returning to turning

[thescoot]

Hi guys. just thought i would introduce myself. I have been a mechanical engineer for almost 4 decades and a cabinet maker for the last 10 years working primeraly in oak,ash and mahogany. i have been turning metal all my life and several years ago dabbled in wood turning when my father gave me an old clarks hobby lathe, the head of which i still have. i was also given a small tyme lathe that i loved working on and i feel turned out some reasonable projects on it. mostly small stuff and some bits for my furniture,little finials,handles etc. Then just before christmas i got a fancy to do a bit more turning and fell in love again!!!!
So i started trawling the net to find a decent size of lathe only to find the prices of all i thought suitable way too much for my budget.I was gutted. It was then i spotted a very old A J Cooksley and Son on e bay and placed a bid. winning bid £51.I could hardley believe my luck although it cost a bit for the transport it would be well worth it. It arrived about a month ago and thats when the problems started. It was three phaze 400v and my workshop isnt.Looking at all the options i felt an invertor was the best way to go so i purchased one of these MAGIC boxes and contacted an old mate of mine to help with the electrics. Hey presto. he converted the motor to 240 3 phaze(dont ask as iv not got a clue how that works) and added a potentiometer to control the hertz frequency.Wow 4 speed belt and pully lathe with 0 to 50 hertz speed control which gives 0 to 4500 speed fully variable.
Problem is, enough isnt so my engineers brain kicked in. Out came the pencil and off i went designing a bespoke hand made unit. It took 3 weeks and a lot of work but boy was it worth it! I am now the very proud owner of a 3hp direct drive lathe with a fully variable speed range of 0 to 3000rpm which can turn up to 1200 dia. now i just need to get some practice and make lots of shavings.

[Terry Miller]

Welcome to the forum.I hope you enjoy the banter and the rants and the very useful hints and tips.

Regards

Terry

[julcle]

Hi  --  Welcome to the forum, sounds like an interesting project. You could post some pics
on the site and show us what you did, if it's the little phase inverter that you can buy on e-bay
for about £20 or so depending on the power rating I have used used one of these in the
past to good effect. Perhaps also you could fill in your profile and let us know a little more about
yourself, you can set it so that only forum members can view if you wish. - Best Regards - Julian

[Doug Barratt]

Hi & welcome,

As has already been said photos are always welcome

I`ve recently converted a 3 phase wadkin planer with the aid of an inverter & at the risk of teaching mother to suck eggs, I would suggest you place it in a filtered housing, if you haven`t already, as they don`t half suck in the dust.

Best wishes with the turning.

Cheers

[thebowlerhattedturner]

Hi and welcome to the forum. Glad to hear you have returned to turning and have managed to sort out your lathe. I too have a phase convertor, it was with the machine when I got it so I didn't have to deal with anything complicated,just plug and go.I agree with Doug about putting it in a housing of some sort as they do suck up the dust like nobody's business.
Regards
John BHT

[thescoot]

as requested ... a couple of pics

[thescoot]

Sorry guys. that was just to test if i could get the pictures up ok.o how i wish it was one of the £20 invertors off e bay! unfortunatly its a 5kw unit which is fully programable up to 5.5hp and was SLIGHTLY more than £20. Yes its inside a filltered box and is away from most of the dust. If you look at the picture you will notice a small controle above the motor. This is a remote which attatches with magnets and can be simply transfered between the two lathes depending on which i want to use.
I have only produced a couple of small bowls since i got things up and running which are to be fair not brilliant but im re- learning the craft after all.
Pic 1 is a bit of oak i had lying round just to try it out. Its about 700mm and the lathe turns it no bother at all. I have changed the floof bolts to a larger size as it did try to wakl a bit. it wont now!

[John D Smith]

Hi Welcome to the Forum thanks for posting the photographs it made the interesting story come to life.

                                                                            Regards John

[Bryan Milham]

Hi and welcome to the forum from me (Bryan).

So you're returning to wood turning by building your own 3Hp variable speed lathe that can throw 1200mm dia. Oh boy, this is going to be one to watch.

All I can ask is Post - Post and Post... I think that your out to produce some big pieces.

[Woodcrafts]

