Metalworking Lathes and ideas?

[LadyV]

Hi everyone,

I am Andyb's mrs to be and i'm thinking about getting him a lathe as a wedding present, but in true girl style i have no idea what lathe to get him. has anyone got any ideas of A which one to get him and B where do i get one from! It doesn't have to be new just has to be fit for the job!

Many Thanks

Lady V

[smo]

Aaah cool, is it gonna live in the workshop the vicky??????

P.S - i need to catch up with Andy, got some rent for him!

[Astro_Al]

Hello LadyV - can you tell us how much space is available, and if the power supply is regular mains or something more industrial?

Are there restrictions on access (i.e. does it need to be carried up stairs or anything)?

Also, budget will be a factor, but how one politely asks about that in a public forum I have no idea!

Cheers, Al.

[simonr]

I would say, for most people and most purposes a Myford is a good choice. A ML7 or Super7 is the preferred choice - and if you can find one with a screw-cutting gearbox - even better!

I'd be doubtful of buying any of the chinese Lathes you can buy new for the price of a Myford - there is a reason for the price being low!

This is without the screwcutting gearbox. They tend to go for between £400 and £700 depending on the condition and how many accessories are included.

This is a Super 7 with the gearbox:

This is an ML7

There are a few differences between the two. Super 7's have a few extra features - but not having them isn't a big deal.

Most Myfords run on Single Phase 240v - so you can just plug it in to a mains socket. Bigger lathes are mostly 3 phase needing a converter box to run off regular mains.

If you need somethig bigger, Boxford and Colchester made decent mid sized lathes.

Si

[Gazzar]

I know what I want for Christmas!

Yum.

G.

[Mark]

Can't add too much more than what Simon has said, other than they are often advertised privately on homeworkshop.org.uk or if you would prefer to buy from a dealer, I have had good service from home and workshop machinery but they certainly are not the cheapest way to do it.

To add, Si has a super7 and I have an ML7, and can recomend either.

if 3 phase and a bit of space is available then you have a really wide choice really nice machinery at a reasonable price.

Cheers

Mark

[simonr]

Simon feels he may have outgrown his Myford a bit and is looking out for a nice Colchester Student - something like this:

One day!

Si

[ciderman]

The myford Super 7 is a damn good bit of kit , I picked one up with a stand 2 spare chucks from a factory sale and paid £100 for it ,

Its earnt that back already .

[LadyV]

Thanks everyone, space is apparently not an issue as he'll "make space for it!" but it does need to be single phase.

Smo andy says that the rent will go up if the lathe comes in!!! he he

again thanks to everyone all help very much needed!!!

Thanks

Lady V

[Mark]

There are some fairly economic ways of running 3 phase kit off a single phase supply, so if space is not an issue, then you may well be better off looking for a secondhand industrial machine and an inverter.

What sort of stuff is he going to want to do on it?

Mark

[smo]

Strangely enough i was using a Myford super 7 earlier as my dad has one, its gorgeous but was more than the prices quoted here as it is a genuine factory refurb job and is like new!

[Night Train]

There are some fairly economic ways of running 3 phase kit off a single phase supply, so if space is not an issue, then you may well be better off looking for a secondhand industrial machine and an inverter.

What sort of stuff is he going to want to do on it?

Mark

I tend to but 3 phase industrial machinery too. I change the motor rather then mess about with 3 phase converters so that might be an option.

[LadyV]

Many thanks to everyone for all your help, sadly he has found another thing that he wants more so thats what he's getting, however if anyone does know of one going spare, then he might get it as a Christmas pressie, if he's been good!!

Thanks again!

Lady V

[integerspin]

I tend to but 3 phase industrial machinery too. I change the motor rather then mess about with 3 phase converters so that might be an option.

Rotary phase converters are really simple. I used all new parts inc a custom built transformer[7.5kva@100%] and the cost was around 200 quid. It has been running my workshop for 5 years. I can just buy cheap 3 phase stuff and wire it up. I run a compressor/plasma/lathe/mill/grinders/drill/power hacksaw/ bandsaw/polisher.

