I have replaced the 1/2 hp single phase motor with a 1 hp three phase and VFD on the Tom Senior light vertical which the museum inherited. One reason was that the spindle was converted from MT2 to R8 and a bit more power would be useful. The motor speed control is a bonus, with a 6 pole motor running between 25 and 75 Hz, it runs between 450 and 1350 rpm giving the mill, which also has 4 speeds by belt, a good range. VFD's can be programmed to reverse the motor if required and also the acceleration and deceleration can be programmed. Also, a lot of 3 phase ex industrial manual machinery has come into hobby use and it is often easier and cheaper to dispense with the complicated 3 phase switchgear and run from domestic mains which is usually single phase. Three phase motors run smoother than single phase.

Edited By old mart on 20/01/2023 21:32:14

Edited By old mart on 20/01/2023 21:33:01

I agree. The only mistake I made was going for a 1/2HP motor instead of a bigger one, but hey ho.

I have seen a lot of modelers install VFD's in their shop.

They seem to be popular here (US) too.

I have resisted using these devices so far, although I could use one on a hacksaw I purchased that has a 3-phase motor.

The reason I don't use these is as follows:

1. I am concerned about the long-term reliability of the electronics.

2. I am concerned about the spikes that VFD's can put on the input and output, which in turn spikes the motor windings and motor cable, which can cause both to fail over time.

3. I am old-school, and I prefer to use as few electronics as possible in the shop.

Some folks have said that given the small horsepower involved, and the limited usage of hobby shop equipment, the reliability and spike issue is not a problem.

I have specified industrial VFDs for many years, and I use an input inductor to prevent line spiking, and an output filter to prevent motor winding and cable spiking.

Industrial VFDs will indeed ruin your system if you don't watch out for the input/output spikes.

Some new motors are "VFD-rated", but most motors I see are not rated for VFD service.

I don't see VFDs in the hobby going away.

As many have mentioned, they are just too convenient (when they work).

It is similar to how my dad used mechanical dials/readouts on all of his shop equipment, and would not use a digital readout on anything to save his life.

I use digital (electronic with LCD screen) vernier calipers for all sorts of things in the shop, and I would not do shop work without them. I use digital vernier calipers as poor-man's DRO's on the lathe and mill, with great succes and very low cost.

My dad straddled the line with some of his micrometers, which had mechanical digital readout, like the old rotating drum clocks, where the drum rotates to different digits.

My dad swore off all things electronic and computer.

I am not able to avoid computers and such, but so far I don't have any VFDs.

I did buy a nice little kiln controller with SCRs.

Some times you just need and want electronic controls.

I do envy those who have nice DRO on the lathe.

I have to spread my hobby money across foundry and shop machinery, and so I have to be selective about which luxuries I buy.

.

Edited By PatJ on 20/01/2023 23:16:54

Perhaps people in the antipodes really are years behind the times! Dons crash helmet and prepares to take the flak, and the dog out for a walk. Only joking, honest.

Hi Simon

I think I must be one of those secret squirrel model engineers that are lurking about in darkest Australia.

I have three phase and VFD on my ML7 ( Newton Tesla ) plus a number of other sets planned for installation on other small machines.

On the ML7 the advantages are very smooth operation and variable speed control ( within reason ).

Why is it less common in Australia? – I think possibly it is due to the cost ( high ) and availability ( low ) of small three phase motors. VFDs on the other hand are reasonably inexpensive ex China and not to expensive to ship. Cost for importing a motor on the other hand can easily exceed the cost of the motor.

Oddly I suspect the motors may be available locally, just very hard to find ( It's a small market&nbsp. The motor for my ML7 was purchased locally some years ago but whether the firm is still operating or making small motors I am not sure.

I have also contemplated changing my big 3 phase machines to VFD operation for the same reason as with the ML7 – i.e. smother operation and some greater flexibility in control. In these cases the the motor stays the same and the VFD is three phase in and three phase out. Again these VFDs are quite reasonably priced for fairly large motors, 7.5 HP in,my case.

Is it essential – NO. Is it nice to have – YES. Will the machine do the same things as it did before – YES.

Is it worthwhile – QUESTIONABLE. Only the individual can decide.

Pero

I think it is the cost factor here in Australia for good quality VFDs and motors. Cheapos are available from China but quality is ahem variable.

In the UK you can buy an already set up VFD and motor for Myford for way less than it costs to buy the same quality components here in Oz and set it all up yourself. When stuff is cheap and easy , people will do it.

Personally I haven't felt the need. Using carbide tooling I leave the Myford in top speed belt setting almost all the time and on the odd occasion I have to change it or engage back gear, so what? 30 seconds lost. Smoothness of three phase is nice but not something I feel the need to pay good money for. Heavy steel bench firmly bolted down and to the wall and carefully balanced pulleys is good enough for me.

It is a mystery to me why anyone would feel the need to be constantly adjusting the speed of a drill press. I leave it on about the 800rpm belt setting for 90 per cent of work that I do, drilling one or two holes in steel or aluminium from about 1/8" to 1/2" diameter. Changing the belt on the odd occasion to drill a tiny hole or a very big hole, well another whole 30 seconds wasted.

