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Main Carriage speed

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ab56452001

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Hi all , newbie from OZ here . Ive added a Sieg C3 55w mini lathe to my arsenal !. without an integral DRO can any body please tell me the Carriage powered shaft RPM to spindle RPM ratio ? , thanks.
 

DAT510

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Welcome to H-M,

Looks like the C3 uses the Lead Screw as for both Treading and Power Feed..... If I'm reading the manual correctly, (Page 28, 32-33) it is set from the factory with the following gears A=20, B=80, C=20, D=80, which I think is 64 tpi, according to the table, which = ~ 0.0156" per revolution. (Though that seems a bit course ).

https://littlemachineshop.com/images/gallery/ug/5100 Mini Lathe Users Guide.pdf

You could always put a dial indicator on the carriage, engage the power feed and manually turn the spindle, counting the number of turns and then divide the distance traveled by the number of revolutions you turned the spindle.

Hope this helped.
 

higgite

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#4
Welcome to H-M,

Looks like the C3 uses the Lead Screw as for both Treading and Power Feed..... If I'm reading the manual correctly, (Page 28, 32-33) it is set from the factory with the following gears A=20, B=80, C=20, D=80, which I think is 64 tpi, according to the table, which = ~ 0.0156" per revolution. (Though that seems a bit course ).
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The gear combo for 64 tpi is 20-any gear-80. A 4:1 ratio. The normal gearing on that lathe for turning is 20-80-20-80, as you pointed out. But, that is a 16:1 ratio, equivalent to 256 tpi.

Tom
 

ab56452001

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Thanks for replies , if I got that correct does that mean if the Chuck/Spindle is rotating at 400rpm the Power Feed drive is doing 100rpm ?, cheers
 

higgite

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Thanks for replies , if I got that correct does that mean if the Chuck/Spindle is rotating at 400rpm the Power Feed drive is doing 100rpm ?, cheers
No, that is incorrect IF your change gears are set up for normal turning. With the normal 80-20-80-20 gear setup for turning, the leadscrew turns 1/16 of a rev for each rev of the spindle. So, for a spindle speed of 400 rpm, the leadscrew is turning at 25 rpm. May I ask why are you concerned with leadscrew rpm vs spindle rpm as opposed to carriage movement per rev of the spindle?

Tom
 

ab56452001

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#7
As my Lathe has no rev counter was looking for an easy way to work out rpm and put incremental markings on the speed dial , ive since bought a cheap led rpm indicator that i can do this calibration with , cheers.
 
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