[smo]

Rotary phase converters are really simple. I used all new parts inc a custom built transformer[7.5kva@100%] and the cost was around 200 quid. It has been running my workshop for 5 years. I can just buy cheap 3 phase stuff and wire it up. I run a compressor/plasma/lathe/mill/grinders/drill/power hacksaw/ bandsaw/polisher.

Ooh, fancy writing a guide on how you made the 3 phase converter?

[integerspin]

OK.

Basically look for yank pages on Balanced converters, look for Fitch Williams write up if possible. Ignore the values and stuff

they mention as they don't have proper voltages. You will want an auto transformer to up your voltage to 420-440 volts.

then you build the converter as the yank ones, the starting caps will be of the order of 200Uf for 10hp.

the balancing caps will be ~30 and 60 Uf for the 10hp motor.

The best cap values will be found by playing around, you would be amazed[maybe not] at the possible capacitances you can

make from 10 or so caps, I bought an assortment[£60 worth] and trial and erroed it.. Your attempting to get three phases with

the same phase to phase voltage under load. I have something like 426-427-429 with the lathe cutting. the compressor drops

one of them to 400. you can add some capacitance to each machine to fine tune but it's seems to work ok how I have it.

The yanks use a potential relay to switch the caps, I couldn't find one, so made a little circuit with a resistor, capacitor

and rectifier to switch the contactors. I will add a diagram. By altering values of the components you can alter the

voltage of the generated phase that the caps are switched at. Generated voltage means the motor is spining, so once it's

spining the start caps can be removed and the run caps switched in, I did wonder about leaving the run caps in and adding

more caps for starting but I found a reason not to do it?

It's pretty simple but it runs a 5hp polisher all day without overheating it, I ran the polisher from a static converter for 15 years

and we had to cool the thing down after a few hours use.

I bought the transformer from a place called Morite windings.

The caps came from a place in merseyside, do a search for 'orange book run capacitors'

You can alter site transformers or even run a pair of smaller transformers on the output of the converter.

I built the whole thing on a bench and played with values till I got it how I wanted it.

rotary_002.pdf

I bolted the majority of the stuff in a box which is wall mounted, I had great plans for an automatic control for the compressor so it can be set to only come on in the day when nothing else is in use, needless to say I never got round to it. and I was going to install a 12V on off system wired round the sheds and garage so I can control it from near every three phase bit of kit. No didn't get that done either... The wall box was a fire alarm panel, It came with all those holes, the top and botom switch are on and off. The transformer lives in the blue box with the L1-L2 caps[C1-C2 on the diagram]. It could all be a lot neater but I wanted to use it.

The motor isn't shown but there is a 7.5kw[or was that 7.5hp?] idler motor which is on foam pads on the floor.

You press the on button and you have three phase.

There is only one problem with it like this, the off/on contactor coil remains on for a second or so after the converter is switched off so you need to hold the off button for a second, if you stab at it it will either pop the 32 amp breaker or if your a bit slower you will reverse the idler;-). I was going to swap the coil for a 240 volt coil but it's another thing I never got around to.

The contactors were cheap as chips from ebay..

I am sure there are some lectricians here that could improve it

If you look up converters you will find some people just running a three phase motor with no capacitors. Try it. connect switched single phase to two of the phases of a motor and spin the motor with a bit of string, when it's rotating switch on the power, it will come up to speed and if you check the voltages of the phases you have a generated voltage. I actaully ran my cutter grinder like this from an old 3 hp 3phase motor. I have found write ups where people are running commercial workshops like this! This is the basis of the rotary converter, the caps are to balance the voltages and provide a phase shift to get the idler rotating.

Should I read thru this to see it makes sense and hasn't got to many spelling mistakes? nahhh

[Night Train]

I used to have a rotary 3ph converter in my workshop in London and a huge abundance of 1ph and 3ph motors as we were repairing and selling them. Up here I still have a small stash of 1ph motors left over but no converter. It was easier to just change the motors in the machines I have, as they are belt driven, then to get another converter and start adding a 3ph supply to my workshop. It is bad enough that I have 240V and 110v without having to have 415V circuits as well.

