Hello from West Sussex, looking for ID for my first lathe

[magpieParticipant @magpie]

RDG tools give good service, but not so hot on quality with some items.

Dek

[Andy CarlsonParticipant @andycarlson18141]

Not sure which RDG chuck you mean… they have 'economy' ones, HBM and Pratt Burnerd ones. The latter are a very well regarded brand (and cost more). I can't speak for the other two but others may have some experience.

The snag from your perspective is that all of them will need a backplate and the backplate needs to fit both your lathe spindle and the specific chuck.

This page explains a lot about backplates http://www.lathes.co.uk/latheparts/page7.html

If you look at one of the RDG listings you will see it tells you the 'locating recess diameter' – this is the diameter of a step that needs to be turned on the front face of the backplate. This step should be a close fit for the chuck recess because it keeps the chuck concentric with your spindle.

The listing will also tell you the 'PCD' or pitch circle diameter. Your backplate will need holes to accept the screws which will hold the chuck onto the backplate. The centres of these holes must be exactly half of the PCD away from the centre of the spindle. A 3 jaw chuck will need three holes equally spaced around the circle. A 4 jaw chuck will need four.

Backplates can be machined from blanks but it's not an ideal job if you are learning… plus you need a working lathe.

[old martParticipant @oldmart]

It's a shame about the lockdown, there is a little faceplate about 5" diameter lying in some junk at the museum, and the thread is small, but I can't get in there to look at it.

[JAMES HUGGINSParticipant @jameshuggins32733]

Posted by Andy Carlson on 01/06/2020 17:29:02:

Not sure which RDG chuck you mean… they have 'economy' ones, HBM and Pratt Burnerd ones. The latter are a very well regarded brand (and cost more). I can't speak for the other two but others may have some experience.

The snag from your perspective is that all of them will need a backplate and the backplate needs to fit both your lathe spindle and the specific chuck.

This page explains a lot about backplates http://www.lathes.co.uk/latheparts/page7.html

If you look at one of the RDG listings you will see it tells you the 'locating recess diameter' – this is the diameter of a step that needs to be turned on the front face of the backplate. This step should be a close fit for the chuck recess because it keeps the chuck concentric with your spindle.

The listing will also tell you the 'PCD' or pitch circle diameter. Your backplate will need holes to accept the screws which will hold the chuck onto the backplate. The centres of these holes must be exactly half of the PCD away from the centre of the spindle. A 3 jaw chuck will need three holes equally spaced around the circle. A 4 jaw chuck will need four.

Backplates can be machined from blanks but it's not an ideal job if you are learning… plus you need a working lathe.

When you say exactly, are you talking scribed and centre punched by hand and drilled in a pillar drill? Because that isnt out of my capability or are you talking via a milling machine? My father in law has a large functioning lathe and I know people who have access to industrial machinery at a heritage railway so if its not something I can do in my workshop, I can get it done elsewhere.

[JAMES HUGGINSParticipant @jameshuggins32733]

Posted by old mart on 01/06/2020 18:12:05:

It's a shame about the lockdown, there is a little faceplate about 5" diameter lying in some junk at the museum, and the thread is small, but I can't get in there to look at it.

Thanks for the kind thought though 😊

[Andy CarlsonParticipant @andycarlson18141]

Posted by JAMES HUGGINS on 01/06/2020 18:34:02:

Posted by Andy Carlson on 01/06/2020 17:29:02:

When you say exactly, are you talking scribed and centre punched by hand and drilled in a pillar drill? Because that isnt out of my capability or are you talking via a milling machine? My father in law has a large functioning lathe and I know people who have access to industrial machinery at a heritage railway so if its not something I can do in my workshop, I can get it done elsewhere.

The parts where the fit is critical are the machined surfaces that fit your spindle, which is the back face (or at least the middle of it), the threaded hole and the conterbore. The outside diameter just needs to match your chuck for appearance sake. The chuck registration step is best left a little oversize initially and finished on your own lathe. The PCD holes are not too critical if they are plain holes but more tricky if they need to be threaded.

It will most likely be cast iron which is not the nicest stuff to machine.

I'd strongly recommend that you get someone to help you.

