Backplate casting

[jmk89]

As you may remember, the Zyto lathe that I bought recently did not come with a 4-jaw chuck or a backplate for such a thing. So I will buy an old 3 1/2 - 4" 4-jaw chuck (Mick Moyles says they have several for me to look at) and try to make or have made a backplate to fit it.

It seems from the Lathes.co.uk site that for a lathe of the vintage of the Zyto (1940s-50s) the backplate should be made from free-drawn cast iron. Does anyone know where one can obtain rough cast backplates of a suitable size? Or do you just use a lump of cast iron and machine it down to the required sizes?

Do you reckon that I should be able to do this machining job by holding the cast iron in the 3 jaw by drilling and tapping a 1/2" hole in the back of the cast iron and loctiting a stud in for the jaws to grip while the rear face is turned down. Or should I get an engineering shop to make one for me? If the latter - any suggestions for a Sydney-based shop that would do such a weird one-off job and not charge an arm and a leg?

Sorry for some of the stream-of-consciousness, here, I am just trying to work out what the best way to proceed is likely to be.

[snowyskiesau]

Jeremy
Similar thread here.
I'm still waiting to hear from a local supplier whether they can get the backplate I need.
If not, then I'll also be looking for a place to make one for me.

As you're looking to install a smaller chuck, these cast plates may be suitable as a start point.

[DavidG]

There was a post somewhere on here of a plate made from a cast iron weight lifting weight. (I think it was here)

[jmk89]

I've been following your thread, Geoff.

I had forgotten Hobby Mechanics - I reckon one of their castings would be fine for me - I will just have to work out how to bore the centre hole and thread it accurately. Should be doable. If not someone should be able to do it or me, once I have bought my 4-jaw.

[pipeclay]

You can get pieces of cast iron 4E I sourced some prices for 150mmODX50mmTH round figures $30.00 and 200mmODX50mmTH $50.00 this material would be suitable for your backing plates,these sizes are just an example.

[snowyskiesau]

You can get pieces of cast iron 4E I sourced some prices for 150mmODX50mmTH round figures $30.00 and 200mmODX50mmTH $50.00 this material would be suitable for your backing plates,these sizes are just an example.

That's cheaper than I thought it would be. No problems in getting small sizes like that?

[malb]

Jeremy,

It should be possible to do it yourself if your lathe has appropriate screw cutting facilities.

It is simply a case of mounting the raw backplate in the 3 jaw and drilling a basic undersize center hole, then maching that to size. If at all possible, cut a thread to match the spindle rather than tapping it. Test regularly while cutting the thread by removing the complete 3 jaw and backplate setup, reversing and presenting to the spindle to test.

Once you are satisfied that the thread is good and a well fitted, remount as a set and turn the boss and what will be the back face of the plate until you are getting an even cut over the surface and turn any registers that are required for the spindle.

Only then should you release the unit from the 3 jaw, mount it directly on the spindle and machine the face and edge to match the chuck.

This sequence should result in a chuck that runs true with a well balanced backplate. It should be possible to remove the chuck and backplate as a unit and return them to the spindle without affecting setup accuracy etc.

[pipeclay]

Jeremy,

It should be possible to do it yourself if your lathe has appropriate screw cutting facilities.

It is simply a case of mounting the raw backplate in the 3 jaw and drilling a basic undersize center hole, then maching that to size. If at all possible, cut a thread to match the spindle rather than tapping it. Test regularly while cutting the thread by removing the complete 3 jaw and backplate setup, reversing and presenting to the spindle to test.

Once you are satisfied that the thread is good and a well fitted, remount as a set and turn the boss and what will be the back face of the plate until you are getting an even cut over the surface and turn any registers that are required for the spindle.

Only then should you release the unit from the 3 jaw, mount it directly on the spindle and machine the face and edge to match the chuck.

This sequence should result in a chuck that runs true with a well balanced backplate. It should be possible to remove the chuck and backplate as a unit and return them to the spindle without affecting setup accuracy etc.

My interpretation of what he was doing was because he couldnt hold material in his 3 jaw (the reason for tapping the block).

[pipeclay]

That's cheaper than I thought it would be. No problems in getting small sizes like that?

No problem at all that was just an example different diameters and thicknesses available.

[jmk89]

My interpretation of what he was doing was because he couldnt hold material in his 3 jaw (the reason for tapping the block).

Quite right, pipeclay. I have sourced some 2P cast iron rod which I could hacksaw into a disc, but I could not hold that disc in the 3-jaw. However, I could tap in the rod and turn the back down so that it has a boss on it that could be held in the 3-jaw and then proceed as malb indicated. The only problem I have is that I am also missing some of the thread cutting gears....I will have to see if I can do a 9tpi internal screw....

[jmk89]

You can get pieces of cast iron 4E I sourced some prices for 150mmODX50mmTH round figures $30.00 and 200mmODX50mmTH $50.00 this material would be suitable for your backing plates,these sizes are just an example.

Where do you get your cast iron? If this is a state secret, please send me a PM...

[pipeclay]

No secret Edcon.

[.RC.]

I get my cast iron from the local bolt and steel supplier...

[jmk89]

No secret Edcon.

t'rific - they are good people to deal with

[Dano48]

Try this lot,
http://www.lprtoolmakers.com/index.p...689ca86f75285a

Cheers.