm, and not much cash). just food for thought.

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.🙂

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!