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Red lathe woes..or 'The joy of owning a piece of history'
DavidA:
Norman,
I'm relieved to hear the nurse has arrived. Clearly your meds are beginning to lose efficacy.
You (may) recall I wrote, right at the top of this thread,
...I'm going to note down some of the odd things as they become apparent. All those of you with (relatively) modern lathes may consider yourselves blessed...
And that is all this is about. The odd quirky things I come across with this machine.
As for t'old meister wi't weskit an' flat cap, well, I reckon he would have swapped his bit of chalk for a decent set of calibrated dials given half a chance.
If I really want accuracy I do have a Denford Viceroy 280 Synchro with twelve speeds and more threading options that you could shake a stick at.
Keep taking the tablets.
Dave.
beeshed:
Nothing wrong with a 6tpi leadscrew. It's just less twiddly than 12tpi. 12 inches to the foot, so natural to use 12ths or sixths next. Problem is with those weirdos who want to use thous instead of 864ths or 1728ths.
hopefuldave:
Also in the 6tpi leadscrew's favour, there's the old machinist's tale that you shouldn't cut threads coarser than your leadscrew - although my QCGB goes down to 2 tpi with a 6 tpi leadscrew if I engage the back-gear...
As long as you make the threading dial a whole (preferably even) number of inches per turn, and graduate it at inches/halves/quarters of leadscrew travel you can use it to pick up imperial threads like any other, so a 24-tooth with 8 numbered marks and intermediate ticks lets you pick up pretty much anything you're likely to want to cut on it :)
Now to work out how I can cut a 3 inch-per-turn thread for a mod on the lathe!
Pete.:
--- Quote from: hopefuldave on June 16, 2015, 06:06:45 PM ---Now to work out how I can cut a 3 inch-per-turn thread for a mod on the lathe!
--- End quote ---
Add a 1:6 ratio into the 2tpi train and drive the leadscrew, not the spindle :)
hopefuldave:
I was thinking that, bicycle chain and sprockets would let me get the ratio! It's to cut a DIY ballscrew for an actuator, so I was thinking I'd put a router on the toolpost at the lead angle (45 degrees) and hit the screw-to-be with a carbide endmill...
Better not hijack the thread though ;)
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