I currently have the Makita router (10k-32k RPM iirc) - great for plastics and wood, “meh” for aluminum.
Can these “cheap” VFDs run sub 8k RPM?
Also, what is the max RPM of these spindles?
I don’t think I’ll be getting one anytime soon, just curious! 
Hey jarrfarr,
it’s not the VFD that limits the lowest speed of the spindles, most VFDs offer 0–400 Hz, some do 580 Hz like mine. It’s the spindle and the way it is built that limits the lowest speed.
Since the rotational speed of the spindle is calculated this way:
SPINDLE_RPM = $VFD_FREQ × 2 × 60 / $SPINDLE_NUMBER_OF_POLES
e.g. 400 Hertz × 2 × 60 seconds / 2 poles = 24,000 rpm
this means with a spindle with two magnetic poles a VFD can deliver 0–24,000 RPM spindle speed.
Note that most 24000 RPM spindles with magnetic 2 poles have a minimum speed allowed by manufacturer of something between 8000 and 6000 RPM and running them slower can damage them, it would be good to set “Lower limit of frequency” inside the VFD to something between 133 and 100 Hz.
Those spindles with 2 magnetic poles usually are rated 6000–24,000 rpm.
Some are rated at 8000–24,000 RPM. See datasheet/manual of your spindle.
If you want to mill steel or plastic, it would be better to buy a spindle with four magnetic poles. This means that with the same frequency coming from the VFD, those run at half the speed but double the torque.
Since the rotational speed of the spindle is calculated this way:
SPINDLE_RPM = $VFD_FREQ × 2 × 60 / $SPINDLE_NUMBER_OF_POLES
e.g. 400 Hertz × 2 × 60 seconds / 4 poles = 12,000 rpm,
those spindles with 4 magnetic poles are usually rated 3000–12,000 rpm,
so good for the slower speeds needed for milling steel and plastic.
Most spindles with 2 magnetic poles are rated with max. 24,000 RPM. Higher speed of up to 60,000 RPM is offered for the industry but I don’t think many here need this, and it becomes very expensive then. Mechatron offers some variants of its 24,000 RPM model with 30,000 RPM and 40,000 RPM. But in fact what is demanded more often here is to have a spindle that runs slower than the usual that min. out at 6000 RPM.
Thanks for the in-depth explanation, it was very helpful to see the math behind it all!
Wow! Thank you for your detailed explanation of those prameters. However, I have the HY 110V 1.5Kw spindle purchased through Amazon made or marketed by MySweety. It is rated 24000rpm. I watched their amazon video how to set it up. Turning the dial to max reads 400Hz on the freq reading but on the rpm reading it reads 11,520rpm. Again, it was rated 0-24000rpm. What could be the problem here?
Thank you
Hey Olan,
maybe the settings of “Rated Number of Poles (PD143)” and “Rated Motor Revolution (PD144)” are not set correctly. See here.
Thank you for your response. So I checked the VFD PD141, it says 220. But the spindle is rated 110V. Another shocker is the amperage is 8A as it was imprinted on the spindle itself. How can it be?
On the VFD box, -110V, 13A, 1.5KW
On the Spindle- 110V, 8A, 1.5KW
On the attempt to change the PD142, it doesn’t allow a change more than 007.0
Hey Olan,
The setting should be 110 if it is a 110 V VFD and if it is connected to a 110 V outlet.
However it is unlikely that it is set to 220 if it is a VFD made for 110 V. What is the exact model number?
Did you read the VFD manual and the spindle manual?
If it is a 1.5 kW 110 V spindle then there should be rated 13-14 A printed on the spindle name plate.
1500 W / 110 V = 13.63 A
8 Ampères at 110 Volts are 880 Watts (=0.8 kW)
110 * 8 = 880 W
If you connect and operate a spindle and a VFD, you are responsible for the right settings. They are no work-out-of-the box devices. Did you read the VFD manual and the spindle manual?
