About Laguna Revo 24/36

[iclark]

No one should need to worry about imbalance with a leg splay greater than the radius of the turning.  A bandsaw and low rotation should account for virtually all imbalance, though I have turned a couple-three pieces that were so different in radius and/or depth one side to another that I found it advantageous to lag on a few washers in the waste area to balance up the rotation.  You can also bore holes to remove weight from the heavy/longer end, if things are that messed up.

I would phrase that a bit differently.

Everyone should worry about imbalance.
Having a leg splay greater than the radius of the turning, roughing the blank to nominally round (whether by bandsaw or chainsaw), and low rotation speed all help to mitigate that concern.

One of our club demonstrators told a story on himself during a live-edge demo. He grabbed an interesting piece off of his firewood pile. He centered it up geometrically on the lathe, verified clearance, and turned on the lathe. Unfortunately, he had forgotten to turn the lathe speed down and the blank was extremely different in dryness from one side of the log to the other. The side that had been resting on the pile was very, very wet. He apparently happened to hit resonance and his PM3520 almost fell over on him before he could brace it and hit the off switch.

He told the story on himself to emphasize the importance of always starting the lathe at low speed (if it is variable speed) and to educate people that wood is not necessarily a homogeneous material and some portions of a blank can be very much denser than other parts.

[iclark]

iclark, DFJarvie, thank you - About your questions:
1) what sort of experience do you have using a wood lathe? --> My experience is low/average, just two years with a Rikon MIDI lathe, but what I like most is to turn bowl so this is why I'm looking for more capacity (currently the Rikon is 12" from spindle to bed).
2) when your arms are hanging straight down at your sides, how high are your elbows from the floor? --> About 46"/3.82 ft
3) why do you want the lathe spindle at neck-level? --> I don't. I think I made some mistake with my assessment and math (as Angus pointed out in his reply) and perhaps I should have verified this earlier, sorry. I'd like the spindle height to be at elbows level, so it looks like it is ok because my elbows are at 46" and the spindle is at 44.5", so pretty close. I think I may try to work on that lathe as it is, and then in case make some efforts to buy the riser kit, as DFJarvie suggested.

Thanks, I appreciate your feedback

Luca

You are welcome. Thank you for telling us more about yourself and your experience.

Looking at the specs, my Jet 1642 spindle height is 44-1/2" which is the same as the Laguna that you are looking at. I used to be 5'10" (still close to that on good days) and my Jet's spindle is a good height for me. I do tend to use an overhand grip on tools. If the lathe were higher, I suspect that I would more often use an underhand grip. For the shorter members of the family, I have some pallets that I top with 3/4" plywood.

If you only need a couple of inches and do not need mobility, then I would probably get a 2x10 or 2x12 and make a riser for each end with holes drilled for the foot pads.

FWIW, I had not looked at the Laguna 18-36 enough to realize how low its spindle is.

[robo hippy]

Mouse, I have turned on lathes with no cone (PM3520), minimal cone (Robust), and the Laguna, with a long cone. It cantilevers the piece you are turning farther away from the mount/base. This does make a big difference, exactly the same difference that turning a long hollow form does, which is why they use steady rests when turning longer forms. Experience is a great teacher... 

robo hippy

[MichaelMouse]

Mouse, I have turned on lathes with no cone (PM3520), minimal cone (Robust), and the Laguna, with a long cone. It cantilevers the piece you are turning farther away from the mount/base. This does make a big difference, exactly the same difference that turning a long hollow form does, which is why they use steady rests when turning longer forms. Experience is a great teacher... 

robo hippy

No cantilever when the bearings are located at the end of the "cone."

[MichaelMouse]

I'm guessing you read something different than my intent.  If you prepare your stock properly, spin it modestly and have a properly made stand, imbalance should not be any real danger. 

Assuming you stay out of the throw zone.

Betting even a lot of folks here don't take the simple step to reduce imbalance on the half log "standard bowl.



If you just make it circular, it is imbalanced.  By tilting and trimming you minimize differences in weight distribution.  Free hint for those with the standard 6" cut bandsaw - undercut with your chainsaw, leaving about 4.5" (to clear the guides) depth of wood, similar to the remaining vertical section on this small bowl, and you can easily make stuff 9-10" deep roughly circular. 

Consider the laws of physics, and you know that the largest diameter, when circular, is what is critical to balance.  Stuff near the center doesn't exert as much centrifugal force.

[robo hippy]

While bearing size and strength do play a role, so does the cantilever, which is a lever arm. The base mounting point is another lever point, and the farther away from that base the mounting of the piece to be turned is, the higher the additional vibrations will be. This is why spindle adapters add to vibration. This is why extended jaws add to vibration. Well, maybe they don't add to it, but it is much easier to get vibration the farther away from the base mount the piece that you are turning is. Not theory, experience, unless you have another explanation for it....

robo hippy

[Luca Fumagalli]

First of all, thank you everybody for the great feedback and discussions. I have a lot of material and inputs to work on and to think about.

I've edited my original post in order to fix my assessment error on lathe's height.

Thanks, Luca

[iclark]

If anyone mentioned it, I missed it.

Craft Supply gives really decent discounts on the demo machines that it takes to woodturning symposiums. You reserve one of the demo machines in advance and they load it into your vehicle at the end of the symposium. I got my PM3520B at the AAW symp in Tampa along with a used bed extension (traded in by someone trading up) and a new set of mobility wheels for a very good package deal. The hardest part was unloading it at the shop when I got back. The parking lot at the shop slopes more than I thought and it made it hard to slide the bed uphill to the back of the minivan to walk it onto my shop lift for assembly.

If you are considering going to KC next month, you might check with the different vendors to see what discounts they might give you for a demo lathe. For me, getting a lathe with ~20hr of professional run time had the advantage of having the vendor and pros debug the machine and find/fix flaws. I also did not have to pay for shipping.

On a different note, our local Woodcraft now offers free delivery of machine tools bought from them (within a reasonable driving distance). Your local store might be willing to do that as well or some of their employees might be willing to do it for a small fee.

[MichaelMouse]

While bearing size and strength do play a role, so does the cantilever, which is a lever arm. The base mounting point is another lever point, and the farther away from that base the mounting of the piece to be turned is, the higher the additional vibrations will be. This is why spindle adapters add to vibration. This is why extended jaws add to vibration. Well, maybe they don't add to it, but it is much easier to get vibration the farther away from the base mount the piece that you are turning is. Not theory, experience, unless you have another explanation for it....

robo hippy

So you have abandoned the mechanically silly assertion that the shape of the casting enclosing the spindle has an adverse effect?  Good, now take a look at the thread on weak links.