CovMac Lathes

[john fletcher 1Participant @johnfletcher1]

The dust and muck needs to be sucked out not blown in and compressed air often contains a lot of water. As Phil says put the motor in a warm place to dry out /remove any dampness. If you know an electrician get him to carry out an insulation test on the windings. I'm assuming its a three phase motor, have a three phase supply or are you going to invest in an inverter ? Motors that age often had their windings insulated with natural resins so if the insulation resistance is low don't despair, your local rewind shop can dismantle the motor and re dip the stator for you. Hopefully not necessary. Tell us more about the Startrite box on the wall, certainly take it home. I'm following your task with interest.Ted

[Brian WoodParticipant @brianwood45127]

John, Phil, Chris and Martin,

I did suggest to Chris in an earlier email exchange that the motor is given a day in front of a fan heater to gently warm it through and dry the windings out. It used to take out fuses in the house supply according to the previous owner, but that really isn't much of a guide.

The insulation checking by megger test has already been well aired and taken on board.

John. Phil said earlier on this was a commutator motor, as is his version of the lathe, and Chris's pictures show a standard 3 pin plug [Yuk] on the end of a heavy cable so it will be single phase. The speed rating is 750 rpm so it might also be multi-pole. I can't say I spotted a contactor but the grotty plug suggests it wasn't in use.

Woody

[Phil WhitleyParticipant @philwhitley94135]

Right Chris,

Had a look at the motor, and I am not sure if it is the same as the one on mine, but I will be back at the shop later today, so I will look. My motor has a direct on line Allan West starter. Yours seems to have the AEI stayrite starter box with it, if this is the starter for that motor make sure you get it with the lathe! On the motor, you can probably get the grilles of and blow through with compressed air (wear a mask!) There is nothing you need to do to bring the motor up to modern standards (which TBH are not as high as they used to be anyway, but thats another thread!) Given a bit of volts drop on the probably too small supply cable to the shed, I am not entirely surprised it blew the house fuses, but it wants checking out before running.

Martin, if you look at the lathes uk pics then flip it round, that bolt does seem to me to be in the right place, and you can perhaps see the end of one of the pegs just to the left of the shadow of the gearchange knob, but you will find out tuesday anyway. Constant loss oil system in the sc gearbox, so there wont be much in it but muck 'n swarf. Looking at the lathes UK pic it does look like the leadscrew will come out when the taper pin is driven out, and it looks like the feedshaft is keyed into the gearbox as on mine there is a keyway visible in the boss that the feedshaft goes into. I think the "sliding gear outboard of the feed box" remark refers to the two gears which can be seen on the back view which are in the seperate case where the feed and leadscrew emerge from the box.

[Phil WhitleyParticipant @philwhitley94135]

my motor, note the round bakelite knob for speed adjustment, it is 230V 2hp 500-1000 rpm If you turn the speed adjustment far enough it reverses the motor. Speed adjuster moves part of the brushgear around the commutator.

I need to be more carfull when I am pointing the blockwork above the motor with no terminal cover on it Actually it is missing and there was a worrying amount of swarf in there when I got it!

Phil

[Phil WhitleyParticipant @philwhitley94135]

I did want to convert to 3 phase but the price of a new 3 phase 750 rpm motor is about what the lathe cost me! I may go along with this one till I can get summat else.

Phil

[CHRISTOPHER MILLS 1Participant @christophermills1]

CovMac Progress – Sorry to have been so long winded with all of this, but the final move of the lathe should take place next week. Here are a few photographs of the raising of the headstock, using a 2 tonne rate engine hoist I bought on eBay for £117. The crane is absolutely fabulous in use, barring its steel wheels, which are terrible over uneven concrete. The power, and the overall balance in the crane is really confidence inspiring. It lifted the head like a piece of angel cake. It is a little limited in its hook capacity – it will only take two lifting sling loops. Apart from those caveats, the crane is highly recommended. It is smooth in action, with its 8 tonne bottle jack, and highly predictable in lowering. We had to pull and drag the hoist quite roughly, to reposition the headstock on its pallet, and never was its

overall balance a worry. I have been on a tight budget for this project, and the cost of this crane, at £117, really saved the day. Since these pictures, Martin Whittle came down with me, and we removed the screw-cutting gearbox. Will post a few pictures of the gearbox, shortly. It was a privilege to work with Martin on the day. I learned a lot. All that remains to be moved is now the bed, headstock and carriage.

[Roger Williams 2Participant @rogerwilliams2]

Hello Chris, seems excellent value at £117, makes you wonder how they do it for the price !. Keep the write up coming on the Covmac, inspiring stuff.

