Back plate

I am looking at getting a ER32 collet chuck and wonder if Ali will be suitable as a back plate. If I was mounting a 3 or 4 jaw chuck I would definitley go for either steel or cast material.

But concidering that ER32 collets are normally used for short smaller sized material would it be suitable as I have a large lump of Ali round billet sitting doing nothing. Mind you I would still need to find a way of cutting it in half.

It can be either one of the two pieces but the top piece I have a project in mind for as it is already very close to the size I need

Edited By Derek Lane on 03/06/2022 09:59:56

If its a good grade of ally it should be ok. I cant imagine anything in an ER32 creating untenable flex through a lump like that. In industry you wouldn't, due to considerations of durability and resistance to dinging etc but in the home workshop with it's typically low use rates and careful owner care should be fine I reckon.

Do you have to use a backplate?

If not, then a shop-made chuck for a screwed spindle is a possibility:

Edited By ega on 03/06/2022 10:59:09

Although I have an ER32 collet chuck I usually use a Stevenson's square ER32 Collet Block in my 4-jaw chuck. Or, if not requiring the greatest accuracy, a hex block in my 3-jaw.

Thank you guys I forgot to mention that it is not a screwed fixing like the Myford lathe as it is going on a Warco WM280v lathe.

Unfortunately I do not know the grade of Ali, it came from a model engineers workshop that was falling to pieces and his nephew rescued some metal the two pieces above and also these as well as a lathe which I have not yet seen.

The smallest being 1 1/8" diameter and the largest is 2 5/16. the top and middle piece are both over 2ft long and the rest about 1ft long.

The only one I am not sure of is the large piece at the bottom of the picture

The aluminium will make perfectly good backplates for smaller lathes. You can try a test cut in the metal to ensure it is nice to work with or not. I doubt if the aluminium would be a nasty soft type to machine grade seeing where it came from.

I have machined the smaller piece and it certainly does cut nice as well as give a good finish. The larger one has been painted on one face as though it was cut off of a long billet. The problem is even though it is painted red this could be from a supplier or the company that originally used it before the model engineer got his hands on it.

To machine the larger one of the two will need a little thinking about as it is 6" diameter and all I have is a 5" chuck. I could mill three small flats in the circumference at 120deg to each other as I don't need the thickness so these will not interfere with making a backplate if I go ahead

Take the jaws out of your chuck, assuming that you have some external ones and place one at the radius required by the workpiece. You can assess the number of teeth on the jaws which would be engaged by the scroll, it may be enough for safety. I would not be happy with less than 3 teeth engaged. You need not tighten the jaws much to allow facing cuts and maybe reduce the diameter carefully and then turn the work around. Three flats would certainly be a safe way although the work would probably run eccentrically at first.

Already tried that and with 3 teeth engaged still will not fit. I have experience with chucks mainly woodturning but I apply the same principle if I have to grip an odd piece but mostly have the jaws so that they form a near perfect circle for best grip on the wood(different design to metal working chucks)

Go for the three milled flats then, they only have to be as deep as the ends of the jaws and will not matter with a small er32 plate. Shame about the thickness, though. I would stick a parting blade in about 1/4" and use the groove for a hacksaw guide. I bought some Starret blades for plastic and aluminium with 14tpi, but even with those it would take a long time to cut. If you go for partial parting, then use the tailstock to steady the work, it will be safer.

That was the only solution that I could see. I agree the parting blade in a small way and then spend a week plus hacksawing it. I keep looking at getting a power hacksaw but other things seem more important to buy for my set up and things like this will only come along very rarely, I will not say never come along again as that is tempting fate

Not 100% conclusive but Parker Steel have Ali which they mark with red paint as AW-6082 EN,  AW-AlSilMgMn,  HE30, If any of that makes sense. And as they are just down the road it may have come from them

Edited By Derek Lane on 03/06/2022 21:05:55

I would be inclined to buy a backplate from Warco ready to go. You then just have to machine it to fit your collet chuck. Did the same for my WM250 some time ago. Details here *** Fitting Collet Chuck ***

John

I looked there and as always they seem to be out of stock

Hi Derek, you could cut as deep as you dare with a parting blade and drill and bore a hole in the centre as big as you need to the depth of the thickness you need, that way you would have less hacksawing to do.

Regards Nick.

Edited By Nicholas Farr on 03/06/2022 21:12:33

Does your 280 use a 125mm chuck with standard 95 register and 108pcd bolts ? - I tried one of ARC's 125mm ER32 collet chucks directly on the flange of my GH600 and (after clocking it in each of the three possible positions) am getting about a tenth runout in the mouth of the collet seat..

..would recommend it for a try-out, at worst you get to make a backplate as planned, at best you save yourself the trouble and win a big lump of ali.

Ideally, the backplate should start by being machined to fit onto the spindle of the lathe.

If a flange fitting, first machine a register that is a tight fit on the flange. (If it can't be fitted into a chuck, mount on the faceplate, and centre as well as possible ).

Having fitted it to the spindle flange via the new register, you can then machine a register to take the collet chuck backplate.

It will be worth boring the middle of the backplate to at least the same maximum bore of the spindle, so that you can pass long work through the spindle bore..

Hopefully, when you clock the internal taper to check concentyricity, there will be almost no fluctuatioinnofnmthe needle.

Howard