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CovMac Lathes

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Phil Whitley21/06/2018 20:22:01
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1060 forum posts
137 photos

todays Covmac progress was mainly repainting the legs , plinth and chip tray, and seeing if I can remember how it all goes together. It is pretty obvious, apart from a bracket which has something to do with the belt guards, but I am sure its position will become apparent as I reassemble, which I am not going to do till it is in the new "machine shop", which may be tommorow, if the paint dries overninght, otherwise, Monday! The mystery bracket bracket is the one on the floor by the plinth in pic2. it is, needless to say, not original. Although the coolant pump is "a bit of a rig" I have decided to refit it, as I like the fact that it runs from the spindle drive, and so coolant stops when the chuck stops. Now heres a thing for Chris, is your chip tray cast or welded from sheet steel? they are cast on the lathes.co.uk pics, but mine looks like it may be a replacement, although it is an exact copy, and both yours and mine are later versions of the ones in those pics.

Yes, I know! Its white, and the lathe is a sort of faded magnolia, which was probably white once, and then got thoroughly oiled for about 60 years, if I can't live with it I will tone it down with some "White with a hint of wayoil" During the cleanup for the paint, it looks like the original colour was a dark grey, the same as the one Chris has , so it looks like it was repainted at IL Berridge, where it was reconditioned in 1955. Meanwhile, in the spirit of every TV presenter from Fanny Craddock to Blue peter, " here are some I prepared earlier" in their new less cramped habitat.

Phil Whitley22/06/2018 19:13:59
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1060 forum posts
137 photos

Well, the paint was dry, so I cracked on and moved the lathe into position, and got most of it reassembled, including refitting the motor plate. Next job is to get a motor!

Edited By Phil Whitley on 22/06/2018 19:15:39

Roger Williams 222/06/2018 19:40:18
331 forum posts
1 photos

Lovely to see tha Covmac on the ME site again !. Looks a treat.

CHRISTOPHER MILLS 122/06/2018 19:54:38
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152 forum posts
61 photos

Phil,

What sort mechanism do you think there is within the big clutch drum?

Chris

CHRISTOPHER MILLS 122/06/2018 19:57:44
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152 forum posts
61 photos

Phil,

I cannot recall my chip tray, whether cast iron or steel, but I will look next week, when I go to Somerset

Best

Chris

Brian Wood23/06/2018 09:20:40
2072 forum posts
37 photos

Phil,

Looking at Chris's photos I think he too has a sheet metal tray, the sections are not quite thick enough for a casting in my opinion..

Your new shop is shaping up nicely, you have put a great deal of work into that.

Best wishes Woody

Phil Whitley23/06/2018 20:01:02
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1060 forum posts
137 photos

Cheers Woody, it has been a long haul on the workshop, but almost finished now, just have some rendering on the outside of the "blacksmiths shop" wall, a ceiling to plasterboeard and skim. then a bit of paint, and we are finished! The reason I have moved the covmac now is in order to get that part of the building empty so I could do the final work. Still to come out are forge (in bits, sl easy to move) Brazing hearth, a startrite bandsaw, and a Grafton drill press on stand, a workbench with three grinders on it, and all my metal stock! Thats next weeks job. I was reading about your eye problems, engineers must lead parralell lives!, I have had cataracts in both eyes removed, but only suffered one detachment in my right eye! I don't like night driving either, I dont think any glasses wearer does, as any slight lense scratching which is unnoticable during the day is a curse at night.

Chris, Clutch mechanism? short answer is, I dont know, as I havent stripped it, but from the feel of the way it works, it seems to snap into either the run or the stop positionI would guess at some sort of lightly sprung over centre mechanism which uses friction pads to take up the drive. It couls be along the lines of a brake drum where the shoes are released and forced against the wall of the drum to initiate drive. I dont think it is a dog clutch, as it seems totally smooth and silent in operation, but ATEOTD, I am just guessing! Did you get any change wheels with your lathe, as I have noticed that the brass plates on the banjo gear cover gives all the different change wheel and SC gearbox set ups for metric threads. Whwn I have a minute, I am going to make a list up and see if, for completeness if nothing else, I can match some up!

Phil

Edited By Phil Whitley on 23/06/2018 20:02:40

Edited By Phil Whitley on 23/06/2018 20:03:06

Neil Wyatt23/06/2018 21:34:29
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17321 forum posts
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That sure is a hefty machine, nice to see it coming along.

neil

Phil Whitley24/06/2018 11:25:23
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1060 forum posts
137 photos

It is Neil, and very top heavy, which is why I put the crane on it. The crane is rated 750Kg, and will just lift the heavy end, but I used it as a safety to keep the lathe upright, and to ease the weight on the rollers. A big sigh of relief after it got there upright and in one piece though! I moved it by myself, as whenever I have had "help" in the past, I have spent more time stopping them getting a rupture or turning the thing over than I have actually moving the machine. Slow and steady wins the race. It took just over an hour to move it about 9 metres! You can move just about anything with a couple of good long prybars, and some 1" rollers, oh, and a smooth CLEAN floor helps too!!

Ian S C24/06/2018 12:11:56
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7468 forum posts
230 photos

A car jack and some bits of 4x2 can be a big help too, and don't rush things.

