myford super 7 motor problem

Hi guys

I just purchased a more or less brand new and very very little used myford super 7 lathe. Everything on it is tight and smooth, i put a bit of alluminium in the chuck and engaged the lead screw for automatic feed, within 4 minutes the motor shaft and aluminium pulley went really really hot, the reason i noticed was that the chuck slowed down even though i was taking a really light cut with a sharp tool. When i turn the lead screw by hand it feels quite tight from the tail stock side. Any ideas would be really helpful and much apprecciated.

thanks

Hi Hugh,
If the pully (And NOT the motor.) is getting hot then the belt is slipping on the pully or the pully is slipping on the shaft. When you say the leadscrew is tight you do not say if that is with the gear removed from the headstock end (To eliminate any tightness in the change wheel gear chain.) or with the half nuts engaged or disengaged. If the belt is slipping you will need to adjust the belt tension. If the pully is slipping on the shaft then the key that goes in the groove in the motor shaft is missing or the grubscrew is loose if the pully is not keyed to the shaft.

Les.

Hugh,>>

It may not be a motor problem so I suggest you try the following:>>

Ensure the saddle lock is not partially deployed. If it is it will impose a considerable load on the whole drive system and could result in broken teeth on the fibre tumbler gears and would make the motor struggle.>>

Does the motor heat up if the it just drives the countershaft i.e. with the clutch deployed so that the spindle does not turn?>>

Is there any end play in the spindle? If there is the end load exerted on it when turning could cause the front taper bearing to partially bind.>>

Are the gears in the drive train too tightly adjusted? (I assume you do not have a QC gearbox)>>

Is the lead screw hard to turn by hand with nothing connected to it? If it is the right hand bearing could be binding.>>

If the motor heats up after the first test it is likely that it is at fault. If it is a single phase motor the start winding could be still in circuit. Can you hear the centrifugal switch at the rear end of the motor working particularly on run-down? >>

If fitted with the usual Dewhirst switch this could be at fault. They are not really designed to turn the power on and off too often just provide forward and reverse options. When used to start and stop a single phase motor the contacts eventually burn and can give all sorts of problems.>>

I hope this may be of some help.>>

Best regards>>

> >

Eric>>

Hi Les

The lathe has been lying for 30 years unused more or less, its not run in at all. the belt is not slipping and the pulley its secured by the key perfect, it turns by hand easily without any belts attached and it spins fine when switched on. Under load the shaft coming out the motor goes really hot and heats the aluminium pulley so hot you cant touch it without burning your fingers. The lead screw (right hand side) has a hand turning pulley that you can turn the lead screw with by hand, now this is quite hard to turn ingaged or dissingaged without the two half nuts on the threads. If i turn the chuck by hand there is some resistance there as well and it becomes even more resistant with the belts on, my first thought was that the belt that goes from the motor to the pulley was too tight and i lifted the motor and tightened the nut but the belt started slipping so i put that back to the way it was. there seems to be a good force for the motor to spin the spindle with the chuck on the end, there is no tight spots that i can feel if i take it full circle but there is a constant force all the way round. Trying to explain this is hard for me because i'm kinda new to the terminology and such. All the gears have slight play in them and are fine there not obstructing anything from spinning. I'm going to have another wee look at it today to see if i can get things spinning easier without straining the motor every time i switch it on. If i fix it i'll let you guys know what the problem was, if not i'll probably have a couple of questions to ask you guys. I really appreciate all the help you guys are giving me thanks!

Hugh

If the mecahnical side of thge lathe is OK then you REALLY DO need to get the motor checked to make sure that the centrifugal switch is opening. If it isn't then you WILL burn the motor out - and quite quickly. At the very least you'll fry the insulation and run the risk of an electrical breakdown in the windings.

You say the lathe has stood for 30 years unused - in which case the switch is almost certain to be stuck - speaking from experience!

Keith

Hi Eric

The saddle lock it fine i have used this before so i know what your talking about, its slack so its not that.

I have tried taking the belts off so it not under any load and its fine i only had it running 5 minutes or less though.

There not any play that i noticed but even without the belt on the main spindle its still stiff to turn i thought this would be about right with a brand new lathe, its had no more than 1 hour run time i think and i only purchased it so i havent used it any longer than 10 minutes.

I don't have the gearbox but i checked the gears and they seem fine there is a little play in them which is ok.

The lead screw has never been used on this machine until i used it yesterday so it shouldnt be binding, i also greased all grease nipples and oiled the ports.

Everything is stiff on this lathe, i had to loosen the two screws slightly in order to even move the half nut locking lever!

Yes its single phase and i can hear the switch on downrun,

I think the switch is fine it seems to work perfect and is as new as well,

I'll have a wee look and see what i can find, if i could have a look at another similar lathe i could feel the tension on this to see the difference but i dont know anyone close who has one unfortunatelly.

Thanks

Hugh,

I have to presume that when turning the leadscrew by hand you are in fact driving the gear train in reverse and if it is non QC gearbox arrangement and is configured for fine advance per rev then trying to turn such the gear train will be difficult because it is geared up that way.

I am more inclined to question the spindle condition, Does the spindle bearing (chuck end) warm up when you have run in the previous condition? With the belt lever releasing the belts, does the spindle turn freely? Has the belt [layshaft to spindle] , been over tightened (a common problem)?

