Lathe mass?

[Scott Brandstetter]

Was poking around on the internet and looking at lathes and took a look at Nova 2024. All of a sudden this thread came to mind and I was surprised to see that the assembled weight of this large lathe is only 350#. I know this is a popular lathe but really got me thinking how a lathe of this size could be so light.

[daryl moses]

Was poking around on the internet and looking at lathes and took a look at Nova 2024. All of a sudden this thread came to mind and I was surprised to see that the assembled weight of this large lathe is only 350#. I know this is a popular lathe but really got me thinking how a lathe of this size could be so light.

For one reason it is only 24" between centers.

[David C. Roseman]

I guess I must be missing something in this thread when John and others speak of adding weight "high on the lathe." Sure, higher on the lathe raises the lathe's center of mass. But I'm not sure what that means in the context of several of the Asian-built models mentioned. The cast iron leg design on the Jet, Grizzly, Laguna, PM and others makes it easy to add lots of weight low on the lathe, actually lowering the center of mass considerably. Here's a pic of my Grizzly G0733, with a ballast box made from the lathe's packing crate. I was able to get 450 lbs of masonry sand in the box, no problem, in nine 50 lb plastic-sealed bags. Don't know what the net weight of the lathe alone is, but shipping weight is listed as 547 lbs, and I don't recall the pallet and shipping hardware being more than 100 lbs, if that. So I figure my lathe as ballasted is around 900 lbs. FWIW.

[Cary Falk]

Don't know what the net weight of the lathe alone is, but shipping weight is listed as 547 lbs, and I don't recall the pallet and shipping hardware being more than 100 lbs, if that.

I have issue with the stated weights of the Grizzly lathes. G0733 - net 419lbs, shipped 550lbs; G0766 - net496, 662lbs shipped; PM3520 net 630lbs, shipped 682 lbs. I have many Grizzly tools and none of them came in a 166lb box. 50lbs at best which is what PM is quoting. My ex Jet 1642 had maybe 50lbs of plywood and pallet. I think I will weight the parts of the G0766 when it arrives and report back for the record because I have nothing better to do. Where did you get the bed attachment on the right side of the lathe that the rool rest is sitting on? I didn't think Grizzly offered one.

[John Keeton]

I guess I must be missing something in this thread when John and others speak of adding weight "high on the lathe." Sure, higher on the lathe raises the lathe's center of mass. But I'm not sure what that means in the context of several of the Asian-built models mentioned.

It means one has to add even more ballast to offset the added weight higher on the lathe. I also have considerable ballast on my Jet 1642-2, similar to what you have done.

[Roger Chandler]

Where did you get the bed attachment on the right side of the lathe that the rool rest is sitting on? I didn't think Grizzly offered one.

Cary, there were several vendors around the world that carried their own model of the same 18/47 lathe......David's bed extension likely came from Busy Bee (CT128 lathe) in Canada or perhaps it was Laguna.

[Thom Sturgill]

An adult on a bicycle has a center of mass somewhere near the level of the seat. An adult on a motorcycle has the center of mass somewhere near the level of the wheel hubs. Anyone who has ever ridden both will tell you that a motorcycle is more stable than a bicycle. I think the same logic and physics apply to the lathe, while this idea of putting weight above the lathe seems to be trying to create the effect used by wire walkers.

Having worked many years in power plant construction, I know that there any stationary machine had its legs bolted down on grouted pads after levelling.

[David Delo]

Having worked many years in power plant construction, I know that there any stationary machine had its legs bolted down on grouted pads after levelling.

Had a customer once in MI whose shop burned down destroying his CNC machine. Insurance company gave him a large lump sum of money to replace it only because it was bolted to the floor. If it hadn't been bolted to the floor, he would not have been covered insurance wise because that piece of equipment wouldn't have been considered "a part" of his shop. The insurance company sent their claims guy in there specifically to see if the machine had been bolted down. Not sure if insurance reasons might be why you see equipment bolted down in commercial & industrial setting or not.

