John Brown
Freeloading Social media influenza
Looks like they're in Lancashire. I'm in Gloucestershire, but thanks anyway.
What chuck for Arundel j4 junior m24x2.5 spindle?
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John Brown
Freeloading Social media influenza
John Brown
Freeloading Social media influenza
Hmm... Got a few repeats there..
I do not see a future career as a professional photographer beckoning...
I do not see a future career as a professional photographer beckoning...
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okeydokey
Established Member
Well you get the idea was a Stinchcome address
John Brown
Freeloading Social media influenza
"Engineering in Stinchcombe is a very broad term and is the science and skill of building and designing aspects such as:"
Looks very much like it was AI generated.
I think we need to wait for JG, and his photo interpreting skills, see what he thinks when he has blown them up, looks to me as though it is finer than 2mm pitch. 
J-G
Established Member
At least you have recognised that those photo's don't help much.
The ideal would be a close-up (say from 25mm away) - square on - showing a clear thread-form but even one taken from (say) 120 or 150mm distance - as long as it is square on - could be useful, the inclusion of a ruler is definitely an advantage but again MUST be square on and prefereably a well cleaned thread.
J-G
Established Member
I've just found the last image which might be useful.
If you look at the image with the metric scale then the first two mm graduations do look fairly well lined up. However as you track left and look at the next two pairs, the thread is falling progressively shorter of the mark. So I would say finer than 2mm, but not as fine as 1.75. So my best guess would be it's Imperial, either14 tpi,1.81mm pitch or 13, 1.95. But what diameter? Too big to be 13/16, but surely too small to have been 7/8, which is 22.2. They look worn, but not that much I would have thought, unless whoever made it got the major diameter under in the first place.
Caveat being the pictures aren't the best so could be quite wrong.
I am sure JG will blow them up and come back with a better idea.
Caveat being the pictures aren't the best
so could be quite wrong.I am sure JG will blow them up and come back with a better idea.
Might be useful if you could take measurements of the internal diameter of the thread on whatever accessories you have that screw onto it, would give some idea what the core diameter is.
J-G
Established Member
As @Fergie 307 has already deduced, I now suspect that it is 14tpi. Here is a blow up with suggested dimensions :-
The Yellow lines show a 60° form (Unified) and the Purple lines 55° Whit form. The dimensions are anotated in mm after enlarging the photo so that the OD is 207.5mm (ie. a 10X enlargement)
Although the measured angle is ~48° that is likely to be a red herring and due to the direction the photo was taken. There is a 47½° form - BA but that standard doesn't extend beyond 6mm OD.
It is a seriously truncated form with the depth of thread at best 78% of what I would expect and more likely to be 73% - this will depend upon it being Whit (my guess) or Unified (or metric)
If it is 14tpi Whit form then the full depth should be 0.0457" (1.161mm) and some of the discrpancy could be accounted for by my taking the measurment as a flat root rather than a radiused one. - - - - It is still a heavily truncated form though.
If @John Brown could find three 1mm dia. pins and place those in the thread (one on one side and two on the other) the measurement across them should be between 20.97 and 20.78mm - this would measure the effective or pitch diameter for a 13/16" x 14tpi Whit. form thread 'Free' class.
All this - although looking like a 'fact based assesment' - is of course pure guesswork, albeit based upon the best available evidence!
The Yellow lines show a 60° form (Unified) and the Purple lines 55° Whit form. The dimensions are anotated in mm after enlarging the photo so that the OD is 207.5mm (ie. a 10X enlargement)
Although the measured angle is ~48° that is likely to be a red herring and due to the direction the photo was taken. There is a 47½° form - BA but that standard doesn't extend beyond 6mm OD.
It is a seriously truncated form with the depth of thread at best 78% of what I would expect and more likely to be 73% - this will depend upon it being Whit (my guess) or Unified (or metric)
If it is 14tpi Whit form then the full depth should be 0.0457" (1.161mm) and some of the discrpancy could be accounted for by my taking the measurment as a flat root rather than a radiused one. - - - - It is still a heavily truncated form though.
If @John Brown could find three 1mm dia. pins and place those in the thread (one on one side and two on the other) the measurement across them should be between 20.97 and 20.78mm - this would measure the effective or pitch diameter for a 13/16" x 14tpi Whit. form thread 'Free' class.
All this - although looking like a 'fact based assesment' - is of course pure guesswork, albeit based upon the best available evidence!
Would be well worth giving it a good go with a wire brush to get what looks like a fair build up of debris out of the bottom of the threads.
