Member postings for Justin Thyme

Thanks for all the replies, I do read them all with great interest.

I think I'm going to go with JasonB's post above. We do have a large 4 jaw chuck and on the small lathe the chuck is small enough to grip the inner hole of the work piece.

and if i only have something to make a 36mm hole, can I turn out the rest of it ?

on turning steel, can you start off with something only vaguely round (or even square) and slowly chip away at the high bits until its round. It is what I would do with wood but not sure what can be done with steel.

I am needing to form what can best described as a large washer out of 3mm mild steel late.. 39mm dia centre hole, with a 89mm outer edge.

Could any of this be done on a lathe or milling machine ?

Could I just cut and grind the outer dia and then finish off on a lathe ?

It is a 'pause and rewind' one, so at any moment you can rewind up to one or two hours of whatever side you are on (providing you have not switched channels) So it never ever has a rest. so wasteful in so many ways, but also quite incredible it achieves this, 14 years of non stop spinning and recording.

How are the bearings formed in these HDD ? and then there is that little arm that continuously moves back and forth across the surface of the hard disc with such incredible accuracy.

In light of this thread I was just considering our PVR. Bought in 2009, it is now 14 years old. Due to a fault where it sometimes fails to record from standby, we have left in permanantly on. As it is a 'pause' live tv type then we can assume the disc is spinning at full speed 24 hours a day? (5400 rpm)

so it may ave spun round 45 billion times - impressive bearing!

and if its little 3.5" disc had been a wheel it would have made it around the world 315 times ! averaging just under 60 mph

Edited By Justin Thyme on 06/06/2023 23:03:40

Edited By Justin Thyme on 06/06/2023 23:04:13

When milling, how do you know how much to remove in one go ? is it as simple as 'it doesn't sound right' ?

Loaded to the extent that it is driving the mill at he highest speed.

I think the little bit of smoke may have just been down to the fact the machine had not been used for at least 10 yeatrs (may be 15) it may have just been a few long deceased spiders burning off - there was no electrical burning smell.

How would I test winding to winding with a pat tester. pretend one winding is earth with the live and neutral going to the other?

Absolutely convinced switch is 100% OK

Sorry to drag this back up again, but today has been the first time I have got back to the machine.

AMPS; When running, the run winding is drawing 3.9 amps (rated at 4 amps), starts off at about 4.3 and after 20 seconds settles at 3.9

SPEED; it is rated at 1400 RPM.
No load 1500 RPM
Forwards with belts on 1440 RPM

TEMPERATURE. The lathe motor which appears to be of similar design but 550w. after 20 minutes running, the case was 31.5°C. However the suspect motor after 20 minutes running reached 48.9°C  (infra-red thermometer)

I have not been able to borrow a clamp meter, however we do have a pat testing thing, that tests with 500v DC. . I have been able to check both windings separately with this. Insulation resistance test for both is 19.99 mega ohms (a fig given for every thing that passes) And the Earth leakage on both windings is 0.1ma (both windings and the machine in general pass the pat testing with flying colours.)

Comment and opinions must welcome

-------------------------

As an aside, I did use the machine to mill some bright mild steel today, it seems to be very robust and works well, can take quite a bit of metal with each pass. not that I have much experience of mills, just a micky mouse one that looks like a small pillar drill that seems only capable of taking off tiny bits at a time. This much bigger warco lathe come mill, seems to be like a proper bit of equipment.

Edited By Justin Thyme on 18/05/2023 23:45:22

Why do they call these tool tips "Indexable" ? is there a connection to the word Index

Thankyou. I done this today, made an external switch to control the starting windings. Worked beautifully, both directions, even with all the belts on.

However I am still not convinced. on one occasion (running clockwise) I switched the starting windings off too early, and it tripped the fuse! I tried to recreate this anticlockwise and it won't trip the fuse. But let either direction get up to speed (2 seconds) and it seems to work well. It does seem to run a little slow, but its rated 1400 RPM is not that fast. I will see if I can put an exact speed on it.