[David C. Roseman]

Had a customer once in MI whose shop burned down destroying his CNC machine. Insurance company gave him a large lump sum of money to replace it only because it was bolted to the floor. If it hadn't been bolted to the floor, he would not have been covered insurance wise because that piece of equipment wouldn't have been considered "a part" of his shop. The insurance company sent their claims guy in there specifically to see if the machine had been bolted down. Not sure if insurance reasons might be why you see equipment bolted down in commercial & industrial setting or not.

Thom and David, interesting point. I suspect that is indeed the case in many commercial settings. The way a policy is written may require equipment to be "permanently installed" in order to be covered as part of the premises, as distinguished from being scheduled separately. Bolting a machine to the floor may be enough to make it a fixture in many jurisdictions, hence permanently installed. An identical machine sitting next to it that is not bolted down may be a dead loss. Good reason to read the policy carefully before the fire, hurricane or roof collapse from snow load.

[David C. Roseman]

[snip] Where did you get the bed attachment on the right side of the lathe that the rool rest is sitting on? I didn't think Grizzly offered one.

Cary, Roger is correct. Mine came from Busy Bee, and is for the Craftex CX802 18 x 47 lathe. Bolts right up to the G0733. Here's the link: http://www.busybeetools.com/products...for-cx802.html Price is stated in Can$, BTW. I think I paid around US$100 two years ago, including shipping, so either it's on sale now or the price difference is due to the tool rest not being included. Can't recall if mine came with a tool rest. The banjo height extender is bored to 25 mm, so the OEM Grizzly tool rest fits, in any event. My extension came painted green, but Grizzly had sent me a small bottle of touch-up paint for the G0733, so I just painted it to match.

OP, apologies for the thread hijack!

[Thom Sturgill]

I had not thought about the insurance angle, you may well be correct. I know the only reason we had a safety engineer was because we got enough reduction in insurance to pay his wages plus some. I've often thought that if I sold insurance to woodworkers, I would probably want to raise insurance rates for customers with non-flesh sensing table saws by enough that they would upgrade for the savings, and things like lathe safety cages would have to be installed if I visited. A lot of safety 'regulations' are really insurance related not government and not based on real engineering either.

But this is drifting way off topic.

[Olaf Vogel]

We are talking about stability and IMO there are two separate issues:

1 - Stability - the lathe falling over is clearly not desirable. Design considerations like: a wide stance for the legs, lower centre of gravity, more weight, are all good measures. After purchase customization or install things like: mechanically fastening it down, adding more weight will all help.

There’s many good, easy solutions for this as mentioned above

2 - Resistance to vibration, caused by unbalanced blanks is much more complex.

The motorcycles vs bicycles is not a fair comparison (this is a bit off topic, but give me a chance)

The "stability" of a two wheeled vehicle (bike) is generated by the gyroscopic effect (rational inertia) of he spinning wheels. The wheels on a motorcycle are much heavier and spin much faster than those of a bicycle. Hence a motorcycle could have more "stability".

In fact it could have so much that you would not be able to wrench the bars off a straight line. Both are designed with a angle on the headstock, known as rake, and an offset on that angle, known as trail. Manufacturers spend huge efforts tweeting both to get a blend of straight line stability vs agility, the ability to turn the thing. http://www.motorcyclejazz.com/motorc...heel_stability

A Harley will go straight down a road because it has tons of rake and trail, less because of the high weight, but won't turn that well.
A Ducatti, will have much less rake and trail, hence will turn better,but have less straight line stability. The physics of steering can get really complicated.

So it does;t have much to do with the center of gravity….nor relate to lathes. So what does?
Neither motorcycles or bicycles go in a perfectly straight line. They oscillate left and right around the center line.

Similar to lathes,with an unbalanced blank loaded. They oscillate, left/right/up/down around the spindle.

Assume, that only the front legs are bolted down, so you know have a pivot point: the legs.
(Silly and we’ll never do it, but it simplifies the motion and explanation.)

