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jmk89
22nd Sep 2008, 01:33 PM
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 (http://www.lathes.co.uk/latheparts/page7.html)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.:D

snowyskiesau
22nd Sep 2008, 02:44 PM
Jeremy
Similar thread here (http://www.woodworkforums.ubeaut.com.au/showthread.php?t=78938).
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 (http://www.hobbymechanics.com.au/macaccprice.htm) may be suitable as a start point.

DavidG
22nd Sep 2008, 02:50 PM
There was a post somewhere on here of a plate made from a cast iron weight lifting weight. (I think it was here)

jmk89
22nd Sep 2008, 02:53 PM
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
22nd Sep 2008, 03:14 PM
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
22nd Sep 2008, 03:19 PM
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
22nd Sep 2008, 03:20 PM
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
22nd Sep 2008, 03:26 PM
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
22nd Sep 2008, 03:28 PM
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
22nd Sep 2008, 03:49 PM
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
22nd Sep 2008, 03:50 PM
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...:D

pipeclay
22nd Sep 2008, 04:04 PM
No secret Edcon.

.RC.
22nd Sep 2008, 04:05 PM
I get my cast iron from the local bolt and steel supplier...

jmk89
22nd Sep 2008, 04:10 PM
No secret Edcon.

t'rific - they are good people to deal with

Dano48
22nd Sep 2008, 08:46 PM
Try this lot,
http://www.lprtoolmakers.com/index.php?cPath=285_116&osCsid=1cf32cfcb36626c09e689ca86f75285a

Cheers.

jmk89
22nd Sep 2008, 09:09 PM
Thanks for the link Dano.
They look great

bollie7
22nd Sep 2008, 09:53 PM
Jeremy
You would only be lookng at about 100mm dia for your cast iron? How thick do you need? I might be able to help out.
If not another option that you might not have thought of. an old cast iron wheel from an old caster. you might find one that would be suitable. as long as the centre web is thick enough.
Is there any reason, apart from the original look that you don't want to use steel? If not, yet another option is to go to your local scrap dealer and see if you can buy a small bit of 50mm or so thick plate, if you ask nicely they would probably even cut you out a rough circle with the oxy, you would want about 12mm all round bigger in diameter and don't let them chuck it in water to cool it. once you have your bit of plate you then need to get a bit of something round as big in dia as you can fit in your 3 jaw and just long enough to get full jaw depth plus a little bit more. Bit of bright bar would be nice but desperate men do desperate things, so a nice steel pipe socket would do (called steam pipe) NOT a GAL socket, or a bit of nice round steam pipe. Even a socket from an el cheapo socket set. ( if you are prepared to sacrifice one) The you find the approx centre of your plate, scribe a circle slightly larger and then weld the socket to it with 3 good, equi spaced runs of weld. Now you are set to put it in the 3 jaw and start machining as Malb said. Once the back of the plate is all done and threaded, grind the welds away to remove the socket, then mount the plate on the spindle to machine the front.

Also did you get a face plate with your lathe? ( I haven't read your earlier posts about it which is why I don't know) If so you could also mount you balnk on that.

Anyway if you let me know about the size you need I might be able to help.

regards
bollie7

malb
23rd Sep 2008, 04:36 PM
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....

If you can screw cut it, you can machine to fit the spindle properly, If you can only tap it, you end up matched to the tap, not the spindle. Does the available 3 jaw not have a set of reversed jaws that can hold the plate blank?

Big Shed
23rd Sep 2008, 04:45 PM
Just picked up a copy of Model Engineers' Workshop-August 2008, it has an article on pages 34-35 on Fitting a chuck to a backplate.

