CVA taper turning attachment

[Hugh Venables]

Hi All, I wonder if there is a lonely CVA taper turning attachment looking for a home anywhere? I doubt if my lathe already had the telescopic cross slide screw so I’d need that too.

 

[Martin-Sy]

Welcome to the forum Hugh There's a few CVA owners on here.

My 'go to' for spares is Joe Corner near Burton on Trent and while that's a fair drive for me it's a very long way for you!
He may have a TTA but I guess shipping to Aus would be expensive.
Have you asked on Practical Machinist in the Monarch section?
Or on the Metalwork Forum which is closer to home for you?

There are a few videos of CVA's he's had for sale on UT:

He sometimes sells on ebay as cornermachinetools.
I have no connection BTW except as a customer.
Which version do you have?
Picture please

 

[Hugh Venables]

Thanks Martin. I haven’t been actively looking for one yet but saw this thread with your mention of spare parts.

My machine was bought new for the Faculty of Engineering workshop at Monash University in 1966. I have had access to it from about 1985 to 2020. As I was approaching retirement it began to occasionally loosen the camlocks and the chuck would come loose. Personally I would retighten it and keep working but the precious petals I worked with got scared of it and wouldn’t use it. We surfaced 0.002” off the back of the 3 jaw to get a good grip on the taper but it still came loose. My boss decided to discard it so I put my hand up. I got it home and found that the triple belt pulley on the headstock spindle was missing one of the two woodruff keys and the grub screw had not been tightened causing the remaining key, seat and slot to become badly worn. Because the motor is reversed to stop the spindle there was a lot of hammering that was loosening the camlocks. Over the years I found it difficult to find a neutral between the high and low spindle speeds when rotating by hand on a set up so added a mid hole to the pictured bracket, a very useful mod. I have added a tray and shadow board above the headstock and lowered the floor and added a pullout shelf to the storage cupboard so that all the accessories are in and on the machine. The box on the door contains the change gears.

 

[Hugh Venables]

I went yesterday to visit another CVA nearby. It appears to be an identical version apart from a different electric motor and different ownership of CVA. It looks to be a couple of hundred units later.

 

[Agroshield]

...occasionally loosen the camlocks and the chuck would come loose

A couple of random thoughts on this that might be useful.

Camlock spindles were originally made to US Standard ASME B5.9. That Standard was then paralleled in ISO702-1 and ISO702-2 . pdf copies of these latter two are available online and contain all the dimensions needed to make anew if desired.

As every camlock spindle was made to the same Standard, if you could find a scrap lathe with a D1-3 spindle, that would be a source of spares (i.e. the relevant parts are not specific to a CVA).

It is worth pulling the cams and retainers just to check the small springs in the mechanism are present, intact and not collapsed (see bottom right of lower diagram here for approximately what you should find: http://www.lathes.co.uk/pratt&whitney/page8.html)

The only difference I have found is the thread on the camlock pins in the chuck - some are imperial (7/16" UNF, I think for D1-3, others are metric M10 fine I think).

 

[Hugh Venables]

Thanks Agro, that’s interesting. I suspect the D1-3 on the CVA is a very early version of Camlock. The original cam spindles had ridiculously short square sockets for the key, so short that if you tried to use the camlock key in the socket to pull the spindle around, it just flopped out. As a result of people trying to do this over the years, the sockets were pretty sloppy and one was split down the corners of the socket. I got a replacement set sometime in the 1990s with more “normal” depth sockets. They appeared to be otherwise identical with the originals and we didn’t have any problems until about 2018 or so.

 

[Martin-Sy]

As @Agroshield says the parts should be standard.
These guys in the US sell new nose cams. I don't know if they ship overseas.

Shop | Mac-It Corporation

www.macit.com

I guess yours has the instant stop feature which puts the motor into the opposite direction until the centrifugal switch opens.
Like this one:

It must put quite a lot of extra strain on all the drive train (and the electrical supply!).
Headstock spindle coming loose is also a known problem. In your case exacerbated by the rapid stop.

I like the extra detent for neutral idea.

 

[pressbrake1]

I went yesterday to visit another CVA nearby. It appears to be an identical version apart from a different electric motor and different ownership of CVA. It looks to be a couple of hundred units later.

View attachment 426238

Jameson were rebuilders of cva as well as some manufacturering
I believe they bought rights when cva were taken over by marlow

 

[Martin-Sy]

Yes, the history is complex. I spoke with some ex CVA employees and after K&T took over the toolroom lathe manufacture was outsourced.
J L Jameson in Ewell made quite a lot but later still Coles in Dorking continued manufacture (and re-manufacturing second hand machines).

Plate above is from a 1982 build by Coles.

Joe (mentioned above) recently sold one made in 1985 and that's the youngest one I've seen.

Headstock spindle coming loose

Sorry that should have said "Headstock spindle PULLEY coming loose"

 

[Hugh Venables]

Yes the braking function powers the motor in a reverse rotation as a brake until the spindle stops rotating. The rotation detector is a rotating magnet inside a drum that is constrained by an attached lever mounted between opposing sets of sprung normally open contacts. I assume these are wired in series with the normally closed contacts in the relay giving rotation and the coil in the opposite direction relay.

