View Full Version : Hardinge KL-1

10-09-2013, 06:27 PM
I have fairly recently been lucky enough to get hold of a Hardinge KL-1 lathe, and though it would be good to share some of my experiences with it.

I know the history of the machine for most of it's life as it came from the company at which I work, so most of what I plan to write about is, at least initially, about getting it to function.
I hope this will also be a record for myself as well for what I did, so I apologise if some of the things I write about have already been covered!

This is going in my garage, so no 3-phase there. It's the conversion to single phase - that's the first job.

Here is the lathe:


I'm not entirely sure of the manufacture date, as the serial number lists seem to be for US versions, not UK versions.

Searching the various forums tells me:

The main motor is a dual speed 0.5hp/1.5hp 415V_ac 3 phase motor.

The speed change motor is a dual voltage (240V_ac/415V_ac) 1/20hp three phase motor.

The coolant pump motor is also a dual voltage (240V_ac/415V_ac) three phase motor.

The carriage feed motor is a 90V_dc motor.

My initial aim is to power the dual speed main motor, really just to prove that the lathe is actually functioning, and there’s nothing seriously wrong with it.


10-09-2013, 07:34 PM
I aim to power the lathe using three VFD's, and utilise the original controls of the lathe.

The speed change and coolant pump motors can be converted to Delta 240V_ac operation.

The main motor is something that I definitely want to use due to it's quality, and I've read that I need a step up 240V_ac to 415V_ac transformer and a 3-phase input VFD to run it.

I the months waiting for the lathe to arrive, I gave up waiting for a transformer to appear on ebay, so decided to get a transformer manufacture to make me one.

10-09-2013, 09:28 PM
Paul the money you are going to pump into stepping up for the 415v, you might as well just swap it out for something else. a good quality 3 phase motor that will work at 240v delta with a vfd would be far more logical. I had to do the same for mine and even put a lower hp in, a 2hp instead of the 3hp it replaced. Never regretted it at all.

10-09-2013, 10:35 PM
Would imagine a rotary converter would be the cheapest and easiest way.? Keeps every thing original plus neat and tidy.

11-09-2013, 12:03 AM
Trouble is they are not very efficient and take a bit of room. The OEM motor was meant for a purpose. A replacement motor would be for the new purpose. No problem changing a motor to do job it is meant for. A darn site lot cheaper as well unless you build? Most lathes are sold with different motors for the environment they are to be used in.

11-09-2013, 12:53 AM
Rotary converter effiency depends on how well they're built.

I built an ammeter into mine, and when sitting with no load the needle is barely above zero. The noise of the idler motor does annoy me, although that's probably more to do with it sitting on top of a bit plywood with minimal vibration damping!

I am however considering upgrading to a digital convertor, as the latest purchase is going to be far too much hassle to convert to single phase, and may be pushing the power limits of the current rotary.

11-09-2013, 01:23 PM
I hear what you are saying about changing the motor, but the motor in the Hardinge lathe is a highly balanced motor, with two sets of windings for a low and high speed so there is just no sense in removing it and changing it for an inferior motor. Plus, the cost to convert using a transformer and VFD's isn't really that large.

Yes, I may be going over the top with 3 VFD's, but this is a project and a challenge.
I've also seen another 'mycnc' contributors hardinge powered this way, and it's impressive. It also makes sense to me as it retains all the original lathe controls.

Some calculations for the transformer :

The motor is 1.5hp which is 1.1kW (1hp = 0.746kW)
Assuming a 90% efficiency of the VFD then 1.1kW/0.9 = 1.22kW required.
Approximately, Transformer kVA = 1.22kW/0.7 = 1.74kVA.

However, this rating would be for heavy, continuous operation, which I'm just not going to do, so I have gone for a 1.5kVA Autowound Transformer. This will keep costs and physical size of the transformer down to an acceptable level.
An isolation transformer will be bigger and more expensive, and I've been told it's just not necessary.

This will step me up from 240V to 415V, then this will connect into two of the connections of a 3 phase input VFD.
I'll common up two of the inputs to share the loading on one AC cycle a bit more across the VFD rectifier diodes.

11-09-2013, 02:43 PM
then this will connect into two of the connections of a 3 phase input VFD.
I'll common up two of the inputs to share the loading on one AC cycle a bit more across the VFD rectifier diodes.

