Lathes,,3 Phase to Single Phase

[onehole]

There must be some small lathe users out there,,,,I,m looking for some guidance,,,,,shortly picking up a nice Myford SL7 long bed but its fitted with a 3 phase motor,,,I have to run it on household electrics and I understand there are some options to either replace the motor with a single phase or fit some kind of inverter/converter to the existing 3 phase,,,,,,whats the best way forward,,,anyone/ thank you,,,,,,,,O

[rhhudson]

I dont think its a case of just change the motor, all the switch gear will need changing depending how it works,

 

you can get inverters that will go from 240 single to 415 3 phase, i think that would be the simplest way but there not cheap!!

[Big Al]

If the motor is relatively modern, of the finned variety and able to run in what they calm star or delta configuration then a basic inverter drive will be easy to wire and very versatile, it will turn your 240v 1ph into 240v 3ph, all you need to do is reposition some terminals in the motor to convert it to run 240v three phase instead or 440v 3ph, a job that takes literally 5 mins.

 

If its a really old machine and the motor is an old 440v three phase which can't be switched to 240v 3ph then a new single phase replacement will cost £100 or so, with Myfords the wiring is very simple as there isn't usually a foot brake isolator and a bit of new switchgear is easy to rig up if your DIY minded.

 

It is even possible to generate your own 3rd phase in 240v configuration with a very basic home made static converter using capacitors bought from the likes of Maplins, Ive done it many times and can work well for little cost.

[phoenix]

Definitely an inverter to change from single phase to 3 phase.

Changing to a single phase motor will work out more expensive and cause no end of problems

 

Cheers

 

Bruce

[Tikka4Sika]

https://www.simplypowersupply.com/Single-to-3-Phase-Converter/Static/default.aspx

[eldon]

I have a rotary phase converter and this then allows me to run other things up to 3hp. Beware of static converters as if you have a small motor say a coolant pump and you turn this on before firing the main motor up then you can burn things out. This is where a rotary unit wins hands down but then it does cost more. Mine cost around £500 but has proved very reliable.

 

I have previously converted a 3ph lathe to 1ph and it wasn't a bad job although be careful with the wiring if you want both directions of rotation for screwcutting without disengaging. Some pull in coils will need changing to make it work and ensure you still have a no-volt release system i.e. power failure whilst running doesn't spin the chuck on re-connection.

[Webby]

As an electrician and having just converted one for another member on here. A 230/415 3ph inverter is the way to go.

A single phase motor is a bit of a problem as it will not have much starting torque and will not be powerful enough as well as being unlikely to run at the same speed.

However some knowledge of electrics is required to make all the safety devices on the lathe work properly with the inverter.

Best to change coolant pump to single phase if it is not already

[onehole]

Wow thanks for quick replies,,,,inverter it is then,,,,Webby,,,,,do you or indeed anyone else please have recommendation as best place to source one or would it be better left to a local electrician to get and fit,,,,,.I could probably fit it myself but only have basic knowledge of wiring if I,m being honest,,,,,thanks,,,,O

[alpha1]

I have just done exactly what you are asking. I bought a kit from Newton Tesla I think thats how you spell it. The kit consists of an inverter a new motor and a speed controler. The improvement is brilliant. They do dedicated kits for the myford. It is easy to assemble the biggst problem is siting the motor. It runs of your 240 supply.

http://www.lathespeedcontrol.com

[Webby]

The inverter came from here http://www.drivesdirect.co.uk/downloads.htm They sell the inverters on eBay. Search for Teco Inverter. Would suggest calling them with the spec of your motor so they can match it.

[alpha1]

Ring the guys at Newton Tesla they sell bucket loads of there gear to hobby machinists they will advise you what you need. They a great people to do business with.

[baldie]

Change the motor to single phase Dave. The ML7 is a small, antique [almost ] machine. For what you will be able to do on it, any variation in speeds won't make any difference.

 

The motor that is on it, is unlikely to be std equipment anyway.

 

Ring these guys. They are my myford specialists, and have mountains of stuff [ and knowledge] for them

 

www.rdgtools.co.uk

[Davy]

Places like Drives Direct can supply a full system for a Myford, my son has one and it came with motor, inverter and a local control unit with speed plus fwd/rev. It has impressive torque and infinite speed control plus can be switched from forward to reverse without switching off and it ramps down and up again. Sub GBP300 when he got his.

[onehole]

Thank you again people,,,I really do appreciate your learned suggestions,,,,,,will be talking to the suppliers you have mentioned and go with what I think may be the best option.Seems I may not be disappointed with either route but I,m not too worried about conversion cost as the lathe was a gift!!,,,,,It would not be a first choice as Dave quite rightly puts it in the small and relatively antique class but none the less I am expecting a huge leap in accuracy compared to my embarrassing excuse for a lathe that I,m using at the moment. Once I do get it up and running at home I will see how I get along with it,,,,The other bonus is that I could always sell it as they seem to fetch good money and put this into a more modern machine,,,,,O

[eldon]

Onehole this is where I got mine from;

 

http://www.digi-phase.co.uk/digi.htm

 

They are very helpful people and I would recommend them for advice.

 

If you go the inverter route then in effect you are converting one machine whereas if you go the phase converter route then you are creating a three phase source. Are you likely to want to add other machines later i.e. small miller? I had a nice small Churchill miller running off the same source (one at a time!!!) and I also have a Mec Brown rotary saw that is three phase and for the cost (small 3 phase units are better than 1 phase but less desired) is far superior to any of the single phase saws at a similar price point.

 

 

For future proofing I would go the converter not inverter route!

[Big Al]

Duplicate post.

