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Member postings for Martyn Bannister

Here is a list of all the postings Martyn Bannister has made in our forums. Click on a thread name to jump to the thread.

Thread: BOXFORD Metric Threads on Imperial Model A
14/06/2011 16:53:09
That will probably be this page under "Metric & English Screwcutting"

I have checked all the relevent parts and they are indeed standard imperial parts. It was the lack of the "metric thread chart" which was my problem. I now have the spreadsheet and, should anyone wish to use it, it's HERE.
14/06/2011 13:41:42
And, for all those who are curious, it would appear that the correct formula is......
 
MM Pitch = (56/Box Setting) * (spindle gear/gearbox gear)
 

14/06/2011 13:35:46
Paul, John, many thanks. Nope, I don't have that chart on the inside of the change gear cover. I also avoided buying the "Know your lathe" manual, since I came across quite a few posts which mentioned that it DIDN'T have the chart in it !!!!!
 
Thanks very much for your help. It is extremely clear, once you know. I shall make up a spreadsheet, print it off and laminate it and put it inside my cover.
 
Many thanks again for your rapid and helpful response
 
14/06/2011 12:51:25
Hi all,
 
Forgive a newbie his first question.......
 
I have searched high and low on t'internet and cannot find a definitive answer to my question. I hope someone here can help because SURELY it's a problem solved by many over the years...............
 
I have just purchased a Boxford Model A lathe. It has the Imperial screw cutting quick change box and 8TPI lead screw. It has the standard imperial setup of change gears between the tumbler reverse (AKA spindle) and the gearbox input shaft i.e 20T, 80T idler, 56T (with 40T on same shaft but not engaged).
 
With my lathe came the gears which many sites (incuding lathes.co.uk) specifiy are required to enable this machine to cut metric threads.
i.e. 24, 26, 28, 32, 36, 44, 48 and the all important 127/100 compound gear.
 
What no web site that I can find does explain is HOW are these gears used?
 
I have found mention of how to set up a LOGAN lathe (which apparently has the same box?) and that specifies MM Pitch = (40/Box Setting) * (spindle gear/gearbox gear). From this I deduce that if I put a 24T on the spindle driving the 127T compound and then drive a 48T on the gearbox from the 100T of the compound I should set the gearbox to its 20TPI setting and this should give a 1mm pitch.
 
Unfortunarely it DOESN'T!!!!!
 
Has anyone got the definitive low down on how this should alll work for a Boxford Model A? Instructions need to be clear for a dummy like me!!!!
 
Thanks in advance.

/\/\artyn Bannister
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