The way I would probably approach this, as it does appear to be a one off, would be to first cut a male thread to as closely replicate what you have as possible, then cut a female thread to match. The wires measurement JG suggests would be very helpful in doing this. As JG says it does look as though it hasn't been machined to the standard dimensions, which makes it more awkward. I am guessing on your lathe the backplane or chuck is held in by the thread, but accurate alignment is by way of a larger bore in the backplate, which fits snugly over the slightly larger diameter on the spindle immediately behind the thread. In some cases it may be the even larger diameter behind that which is used. Would be good To have an image of the accompanying backplane or chuck.To make an adaptor you would need to know both the thread size of whatever larger thread you want to convert to, and the measurements of the accompanying larger bore. But I can certainly make you up a simple collar to confirm the thread. I would also need to know the diameter of the shaft immediately behind the thread, the distance from the end of the spindle to the step between the section of round shaft directly behind the thread, and the larger diameter, and the internal measurements of any accessories that screw onto it. That way I can make a collar that will fit the thread, and fit the index behind it. I can make it of sufficient size that If it fits well then you have a basis for making an adaptor in the future. And a fresh image of what it looks like really clean would be helpful too. Long list of stuff, but as I am sure you appreciate by now this is not particularly straightforward
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John Brown
Freeloading Social media influenza
I probably won't get out to the shed to try more photography today, what with it being the most wonderful time of the year and all that, but I have to say that I really can't see it being a one-off, as apart from having two faceplates that fit, and don't, to my untutored eye, look to be one-offs, I also have a collet chuck (possibly Craft Supplies) that fits, and also, I found a picture on the uklathes site that shows this thread, and it looks identical.
Meanwhile, thanks for all the help and suggestions.
What I may try is somehow attaching my DTI to the tailstock and measuring the travel when I spin one of the headstock face plates a few revolutions. I feel that might be more accurate than attempting measurements with calipers.
Meanwhile, thanks for all the help and suggestions.
What I may try is somehow attaching my DTI to the tailstock and measuring the travel when I spin one of the headstock face plates a few revolutions. I feel that might be more accurate than attempting measurements with calipers.
John Brown
Freeloading Social media influenza
1/2" BSP ?
I may have some outside tap fittings to try...
I may have some outside tap fittings to try...
J-G
Established Member
I doubt that you will find out anything more regarding the 'pitch' - though there could well be confirmation - I would anticipate that you will measure 0.071" or 1.81mm for 1 revolution but would also suggest that you test the distance travelled at 4 turns which would be 0.2857" or 7.257mm.
The (probably more) important issue is to determine the thread 'form'. I would meticulously clean the thread first with a wire brush and then with wool yarn, kitchen roll, loo roll etc. then place a sheet of white paper in the background and set up a camera at 1° 41' to the lathe axis (that's the helix angle of the thread) to take the best possible image. In fact, I would use an endoscope, or 'Probe' Camera (since I have one!) to get an image of just the four/five thread crests/troughs.
Another option would be (after the meticulous clean up) to press 'Plasticine' or similar into the thread to take a cast which could then (with care) be cut to provide an image which may be easier to photograph.
I'm sure we all have much more important things to attend to over the next few days though, so I'll not be looking for an early responce!
J-G
Established Member
Ye God's
why did I not consider that ! the nominal OD is 0.825" (20.955mm) and it is 14tpi - - - It seems that the more experienced among us have been blinded by 'knowledge' 
I have a sneeky feeling that you'll find a perfect fit with your outside tap fittings.
(though it does seem an odd thread to use for this application).
John Brown
Freeloading Social media influenza
I'll bet the outboard thread is 3/8" BSP as well.
Maybe odd, but taps and dies easy to find!
Maybe odd, but taps and dies easy to find!
Yes indeed, I suppose we were both blinded by the application, it never occurred to me either.Ye God's
I have a sneeky feeling that you'll find a perfect fit with your outside tap fittings.
(though it does seem an odd thread to use for this application).
To someone making it I suppose the ready availability of taps and dies would make it a good choice.
Every day is a school day
Well done Mr Brown, at least that will mean getting an adaptor made will be pretty simple
J-G
Established Member
3/8" BSP is 0.656" OD (16.66mm) x 19 tpi (0.053" - 1.34mm pitch) so at least you now have a guide as to what measurments ought to be expected.
The only issue might be whether it is a Left Hand thread (non standard) or has a potential for a locking screw.
