How not to lift a lathe !!!

Again, look at the picture! I'll help you a bit: Replace the hook with two rolls. Each roll for one sling. Each sling goes over one roll. Now look at one of the ends of the lathe. Imagine putting some force from the side to the headstock. What will happen? Right, it will flip over.*) Now forget about the rolls but be aware, that the slings of nowadays are Teflon-coated. Teflon? Right, that stuff with the low friction-coefficient. Here they are again, the "rolls"!

You claim that ropes/slings are solids is at least weird.

*) I was wrong saying that the C of G is lifted when the lathe starts to flip over. It is *lowered*. That's what physics call instable and riggers should call stupid.

Nick

Have a look at the Smart & Brown factory lifting a lathe.

Aside from Andrew Mawson's experience with ropey Colchester Student bearings (some would suggest they're all like that) I've yet to hear any definitive evidence. That's not say that I don't I respect the views of Martin P who says it's bad and equally Tom M who's less certain.

Charles

sling goes

nowadays are

friction-coefficient.

riggers should

My bearing problem may have no bearing () on the lifting issue and may have been caused by a tool jam or whatever, but I kept that race for a long time as a 'watchout reminder' !

AWEM

And do you notice the difference?

*Four* slings and not just two like on the picture I'm talking about.

Nick

Only 1 bid of 200 notes - reserve not met. Maybe the photos put the potential bidders off?

Regards, Tony

Without being qualified to enter this debate on machinery moving it's worth pointing out that the lathe in the photograph that I linked to is 2.9 tons. The one that Mark illustrated is 1.2 tons

Charles

Gentlemen,

I've said my bit and then stayed quiet to let you all have your says, as was pointed out in one of the other posts this like all other machines has its designated lifting points which have been designed by the manufacturer to alleviate any problems that could occur. Nobody has pointed out two things in my book which matter to me, regardless of the static load of bearings the sling is around a "hollow" shaft which has been designed to take axial and thrust loads not bending moments. The tail stock is made from a material which is very bad in tension and shear but excellent in compression, most tailstock wheels are cast also and the spindle is also not so big to carry any weight.

Uh! The load on that shaft is far more complex than you obviously can imagine. And most of that stuff on a lathe has been designed for stiffness and not for load. If you know what that means.

Nick

No need to emphasize on that! ;-)

Nick

A few thoughts then... What sort of moment do you think the cutting tool is imposing on the spindle, when the lathe is parting off then? Lathe spindles take both thrust and "radial" loads. A radial load as far as a lathe is concerned is a "bending" load, forcing the spindle away from the tool. A cutting force load can easily equate to the mass of the lathe.

One of the offshoots of modern lathes with hollow spindles and anti-friction bearings, is that the bearings utilised have, because to the necessary inner diameter, a far greater load capacity than is necessary for the job in hand, the limitations of such bearings are of speed.

With the lathe in question, having a spindle bore of 1-5/8" the spindle bearing will have an inner bore of at least 60mm. A roller bearing of that dimension will have a minimum static capacity of 15,000 lb+. The lathe has a weight of 1740 lb. If we take that spindle end strop has 3/4 of that due to the balance point being within a foot of the chuck face mount, that gives a figure of 1305 lbs. 1740/1305 = 11.49 or less than 9% of the static load of the bearing in question.

If you think the "hollow" spindle is going to bend when slung as close as this is to the bearing, you'd never jack another rear wheel drive vehicle from under the diff case.

The tailstock is taking a static load of 435 lb - 1740/4, if it had a cross-sectional area of only one inch, it has more, that is 435 lb in² Even the softest of cast irons has a tensile strength of 16,000 lb in²... That gives a safety factor of 36 : 1, whereas MH call for a worse case ratio of 20 : 1 with cast iron. Remember though that the cross-sectional area is even greater.

As for the tailstock wheel, I can't see that it has any bearing on the matter nor the tailstock spindle, as the strop is around the spindle housing, which on a Colchester, is spigoted into the tailstock housing with a spigot, the diameter of the tailstock quill.

Tom

All the slings I have dealt with were webbing with little or nothing in the way of coatings. I see tow straps that are covered in leather or vinyl, but they are not rated slings.

They behave like solid when loaded up with any weight. Between the tension hardening them up, and the increase in load increasing the friction, the slings won't go anywhere without a severe outside influence.

If you were silly enough to actually go push on the headstock hard enough to move it (very difficult) you would have a couple problems to deal with, not least of which would be a rigger trying to drive his foot up your arse for screwing with a slung load.

You may have not the faith in this method. I have seen it done often enough to accept that it works.

Enough already. I trust it and would use it. You can choose to do otherwise if that gives you comfort.

Cheers Trevor Jones

And a set of spreader bars! Cool Eh!

And a lathe that is bigger by a factor in size, too.

That they used one piece of gear by no means invalidates the use of simple slings, just shows that there is more than one way to get the job done.

Cheers Trevor Jones

Of the two ends of the machine, I would expect the headstock to be least like to suffer dammage.

As someone pointed out, the tailstock is a poorly built part to be used in the manner shown. Perhaps more than adequate, but not a good choice.

Cheers Trevor Jones

Axial, radial, torsional, dynamic, static. Whatever you want, superimposed any way.

Nick

What didn't you understand of the above, Trevor? All?

Tom

The relevant one to the case in hand being "radial", a point, emphasized, that seems to escaped your attention.

Tom

Sorry Tom,

Not a comment on your math or your physics. Just a comment on the thread in general.

No need to get testy. :-)

FWIW iwould estimate that there was better strength in the tailstock spindle than the iron. The load on the iron, if it was applied as per the pictures is not, IIRC in tension, but a bending load, which CI kinda sucks for. (Hows that for technical?)

I have seen a few broken iron castings that were supposed to be strong enough. But they weren't.

Six (or sixteen or sixty) feet up in the air is a bad way to check for casting flaws, IMO.

Cheers Trevor Jones

Whatever, Trevor.