[Big Al]

Thank you again people,,,I really do appreciate your learned suggestions,,,,,,will be talking to the suppliers you have mentioned and go with what I think may be the best option.Seems I may not be disappointed with either route but I,m not too worried about conversion cost as the lathe was a gift!!,,,,,It would not be a first choice as Dave quite rightly puts it in the small and relatively antique class but none the less I am expecting a huge leap in accuracy compared to my embarrassing excuse for a lathe that I,m using at the moment. Once I do get it up and running at home I will see how I get along with it,,,,The other bonus is that I could always sell it as they seem to fetch good money and put this into a more modern machine,,,,,O

 

 

If you have space for a larger machine then that is what I would do, since your into rifles it could open up more possibilities for you.

[silpig]

Another vote for Drives Direct! I have 2 of their digital inverters. One on my Colchester Student and one on my Bridgeport mill. The digital inverters can enable you to do things beyond the normal controls of the machine. On my lathe I have been able to alter the parameters that dictate the time taken for the spindle to reach chosen speed and the time taken to then stop the spindle. My milling machine is the older, belt-change type. The digital inverter enables me to leave the belt in middle position and then alter the spindle speed via a rotary dial. This works adequately well for the majority of jobs. Can't remember the chaps name but he was very helpful.

[onehole]

Again thanks for all advice,,,,I have spoken to all your recommended suppliers and they have been very helpful.I will be going forward with one of them.Seems the existing motor is suitable to "inversion" so have decided to go this route and get local electrician to do a proper installation.Just got to get this lathe moved now and I aint looking forward it !!!! atb,,,,O

 

 

[eldon]

Onehole I have moved a few lathes in my time and a few years back had four in my garage at once. Have a look at the construction and you may find the main casting (underside) has just a few (possibly four) bolts inside the base box. With these bolts out and any wire connections/pipe resolved the top should come off easily making the whole moving process a damned sight easier.

 

I did this with a few Boxford's and managed to easily move them with car and trailer and overhead block and tackle for lifting off. It may not be as bad as what you think

[Davy]

The ML7 can still be a fine little lathe. Breaking them down is easy enough as well. There are two feet or pads that the lathe sits on, remove the top 4 bolts, remove the tail stock and chuck to remove some weight and two of you can lift it. Beware the motor end which is heavy and and tends to overbalance backwards.

 

Once removed the pads can be unbolted from the underside and the pads and tray removed. After that you just have the base to contend with. My son and I moved his reasonably easily however I did make sure he was at the heavy end.

 

When you get it into place bolt the base down and spend time levelling it, then fit the tray and pads and finally the lathe and again, spend time levelling the lathe bed as it twists easily which throws accuracy out. You can use brass shims under the feet of the lathe however you must make sure it is fully supported. A decent level is essential and I have a machine level safely stored for just such jobs.

 

The biggest short coming of the ML7 is your own imagination, they are still widely used to this day by people turning and even milling with an adapter plate to incredible levels of accuracy. Enjoy

[onehole]

Thanks Davy,,,,have just spent two days clearing my garage freeing up shelves etc and a space for this lathe.I have also been working through the huge amount of tooling that I have already collected from the workshop,,,,it was an alladins cave worth with just about every tool one would need.Looking up Myfords accessories I pretty much think they are all there,,,,,the divider still puzzles me,,,but I will get there??,,,,I have spent an enormous amount of time on U Tube and look forward to setting it up to run true,,,,this little beauty is a million miles away from what I have been knocking things up with and in my mind have only scratched the surface into knowing all the things you machinists and gunsmiths have been trained in....I have always suspected but can quite understand the justification our smithy,s charge for what they do,,,,,O

[baldie]

The lathe is the easy bit.

 

If there is mountains of tooling with it, take everything offered, and then sort through it.

 

You will spend 5 times [at least ] on tooling, over what the lathe cost.

 

I spent 2.5k on chucks alone just recently.

 

When you consider one quick change block and a simple tool in it would be 2-250 quid...it soon adds up when you have 30 or so I think I have 15-20 for each lathe.

 

Good tooling is not cheap. It matters not what you can knock up for your own use, but its got to be right when customers parts are involved.

 

A lathe is more fun than a nymphomanic .

[Davy]

Onehole - Items with the make 'Myford' and ideally boxed attract a premium if you decide to sell them. I know someone who collects them without ever using them and assures me they are appreciating in value. Also if you have Pratt Burnerd chucks keep them safe, they are superb and a 4 jaw is always going to be more accurate than a 3 jaw so teach yourself to clock in even when not needed, it is a useful skill. Look out for the old names like PB, Crawford, Dickson and Hardinge accesories, they are still amongst the best money can buy if in good condition.

 

As Dave says, the lathe is just the start of things however you do need to get used to it, Youtube is a fine start for the basics however it does not teach you about touch and feel and the sounds a lathe will make, when to speed things up and when to slow things down. I can turn my back on my main lathe and still know what it is doing just by the sound, same applies to my Bridgeport however that does not mean I take my eyes off them for long! One thing I will add is I use DRO's (Digital Read Outs) on all of my machines, I spent many years winding back dials and re-checking and zeroing dimensions, these days I keep an eye on the DRO however they cannot take the place of a careful touch and a good set of eyes (Or reading glasses)

 

Enjoy the Myford, my son is turning out some cracking stuff with his and holding 0,01mm on some of the parts he makes which is better than 00004" It just takes him a bit longer than it takes me.

[onehole]

Kin Ell,,,well ,,,,I,m knackered,,,Davy your Son must be built like a brick S H,,,,This took four of us ,,,guess we were not that well prepared but the pick up was difficult some narrow exits and steep paths to a waiting trailer.Two trips one for the lathe and one for the base,,,but all moved today and now temporarily sited in my garage waiting for an electrician to wire it up and jiggle it in for final levelling etc.....I do not want to do that ever again OK!!!!