Speed controller for bench drill

Hi All can anyone help please

I’m looking for a plug in speed controller to operate

my bench drill, I’m sick of changing belts to achieve

different speeds has anyone got one they can recommend

thanks

Steve

Hi,

Make and model of your drill please.

Bear.......

I got one of those brushless vevor sewing machine jobs for under a ton, 750w

Only time will tell on reliability but it ran my drummond M ok as a test

Hi bear it’s a Rexon Lexus DP255A

cheers

steve

From the info on the web it looks like a single phase induction motor, so you'll have to swap the motor. I wouldn't have thought it was worth the effort, and you will lose power at low speed.

Unless your in to PRECISE cutting speeds and feed, just get used to it ! Other wise VFD and 3Ph motor in delta. REALY NOT WORTH THE EFFORT. Noel.

Steve's Rexon looks to be similar to my 16mm Jet, which is a pain to change belt speeds. I changed my motor to 3 phase with VFD and don't regret it, much more convenient. The ability to slow start, or even go in reverse when centering on existing holes is very useful.

Rod

And tapping!

The following is how I overcome the belt changing annoyance. I think the vfd route is a rather expensive luxury and it would be more cost effective to fit on my Dore Westbury, as it has much more 'daylight' under the chuck than the 'Sharp' mill.

I have a Fobco Star bench drill with several drive pulleys on which they are easy to change the belt. I normally leave the belt on a pulley which gives a low speed for the job in hand. If I need to drill a small hole, I up the speed to max and a very large hole, it's reduced to the lowest. So by my method, 'average' size holes are likely to be drilled at somewhere near optimum, but exceptionally small or large holes are made with a belt change, thus limiting belt changes. Seems to work satisfactorily. Having described that, I don't use the drill so much these days, because I prefer to use a drill chuck on my 'Sharp' mill with the added benefit of X and Y precise positioning. Lack of 'daylight' space on the mill forces me to start a large finish hole with smaller starting series of drills then transfer the job to the Fobco which accommodates the larger diameter drills with their corresponding increase in length. Realignment of the hole under the Fobco's chuck being achieved by a temporary use of the last drill as a guide pin. This method works well for me. I hope to have a DRO system permanently fixed to the DW and do all my drilling on it. Would still be reluctant to sell my very beefy Fobco.

John

Edited By DMB on 05/04/2023 08:48:21

That's down to implementation.

The recommendation for using VFD's for speed control I've had from ABB and others (when discussing pumping and material conveying applications) is thus:

• Purchase an "Inverter Duty" motor which is rated for a given power output (on a curve) over a given frequency range (this varies with vendor/design and includes options like 10-50Hz, 10-100Hz, 50-250Hz or even 40-400Hz for different types of constant torque and variable torque applications).
• You should base the motor selection based on it's rated Power at the RPM corresponding to the greatest highest power requirement.*
• Gear the motor drive so that your lowest required equipment speed is equivalent to your motors lowest rated frequency.
• If you need a very high gear reduction to achieve this use a 6 or 8 pole motor.
• Set the VFD parameters up so that it matches the frequency-power curve of the motor, accounting for the increased back EMF

They were very clear that you should not be running motors below their rated frequency.

Applying that to the use case here, a 40-400hz 4 pole motor with a fixed two stage 5:1 and 2:1 pulley reduction could give a speed range from say 24-2400rpm, which would be suitable for pretty much anything you might realistically drive in a MT2 drill spindle.

If you only do smaller work you might consider a different setup like buying a 50-250 Hz 2 pole with a 5:1 reduction to give 300-3000rpm.

*In our use case this would mean looking at the recommended metal removal rates for drills of various sizes in various materials, developing curves for power consumption and using those identify the point at which the highest power demand is and it's corresponding RPM, so you can match that to the motor's curve.

Edited By Jelly on 05/04/2023 12:34:33

Edited By Jelly on 05/04/2023 12:50:44

400 hz on a 4 pole motor is 12000 rpm (nominal). I can't imagine such a motor is cheap. If you run 2:1 off that you get 6000 rpm rpm spindle speed, not 2400 and I doubt an ordinary vee belt is going to like going at that sort of speed. If you intended 5:1 to get 2400 rpm, then I'm not clear why you need the 2:1

If you're going to have 2 belt speed ranges, you might as well stick with 5, just make it easier to change. My Drilling machine has 500 - 4000 rpm, I don't reckon you need to go any slower for a 1/2" drill

Edited By duncan webster on 05/04/2023 18:17:44