[Swarf, Mostly!Participant @swarfmostly]

James:

You have a PM.

Best regards,

Swarf, Mostly!

[JAMES HUGGINSParticipant @jameshuggins32733]

OK well that all sounds good to me. I'll get my father in law to help turn the recess in the back plate when I get one if I don't manage to find one that is matched to a specific chuck. It's just what to search for chuck wise really to begin with. Oh and also a small pulley to fit my motor. I will get some round belt for the 7mm pulleys but I will also need a small pulley, any recommendations of where to buy?

[old martParticipant @oldmart]

There are a couple of faceplates I just noticed on ebay, they might be the right size for your lathe. 303607680392

[JAMES HUGGINSParticipant @jameshuggins32733]

A quick update if anyone was interested.

Bought a used 4 jaw prat Bernard 4" chuck and turned a face plate for it. I had some hurdles on the way and still need to fettle the electrics slightly but is working OK. Very crude motor mount for the time being just until I get it turning and decide if its a venture worth continuing. So far not bad…

i bought some 12mm steel to make a back plate from, welded a 3/4" 12 nut on the back which I had ground parallel on the diamond plates. Managed to get it to run 0.01mm on the spindle with not much problem, these nuts come pretty true it seems. How did I get it central you may ask? Well I drilled a 3/4" hole in the center of the plate which allowed the threads of a 3/4 12 bolt through but stopped at the shank, then wound the nut up to the plate and tack welded the nut on, kept the heat to a minimum and all was good.

The plate had been plasma cut and the edges were as hard as granite which I learnt after having destroyed a freshly ground tool! So I'm going to grind the final shape down a bit more yet but manage to turn a good recess in the face for the chuck with about a 0.05mm (10thou) gap between chuck inner face and the plate, I've read you want a slight gap there with 4jaws, not sure if that's right?

Lastly I drilled the bolt pattern and bobs your uncle! Chuck runs nice and true, within 0.05mm. I've still got to dial a few things in, like checking the bed for twist etc but I'm no tool maker and I don't need anything crazy accurate. Should make for a nice learning lathe.

I forgot to mention, whilst trying to turn the recess on the plate, the cross slide lead screw nut gave way, no threads left! So I bought a new screw and nut and cobbled it together to get the lathe working to finish the chuck. So my first jobs is probably to get the cross slide working properly again 😆 all good fun though.

I'll post some pics shortly.

[JAMES HUGGINSParticipant @jameshuggins32733]

[old martParticipant @oldmart]

Thats a novel backplate, I hope your welds are good. With a four jaw independent, the main thing is making sure the front of the faceplate is faced dead flat and square to the spindle axis. Radial runout is slightly less important with this type of chuck. The best check for the faceplate would to screw it on ond off several times and check with a dti that it stays true on the face.

I'm back at the museum next Wednesday, I will have a look for the faceplate.

Edited By old mart on 11/07/2020 15:27:57

[not done it yetParticipant @notdoneityet]

Rough and ready, perhaps, but not machined for the registration on the spindle and is it 3/4 by 10 or 12 (you seem to have changed your mind on that)?

You should really have faced the nut and cut the register before welding on the plate. It would have been fairly easy doing it first.

[JAMES HUGGINSParticipant @jameshuggins32733]

Posted by not done it yet on 11/07/2020 16:55:03:

Rough and ready, perhaps, but not machined for the registration on the spindle and is it 3/4 by 10 or 12 (you seem to have changed your mind on that)?

You should really have faced the nut and cut the register before welding on the plate. It would have been fairly easy doing it first.

Doing it this way, I was concerned the weld heat would move things. So I welded it then faced it. And regarding facing the nut, there was barely any measurable runout once I had ground it, probably less than what adding the steel plate added. It all seems pretty good.

 

I put a 200mm precision ground round bar in the chuck and adjusted the headstock (there are bolts believe it or not to do this), and with an indicator I now have 0.02mm over the 200mm so 0.02mm taper.

 

This lathe is a bit laughable really. Fingers crossed those welds hold 😆

 

Sorry yes it's 3/4 10 

Edited By JAMES HUGGINS on 11/07/2020 21:18:33

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