I've never heard of this done before. Devices inside the drive use a particular phase for synchronisation, that's why they specify which terminal to use if you are on single phase input, also a 3phase rectifier relies on phases being 'out of phase' for the return current but 2 of yours would be 'in phase'.
I hear what you are saying about the original motor but to be honest a modern 240v 3 phase motor is going to be just as good, the 240v drive will be cheaper and you won't need a transformer.

11-09-2013, 03:01 PM
"I've also seen another 'mycnc' contributors hardinge powered this way, and it's impressive. It also makes sense to me as it retains all the original lathe controls."

Not sure if it's mine you saw but if so thanks! Mine's written up at

HLV conversion to VFD - circuit and pics (http://www.practicalmachinist.com/vb/bridgeport-hardinge-mills-lathes/hlv-conversion-vfd-circuit-pics-117085/)

Six years on it's still working fine. If I were to do it again I'd probably somehow add an interlock to the speed change as various people suggested just to be on the safe side and also an external speed pot. But neither is likely to rise to the top of the projects list for a while.

11-09-2013, 04:05 PM
"I've also seen another 'mycnc' contributors hardinge powered this way, and it's impressive.

But nowhere did I see two of the VFD inputs commoned up as suggested, also LowEnergyParticle seemed to make most sense. Other than being 'romantic' about the old machine I don't see the logic (no pun intended) in not making use of it's digits inputs for control and preset speeds.

11-09-2013, 05:44 PM
It's been suggested to me by a VFD expert at work that this method of using a step up transformer to power the VFD will result in the current in the secondary of the transformer having too high a peak current, and over time damaging the capacitors within the VFD.

He has done a circuit simulation based on some inductance measurements of the transformer I did which were:

0 to 240V shorted, Inductance and resistance measured across 0 to 415v
50Hz 1.107mH 1.59Ω
100Hz 1.094mH 1.59Ω
300Hz 1.090mH 1.612Ω
1kHz 1.0877mH 1.798Ω

0 to 415V shorted, Inductance and resistance measured across 0 to 240v
50Hz 365.2H 0.571Ω
100Hz 365.1H 0.572Ω
300Hz 365.1H 0.578Ω
1kHz 364.3H 0.641Ω

The set-up:

10063 10062

And these were the results:


The secondary current can be seen as the narrow/tall "sine" wave, peaking at 13.599A.
This is based on a 1.1kW power, and the transformer inductance measurments above.

It's been recommended that I add some extra inductance in the secondary of the transformer, and before the VFD input to smooth out the peaky "AC" and lower the peak current. This should stop me knocking out the capacitors in the VFD over time. I'll get to that inductor.

Meanwhile, I had got hold of some VFD's while I had been waiting for the lathe, so have ended up with:

For the main motor - a Mitsubishi FR-D740-036-EC. 1.5kW.
For the speed change and coolant pump - two Mitsubishi FR-S520S-0.2K-EC. 0.2kW

11-09-2013, 06:45 PM
So, the first job was to run up the motor to see if the lathe had any serious issues.

I lashed up a setup using a different motor to check it all out first before moving it over to the hardinge.

A simple setup - the transformer, VFD and a couple of switches to control forward and backwards.
Wired into the lathes original high-low speed switch so I could test forward and backards in both speeds.

10065 10066 10067

11-09-2013, 07:08 PM
Interesting analysis, similar thing applies if motor cables are very long, not a problem in your case.
Power Drive Services - Electric Motor Specialists - Three Phase Line Chokes (http://www.inverter.co.uk/chokes/three-phase-line-choke.htm)

12-09-2013, 07:36 PM
Everything seems to be fine with the main motor. No nasty noises.
The VFD indicates about 2A when running.

Now to re-do the wiring.

I wanted to use as many of the original switches and contactors as possible, but knew that most of the wiring would have to go.

The control box wiring looked like this when purchased:

10077 10078

I'll keep the original high/low speed switch, main power switch, and as many of the contactors that I need.
Wiring from the terminal blocks at the bottom will stay, and I'll just wire the new control into them

So, here is some of the top half removed. The new transformer mounted, together with two of the VFD's.
The top grey one is the FR-D740 for the main motor, the white one to the right is for the speed change motor.


29-09-2013, 06:05 PM
Well, the wiring is pretty much finished now.

There's a little tidying that's needed, but here is the control panel.
The original 'green' power on, and forward/reverse switches do the same job as before.
Theres a red indicator for the 240V_ac being available.
The small LED next to the forward/reverse switch is off when the main motor VFD is at 0Hz.
Theres a key switch to really make sure it can't be turned on accidentally.