jmk89
23rd Sep 2008, 05:21 PM
Jeremy
You would only be lookng at about 100mm dia for your cast iron? How thick do you need? I might be able to help out.
If not another option that you might not have thought of. an old cast iron wheel from an old caster. you might find one that would be suitable. as long as the centre web is thick enough.
Is there any reason, apart from the original look that you don't want to use steel? If not, yet another option is to go to your local scrap dealer and see if you can buy a small bit of 50mm or so thick plate, if you ask nicely they would probably even cut you out a rough circle with the oxy, you would want about 12mm all round bigger in diameter and don't let them chuck it in water to cool it. once you have your bit of plate you then need to get a bit of something round as big in dia as you can fit in your 3 jaw and just long enough to get full jaw depth plus a little bit more. Bit of bright bar would be nice but desperate men do desperate things, so a nice steel pipe socket would do (called steam pipe) NOT a GAL socket, or a bit of nice round steam pipe. Even a socket from an el cheapo socket set. ( if you are prepared to sacrifice one) The you find the approx centre of your plate, scribe a circle slightly larger and then weld the socket to it with 3 good, equi spaced runs of weld. Now you are set to put it in the 3 jaw and start machining as Malb said. Once the back of the plate is all done and threaded, grind the welds away to remove the socket, then mount the plate on the spindle to machine the front.

Also did you get a face plate with your lathe? ( I haven't read your earlier posts about it which is why I don't know) If so you could also mount you balnk on that.

Anyway if you let me know about the size you need I might be able to help.

regards
bollie7

Bollie

Thanks when I get the 4-jaw I will work out what size cast iron plate I will need. The rough cast backplates at Hobby Mechanics may be the easiest way to go as there is a boss already there that can be gripped in the 3-jaw while a suitable hole is bored and threaded. So in the meanwhile I will hold off asking for help in geting cast iron.

The reason for cast iron and not mild steel is that I read this on the lathes.co.uk website:

At all costs avoid steel backplates; they can bruise or otherwise damage the spindle nose and, if they become stuck, will be much more difficult to remove.
Also, I didn't get a faceplate - that's another thing I will need to make a backplate for ....:U



If you can screw cut it, you can machine to fit the spindle properly, If you can only tap it, you end up matched to the tap, not the spindle. Does the available 3 jaw not have a set of reversed jaws that can hold the plate blank?

Yes, the jaws of the 3-jaw are reversible, so I suppose that if I have a round disc of cast iron I could use them to grip it while I turn down the back of the backplate and make a thread to match the spindle nose. If it it not round, then I will be in strife. I suppose that I am just a little reluctant to make one of my first tasks cutting an internal thread - but I suppose it just means that I will need to do some practice on that


Just picked up a copy of Model Engineers' Workshop-August 2008, it has an article on pages 34-35 on Fitting a chuck to a backplate.

Fred

If that isn't at the library, could I ask for a photocopy of a scan of that article?

pipeclay
23rd Sep 2008, 06:00 PM
If you end up getting your Backing plate blank and machine that to suit your chuck,you should be able to buy a piece of cast iron and make your Face plate with the 4 jaw.
There is no need to have a backing plate for a Face plate.
When you get your rough machined Backing plate and bore and thread it, it is before you turn the locateing spigot for your chuck a Face plate.
The size might not be the optimum diameter for a Face plate if you use a second Backing plate blank unless you can get a bigger blank.

bollie7
23rd Sep 2008, 06:20 PM
Bollie

The reason for cast iron and not mild steel is that I read this on the lathes.co.uk website:

At all costs avoid steel backplates; they can bruise or otherwise damage the spindle nose and, if they become stuck, will be much more difficult to remove.
Also, I didn't get a faceplate - that's another thing I will need to make a backplate for ....:U

Jeremy, I suppose there is merit in that, particularly in the bit about getting stuck on, but I think for a small home lathe with only one person using it the chances of jamming the back plate on the spindle would be quite low if it is fitted correctly. As far as bruising goes, same deal. Doesn't seem to bother Pratt Burnard with their high speed chucks as fitted to Colchesters. I've always assumed they are steel but maybe they are just a good quality cast iron.
Re your face plate. a cheaper way of making one might be to investigate using a machined down car flywheel mounted to a cast iron hub that screws to your spindle. It would be a lot cheaper to buy a smaller dia bit of cast than a large piece. I made a circular table for my old Richardson bench drill that way. for a small face plate to fit your lathe 1/2dozen countersunk allen screws would be ample to hold the plate to the hub. Just a thought anyway
bst of luck with it.

regards
bollie7

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