Randa b nose thread

[Jack ColeParticipant @jackcole49924]

Can anyone enlighten me as to what thread the headstck spindle thread is on a Rana B?

It's listed (and measures) one inch, and has 12 threads per inch.

Being a UK pre war design, one would imagine it's BSF, but that seems to be 10 TPI

UNF is 12 TPI at one inch, but I can't imaging a pre war UK manufacturer using a US thread.

Any help would be much appriceated.

[Jack ColeParticipant @jackcole49924]

[old martParticipant @oldmart]

The pitch of threads like these is not often standard nuts and bolts configuration. You might be able to tell the angle with a light and magnifying glass if you have anything with a known 60 degree angle to compare it with.

[Roderick JenkinsParticipant @roderickjenkins93242]

Lathes don't tend to have nose threads that fit within the confines of the standard fastening ranges. It's almost certain that the thread will be a 55 degree 1" x 12tpi. If you are looking for a tap then I'm afraid you are probably out of luck.

HTH,

Rod

[Jack ColeParticipant @jackcole49924]

Thanks for that.

Why I'm asking is I need a faceplate. I do have a suitable candidate but it needs tapping.

So now that idea is out, does anyone know if a Drummond or a Myford ML8 inboard faceplate, which are both 1'' 12 TPI would do the trick?

[BazyleParticipant @bazyle]

It isn't the thread that defines the fit but the register – the plain parallel bit just behind the thread. And a tap will never be true enough for this job. What you can do is measure it all and practice making a few small threaded bushes in aluminium as it is easy to cut. Make sure the fit is not so tight it can shrink on if you put it on warm.
When you are confident you can cut the thread and register accurately make one in cast iron with 1/8 to 1/4 extra all round. Then find a faceplate nobody wants (rather than a useful Myford or Drummond one) and bore it out to take your bush, fitted with Loctite.

[Jack ColeParticipant @jackcole49924]

Thanks for that

Gets more complex by the minute.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Jack, I've made chuck backplates for my father's old RandA B lathe using a 1" UNF tap, and they fit without any problem. I've also made a chuck backplate to fit my mini lathe, to mount the chucks from his lathe, to use on my mini lathe. When offering up a 1" UNF tap to the spindle thread from a RandA lathe, the thread angle is the same.

Just be sure you don't use a 1" NF, as they are 14 TPI.

Regards Nick.

Edited By Nicholas Farr on 23/04/2023 22:29:37

[Jack ColeParticipant @jackcole49924]

Brilliant Nick, thank you very much.

I did suspect 1" UNF might do the trick, as it's 12TPI, but I wasn't sure of the pitch.

Once again, thanks very much.

[Mike PooleParticipant @mikepoole82104]

I think the thread fit is not so important if the chuck fitment is a register. Some early lathes did not have the register surfaces so the thread was more important. If the mounting has register surfaces then my feeling is that the thread should not compete with the register and should just allow the register to locate the chuck and the thread hold it against the register faces.

Mike

[old martParticipant @oldmart]

We have a faceplate at the museum, somewhere between 5 and 7 inches diameter with a similar thread in it. I will have a look at it on Wednesday, it was in some donations and might possible be what you are after, it has no use here.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi old mart, below is a photo of my father's RandA B lathe, with its original faceplate, so if the one you have is the same, it is probably the correct one if the thread is correct.

Regards Nick.

[old martParticipant @oldmart]

The one we have looks like that, but I cannot remember the details, at least I do know exactly where to look for it.

[Jack ColeParticipant @jackcole49924]

Posted by Mike Poole on 24/04/2023 13:19:12:

I think the thread fit is not so important if the chuck fitment is a register. Some early lathes did not have the register surfaces so the thread was more important. If the mounting has register surfaces then my feeling is that the thread should not compete with the register and should just allow the register to locate the chuck and the thread hold it against the register faces.

Mike

Hi Mike

looking at pictures of Randa a and b lathes, I don't think it is a register fit The plate only seems to be on as far as the end of the thread. Could be wrong, but that's the impression I get.

[Jack ColeParticipant @jackcole49924]

Posted by old mart on 24/04/2023 15:12:00:

We have a faceplate at the museum, somewhere between 5 and 7 inches diameter with a similar thread in it. I will have a look at it on Wednesday, it was in some donations and might possible be what you are after, it has no use here.

That would be brilliant. Obviously a financial donation to the museum will be forthcoming if it's the faceplate I'm looking for.

The picture Nick has supplied looks identical to all the ones Ive seen in pictures of Randa A & B models, so hopefully that's what you have.

Many thanks

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by Jack Cole on 24/04/2023 21:41:26:

Posted by Mike Poole on 24/04/2023 13:19:12:

I think the thread fit is not so important if the chuck fitment is a register. Some early lathes did not have the register surfaces so the thread was more important. If the mounting has register surfaces then my feeling is that the thread should not compete with the register and should just allow the register to locate the chuck and the thread hold it against the register faces.

Mike

Hi Mike

looking at pictures of Randa a and b lathes, I don't think it is a register fit The plate only seems to be on as far as the end of the thread. Could be wrong, but that's the impression I get.

 

Hi Jack & Mike, yes there is a register, and a plain portion of 1"diameter, just behind the thread on the spindle, see photos below.

Regards Nick.

Edited By Nicholas Farr on 24/04/2023 22:54:15

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Jack, two photos of the back of my RandA faceplate, first one shows the thread with a plain section at the start, which fits snugly on the plain portion of the spindle. The second one shows how it fits to up the spindle nose register.

The small round holes dotted about, are probably where my father drilled it for attaching work to it.

Regards Nick.

Edited By Nicholas Farr on 25/04/2023 07:39:02

[Jack ColeParticipant @jackcole49924]

Cheers Nick.

You're quite correct.

The reason I thought it didn't have a register is that mine has a tiny faceplate attached to it, which I cannot remove at present.

The lathe is totally stripped down atm, so the spindle is out of the headstock, so I'll not be able to try and remove the faceplate until it's back together.

Many thanks for the pics, it's all becoming much clearer.

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