I am sure many others are the same. I guess in Australia living with the isolation, high import costs of a small market and the time delay to buy things and have them delivered, there is more of a tradition of just making do with what you have rather than regularly buying new toys to be delivered next day. But that is changing rapidly as internet shopping becomes more the norm so I expect we shall catch up in short order.

LOL. Except it is not a joke. When I moved back here after living longterm in the USA it was like a journey back in time. It took me several years to gear down to local speed. Which is not necessarily a bad thing. But it did take some getting used to.

Or you can do what I do and run the drill press at circa 800rpm – 900rpm and use that for your pilot hole, larger hole and deburring. No need to change speeds every time you change drill size. Drill speed charts are optimum speeds for industry to balance metal removal rate with tool life. As long as you don't run too fast and burn the cutting edges, or too slow on sub-1/8" drills and snap them, one speed will do 90 per cent of the work we do. Changing speed every time you change drill size is overkill.  I go for months at a time without changing speed.

If I am working on a small model project where I am repeatedly drilling small holes, say tapping holes for 1.5mm or 2mm threads etc, then I will change to a higher speed for the small drills, and use that speed whether I am using a 1mm bit or a 2mm bit etc. Then when I go back to working on motorbike stuff, all 1/4 to 1/2" holes, i change the belts once to 800rpm or so and leave it a that.

Colchesters and Harrisons are rare in Australia. And what there are have been worked to death in professional environments for the most part. And those mid-sized Chinese gear head lathes say 13" swing by 30" long are widely sold and cost about $3,000 (1500 Quid) so they are popular. Pretty good lathes for the most part other than the noisy steel gears in them. The earlier belt drive models run quieter. They mostly come with 1 phase motors.

Edited By Hopper on 21/01/2023 08:18:43

Smoother running and better control was a good reason to modify my machines (3 lathes and a mill), but another reason was the cost of repairing the original motors/electronics. I did repair the control unit on one lathe myself successfully a couple of times, but it failed again later, and also the DC motor. After looking up the cost of replacement, or the rip-off prices charged to get them repaired, with no guarantees, it was cheaper to buy VFDs and new 3-phase motors, both of which were easy to source from many suppliers, whereas the original parts (in some cases) came from one or two suppliers. Sure, I had to make some modifications to fit different motors, but nothing complicated, and it meant the mill got converted from gear to belt drive – far quieter and smoother running.

In reply to the comments about electronics reliability, it depends what you mean by reliability – you only have to look at this forum to see the number of times the original electronics fails on Chinese lathes. Sure, a lot of VFDs are Chinese made as well, but at least they can be purchased for a reasonable price, unlike the lathe and mill controllers, and I have never had problems with the ones I have.

That said, I for one have had no troubles with my VFDs after doing the conversion, and the machines are much more useable – soft starts, smoother running, speed control, reversible, remote control – the advantages easily outweigh the disadvantages in my opinion.

PS Just checked my drill press. It is actually 970rpm that I leave it set on for 90 per cent of the time, not 800 as I said in earlier post. Seems to be the sweet spot that suits all drills 1/8 to 1/2". For 5/8 I might drop the belt one notch to 800 or so.

As Michael said, the first thing you notice is that the motor runs more smoothly. Single phase motors have an inherent torque ripple as the rotor interacts with a contra-rotating stator field component. This can produce an audible throbbing. Capacitor run motors can be better as they are more true 2-phase. On my Super 7 the highest speed range, i.e. largest motor pulley, was essentially unusable because the motor vibrated so much. I fitted a 3 phase motor and Neston Tesla drive and it transformed the lathe.

Yes, domestic supply is one phase of a 3 phase supply. 3 phase is used throughout the generation and distribution network, mainly because it permits a significant reduction in cost for the same power, using less copper and iron. Also incidentally it enables more efficient 3 phase motors which use less material for the same power.

If you only have a single phase house supply VFDs can generate 3ph for you at much lower cost than having a 3ph mains feed, and incidentally gives variable speed.

To all intents and purposes, VFDs are not applicable to single phase motors. Yes you can kluge them to work, but the speed range will be limited.

3ph motors with VFDs are becoming preferred in all sorts of applications that would once have used "universal" series-wound commutator motors, for example washing machines. They use less material and the VFD permits variable speed. Modern drive electronics can be very robust – though a lot of DC motor speed controllers used in low cost machine tools seem to regularly go wrong due to poor design. Interestingly Tesla cars use induction motors and VFDs but not as we know them.

Your drill press if run from 3 phase would allow you to set the right speed every time. I fitted a 3ph motor to my Myford VMB mill partly because the belt change arrangement was so clunky. I eliminated one step pulley and got variable speed and reverse. That means I change pulleys much less frequently. It also means that I can set the spindle speed very low and use the machine to tap a just-drilled hole in exact alignment; then reverse the tap out of the hole.