[modeleng] Progress on little lathe

Hello everyone
I have progressed with the construction of my little lathe.

I am feeling quite chuffed.   I have made the tumbler gear for my leadscrew, 
placed on the right-hand side of the supporting 'wall'.   This gives me 
forward, neutral and reverse, and above all, allows a stub 'leadscrew' to be 
placed about 2" lower than the actual leadscrew, thus making space for a normal 
Myford 'banjo' and Myford change wheels (of which I have a large selection).    
I cut the leadscrew to 10 tpi Acme thread.   10tpi = 2.54mm, which I considered 
to be near enough to 2.5mm.    I have tried my first metric screwcutting - a 
.5mm thread, and I am delighted that there is no detectable error.    This 
avoids the necessity of a conversion change-wheel.

On the right-hand side of the leadscrew, I have installed a poly-vee pulley 
system, driven by a car wiper motor and controlled by a power source. giving 
variable speed.     When the tumbler gear is in 'neutral', I can use this for 
'sliding' the saddle.    I have got it down to 4 rpm, thus enabling me to cut a 
very fine finish.

The mandrel is driven from a 3-phase motor, via a poly-vee belt, controlled by 
an inverter.    When cutting heavier threads, the slow speeds do not have 
enough torque.   I have mocked up a 'back-gear' system, using some gears I 
happened to have lying around.      This gives an 8.7-1 speed reduction.     My 
little lathe design did not include back-gear, partly because of the restraints 
of space and mainly because I did not wish to want to have gears driving the 
mandrel and affecting the turning finish.      I will place this free-standing 
reduction gear behind the lathe, and drive the mandrel by a poly-vee belt.

Once all of this is finished and working, I will send you a series of pictures, 
which will show the system.

Glad to see an upsurge in messages - always so welcome!.

Cheers!   Hubert



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