Would You Do This ??

[JoeLee]

I sure wouldn't. At the speed that lathe is turning and that round is loose in the chuck, that's an accident waiting to happen. https://youtu.be/gay7fEwSV0o

I could use a dial, turn the spindle by hand and tap the part into running true in about the same time or maybe less with out the worry of having an accident.

JL.................

[paul463]

I do it all the time. You have to know the difference between snug enough and loose.

[The Metal Butcher]

I do it all the time. Typically a bit slower. I've had parts pop out maybe a few times with this method but it's never been a big deal.

[10KPete]

It is amazing how tight the chuck can be and still easily move the part. I use the technique a lot!

[BCRider]

Video can play tricks with what the speed looks like. It might only be around 450 to 600. And that's not all THAT high.

I've used the same trick on parts that are roughly that size at 450 and it's not scary.

[JoeLee]

OK, well it scares me as I've seen parts come flying out of chucks at a couple shops I've worked in over the years.

JL.............

[Paul Alciatore]

I would think that there is a significant difference between a part being thrown by the rather strong forces of cutting and having it come out of the chuck while applying almost zero force to it just to true it.

That bearing does not really dig into the part so if it comes out of the chuck, it may be spinning, but there will not be an off-center pivot, like the tip of the tool, to translate that rotation into a linear motion. So the rotational momentum will remain as just that. It will continue to rotate as it falls into the chip tray. It may hit the ways or something else, but that will be a frictional contact so the translation into linear momentum will be quite inefficient.

On the other hand, if the forces of cutting pull a part from the chuck it will not only continue to rotate, but the tool tip, which is probably at or near the OD, acting as such an off center pivot point. That would quickly convert the rotational momentum into a linear one. And the part would be flung across the room at a high speed.

OK, well it scares me as I've seen parts come flying out of chucks at a couple shops I've worked in over the years.

JL.............

[J Tiers]

Hmmmmm.... The parts I have had come out of a chuck, even when cutting on them, just pretty much fell out and did not go flying. No more than the chuck that unscrewed went flying.

It's different with CNCs that often run high rpms, apparently. But those seem to be larger parts, the size that can shatter the window in the cover and knock people down as they fly.

[brian Rupnow]

I do it all the time to get my stock running true. It's never been a problem.---Brian

[Mcgyver]

Another frequent flyer. Like anything, the application of some common sense goes a long toward body parts remaining attached. The part is not really loose in the chuck, just not fully tightened, you should have a reasonable amount held in the chuck compared to how much you're are trying to move it, the speed is reasonable (can be deceptive judging speed in a video) and you start with it pretty straight to begin with so its a bit of gentle nudging not major surgery.

Slightly seemingly more scarier, but still (imo) safely doable, You can do the same to align things with the lathe's axis. Say a larger piece you want to nudge into alignment to centre drill the end for example. That ball bearing tool deserves a permanent spot in a tool holder

Give it a try at a slow speed with minor nudging and I bet you'll quickly get comfortable with it

[Doozer]

You should be afraid.
Don't do it.
Leave it to me to do it
and I will get the job.
And you go hungry.

I have a reputation for being able
to do the things no one else can.
And I get paid handsomely for it.

-D

[A.K. Boomer]

OK, well it scares me as I've seen parts come flying out of chucks at a couple shops I've worked in over the years.

JL.............

Im with you and in fact think it's a stupid demonstration for people who don't know how to machine lol for one if the face of the part doing the "truing" was that true then why didn't the idiot just toss that side into the chuck first and bottom it and then save a bunch of time with also ZERO risk...

honorable mention number two is the fact that the jaws were starting off grabbing a "cocked piece" which means they can only LOOSEN when the piece then gets centered,,, yeah sorry that's not good...

To each his own though - im not a machinist - Im just really good at observing things and coming up with great bombproof common sense reply's....

[old mart]

I have not seen that method used, but as long as care is taken, it should not be dangerous. The workpiece has to have a gap in front of the back of the jaws to be movable, and I would simply seat it right back in the first place. Trouble is that some people copy things like this without thinking about it much first, they are the ones who have the accidents.

[Noitoen]

I think that the part was deliberately chucked with as much wobble as possible for the video. Normally it should be "almost aligned" and the bearing does the final job. Don't see any harm in the method.

[Rich Carlstedt]

Why use that method for squaring parts --especially if it makes you nervous ?
Here are two ways that are faster and get the same results. And do not require a spinning chuck

First I have a Morse taper that fits in the tailstock and has a flat plate 90 degrees to spindle C/L
Place stock in chuck, slide tailstock up to stock --press stock against tail stock plate and clamp- done !
Or
Run Aloris Tool Post up against the face of the chuck to allign it and clamp the post to match chuck face - Like you do before parting
now mount work and use the tool post for setting- done !

Rich