Thread: Variable Speed for old Lathe - where do I start

Go to the Electronics sub-forum (https://www.woodworkforums.com/f271) and read the the two top stickies in that forum.

As you will see it's not always as easy as it sounds although sometimes folks get lucky.

Some time during the 90's, I bought a complete variable kit from Woodfast. Since then a lot has happened to Woodfast. Might be good to contact Jim Carrol at "Carroll's Woodcraft Supplies", to see if those kits, or something similar, is still available. Might save you a lot of heart ache?

Jim

Well much depends on your budget.
But you have to work out where and how your gonna put the three phase motor and if your going to change the pulley set up.Presuming you have already worked out what size you want Its often a good idea to have or keep a stepped pulley set up to make up for any loss of torque. Also you want to look at ebay or FB market place for a motor, it will be cheaper.
Then sort out your VFD, you can get them on ebay as low as $90 to drive a 2.2kw motor. The manuals can be a challenge with strange english etc. Dont forget to get a pot I would recommend 10 turn this will give fine motor control and also if you bump it , it wont change the speed too much. With one turn this can be very hectic, also available on Ebay very cheap. Also you will need a electrical box of suitable dimensions to allow the VFD to dissipate the heat, you can if you wish mount the whole thing on the wall. But if likely to move the lathe it might be better to mount it all on the lathe. Depending the VFD you may need a contactor with a 240 volt coil. But above all else if your not a sparky, go find one preferably a mate.

Alternately you buy DVR type set up which is expensive or a EU/Japan/USA etc made VFD etc which aint cheap. My first one was Lenz made in Germany original price was 1400.

Originally Posted by hughie

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Dont forget to get a pot I would recommend 10 turn this will give fine motor control and also if you bump it , it wont change the speed too much. With one turn this can be very hectic, also available on Ebay very cheap. .
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I've tried using a 10 turn pots but found they were too slow.
If VFD remote pots are well positioned they should not get bumped.
I've got 9 VFDs in my shed and have had them for up to 11 years and not once do I recall bumping one.

An alternative to a 10 turn pot for fine speed control is to use two pots (one for coarse control and one for fine) and a couple of resistors.
There are several wiring arrangements that can be used and I describe one (H-Pattern wiring, easily found on the internet) in this post where I installed this on my MW lathe.
VFD install summaries

I also installed two pot control on my MW mill, but on my DP I just used a bigger knob and find that to be fine .
This one is from a clothes dryer timer.
Switch.JPG

Originally Posted by BobL

An alternative to a 10 turn pot for fine speed control is to use two pots (one for coarse control and one for fine) and a couple of resistors.

I can’t imagine needing that level of control on a woodworking lathe. I suppose if you’ve got OCD* and need it to be running at a round number but I don’t find any practical difference between 700 rpm and 723 rpm.


* I started off trying to fiddle with it for round figures, because that’s neater, but gave up quite soon. I often don’t know what speed I’m using, just a general feel where it is and of how safe it is for what I’m busy doing.

Originally Posted by Colin62

I can’t imagine needing that level of control on a woodworking lathe. I suppose if you’ve got OCD* and need it to be running at a round number but I don’t find any practical difference between 700 rpm and 723 rpm.

I agree, a bigger knob is probably good enough for a WW lathe. I even have a Tacho but I put that on mainly because I had a spare one and so a young bloke I was teaching could adjust the speed to what I recommended without me being there all the time. I don't really use it myself except sometimes when I make the BMHs - if it's too slow it can overheat and even stall the motor - if it's too fast it self cools the heated PVC and makes it harder to form the bell mouth..

Garry, I wrote about my experience at post #21 of this thread: Restoring an early 80’s Woodfast Lathe

I use 10 turn on all my lathes. The pot knobs I use allow me to turn using one finger, so its never been an issue for me.

I like the variable speed pots used on the 9000 series VFDs.

The knob is not really attached to a pot (knob turns endlessly) but a pulse generator(?).
Regular slow turning changes frequency to the 0.1Hz level but the faster you turn it the MUCH faster the frequency changes. They take a bit to skill to master but once you get the hang of them they are very good. They are definitely overkill for WW lathes but useful for other machines.

Originally Posted by BobL

I like the variable speed pots used on the 9000 series VFDs.

The knob is not really attached to a pot (knob turns endlessly) but a pulse generator(?).
Regular slow turning changes frequency to the 0.1Hz level but the faster you turn it the MUCH faster the frequency changes. They take a bit to skill to master but once you get the hang of them they are very good. They are definitely overkill for WW lathes but useful for other machines.

Toys Bob we all love our toys

Originally Posted by Colin62

I can’t imagine needing that level of control on a woodworking lathe. I suppose if you’ve got OCD* and need it to be running at a round number but I don’t find any practical difference between 700 rpm and 723 rpm.


* I started off trying to fiddle with it for round figures, because that’s neater, but gave up quite soon. I often don’t know what speed I’m using, just a general feel where it is and of how safe it is for what I’m busy doing.

For me, its fairly simple change speed to suit what I am doing or till run smoothly. A rev counter would be something else to look at. But in Bobs case the young pupil wouldnt have an eye for rev/speed so it would be useful

Originally Posted by hughie

For me, its fairly simple change speed to suit what I am doing or till run smoothly. A rev counter would be something else to look at. But in Bobs case the young pupil wouldnt have an eye for rev/speed so it would be useful

Me too...

I've never had a rpm readout on any of my lathes. I start slow and gradually wind up to the max speed before I see/hear any vibration, then increase the speed as the blank comes into balance. Occasionally I accelerate through the harmonics to get to vibration free running at a higher speed, but that takes some judgement as to whether that can be achieved before doing it... get that wrong and even a heavy lathe will want to walk out the door by itself!

Like Bob, I've found the rpm readout on the lathe at the local men's shed to be useful when giving advice to inexperienced turners. One of the few good things about that lathe is that it resets the speed to zero every time it is stopped. It would drive me mad but it's ideal for that setting.

Originally Posted by LanceC

Garry, I wrote about my experience at post #21 of this thread: Restoring an early 80’s Woodfast Lathe

Lance

Your reported experience after implementing your VFD precisely summarises my experience.

Thanks for all the Input.

Looking at ebay I see a 2hp motor VFD combo for sale for around the $600 mark. Single Phase variable frequency drive with 1.5kw Electric motor for belt sander | eBay
any input on this Motor VFD Seller combo appreciated.

Current Motor Pulley has a 19.05 bore and 2 grubscrews, motor listed has a 20mm shaft with a key, Current motor is pretty big, don't think I would have Issues mounting the one in the link in place of the existing motor, but havent measured anything yet, will open it up at some point and try to get either a Manufacturer + part number or actual dimensions.

The lathe has a removeable front panel which currently houses the on/off switch, mounting the VFD here would probably be sufficient, haven't looked deep enough to see whether the linked VFD has a remote option, or whether I even care that much, The VFD linked above has what I assume is a speed control knob on its faceplate.

Is there any advantage in going to 3hp, cost wise it would be $100, of what will probably end up being a $1000 upgrade.


Garry