PS: Got to leave now! Will be back later.
I read all the manuals
On the VFD box, -110V, 13A, 1.5KW
On the Spindle- 110V, 8A, 1.5KW
On the attempt to change the PD142, it doesn’t allow a change more than 007.0
Thank you i appreciate your kindness
Hey Olan,
maybe it’s a 0.8 kW spindle.
Anyway for a 24,000 rpm cheap chinese spindle, setting “Rated number of poles (PD143)” to “2” and “Rated Motor Revolution (PD144)” to “3000” should be correct, as explained here. With this you should get the spindle spinning at the right speed (24,000 rpm at 400 Hz).
Thanks! I will let you know if it fixes it
Hey Olan,
another idea that came to me later: Maybe the “Rated Motor Current (PD142)” setting is limited to 7 A as long as the “Rated Motor Voltage (PD141)” setting is (incorrectly) set to 220 V? Maybe you can set the current to 14 A only after you have set the voltage correctly to 110 V? In both cases the power would be set to 1.5 kW:
( 220*7 = 110*14 = 1540)
110 V * 8 A is 880 W (0.88 kW), in this case the writing “1.5 kW” is simply wrong. Or, the “8 A” is wrong. That does not fit together!
Hey all, especially VFD/spindle beginners,
(hey Olan, I don’t suspect that you have made these things wrong, but I take the opportunity to comment what I have seen on that page)
this is obviously the cheap chinese offer ASIN B01N1EJEQ1. On the page, there is a video that intends to show how you program the VFD and then how you connect the spindle.
Don’t use that video! Don’t do this at home!One good rule that I can recommend is: Don’t make any settings on a VFD that you don’t know what they mean. But also don’t plug it in without making sure you’ve programmed everything mandatory (and correctly too).
Always first know what you are doing. Please always remember that when connecting spindles and VFDs, you can burn down your house or seriously injure yourself.
The video shows connecting the VFD to an outlet with a 2-wire/2-pin plug.
Don’t do this!
Never use two-wire/two pin plugs for a device that visibly has an earth contact!
Use only three-wire/three-pin plugs between wall outlet and VFD!
While some settings are shown in the video, the settings that are mandatory for the correct installation of a spindle are not made, let alone checked. Failure to do so may damage or destroy your spindle and/or VFD!
For a quick explanation on how to program these mandatory settings on any VFD please click here!
The video shows connecting the spindle with three wires, omitting ground.
Don’t do this!
Always wire the fourth contact of the spindle to ground on VFD, and always make sure that from VFD it is connected to ground on your wall outlet as well!
Use only four-wire connection (3+PE) between VFD and spindle!
Use only three-wire/three-pin plugs between wall outlet and VFD!
Furthermore the video shows clamping bare stranded wire ends, or even worse, soldered wire ends into a screw terminal. Don’t do this! Especially screwing down a soldered wire end is dangereous since the screw by its pressure destroys the internal cristalline solder structure.
On all power wires and terminals (=on input wire from wall outlet and on the connection between VFD and spindle), always use the connectors described in your VFD manual, which are likely to be either ring connectors or wire ferrules (depending on model)!
Thanks Aiph5u for all the clarification here.
I recently went through an evaluation of Chinese spindles and came to conclusion that if I were going to buy Chinese, it needed to be a genuine HY. The pathway that I had the most trust in was their store on Amazon.
I ended up not buying Chinese since I could get no definitive answer on constant torque speed range for the water cooled spindle I was considering. I did get an answer from the HY person who responds to Amazon sales that they recommended no lower than 10k rpm for their 2.2 kw water cooled spindle. They could offer no torque curves or real data. I was a bit surprised by that but it helped move me in a different direction.
For those buying Chinese spindles, just know the path is not always clear and getting what you order seems to be a bit arduous. So stick with the more reputable supplier.
Oh wow! You are the best man. Thanks a lot