[CHRISTOPHER MILLS 1Participant @christophermills1]

Roger,

Thanks for that – the price of these cranes has since risen to over £145. They are very well made, and nicely finished, too.

Will post some gearbox pictures, shortly. Unfortunately, the screw cutting gearbox needs a rebuild, as it has a lot of damage, chips to the tumbler teeth, but we have that in hand. I have almost finisihed stripping it, just one stubborn pin to drill out, and she is apart.

[davebParticipant @daveb17630]

Christopher, buy yourself a large D shackle, attach the slings to it and hang shackle on hook. Nice old lathe!

Dave

[CHRISTOPHER MILLS 1Participant @christophermills1]

Thanks Dave – I have inherited a few heavy duty looking shackles with the lathe, but they are not weight rated, not marked on them, so I have been a little bit reluctant to use them – Can I judge just by their dimensions? They are pretty solid items, with stout screw-pins.

[CHRISTOPHER MILLS 1Participant @christophermills1]

CovMac Screw-Cutting Gearbox – I have decided to remove the screw-cutting box, early, for three reasons:

1) To give me a winter project, and for the gearbox to act as a pilot for the whole job of restoration.

2) Cautions were expressed about lifting and transit, as to protecting lead-screw and power feed bar, and we thought it better to attempt their removal. (Wisdom from Phil Whitley and Brian Wood).

3) A very generous offer of help on the day from Martin Whittle, who only lives 8 miles or so from Totton, where the bulk of the lathe still lives.

This third was very fortuitous, for I would not have managed gearbox removal alone – Martin was the star of the day, and he even managed to christen his 3/4 inch socket set. I learned so much from him, hands-on, to add to the distance learning I have received from other members of this forum. We safely removed screw-cutting box, lead-screw and power bar.

The gearbox is relatively simple – an input shaft, tumbler gear shaft, with seven tumbler wheels, and an output shaft with an A & B speed setting. Altogether it gives 14 changes of thread pitch without change wheels. Although this was relatively restricted, even by standards of the 1940s, particularly American lathes, a full set of change wheels boosted this to 42, in imperial, and another set was offered to make a metric transition. As a museum project, I might aim to restore all change-wheels, in time – when I own a milling machine – medium term future. Gears are slected using chunky cylindrical knobs, with powerful springs within, and a pin is retracted and replaced into the casing on each change. They have a positive feel to the. The A B lever was jammed when I got the lathe, but freed off reasonably easily, using emery cloth to grip, and water-pump pliers.

Here are four pics of the box – three with it still pretty filthy, inside and out, and a bit cleaner. So far, with painted areas, I am having great success with an initial bath of Nitromors, washed with detergent and hot water, and dried off, then a spray application of Mr. Muscle oven cleaner, again washed and heat dried. The two work very well in tandem. Of the two, the Mr. Muscle is by far the more toxic, and really must not be breathed in. It is not nice. The CovMac, being wartime produced, never had any strong enamel paint, and its two coats of paint (originally a dark grey, over-painted later in a lighter battleship grey) are pretty crumbly, not difficult to see off. Internals, I have bathed with a mix of 95% white spirit, 5% engine oil. That seems to work well enough, and is relatively cheap.

The brass label has full spindle speed, screw-cutting and sliding and facing values. The gearbox is of total loss design, yet with a sump plate and drain bolt. The box has a copious number of little oiler cups, some missing their top caps, which have a patent number on them. Luckily, we can still buy these little oilers, new. I need a good number, as they appear all over the CovMac.

Once clean, it was immediately apparent that there is serious damage to a number of tumbler wheel teeth, and we need a rebuild. At least five out of seven wheels have serious chips, and their gears mesh in pretty bad tempered, graunchy fashion. An engineer as educated and experienced as Brian Wood has no real idea of what might have caused such damage – apart, perhaps, from one of the Union chucks, into which somebody once drove a cutting tool, and tore away 25% of the inner face. It would be interesting if anybody can come up with any other answer. All suggestions will be entertained. I found nothing in the box to prove cause of such damage, just a medium level of swarf. The other five wheels in the box, are in reasonable, general shape. The only other item of note, on first appraisal, was an amount of lateral slop in the output shaft, but its teeth are the best in the box. The blue marks on teeth in the cleaned-up picture are my black felt tipped pen, where I was trying to do a wheel count. It is not easy to count them in situ. All I am sure of, until the full strip-down is completed, is that the biggest tumbler wheel has 44 teeth. I am [pleasantly surprised by the simplicity of this gearbox- this is fortuitous, since, being a beginner, simple is all I need at this stage of my learning curve – it is steep, but, with a bit of help, I am enjoying every minute of it.

