Looking into thread cutting and I think Steve Jordan has the right idea:
To that end I made a not-pretty-but-it-works spindle handle with an acetal collet to lock it in place by friction:
Re: JSR's workshop chronicles
Posted: Wed Dec 16, 2020 6:42 am
by mrfoo
Neat. Yeah, hand-cranking is the safest way to go, but it's properly slow. The next one is to thread away from the chuck, for normal threads that means mounting the tool upside down and running the spindle backwards.
The next one is to thread away from the chuck, for normal threads that means mounting the tool upside down and running the spindle backwards.
Good tip, hadn't thought of that! You can still crash into the tailstock but there's definitely more margin for error.
Re: JSR's workshop chronicles
Posted: Fri Dec 18, 2020 7:34 am
by mrfoo
Do you have a threading dial on your carriage? They save an awful lot of pissing about - without one, you need to stop the machine, reverse back to your starting position, feed in a bit, rerun your thread, lather rinse repeat until done, all without disengaging the carriage feed. This puts extra strain and wear on your half-nuts, and the leadscrew.
With a threading dial (for most thread pitches, at least), you can disengage the nuts, feed back manually without even stopping the lathe, wait for the relevant point on the dial to come round, and re-engage. It's approximately a trillion times faster and largely idiot proof, especially if combined with threading away from the headstock.
Making a finish pass away from the headstock when doing "normal" turning can help with surface finish issues as well, you're changing the way the headstock bearings are loaded up, which can help if your bearings are getting a bit tired (like mine, but I can't afford the 800€ to buy new ones) or just not terribly good from the factory (as can be the case with chinese lathes)
When turning away from the headstock, mind, it's a very good idea to have a center in place, as you're pulling the workpiece away from the chuck...
Do you have a threading dial on your carriage? They save an awful lot of pissing about - without one, you need to stop the machine, reverse back to your starting position, feed in a bit, rerun your thread, lather rinse repeat until done, all without disengaging the carriage feed. This puts extra strain and wear on your half-nuts, and the leadscrew.
With a threading dial (for most thread pitches, at least), you can disengage the nuts, feed back manually without even stopping the lathe, wait for the relevant point on the dial to come round, and re-engage. It's approximately a trillion times faster and largely idiot proof, especially if combined with threading away from the headstock.
I guess I do!
Re: JSR's workshop chronicles
Posted: Tue Dec 22, 2020 5:37 pm
by jackssmirkingrevenge
Actually gave it a go and pretty happy with the result.
Re: JSR's workshop chronicles
Posted: Wed Dec 23, 2020 2:43 am
by mrfoo
Yay! Nice results. Threading is hard to get right.
Is the threaded piece in the foreground 2 pieces stacked on one another, or is it camera distortion that makes it look - ummm - "bent"?
Meanwhile, and polluting your thread a bit (sorry) but it's a workshop thing, my surface plate is getting there. 2 corners are still a bit low, putting me at class 1* overall, but the central par (800x200) is at class 0*. I'm pretty happy with that, it's more than I need.
* For this size of plate, that means, compared to the theoretical best plane, the total deviation of highest and lowest points must be less than 11.2µ (4.4/10000") for class 1, and 5.6µ (2.2/10000") for class 0.
That was actually an amusing and informative watch, I can see why you thought my workshop was more organized... obviously you've just been at it longer
J'ai aussi apprécié le contraste avec le bloke anglais pottering about dans son atelier avec la radio francophone
Is the threaded piece in the foreground 2 pieces stacked on one another, or is it camera distortion that makes it look - ummm - "bent"?
It's one piece, the reflection makes it look weird.
Here's some more efforts in steel this time, I have to say that after being the bane of my machining existence for many years cutting threads is a real pleasure now!
That was actually an amusing and informative watch, I can see why you thought my workshop was more organized... obviously you've just been at it longer
J'ai aussi apprécié le contraste avec le bloke anglais pottering about dans son atelier avec la radio francophone
Is the threaded piece in the foreground 2 pieces stacked on one another, or is it camera distortion that makes it look - ummm - "bent"?
It's one piece, the reflection makes it look weird.
Here's some more efforts in steel this time, I have to say that after being the bane of my machining existence for many years cutting threads is a real pleasure now!
Beautiful machined parts, as we would say around here "the child's perfect dream" !!
I don't understand anything about machining but what I see is great. May this new year 2021 be very good for you, and for all the colleagues on this site. CONGRATULATIONS!!!