I've put two fans in the front to get blow some air circulation in through the VFD's, and when I can get to the rear, I'll put two more in to suck air out of the cabinet.

And the cabinet wiring.
10273 10274 10272

I think it functions quite well. I like the fact that I don't have to fiddle around with the vfd controls to work it, and overall, the lathe feels just like it would if powered from 3 phase.
The original lathe forward/reverse, high/low speed, faster/slower and pump on/auto switches all work the vfd's
The only thing I have yet to sort out is the brake.

A small niggle is that it is possible to have the high and low speed contactors trying to be on at the same time if I move the lever from high to low before the vfd has reached 0Hz.
It's not a big problem as they are interlocked so they cannot actually be on at the same time, but they buzz a bit if I don't wait until the motor has stopped.
Something to figure out later I think !

As soon as I can figure out how to save the circuit diagrams in sufficient detail, I will post them up.

29-09-2013, 06:31 PM
In the last photo of the previous post, in the bottom left is the inductor that's between the 240V_ac to 415V_ac transformer and the main motor vfd.

Based on the modelling, it's wound to be approximately 11mH.

The laminations are from a microwave oven transformer!
These transformers are great since they are an E-I configuration, welded together.
The weld can be carefully ground away to open up the laminations and get the original windings off. And the new ones on.

It is now gapped slightly, and held together with the clamps.

Unfortunately, it makes no noticable difference! Which I guess is good.
Only if I was to measure the current should I see a reduction in the peaks, otherwise I have to assume it is doing what the modelling says it should do...

29-09-2013, 06:40 PM
I've also decided upon some paint for the bits of the lathe I have cleaned up.

Trials of various paints seems to show this stands up well to the cutting fluid I have.

The paint is P383 Hi-Gloss one pack Polyurethane, manufactured by NEXA Autocolor.
I've gone for "Gun Metal Grey", code 2758.
Costs 26 per litre.

It's brushable, but can be sprayed if needed. although it brushes very nicely.

I'll let you know how it stands up to use!!

The collet closer is the first non-electrical bit I cleaned up and painted with the polyurethane.
From these grubby bits:

To this:
10277 10276

29-09-2013, 08:02 PM
Single phase to three phase conversion (3 phase converters) (http://www.isomatic.co.uk/3phConverter.htm)
What about going this way ----single to three phase convertor and leave the machine as is !

02-10-2013, 06:40 PM
Hi 'Ulsterman'
There are certainly many ways to achieve the same outcome, and this would be one of them.
It would probably have meant that I could have left all the wiring as is - but where is the fun in that !!

I also didn't want a second motor whirring away constantly, and as I'd need at least the 2.2kW, at 566+VAT+postage - pushing 700 for one of these, this is far more than what I've spent on some second hand VFD's and some wire!!
The 2.2kW version is also a 15A input, so couldn't run off a 13A plug top.

02-10-2013, 06:45 PM
I don't know how clear these are going to be as there is a lot of detail on them, but here goes.
These are the circuit diagrams for the lathe.
They are split into 'Power', 'Main Motor and Speed Change', and 'Coolant Pump and Carriage Feed'

10304 10305 10303

16-10-2013, 10:58 AM
Looking good Paul :)

I'll have to find the time to pop in


16-10-2013, 12:20 PM
This arrangement would work better for me.


With RL1 closed the Speed Selector Switch is moved to 'Low'
3M coil is energised and the NC contact in series with 4M coil opens. (preventing 4M being energised at any point - 'cross interlock')
3M contact across Speed Selector Switch closes to retain 3M should the switch be moved.
RL1 opens thus isolating the Speed Selector Switch from the 3M / 4M circuits.
If the Speed Selector Switch is moved then nothing will happen until RL1 closes again i.e. VFD at zero speed.

Same applies if you select High speed. The cross interlocks in series with 3M and 4M coils is standard practice and is in addition to mechanical interlocks that I think you mentioned.

18-10-2013, 07:31 PM
Hi Eddycurrent,

Yes - that looks like a good solution to the problem.
I've run into the situation where I have accidentally changed speed before the speed has dropped, so 'll definitely look at re-wiring. Shouldn't be too hard.
Thank you.

Bill, thanks - pop round when you can !

Cheers all.