[CHRISTOPHER MILLS 1Participant @christophermills1]

CovMac Update – The final lift, of bed, headstock and drip tray is due for some time this next week – I am just awaiting a replacement driving licence, and will hire a flat bed 3.5 ton truck, to move the headstock, bed and drip tray.

Here is what remains in the shed at Totton. All I can say, with this first phase, the move, almost complete, is that there is an awful lot to a big lathe, and it is all tremendously heavy stuff – even individual pieces, the smaller items, like tailstock and back guard, need real effort and concentration to lift and shift about. There are twin items, which can only be moved about by two men together – the motor and the headstock plinth with motor plate. The motor alone, it is hard to accurately estimate these things, must be over 220 lbs in weight. The tailstock is likely over 120 lbs. In a way, I will miss this old shed at Totton – it has been fun, taking into ownership CovMac Serial Number 1097G. A War Office owned machine, she likely spend the first 6 years of her life assisting in the war effort against Hitler's Germany, making munitions, perhaps in one of the Royal Ordnance factories. As Phil Whitley said, I am lucky enough to be in the position of preserving a piece of our engineering heritage – That this wonderful machine very nearly went to the scrapyard, but did not. We still have it for the future.

Above shows the headstock end of the bed, and the little red oxide painted cavern where the screw-cutting gearbox sat. You can see locating dowels which helped support the case. The 'eye' hole which CovMac designers thoughtfully put through the bed, and its lifting bar, was worth its weight in gold when raising the bed. This is what we have left, and which I will move, hopefully, this coming week, or so. She will be home for Christmas – none of the wars were over for Christmas, but this move, at long last, will be:

 

Edited By CHRISTOPHER MILLS 1 on 29/11/2014 08:07:26

[CHRISTOPHER MILLS 1Participant @christophermills1]

Here is a small selection of the goodies which came with the CovMac – Much of this looks a bit rusted, but it is all cleaning up splendidly. It included five chucks and three big face plates, a big centre steady, a six inch Record engineers' vice, and enough cutting tools to last me a lifetime. Altogether, I filled three car loads with stuff. The spoked wheel in the picture is the metric change wheel, of 127 teeth – it has cleaned up wonderfully. That one begins my metric change wheel set – there were about 24 metric change wheels offered originally. On the left in the background can be seen a lapping plate. In the toolbox in the foreground is one of the big shackles, which I would use if I knew its weight rating, but it looks pretty hefty. 

 

Edited By CHRISTOPHER MILLS 1 on 29/11/2014 08:14:14

[Neil WyattModerator @neilwyatt]

Safe load for a shackle should be the same as a matching chain.

According to my copy of machinery's handbook a 3/8" chain (i.e. links made of steel 3/8" diameter) has an SWL of 1 tons. 1/4" is 1/2 ton. That's for wrought iron… so modern steel should be a bit stronger.

That would make the shackle my workshop key is on good for 1/2 a ton, and it's tiny compared to yours, which I guess uses 1/2" diameter stock, so good for 2 tons by this book.

Neil

[Brian WoodParticipant @brianwood45127]

That is a heroic workshop key Neil, 1/2 ton, better than a medieval church key; I am truly in awe!

Brian

[Brian WoodParticipant @brianwood45127]

Seriously, I have just measured my unmarked shackle, the pin and shank are both a nominal 3/4 inch diameter and I used to pull fully grown dead elm trees over with that.

Chris's, even though it is longer in the throat, mine is a little under 3 inches, is getting towards those sizes.

So I am sure Neil is right and it would be plenty strong enough for the lathe bed lifting. The limiting factor really is whether Chris can get the pin through the hole in the lifting arm

Brian

Edited By Brian Wood on 29/11/2014 11:22:45

[Michael GilliganParticipant @michaelgilligan61133]

Re. Shackles … This might be of interest.

MichaelG.

[CHRISTOPHER MILLS 1Participant @christophermills1]

Neil's guess on my shackle is correct – they are of 1/2 inch bar – so this increases the range and versatility of the crane exponentially. I have three of these – two are virtually unused.

Brian is right in that they won't go through the bolt hole on the hoist, but I can use them in conjunction with the hook, and I think a shorter length of chain.

I will have the confidence to use them now, and I had't before today – I had cleaned them up, ready for something.

[Neil WyattModerator @neilwyatt]

Useful confirmation, Michael, they work out at the same loadings.

Neil

[Michael GilliganParticipant @michaelgilligan61133]

A gently amusing tale:

One of my previous employers used to insist on all shackles being individually tested and certified. … So far, so good.

What always surprised me was that after testing, a flat was carefully filed on the body and its new serial number was applied with hammer & punch. … Stress Raisers par excellence !!

So far as I'm aware, there was never a failure; but it felt wrong to me.

MichaelG.