Now spin up an unbalanced blank; lathe will rock back and forth, pivoting on the front legs, at a certain frequency, with a certain amplitude. The beat up General at the local high school did that beautifully. Narrow stance, lousy bolting made it worse.

So how to minimize that vibration?

Here’s an example:
Take a soup can, hold it close to your chest and shake it up and down by 3 inches, 3 times a second. Easy
Hold it at arms length and try to shake it at the same frequency and amplitude. Very Hard.

So to dampen vibration we want the mass as far away from the pivot point as possible.
In lathe, you want it as high as possible (spindle height or higher)

So what about adding more mass? That always helps right.

Replace that soup can with a 20 lbs weight, shake to close to you body. Much harder than before to hit the same frequency.
Hold it at arms length and repeat. Likely impossible to shake at the same frequency and amplitude.

So more mass, farther from the pivot point (the floor) is even better.
Assume you could rigidly bolt the mass to the top of the headstock, this will provide even better vibrational resistance.
In my case the headstock assembly is about 1000#, all rigidly bolted together.

That's serious vibration damping.

__________________________________________________ ___________________
OK but we’d never set up a lathe with only the front legs bolted down. Normally we would:

Not bolt it down at all. The weight of the lathe will resist vertical vibration.
But if there’s little mass at the top, there not much resistance to vibration front to back. This would severely limit the size/weight of working with raw blanks.

Or: securely bolt all four feet down. Now you are trusting the lathe to provide mechanical stiffness and strength. The headstock bolts to the bed, likely very strong. The bed bolted to the legs, likely very strong. Triangulated legs, likely very good. So all that vibration is being rigidly transmitted to the feet, not always that strong and could break.

The bolts and anchors holding everything to the floor - not that good. That vibration over a long time can works a lot of things loose, included lag shields in concrete. In my case, I don’t trust them, and just poured more concrete to ensure nothing moves.

Overall, it depends on the problem you are solving.
(can you tell I was a physics geek?)

Olaf

[carl mesaros]

Carl........the Laguna line used to be the same as the Grizzly.......at least in the 18/47 lathe. My [well it has been sold now, but] Grizzly G0698 has a D/C brushless motor [2 hp] and it has been going strong for over 5 years with pretty steady usage. I did some research on D/C brushless motors, and they are smaller than A/.C and are generally more efficient than a carbon brush motor on most A/C for the same hp rating. They can be used with a controller inside the motor to read torque requirements so they are suited to applications where low rpm and high torque are required, such as wood turning. They also run much cooler than a brushed motor.

I would think you would be in good shape with the Revo 2436. There is a NZ turner who has gotten one [basically same lathe with another label on it] and he speaks highly of it over on WOW........don't remember his name off the top of my head. The Revo 2436 has a place to connect an outboard attachment at 90 degrees to the ways, if I recall, so you might like that feature as well.

Do a google search for brushless D/C motors and read up on them........they are used in lots of industrial settings where reliability is required, so if you educate yourself, you might alleviate your concerns.

Well I did it. Last Friday I drove to Columbus and picked up a new Laguna 2436 lathe. I took advantage of Woodwerks Laguna 10% off sale and by purchasing the 20" bed extension they gave me the 12" swing-away.
I will submit a full review once I have it set up and the shop re-organized.
I will say it was packaged very well. Thanks to my neighbor and his tractor, end loader,and Gator we got it unloaded and the legs mounted. What a job!

[Roger Chandler]

Well I did it. Last Friday I drove to Columbus and picked up a new Laguna 2436 lathe. I took advantage of Woodwerks Laguna 10% off sale and by purchasing the 20" bed extension they gave me the 12" swing-away.
I will submit a full review once I have it set up and the shop re-organized.
I will say it was packaged very well. Thanks to my neighbor and his tractor, end loader,and Gator we got it unloaded and the legs mounted. What a job!

Congrats Carl on the Revo 2436..........looking forward to hearing about your impressions and experiences on the first couple of projects!