A1-4 lathe chuck

[Swarfing]

Hi guys it has come to a point where i need to make a backplate for a 200mm 4 jaw chuck. The question is do i or shall i just machine the back of the chuck? i know it ill be an expensive cock up if it all goes wrong but what would you do?

The only way i can handle the material for the back plate is the existing 160mm 3 jaw. whats your thoughts?

Paul

[bambuko]

Have you got a faceplate? or is 3 jaw your truly only option?
In which case you could try something like this  :


Chris

ps I think I got this photo originally from John Stevenson's web page?

[maybecnc]

A faceplate would be the best, but it also works with your 3 jaw chuck. Make a drawbar like the ones on the bottom of this page:
http://www.toolsandmods.com/lathe-drawbars.html
For your lathe make it from larger stock.

Then drill a hole on the center of the piece you will work on for the drawbar to pass through. External jaws on chuck work better.
Close the chuck jaws until it tights the drawbar. Don't worry if external jaws don't hold the drawbar truly centered.
Turn the front register (oversized to finish later) and then you can reverse it and hold it directly on the chuck.

Jose

[bambuko]

Another alternative would be, to take another disc of metal (small enough dia to fit in your 3 jaw chuck), bolt it the bigger (backplate) disc and use it to hold your backplate for the first op. Make sure the bolt holes are where it will not matter later.

Chris

[Swarfing]

Great ideas and the face plate is what has been at he front of my mind. I do not have one so attaching to the 3 jaw could be the option, issue there is no outside jaws :-(
Something else for the shopping list i suppose? what makes it awkward is the stepped nose. fixing in the middle means i can not machine the centre of the back side but now i have some ideas i will see what i come up with and post the solution back here.

thanks guys

[75Plus]

You might also try removing your 3 jaw from its backplate  and use the backplate as a face plate to hold the work piece. Maybe not the ideal solution but could work.

Joe

[Swarfing]

Joe

i think im going to look at fixing a new plate of some sorts. i have som 100mm/ 4" plates that i could machine up as the base then bolt some fixings too it some how, i'm building a picture at the moment. The lathee i now have is a Vernier TV-280, common as muck in France but not here. It uses a Metric DIN fitting which is a bit of a pain to find off the shelf and to top it off has M9x1.25 bolts on the inner side circle. I just machined some M10x1.25 bolts down to replace the inner ones as they knacked for the 160mm 3 jaw. I bought a new 4 jaw for it and forgot what a pain it is to machine a new back plate up with what you got. I could use the mill but too much backlash to compensate for that much accurate work.

[bambuko]

...It uses a Metric DIN fitting ...

So, is it DIN fitting or A1-4" ??
definitely not the same animal 
BTW mine is DIN 55021

Chris

[Swarfing]

Chris

it is an A1-4 with metric bolt holes, i believe it to be what they call an English/ European din standard. The Germans have their own A1-4 Din standard also. The information about these type of fittings is pretty poor and confusing as most info is for the American standard which differs by using 7/16 bolt holes. Once i make up one plate for it then i should never need worry about it really. It is classed as a short nose taper though and i would be interested if anybody else has had experience with this particular chuck mount?

You can see the lathe in question here http://www.lathes.co.uk/vernier/

i will even have to modify my qctp as well because it is too big and the next model down is too small. trials to keep us busy as usual 

[bambuko]

Looks like very nice lathe indeed!
There is plenty of info about the fitting and it's not confusing at all  :
DIN standard info
American A-1, A-2 etc info
About the only thing they have in common is the taper angle (1:4 or 7deg 7min 30sec)
The rest, ie PCD of the bolts, bolt sizes, taper dia, etc, etc all differ.
I have DIN 55021 #3 in my lathe and I doubt that A-1 3" chuck would fit on my lathe without problems (although never had a chance to try yet).
They are great apart from the fact that chucks etc, with back ends to suit and allow direct fitting on the spindle, are very expensive and not as common as other lot (here in UK), so one ends up using backplates anyway...
For you with A-1 and people with D1 it should be easier, because they are (being american I'd guess) a lot more common.

Chris

[John Stevenson]

I think I might have some backplates and a face plate, need to dig around a bit and get some pics.

John S.

[Swarfing]

Chris that is were i got most of my info from before.i've made backplates for threaded noses which seems a lot easier some how? just off now to source some steel for a back plate and and something for a face plate.