Hi Scoot,
Welcome to the forum from another ex-engineer. I am most impressed by the conversion but, not wishing to be a 'downer' on the project, can I make some comments about the conversion. I have done several inverter/three phase conversions for other turners but we have always kept the pulley system intact, as that allows you to let the motor run at reasonable speed even though the wood is turning slowly. There are two reasons for this - the full power of the motor is only available at it's rated speed, even for vectored inverters, but more importantly, these motors rely on a shaft impeller to cool the motor. If the motor is run slowly for an extended time, it can overheat. One tip, I set all the lathes I have converted to have a minimum frequency of 5Hz, so that you know if the power is on by the motor moving. If it is left at zero there is still power going into the motor even though it is not turning, and that can burn it out. Even with it set at 5Hz, it should not be left at that speed for any length of time.
Having said that, there are a couple of advantages of these inverters which I am not sure if you/your friend are aware of. First the motor can be switched to run in reverse very easily. (I couldn't tell from the photos if the switch on the remote was for that purpose or not.) Reverse is very handy for sanding but if you do use this option, make sure the chuck/faceplate is locked onto the headstock. Large lumps of wood coming off the lathe are quite spectacular! And if you do have a fwd/rev switch, keep it separate from the run/stop switch. Too many conversions use three position switches, with off at the middle position.  I watched a demonstrator lean on top of the piece which he thought was stopping, when it was actually going to continue at full speed in reverse because he had knocked the switch past the central position.
Having mentioned wood coming off the lathe, another potential accident if the chuck/faceplate is not locked to the headstock, is the momentum of the wood unscrewing itself when you stop the motor. Make sure the braking in the inverter is set to 'free run', not DC braked. That will also prevent overheating if you start/ stop the lathe too often.
Second, but this only applies if you are turning very small spindles (didn't know if you intend to do that as the setup looks to be just for bowl turning), you can increase the frequency past the usual 50Hz, thereby taking the motor speed past its nominal speed. Actually you are probably already aware of this as I notice you say you are "very proud owner of a 3hp direct drive lathe with a fully variable speed range of 0 to 3000rpm" I assume you have used a 4 or 6 pole motor and got the speed up by increasing the maximum frequency.
Sorry about all of this but hope it helps.
Like the other posts, I look forward to seeing the end results of this machine.

[thescoot]

Firstly thanks for the possitive comments,i didnt know if anyone would even be interested in this type of post. a couple of good points by woodcraft. my electrician pal did try to explain exactly how these digital invertors work( if they were mechanical i would have understood)but he lost me at delta and star so i just let him set everthing up to work with the motor he supplied on which the plate says 3000rpm @50hz. it was a spare off some kind of high speed mixing machine from the pharmasutical industry and he again tried(in vain) to explain all this to me about going over frequency etc.
If you take a look at the pics you can see a stud wall to the rear of the motor through which the cowl of the motor now goes. The intention being to A keep it out of the dust as much as possible and B i am designing a cooling system to deliver cool air to the motor fan. wether this will help very much im unsure but it cant hurt,can it? To be honest, i dont tend to run slowly as even when well out of ballance i get very little in the way of movement and tend to get the speed up asap. Iv not put a reverse switch on as i simply swap lathes where possible if i need or want to rub backwards. Spoilt or what?
 I will post pics of whatever i manage to turn out but its not easy getting lumps as large as i have the caperbility of mounting. The oak in the picture is now a very plain shallow bowl set to dry but i will photograph it and post(on the understanding you all know it aint done)
Again thanks for the comments and advice.

[Woodcrafts]

Hi Scoot,
Thanks for taking my comments in the way they were intended. I always find it difficult doing that sort of thing as some people get really annoyed, thinking I am telling them what to do. It sounds like you've addressed my main concern, about overheating the motor.
I would still recommend a reverse switch as it is extremely easy to do, just another wire to one of the control terminals on the inverter (at least it is on all the inverters I have come across ). And reverse can be very useful. In fact looking at the position of your toolrest, you could turn on the other side of the wood. Might be handy if you have some 'problem wood' but you would definitely need to 'lock' the faceplate to the spindle. But having seen the rest of your 'engineering' I get the impression that would be a very simple job for you to do.
Have lots of fun,

[woodndesign]

Welcome to the Forum and an interesting introduction, what away to return and a lathe from the pictures, should see you turning for years to come.

Not a bad looking pieced sat there as is it, will watch for more and be kind ..  ..

Cheers      David

[BrianH]

Hi Paul
Enjoyed reading your eeeelecktronic explanation. I tried my best not to duck but, I'm sorry to admit, most of it still went over my head. Since the nice man at Axminster fitted a new speedy gizmo to the monster I have made something of a habit of using the speed dial to stop and start the work. Is that advisable?
Also my gizmo has cooling holes across the top and I usually keep a rule over them to keep the dust out. Would you advize me to think about a more permanent way of covering them?  Box arrangement opening dowwards perhaps.
Thanks in advance
Brian

[thescoot]

Hi Brian. mark here. just read your post and thought id pass on what i was advised regarding the invertor i use. the two guys who helped with this project have a wealth of knowlage between them and they both advised not to stop the motor with the speed control but to use the switch which i always do. As u will see from my original post the invertor is in a box and has a fillter to stop the dust. Its only made from scotchbright but will stop dust ok. The two guyes who helped with this project have just been in my shop to check things over (its after all still in a bit of a development phaze) and up to now things a fine. perhaps a little more bracing might be required at a later date as i knoticed a little vibration at the rest when up above 1000rpm (i did have a 700mm dia lump of oak in and it was out of ballance) but it will wait.