A converter is a more convenient way to go as a fresh start but given the stash of 1ph motors it was simpler to go that route for the first machine, then the second and then the third.

[TSD]

Coincidentally, I was given an ML7 last week

Or more accurately, I was given four boxes of bits which should turn back into an ML7 at some future point...

[Rustyrangie]

OK.

Basically look for yank pages on Balanced converters, look for Fitch Williams write up if possible. Ignore the values and stuff

they mention as they don't have proper voltages. You will want an auto transformer to up your voltage to 420-440 volts.

then you build the converter as the yank ones, the starting caps will be of the order of 200Uf for 10hp.

the balancing caps will be ~30 and 60 Uf for the 10hp motor.

The best cap values will be found by playing around, you would be amazed[maybe not] at the possible capacitances you can

make from 10 or so caps, I bought an assortment[£60 worth] and trial and erroed it.. Your attempting to get three phases with

the same phase to phase voltage under load. I have something like 426-427-429 with the lathe cutting. the compressor drops

one of them to 400. you can add some capacitance to each machine to fine tune but it's seems to work ok how I have it.

The yanks use a potential relay to switch the caps, I couldn't find one, so made a little circuit with a resistor, capacitor

and rectifier to switch the contactors. I will add a diagram. By altering values of the components you can alter the

voltage of the generated phase that the caps are switched at. Generated voltage means the motor is spining, so once it's

spining the start caps can be removed and the run caps switched in, I did wonder about leaving the run caps in and adding

more caps for starting but I found a reason not to do it?

It's pretty simple but it runs a 5hp polisher all day without overheating it, I ran the polisher from a static converter for 15 years

and we had to cool the thing down after a few hours use.

I bought the transformer from a place called Morite windings.

The caps came from a place in merseyside, do a search for 'orange book run capacitors'

You can alter site transformers or even run a pair of smaller transformers on the output of the converter.

I built the whole thing on a bench and played with values till I got it how I wanted it.

rotary_002.pdf

I bolted the majority of the stuff in a box which is wall mounted, I had great plans for an automatic control for the compressor so it can be set to only come on in the day when nothing else is in use, needless to say I never got round to it. and I was going to install a 12V on off system wired round the sheds and garage so I can control it from near every three phase bit of kit. No didn't get that done either... The wall box was a fire alarm panel, It came with all those holes, the top and botom switch are on and off. The transformer lives in the blue box with the L1-L2 caps[C1-C2 on the diagram]. It could all be a lot neater but I wanted to use it.

The motor isn't shown but there is a 7.5kw[or was that 7.5hp?] idler motor which is on foam pads on the floor.

You press the on button and you have three phase.

There is only one problem with it like this, the off/on contactor coil remains on for a second or so after the converter is switched off so you need to hold the off button for a second, if you stab at it it will either pop the 32 amp breaker or if your a bit slower you will reverse the idler;-). I was going to swap the coil for a 240 volt coil but it's another thing I never got around to.

The contactors were cheap as chips from ebay..

I am sure there are some lectricians here that could improve it

If you look up converters you will find some people just running a three phase motor with no capacitors. Try it. connect switched single phase to two of the phases of a motor and spin the motor with a bit of string, when it's rotating switch on the power, it will come up to speed and if you check the voltages of the phases you have a generated voltage. I actaully ran my cutter grinder like this from an old 3 hp 3phase motor. I have found write ups where people are running commercial workshops like this! This is the basis of the rotary converter, the caps are to balance the voltages and provide a phase shift to get the idler rotating.

Should I read thru this to see it makes sense and hasn't got to many spelling mistakes? nahhh

This looks very interesting! Thank you!

Never come across it before even though I worked in electronics for 40 years. So basically you use a 3 phase motor with some capacitors to make it start up on single phase supply, then when it's running the 3rd phase is generated by the motor. Transformer & contactors to get the switching right plus a few capacitors/resistors to get the phase balance correct and away you go. Cheap 3phase industrial kit instead of cheapo chinese single phase, brilliant! Farm machinery sale up here next weekend so I'll be on the lookout for 3 phase motors and stuff!

Bob