I was surprised at the crude way the rotation detector was mounted to the cast face of the motor with no attempt at concentric location with a predictable result as pictured. Also my drum had been loose for a very long time and the 1/16” axial drive pin long ago sheared. I welded the bar across the two impossibly worn pegs in the armature shaft and made a new shaft for the rotation detector and machined a spigot and flat mounting face on the motor end plate.

 

[Hugh Venables]

Correction: the drum rotates around the magnet which is restrained…..

 

[pressbrake1]

Yes, the history is complex. I spoke with some ex CVA employees and after K&T took over the toolroom lathe manufacture was outsourced.
J L Jameson in Ewell made quite a lot but later still Coles in Dorking continued manufacture (and re-manufacturing second hand machines).

View attachment 426281
Plate above is from a 1982 build by Coles.

Joe (mentioned above) recently sold one made in 1985 and that's the youngest one I've seen.


Sorry that should have said "Headstock spindle PULLEY coming loose"

Jameson also made some BIG lathes

I’d love to find the drawings , schedules and foundry patterns. I know someone with the facilities, abilities and stupid enough to try…

 

[ejtrent]

Hey guys! Stumbled upon this whilst searching for info on the brake in the lathe,

I have a 1977 CVA made by E.F Cole in Dorking, I picked it up about a year ago and it was in a bit of a sorry state - but you could see all the bones were good!

I stripped it down entirely, replaced any seals that had gone - of course the gearbox shaft seal was done! Flushed the lot with paraffin, cleaned it all up, rebuilt the little feed clutches in the apron and the lubrication system and of course a paint job!

So my question is, I'm not sure my brake is working, it stops pretty quick but I assumed that was just resistance from the gearbox. I have that unit by brooks on the end of the motor which I think its the brake? How quick should I be expecting this to stop?

Pictures for good luck:

(right on the limit of the load rating on this truck!)

 

[Hugh Venables]

Hey guys! Stumbled upon this whilst searching for info on the brake in the lathe,

I have a 1977 CVA made by E.F Cole in Dorking, I picked it up about a year ago and it was in a bit of a sorry state - but you could see all the bones were good!

I stripped it down entirely, replaced any seals that had gone - of course the gearbox shaft seal was done! Flushed the lot with paraffin, cleaned it all up, rebuilt the little feed clutches in the apron and the lubrication system and of course a paint job!

So my question is, I'm not sure my brake is working, it stops pretty quick but I assumed that was just resistance from the gearbox. I have that unit by brooks on the end of the motor which I think its the brake? How quick should I be expecting this to stop?

Pictures for good luck:

(right on the limit of the load rating on this truck!)

Hi ej,
It’s nice to hear of another one being appreciated.

I take it that there wasn’t an unloved taper turning attachment looking for a new home.

It should stop as quickly as if you moved the stop start lever straight from forward to reverse or reverse to forward.

 

[ejtrent]

Hi ej,
It’s nice to hear of another one being appreciated.

I take it that there wasn’t an unloved taper turning attachment looking for a new home.

It should stop as quickly as if you moved the stop start lever straight from forward to reverse or reverse to forward.

I wish I could help you there but unfortunately mine came without any accessories, empty collet rack (boo!), no chucks, luckily I found a nearly perfect match in a pratt burnerd chuck from nearly the same year and happened to be from their super precision range!

Ok ill start investigating the brake - is it that unit solely that controls it or is it a relay in the back?

Elliott

 

[Martin-Sy]

Welcome to the forum Elliot.

If it's any consolation mine came with an empty collet rack and no TTA either!

Regarding the brake, does yours have the centrifugal switch on the rear end of the motor like @Hugh Venables machine?
If so, then yes, it controls the forward/reverse contactors (relays) in the rear cupboard.
When the apron control is moved to the central position the opposite direction relay is pulled in until the speed falls and the centrifugal switch drops out which releases the relay.
However, not many machines were fitted with this option. Mine doesn't have it.
It's quite hard on the machine (as Hugh has said) and also on the electrical supply. IMHO Totally unsuitable for a VFD (which could implement a braking function anyway), and not great on static or rotary phase converters.

Do you have a serial number for yours?

Martin.

 

[Hugh Venables]

Hi Elliot, I’m more mechanical than electrical but here goes. A lot of contactors have normally open contacts as well as normally closed ones. These are single contacts in addition to the triple contacts to drive the motor. The CVA will probably have a forward contactor and a reverse contactor. When running forwards the forward contactor will close so the normally closed contacts will be open. There will be a wired circuit that includes those (now open) contacts, the rotation detector contacts in the Brooks unit on the back of the motor and the coil in the reverse contactor. When the motor is turned off the normally closed contacts in the forward contactor will close, completing the circuit and closing the reverse contactor until the motor stops and the contacts in the Brooks unit open, dropping out the reverse contactor. I’m speculating a bit but that seems logical to me. Mine works perfectly for forward rotation but not always from reverse. I assume a dirty contact in either the Brooks or the normally closed one in the reverse contactor. The Brooks has two contacts; one for forwards and one for reverse.

 

[Hugh Venables]

My Brooks unit is rotary magnetic, like a car speedo.

 

[Martin-Sy]

Any luck with the TTA @Hugh Venables ?

 

[Hugh Venables]

Any luck with the TTA @Hugh Venables ?

Hi Martin, no luck and no reply to my email to Joe Corner. Maybe he didn’t get it?
Hugh