Perhaps an obvious and silly question, are all bearings lubricated properly with NUTO H32 oil?

NB, What you have called grease nipples ARE NOT for grease, all oil ONLY.

Edited By KWIL on 16/09/2013 10:38:04

Hugh

I suspect that Keith is right here .

Put the tumbler reverse into neutral to disconnect the gear train and start the motor. Then switch off the motor and as is slows down you should hear a distinct click as the contacts of the centrifugal switch close. If you do not hear this then the switch is sticking and that will need to be sorted , as Keith says, before the motor burns out!

Norman

OK sorry!  I was too long typing- I see that you have checked that! Well that is comforting and means that you are not about to trash the motor! If it really has stood unused for that long then it will certainly need a good clean and lubricate.I can't better  KWIL's advice so spend some time with that  - getting to know your new machine in the process - and come back to let us know the result.

Regards

Norman

Edited By NJH on 16/09/2013 10:49:21

I have to go out thismorning but when i get back i'm going to have a good look with all your suggestions in mind and see if i can get this running without burning this motor out! I will try to get a video clip for youtube organised to let you see what i'm trying to explain a bit easier. Thats if its ok to post a link through here?

Thanks everyone for assisting me!

Hugh,

Just noticed that you say the spindle is stiff to turn without belts, please adddress my question regarding the temperature of the chuck end bearing when you did run it because if the spindle is not setup properly then this is a possible cause.of excessive drag and it does not do the bronze bearing much good either.

Here is the lathe im trying to get working correctly I hope you get the image its the first time uploading a picture

I'll come back and answer the other questions later i have to take the misses shoping and get my dog out a walk.

Thanks guys, you have gave me a few things to think about here!

I'd run the motor on its own for a least half an hour to ensure that it didn't get hot offload. If the motor runs fine offload then I'd start connecting bits in sequence to see at what point it all went pear shaped.

If there's a bearing that is too tight then it should be getting hot. The energy from the motor must be going somewhere. So look for something hot that shouldn't be.

Andrew

I would think if any shaft is getting hot it's either too tight or a lubrication problem the wick to the headstock is probably dry as well An old army dictat If it moves oil it if it dosn't polish it

Roy

I have slackened both belts and run the lathe for a short time on high speed then felt the pulley it was cold but the outside of the motor is hot, is that usual? that was the motor just turning the chuck without cutting anything on it.

The bearing behind the chuck is cold thats not heating up.

I have the leaver that engages the gears in the middle setting so the lead screw isnt turning its still hard to turn from the had wheel on the right of the lead screw even though its set not to spin when the chuck turns. I havent taken any gears off to try it yet that will be my next move but there is play on the lead screw gear so im not sure if that will make any difference.

When i changed the belt that drives the clutch to the outer pulley for faster speed there is a right screatching noise, its not the belt slipping, not sure where its coming from?

I can use the lathe without the leadscrew but i would have to keep checking the heat on the motor and alu pulley just incase its overheating before i'll feel comfortable.

I was going to make a wee video but ill need to get my son to hold the phone while i twiddle things! he's not in just now.

I think the next step is taking the gear off the leadscrew to feel the tension as i turn it by hand, it could be a combination of both belts being tight as well as the leadscrew being tight just putting too much stress on the motor before the cutting tool even touches the work.

I meant to say also that the carrage moves really nice and smooth with the hand wheel, there is no obstructions or tight spots at all so i have eliminated that out of the equasion altogether.

One thing i completelly forgot about (i just remembered) is that when i greased the nipple at the right hand side of the leedscrew with the gun the brass or oilite bush poped out, i had to take the nipple off to relese the pressure and grease to push the bearing back in again, thats the bush on the leedscrew at the headstock side that goes through the leedscrew. I used a spanner over the shaft and tapped it back in and as i did that grease came out the nipple hole (obviously too much grease went in with the gun). The bush didnt come all the way out and it went back in with relative ease so that should be fine. The grease gun i'm using is a really good one not a cheap version i'll need to watch that in future!

I think you had better remove the belt from the motor pulley and just run the motor alone. After some time running on its own it should be warm but not hot.

The lever that disengages the leadscrew from the spindle is called the Tumbler Reverse lever., even when in the centre position the high gearing that I mentioned above still applies.

Simply remove the gear from the first stud before the gear on the left hand end of the leadscrew remove all gears from the equation, leaving you with the leascrew only in its two bearings.

Hugh do not use grease. Read the Manual

Where are you located, perhaps we can find a nearby Myford user?

Edited By KWIL on 16/09/2013 14:26:36

take the belt OFF the motor pulley completely and just run it on its own for a while. when the motor gets hot just running on its own then that will confirm that its the motor thats the problem. Then go get it fixed, or buy a new one. whichever is easiest for you.

turning the handwheel on the leadscrew will get you nowhere if the gearing is set for a slow advance or a fine thread - ever tried pushing a car while its in first gear ???? damn near impossible. Having " the leaver that engages the gears in the middle setting so the lead screw isnt turning" doesnt disconnect the gears themselves form the leadscrew. they are still all connected and will be unless you physically remove them from their respective studs. it merely disconnects the gears from the turning spindle.

fix the motor problem first, then do some light reading on how the leadscrew should work before going any further

z

bugger, you got in while i was still typing