I think I probably will replace this motor rather than fit new points in the centrifugal switch, but I would still like to know what is wrong with it. I much prefer fixing stuff than replacing.

Thanks for the suggestion.

Yes, it has gone on a bit. Time of year, so much to do in the garden, plus other more urgent projects means the lathe is well down the list.

However today, the poor weather men't no garden and some old folks getting married on the TV seemed to occupy the wife......

I did give readings for the windings earlier, 15 ohms for the starting and 5.8 for the main.  lrakage to earth readings from windings were zero

And I do put a great deal of due diligence into stuff like this, I do also have a fair bit of experience with electrics, but this is the first time I have got so involved with an induction motor, changed a few capacitors on them over the years, but this is far more challenging, and interesting problem that I would like to understand and fix

I will take great care I promise.

Edited By Justin Thyme on 06/05/2023 23:05:46

Edited By Justin Thyme on 06/05/2023 23:10:04

Indeed, I touched on that in my earlier post. They need to be closed to form the circuit, and since the motor does start (in a fashion) then I presume they are pushed together when it is assembled ? I am going to try and work that out when I next get a chance to work on it.

My intention, unless otherwise advised, is us to clean the contacts up as best I can, and then if it all works I can try and source a new set of contacts. So my question is - should it work, if only for a week or two (lets say 50 start up) if I just clean the contacts that are fitted up ?

I was just going to pull some emry paper between them until they worked

Any other suggestions?

I am hoping this is the problem, contacts are a bit of a mess, pressing them together doesn't always make an electrical connection.

Not sure why they are open ? presumably when assembled they must be touching. it couldn't have possibly been starting this far open?

should the the contact have a hole in, or do you think there is something missing ?

i have now been able to measure the starting winding at 15 ohms, this compares to 5.8 for the main winding - does that sound about right ?

the one that is on is 160µF could that be an issue ?

If the starting winding is open, why is it starting? I did double and triple check this winding with the cap removed and could not get a reading.

When the motor starts I hear a click as it picks up speed, and also hear it at similar RPM as it is slowing down after switching off - I guess this is the centrifugal switch ?

I could only get a reading out of one of the coils, and this is a diagram of the wiring. Does the centrifugal switch have to be engaged to get a reading from the other winding?

So a recap on what we have.

The forward Reverse switch seems OK and has now been rewired to work in the correct direction, it looks as though someone had clearly rewired it the wrong direction in the past!

With no belts on, the motor often runs well in both direction, but sometimes trips the fuse in anticlockwise (may be just when its hot)

With the belts attached it starts poorly and then runs well in clockwise, but mostly 95% of the time trips the fuse anticlockwise.

I am now wondering, if the capacitor has lost its umph (can that happen, I thought they just suddenly died), may be it can't get the motor to spin fast enough for the main winding to kick in ? (is that a silly theory?) this would explain it working better with belts off, but doesn't really explain the direction issue.

Anoteher thought on the capacitor. It is clearly not the original, real DIY soldering for connections. I am also wondering if it is of the correct size, if it was too small would that also cause starting problems?

What size of capacitor should a 370w motor such as this be using ?

The motor for the lathe works well but is 500w. could I try the cap off that on the smaller motor

Had the For/Rev switch off today, sorted the wires so that it now runs in the correct direction, switch works well, can't find any eath leakages!

But it still trips the fuse in the clockwise rotation, and slow to get to speed in reverse.

Will try and get some readings from the windings the morrow and report back.

triping only occurs in one direction when its hot.

The manual suggests it should be connected to a 20 amp supply - but there is only two motors on the lathe, one 500w and the troublesome one which is 370w. (and I cant invisage both motors run at the same time). Even with a start up surge, a requirement of 20 amps seems more than excessive.

there is no central position - and would what you are suggesting result in a large heat build up ? and working well in both directions when cold?

will get some images, but probably won't be back in the workshop until friday. not sure how they will come out, most of the wires just seem black (may be they just need a little clean first)