[CHRISTOPHER MILLS 1Participant @christophermills1]

Final CovMac Move – I now have a replacement driving licence, and bed, drip-tray and headstock will be moved this week. I hope to get a flatbed 3.5 ton truck, with a tail lift, which will make the job a bit easier. I am building a custom pallet, just over 7 feet long, with two four wheeled dollies. I will need to run it over plywood to get it out to the road – there is some lumpy concrete, and a three inch step to be negotiated. Using the bar through the eye, I am going to bolt it down using twin piles of wood either side. I do not want it tipping over, and it is still quite a top-heavy piece of kit. I will take any advice offered upon shackling the pallet down.

English Electric 3 HP Single Phase Induction Motor

I feel that I now know enough to test run the motor, too – I have carefully taken a lot of advice on this, because I fear electricity, and want no mishaps. The motor is a huge, handsome lump, built concurrently to the lathe (it is original – it has the dark grey CovMac colour underneath a green repaint, and the motor plate has only ever had the one bolted to it.) As a museum project, I am sticking with this motor, even if it needs a re-wind. I will pay if I have to – junking this motor is not an option for an historian. We have our burdens. It runs at 1450 rpm. As previously posted, the weight in this motor is almost unbelievable. I could neither put it in, nor take it out, of my car alone.

I have been advised to thoroughly dry it out, and clean it as far as I can without either dismantling it, or getting it wet. Then I will re-wire it and run it through its Stayrite starting box. Have been advised to run it on a ring main, with a suitable MCB protecting it. I understand now how to apply a mega tester, to check insulation on the case to the motor; by testing each terminal against the case. I quite love the brass English Electric label – let's hope it makes the lathe go like a Lightning!

The Stayrite box looks to be 1960s or 1970s technology – Does anybody know how the motor would have been started and run, originally, in the 1940s?

I imagine this thing might eat electricity? Or, being so big, could it even be economical? Clearly, I will not be putting it to any huge strains. Is there a modern equivalent of "Shell RB"?

Will there be a big fan in the casing?

Both its old pulleys are pretty knackered – presumably I can still buy replacement rubber pulleys? A source of these would be greatly appreciated. I have kept originals for dimensioning.

I will film the first firing up of this motor! We should keep that record.

 

 

The starting capacitor is hiding in the box – it is lower right, beneath a shield of its own. Luckily, despite rather thoughtlessly snipping off five red cables, without recording them, when I opened the motor's terminal junction box, the previous owner had written me a wiring diagram which corresponded exactly with markings in the Stayrite box. It was as if he was predicting my naivety. I was grateful, after being rightly called a dummy of the first order for doing the thoughtless snipping.

Many thanks for everything so far, gentlemen. I know you will be wishing me luck this week. I promise you a picture of the main lathe bed in the air. 

 

 

Edited By CHRISTOPHER MILLS 1 on 29/11/2014 17:53:58

Edited By CHRISTOPHER MILLS 1 on 29/11/2014 17:55:49

Edited By CHRISTOPHER MILLS 1 on 29/11/2014 17:59:32

Edited By CHRISTOPHER MILLS 1 on 29/11/2014 18:00:38

[Brian WoodParticipant @brianwood45127]

Hello Chris,

Just a terminological correction, oh how I like to throw my knowledge about!!

The rubbers you refer to are actually belts, those look to be A section. Ask for rubbers and you will get something else, and with raised eyebrows over the size!

I imagine the motor also includes a fan; dried out and checked out on the megger there is no reason why it won't run. Don't forget to brace it against reaction torque on starting. The start capacitor is in the box, that may have got tired but they are easy enough to replace. Check with Phil, more in his field than mine.

We are all watching this time

Best wishes

Brian

[CHRISTOPHER MILLS 1Participant @christophermills1]

I have crawled right back under my stone, to the sheer embarrassment of it all!

[Neil WyattModerator @neilwyatt]

The plate tells you what you need to know: 13.2 Amps, 230V.

Although UK mains is notionally 230V for European consistency most of us have nearer 240V… (near the top of the allowed range of variation). It will draw 3 or more kilowatts.

You shouldn't really run it of a 13A plug, so I wouldn't run it of a standard ring main.

The starting current could easily be twice or more the notional 13A. I would get a custom spur wired in for it with a 20A circuit breaker – I think it's a c-curve MCB that allows a delay to prevent tripping from starting surges, these are used for things like storage heaters that also have a seconds-long starting csurge. Check with a sparky.

Neil

[Brian WoodParticipant @brianwood45127]

Oops, senior moment there. Belts instead of pulleys.

I've been machining rubber mountings today, that's my excuse.

Brian

Edited By Brian Wood on 29/11/2014 19:30:04

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