[modeleng] Re: coarse threads


I am restoring an old lathe.

The thread cutting chart attached to its lists threads down to 2 and 1tpi.
 What on earth would use those?

Alan Stepney


Alan, et al,

The old Lodge and Shipley lathe (1900?) at the sawmill will cut threads that 
coarse.  When a friend and I had a small machine shop in Jackson, we had a 
guy come in who wanted 3/4 turns of thread per inch.  This is about the 
pitch of the "Bendix®" drive threads in auto mobile engine starters and he 
was working on a four wheel drive patent of some sort.  Anyway, we had 
nothing that would cut less than 4 tpi so I put a chain drive from the 
spindle to the lead screw and cut the piece for him.  Only one problem, no 
matter how I tried to use the threading dial, I could not make it track on 
the previous groove.  Finally resolved that I would have to reverse the 
lathe and back the carriage w/out disengaging the lead screw.

When you wonder why threads would be really coarse, think winding drums for 
mine hoists etc.  They are grooved 1tpi or less as are the flywheels grooved 
for the old "rope drives" used in mills.  The sawmill at Bruce Mississippi 
had a rope drive to the line shaft and it used 1" Manila rope that was 650 
feet long instead of "V" belts.  I have photos of the engine and drive 
somewhere on 35mm and video.

Oh, just for the record, when I worked at the railroad I cut a metric thread 
on an Imperial lathe.  They needed a special test fitting for the fuel 
injector rebuild shop and no one seemed to be able to cut the metric 14mm 
thread, but I figured out how to do it and made the part.  This was made on 
a brand new 18" Lodge and Shipley.

Jesse the Tennessee Redneck

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