drill press VFD ready made 'mod box'? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: August 02, 2025, 10:42:23 pm
content: Is there like a box that has a cable attached to it that can control a drill press for RPM for slow things like winding inductors or drawing scribe lines or heating an object with a torch uniformly or stuff like that?I mean like weak. I see with a real VFD, you can do things like slow it down for using hole saws or big drills, and it has alot of torque. But I am wondering about some underpowered device that would cost less and simply halt the rotation if there is excess torque.I mean like plug and play, no wiring. There used to be a PID oven controller like that, which was just a box you connected the toaster oven into, and it would work (other then the thermocouple).My plan right now was just to make some thing that interfaces with the belt to use a small hand held drill with a zip tie on the trigger.Is there perhaps some form of lamp dimmer that could work? And by inductors I mean like 30awg wire not some behemoth. For a small benchtop 110V drill press.I am not interested in modding anything, but am willing to spend a little bit of money on this capability if its plug and play and works for small motors.

author: Whales
author_rank: Super Contributor
timestamp: August 02, 2025, 10:54:24 pm
content: Most drill presses are single-phase induction motors. I know of 3 ways to get lower speeds out of these:(1) Change the AC frequency. I've read that their magnetics don't like running at lower frequencies because their impedance drops too much? If anyone has tried this then please share.(2) Add mechanical reduction to the output (gearing, pullies)(3) Run them at high slip factor. This means underpowering them (eg series capacitor or variac). It's very hard to get consistent and reliable speed out of this method unless you have a large load attached to the motor (like a fan). Your controller box would need a speed sensor in it and a full control loop. I don't think a triac dimmer is a good idea with an inductive load like a motor, it would need to do something else.Suggestion: consider making a separate tool for these low speed tasks. A stepper motor, stepper motor control board (with pot knob for speed) and a jacobs chuck, perhaps?

author: coppercone2
author_rank: Super Contributor
timestamp: August 02, 2025, 11:12:24 pm
content: I was thinking about that but I just need to make sure there is nothing that already exists that does exactly this.The idea would be no money and it can be thrown in a drawer easily when not in use.The most appealing "option" i thought of is to thread a hole in the side of one of the rollers for the thermal laminator machine (which rolls slowly) and thread a small 3 jaw chuck on the side. It would not need to be a big mod because the force is mega low, so like a 10-32 screw would work. That machine is also substantially heavy so it might just work for the intended role. This could result in a thermal laminator being mounted to the top of a drill press (the column of the drill press is useful for magnetic clamps to hold a torch or what have you random thing that needs slow spinning)

author: Whales
author_rank: Super Contributor
timestamp: August 02, 2025, 11:17:06 pm
content: Yeah that could work. I think most laminators use slow synchronous motors with a bit of gearing (similar to the motor in a microwave over turntable).

author: coppercone2
author_rank: Super Contributor
timestamp: August 02, 2025, 11:19:06 pm
content: I have one of those turn table motors I forgot about it.I wonder if I can just stick it on a magnetic block (the twist on ones that have screw mounting points on the side for welding) on a simple bracket to interface with the drill press column. I can simply rotate the table 180 degrees and use the back of the drill press. !!!!! Brilliant. That motor is even somewhat strong.!It would even be rather true to the column because the mag block is pretty precisely made and if you just use a flat bar steel to join the motor to the block it would be pretty flat and strong. !!!! And it fits in the drawer. And you can splice a aux power connector to the cable near the drill press motor in a small junction box.That solves about 30 problems I have been having.It does work upside down right? the motor from the microwave oven

author: coppercone2
author_rank: Super Contributor
timestamp: August 02, 2025, 11:23:28 pm
content: Like will the microwave motor break if something is hanging from it? Must it be loaded from the top?

author: WattsThat
author_rank: Frequent Contributor
timestamp: August 02, 2025, 11:49:48 pm
content: In a word, no.From a control perspective, a single phase motor is not a good starting point. Slowing a motor down requires controlling both the voltage and frequency applied in a controlled ratio. Controlling its torque involves controlling two out of phase currents and ultimately, attempting to control torque at zero speed is physically impossible with a single phase motor due to the loss of its rotational vector when the applied frequency approaches zero.It’s amazing single phase motors work as well as they do, given the electrical voodoo going on inside the copper and iron. Slowing it down and still being able to start it reliably is a real challenge, sometimes quite the science fair experiment. This is evidenced by the fact there is only one, count ‘em one, maker of single phase VFD’s in the market, Invertek out of the UK.So let’s play the “what if” game and say you had a three phase motor, rather than a single phase machine.Controlling torque up to and including stall torque can be done with an ac vector VFD drive. The ABB Direct Torque Control drives (ACS800, ACS880) excel at this in open loop (no encoder). With a plain old Volts per Hertz VFD, you can limit total current, which is not torque, but this is slow and imprecise because the total motor current is combination of both the motor magnetizing current and the torque producing current with those currents being out of phase with one another.You could of course apply a vector VFD but that still doesn’t get you there. Why? Because coil winding is application specific task and trying to adapt some other motor driven machine will just lead to heartburn. What gets overlooked is the basic physics of the actual task and attempting to use a one-half or a one horsepower motor when the task requires 0.01 total horsepower, you’re not going to have a good result no mater how you go about things. Things like friction and inertia get glossed over but the physics always wins and things never work well or at all, depending upon who and what’s involved.As a final example of physics not being your friend, look at what happens when you change the ratios on the drill press. The lowest ratio (say 1:1) means the highest speed but the lowest torque. Now go to half that speed with 2:1 and while you have a slower speed, you’ve now have twice the torque. This “feature” of changing ratios is overlooked when attempting to put VFD’s on drill press and lathes. Put the device in its highest speed and then slow it down with the VFD and you’ll find no useful work can be done because of the loss in torque.

author: coppercone2
author_rank: Super Contributor
timestamp: August 02, 2025, 11:59:31 pm
content: I just needed to make sure there is no edge case with some hack that works for really low torque for like zero work things. I think the microwave motor will workThere is a number of things that require spinning with low torque but require the stability of a drill press.Also you over estimate the quality requirement here. This is for bootleg exploration work. Lets say a electromagnet that is less effort then by hand. The majority of the equipment is over built for the little jobs I seek help withfor now its OK i managed to use a drill with a number of vises to do what I needed