My Old Landy
Engineering Mayhem
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I only have a leadscrew on my S&B model M. It says in the manual to engage them for a power feedUsing the half nuts to power feed will wear your leadscrew
I only have a leadscrew on my S&B model M. It says in the manual to engage them for a power feedUsing the half nuts to power feed will wear your leadscrew
I'll.have to try it. Just wasn't sure of what lever does whatWhy not? That's what the power feed is for. So long as you'd don't use the half-nuts it'll be fine.
The Boxford only has a lead screw. However, there is a slot along it which drives the power feeds through a keyed gear
That's great! Put my mind at ease
This is my second lathe - my first didn't have any leadscrews so all this new fangled halfnut trickery is new to me
I will investigate whether there's any kind of stop/clutch/disengage as I must admit to being more than a little concerned about what happens if the carriage or toolpost collides with the chuck!
Using the half nuts to power feed will wear your leadscrew
Makes sense. Mine has two, with separate levers for the threading screw and the power feed screw.If its designed as a power feed, then it's put there to use!
You wouldn't use the threading lead screw for power turning if it's a separate screw - you'd struggle to get a fine enough feed, even if it was a good idea (which it isn't)
The machine manual should keep you right on what it's supposed to be used for, if it's only got one screw
It's a Colchester Student 6", circa 1930sWhat's the lathe? Colchesters (at least some of them) have a twist-grip knob on the engagement lever that can be adjusted to set the trip point... I used to check mine by setting the power-sliding away and then hanging onto the toolpost from the right-hand end of the bed At the higher end of the range I couldn't stop it, so god knows what sort of cut you'd have to be taking to make that drop out! I never needed more than the minimum setting to trip out against a bed stop.
back it out, rewind, push in and repeat
Hang on chaps, what model Boxford are we talking about? On the C or CUD the apron only has one lever, which engages the halfnuts and which is the only way to get power sliding (no surfacing or 'cross-feed') on that model.
The higher-spec models have two levers: the far right one enagages the halfnuts as above (for screwcutting, in collabration with a dial thread indicator) while the one to the left of it has three positions: disengaged in the centre, up for sliding and down for surfacing. The friction clutch is then brought into play, simply by a twist of the wrist as it were, and this when set correctly WILL slip at a preset travel limit. Using the halfnuts for power sliding will quite happily break things if you don't disengage in time.
That's fab - thanks. I'll try to be bolder, next time!You shouldn't be backing the tool out between cuts on normal turning, you can introduce inaccuracy due to the backlash in the crossfeed.
When the cut is finished leave the tool set where it is, wind it back to the end on the bar, move it in by whatever the cut depth is & hit the auto feed.
The only time you back the tool out is when the item is at the finished diameter of if you are screw cutting.
You are taking the right approach by being cautious about stopping the auto feed early, after some practice you should get within 5mm before stopping it.
I would advise you to take heavier cuts, assuming you are turning mild steel.
If I was going from 25 to 16mm on my Myford ML7 I would take 8x 1mm cuts, measure the diameter then set the tool for the last cut according to the measurement. You will get a better finish using heavier cuts, especially using carbide tooling.
On a heavier lathe like yours you could probably take 2mm cuts, check out the @doubleboost youtube vid where he reviews the Banggood carbide lathe tooling.
you back the tool out every time you reverse while screw cutting, or otherwise you'll quickly break something!You shouldn't be backing the tool out between cuts on normal turning, you can introduce inaccuracy due to the backlash in the crossfeed.
The only time you back the tool out is when the item is at the finished diameter of if you are screw cutting.