How to remove this lathe chuck?

I want to remove the chuck from my lathe. I want to see if it is possible to add a collet holder or a 4 jaw chuck. I think I have to remove 3 screws with an Allen key. But they are stuck. Also somebody forced them before, they don't look good. I'm afraid that if I try harder I might destroy the screw top and then I don't see how I could remove it. Is is barely enough space for the Allen key. What would be the best method?

Also why this thing looks like a giant screw? Is it really threaded in the head stock?

Look at the "L" type spindle taper at the bottom of this pdf. The ring you have arrowed unscrews fron the thread on the chuck backplate

Edited By JasonB on 29/04/2023 20:26:12

Thank you! So I have a back plate like this.

Now I found also a video where I could see it better

That's it. There are various sizes the pdf should have the information to tell which you have.

It would be better to keep your existing backplate fixed to your existing chuck. Then get a new backplate for any new chucks as they are best fitted to the spindle nose and finish turned on the lathe to fit the chuck exactly.

No idea what's available in your part of the world, but if you look up "L00 chuck" on eBay, (that's L zero zero) you will see several options which illustrate what's easily obtainable.
Usefully, some sellers list fittings as Loo (all letters) which might lead you to cheaper options, always assuming yours does measure up as that size. e.g. HERE
https://www.ebay.co.uk/itm/353930991295

5C collet chucks seem a viable way to go, but obviously you could use an L00 backplate with a 4 jaw or ER collet system.

Over here in the UK some Boxford, Colchester, Harrison lathes, amongst others, shipped with the l00 taper spindle fittings.

Bill

Edited By peak4 on 29/04/2023 20:53:53

Consider sticking an arrow or similar marker on the lathe to indicate which direction to turn the locking ring for undoing the chuck.

I've known several people who really ought to have known better try to turn it the wrong way. Even in one case to the extent of applying a hammer to the spanner!!! Fortunately the spanner was a casting and broke before the lathe did.

I the days when I occasionally drove a lathe with an L series mount I made sure to think carefully before attempting to change chucks. Never personally actually heaved the wrong way but came close more than once before brain kicked in.

I guess its the inside out thread arrangement that catches folk out.

Clive

As far as I can see in the photograph the Allen screw looks to be more like a Torx head to me.

Chris looks to me like a cap head that someone has rounded the hexagons off.

Agreed, likely a wrongly sized allen key. Easily sorted with the chuck removed from the lathe (unless the others are chewed even worse!).

I have a lathe with L00 fitting. Easy way to change chucks is to hook the C spanner to screw into the headstock. Get a suitable bar to sit between chuck jaws then heave one against t'other.

I like the fitting as it is very quick to change chucks which is useful to a model engineer.

Martin

More than once when faced with a radged-up hexagon socket in a cap head screw, I've been able to hammer in a next-size-up Torx bit and unscrew the offending item. The battering-in of the socket seems to help the offending screw release. I hope it doesn't come to that for you!

Does anyone remember the locking ring on the bottom bracket of old style bikes [1940/1970.] ?

Seem to recall that one of them was left hand thread.

I suspect the your locking ring is likewise. Make yourself a "C" spanner to suit .

Regarding those other screws, like a dog with a bone, leave them alone !

Its a right hand thread

.

... As is quite evident from the second photo in the opening post

MichaelG.

Even though it is obviously right hand thread many folk find the "inside out" layout makes it feel that you have to turn it the wrong way to undo a chuck.

In many cases there is no significant visible thread, the Harrison I used showed about half a turn, which doesn't help.

I always had to think first.

Clive.

Larry Phelan wrote:-

Does anyone remember the locking ring on the bottom bracket of old style bikes [1940/1970.] ?

Seem to recall that one of them was left hand thread.

Classic British bicycles have their bottom brackets tapped 1.370" x 24tpi. The fixed cup which is fitted on the chainwheel side is left hand thread.

The adjustable cup and its lock ring are right hand thread.

Pedals differ as well. The chainwheel side one is RH thread and the other side is LH thread.

Time to go out for a ride I think!

Dave

I stand corrected, yet again !!!

Thank you for all suggestions. I'll leave those screws alone. Now I'm looking for a C spanner. In the end I want to be able to remove the working piece and put it back without loosing the concentricity. I find this to be very annoying with the current 3 jaw chuck.

I would like to use an ER40 collet rather than a C5 type. I read that ER is more tolerant to the diameter of the workpiece. A 4 jaw chuck would be the second option. It is more time consuming to adjust.

Why do you have to take it out and replace it?

Best practice is to work out how to do the operations that need to be concentric without disturbing the part - often it can be as simple as making the the part with extra material to hold in the jaws, and then parting it off once all the critical operations are done.

If you need to make the parted end look tidy then it's okay to put it back in the jaws as a last operation because errors of concentricity in a facing cut aren't always so visible.

Yes, this is true. But these days I have a stainless steel bar and a mild steel bar that I keep swapping. I'm trying different tools. Or sharpen them to see the difference on both materials. Yesterday for example I did a 32 to 12mm plastic adapter for a diamond grinding wheel. And again I had to remove the bar from the chuck. And tomorrow I will put it back because I want to see how is the finish after I hone the tool with the diamond wheel. And so on ...