Bought a CVA No. 8 Screw Machine - Need Information

[Shanghyd]

I recently bought a CVA No. 8 screw machine. I don't have the first idea about this machine. I've watched a few videos on youtube and read the Wikipedia article about screw machines.
This thing seems to be from the WW2 era but is in good shape.
Where can I go to get some more information? An oerators manual would be great.
Does anyone have one that they operate regularly?

[Deco-Doctor]

Hi

I worked on these for the best part of 17 years. I think I may have an operators manual somewhere. I can probably help you in some way, what do you need to know about the machine?

The CVA 8 is a screw machine, but it's not a swiss type. The bar stock is fed to a stop through a collet with a feed finger on the end of a feed tube and then clamped in a fixed position. You can drill, roller box turn and tap from the six hole turret. You can machine with flat or circular form tools on the cross slides and part off with the overhead slide. Some of these machines had a pick up attachment which picked the part up from the cut off tool and swung it away to a back working attachment which could be a slotting saw, a nut tapper or a back drilling/chamfering attachment. There was also a bevel gear turret drive that could drive live tools in the turret, such as counter rotating live drills and milling attachments.

The main spindle had a three position clutch which could be set to give fast and slow, fast and brake or fast brake and slow. The fast could be forward or reverse running so you could drill with a left hand drill in fast and then forward in slow to get the tap in then fast in reverse to get the tap out. When the spindle clutch was in the centre position the drive was disengaged and a spindle brake applied so you could do spindle stop work such as cross drilling or milling etc.

These machines had a few weak points, namely the spindle bearings on the later Mk III machines had very little adjustment for play, wear in the spindle clutch toggles and wear in the bronze worm wheel on the cross shaft drive. If you kept them well oiled they would run high production for a long time.

Are you intending to get it into production? If so did it come with any tool holders for the slides and the turret? Any cam sets? Any cam blanks?

First off you will need to know how to make the cams, or know where you can get them made. I used to make the cams on an almost daily basis. I devised an Excel spreadsheet to make the calculations easier, mark them out with dividers and a centre punch, then blank them out on a band saw and finally cut the rises on a cam mill.

Drop me a line if I can help.

[Shanghyd]

Your message is a like a gift! Finding someone that has actually worked one of these is great.
I have an idea for something that I would like to make. I would like to make about 1000 units.

The machine didn't come with any blank cams. The only cams are the ones that are on the machine. There are two tool holders for the cross slides but nothing for the turret. Here is a link to pictures. http://s724.photobucket.com/albums/w.../ScrewMachine/

I have a CNC mill and should be able to cut any cams that I need. I just need the skills to program the machine and the cam specs.

I've gotten the machine running with a VFD and everything seems to be working for far.

I guess the machine is still setup for the last job it was doing. I have no idea what that job was though.
I appreciate any help you can give me.
I have an email address craigslist9002@gmail.com. You can email me there if it is more convienient for you.

[Deco-Doctor]

Originally Posted by Shanghyd I have an idea for something that I would like to make. I would like to make about 1000 units. There are two tool holders for the cross slides but nothing for the turret. Here is a link to pictures. http://s724.photobucket.com/albums/w.../ScrewMachine/

I think what you have there is an old CVA 8 Mk 1 machine. It looks in a pretty sorry state! From the paint damage and the rusting I would say it has been in a fire. There would have been two metal framed hinged covers with perspex windows covering the machining area which are missing in your pictures.

You might wamt to check the integrity of the plastic lubrication oil tubes leading from the lubrication oil pump at the back of the machine. If it has been fire damaged, as I suspect, these small pipes are likely to be damaged. Without proper lube these machines won't run for long.

It has a pick up and slot attachment, an overhead slide and a swing stop (for feeding stock without using a turret stop).

Without any turret tooling you will be restricted in what you can make on the machine. If you PM me a drawing of the part you want to make I can give you some idea of what tooling you will need to find.

Cutting the cams on a CNC mill is not as simple as it seems. the rises on the cams are not a constant radius. The cam is divided into 1/100ths, and the rises are calculated in rise per hundreth of cam rotation. The cam mill I used to cut the cam rises was actually calibrated in rise per hundreth of cam rotation.

[BSA-OZ]

I have missed out on your blog, been too busy?
I have CVA gear here in Australia, perhaps even have a spindle.
I certainly have toolholders, tools etc.
I have a parts diagram for the slotting attachment you have.
Also if you can send me an email address I can send it to you on a PDF.
I have hundreds of cams from BSA Autos, they may be similar, measure up the dimensions of the cams you need, outside, bore, pin size, etc.
my email is ausgrass@gmail.com
Name is Howard Miller
Tradesman automatic lathe toolsetter
45 years experience
I am currently retired with five BSA working automatic lathes in my garage.

[Deco-Doctor]

Originally Posted by BSA-OZ I have hundreds of cams from BSA Autos, they may be similar, measure up the dimensions of the cams you need, outside, bore, pin size, etc.

IIRC the cams for the BSA 48 are exactly the same as the CVA 8 .

[Carlonorby]

We have cva parts available, including books

[abacam]

I can give you any gen you need on cam autos, I did an apprenticeship on them both setting & fitting, I live in Norfolk,England, give me a call

[abacam]

Originally Posted by Shanghyd Your message is a like a gift! Finding someone that has actually worked one of these is great. I have an idea for something that I would like to make. I would like to make about 1000 units. The machine didn't come with any blank cams. The only cams are the ones that are on the machine. There are two tool holders for the cross slides but nothing for the turret. Here is a link to pictures. ScrewMachine pictures by chander_wellington - Photobucket I have a CNC mill and should be able to cut any cams that I need. I just need the skills to program the machine and the cam specs. I've gotten the machine running with a VFD and everything seems to be working for far. I guess the machine is still setup for the last job it was doing. I have no idea what that job was though. I appreciate any help you can give me. I have an email address craigslist9002@gmail.com. You can email me there if it is more convienient for you.

If you are still in trouble with your CVA 8 I have loads of info and experience on these machines. It may help you to know yours is a Mk.1 which is a copy of a 00G brown & sharpe.Give me a call here or kjones183@gmail.com