Ian S C

CHRISTOPHER MILLS 124/06/2018 20:05:07
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152 forum posts
61 photos

Moving lathe weight is a real knack: My professional machinery mover, Edward Rutter, moved my CovMac bed, headstock plinth and tailstock plinth, 9 inches across a concrete floor, just using his hands and arms, nothing else at all

Chris

Phil Whitley27/06/2018 17:58:36
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1060 forum posts
137 photos

Well, I have fitted the coolant pump, and decided I can't live with it, it really is a horrible bodge! In order to line up the pulleys the pump is spaced off from the plinth on two long "brackets" of bent flat bar, two of which are bolted into the plinth, and two are bolted to the motor mounting plate, which moves when the belts for the main drive are adjusted. Because of the cockamamey geometry of this rig, when the motor plate moves, the pump is twisted out of alignment with its driving pulley, on the left side of the input shaft in pic 2. I noted when I bought the lathe that there was no belt on the coolant pump, or coolant in the lathe, and it seems very reasonable to suspect that this rig up never worked reliably, if at all! Scrapping this set up also means I will no longer need the outboard belt guard, which increases the width of the lathe by about 18". I shall fit a small electric pump under the lathe, near the sump. I also did some bull work on the plates! the long plate on the changewheel cover gives all the gears required for cutting metric threads up to an unbelievable 10MM PITCH. If anyone has any gears 7/8" bore, 1/4" key 12dp (thanks woody!)I may be in the market, especially the elusive 127 tooth metric conversion wheel .

Note to Chris, re the clutch, I noticed the other day when I fitted the drive control bar, that when you put the lathe into run, a wedge lug on the operating mechanism forces two matching wedges apart, and mine appears a bit sticky, so I may be going in to clean up and lube. I will keep you posted.

Phil

Phil Whitley03/07/2018 19:58:16
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1060 forum posts
137 photos

The new motor for the Covmac arrived, and I picked it up today, here it is next to the original motor. It weighs in at 32kg, and I lifted it out of the car boot with little trouble. A few days ago I went to move the old one, managed to slew the shaft end round a few inches, but couldnt move the other end at all! Good thing the new one is lighter, as the next job is to line it up for fixing hole drilling on the motor plate, which is vertical at the back of the lathe, but first, I need to bore the old pulley from 1-1/4" out to 38mm. It already has a steel bush in the centre, so easy job (famous last words!) The old motor is a 2hp, the new one is 3hp!

Brian Wood04/07/2018 14:12:56
2072 forum posts
37 photos

Hello Phil,

10 mm pitch metric thread----I agree with you; unbelievable!! Actually, exaggerated claims for screwcutting performance on lathes is not confined to Covmac, particularly when the leadscrew pitch of 6 tpi is taken into account.

6 tpi is equivalent to 4.233...mm pitch and even threading at 1.5 times leadscrew pitch only gets to a little more than 60% of 10 mm pitch.

I made a 63 tooth wheel for Chris which will happily give a good range of metric pitches up to 4.5 mm all to within 0.001 mm error. The 127 tooth wheel is really not needed and the chances of finding one in 12 DP size is rather small I would think.

Best wishes Woody

CHRISTOPHER MILLS 104/07/2018 14:26:34
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152 forum posts
61 photos

Phil,

I checked my CovMac's drip tray, and Woody is right, it is wrought, or steel, not cast iron

Best

Chris

Phil Whitley05/07/2018 18:56:46
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1060 forum posts
137 photos

Sounds good to me Woody! I have been contacted by a chap for some covmac info, and when I get some pics of the extra plates on the changewheel cover I will post them up here as well. Chris, yes, I suspected as much, probably only the very early models had the cast tray, it would be a good way of reducing costs, especially in war time. amazingly, mine has no rust on it to speak of, just a very even coat of hard black mill scale, never been painted!

Phil

George Jervis05/07/2018 19:14:26
70 forum posts
22 photos
Hi Phil
Thank you for the info you pm me. looking at the the pictures of my father's lathe I have the drip tray is identical to yours if you go on lathes.co.uk covmac the pictures at the bottom of the page are of my dad's lathe, we are not sure how he got the pictures on his site as they are all hard copies and haven't been put on the net as my dad never had the internet
George
Phil Whitley07/07/2018 15:15:12
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1060 forum posts
137 photos

Ok so here we go with the pics, I notice that Cris' Covmac also has the brass plate on the changewheel housing, but Georges doesn't , so for Gearge, and Woody, here it is!

 

Edited By Phil Whitley on 07/07/2018 15:15:45

Michael Gilligan07/07/2018 18:33:00
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14954 forum posts
638 photos
Posted by Brian Wood on 04/07/2018 14:12:56:

Hello Phil,

10 mm pitch metric thread----I agree with you; unbelievable!!

[ ... ]

.

What I know about CovMac lathes is what I have learned from this thread ... so be please gentle with me whilst I speculate:

Although a simple10mm pitch thread seems 'unbelievable' it becomes more credible if we consider multi-start threads ... A five-start thread would be useful in [say] an actuator mechanism, and if the lathe is expected to manufacture such threads, then that might also justify the provision of the 127 tooth change wheel.

MichaelG.

Brian Wood07/07/2018 20:05:30
2072 forum posts
37 photos

Hello Michael,

I have a feeling your logic is wrong somewhere but it is too hot here in Thirsk to grapple with the maths tonight!!

What I do know is that Phil has shown photos of gearing set ups for single pitch threads and the combination listed would create a 10 mm pitch metric thread if the leadscrew and gearing could stand up to the loading.

I know Covmacs were big and rugged lathes but that would be especially brutal on the way it was built if say a 10 mm pitch square form leadscrew was the item to be made

Regards Brian

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