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Stability of lathe when off center turning

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Cadillac

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I have a 14x40 optimum lathe that came with a sheet metal type stand which has doors on each side for storing tools which I have loaded with chucks on headstock and tailstock end. Weight of machine is 1350 alone and with all the stuff I have in it it’s probably close to 1500. The lathe has six feet pads 4 on the headstock and two on the tailstock. Pads came with lathe it’s a 3/4/ threaded stud with a 2 1/2 diameter hard plastic/rubber pad. When I leveled the lathe I have the feet only as tall to level lathe they are at minimum height so lathe stand might be a 1” off ground. With any chuck on the lathe at 500-550 has a harmonic vibe to it anything lower or higher the lathe runs smooth as silk. I had a job to do awhile ago requiring a 4jaw so i mounted the one that came with the lathe and I forgot the job but the lathe was wobbling around to the point that I started looking into the chuck being garbage. It has voids in the back and I figured the casting was off so have had on the project list. I had put on my grinding wheel static balancer and was off alittle not a huge amount.
I just had a job that required between centers it was a shaft about 1/2 diameter 6 inches long. Left the three jaw on turned a center and threw on a drive dog. I turned the lathe on was at 600 rpms and man the lathe did not like it was wobbly. I slowed her down to like 350 and finished the job.
It made me really think about what’s going on with my setup. Drive dog was a homemade one just a touch larger and had a flat piece welded to it and bent driving off the chuck jaw. Can’t be more than acouple ounces off center. I’ve only ran acouple things offcenter on the lathe and nothing real heavy and I know my lathe just doesn’t like it. Ive thought about fastening the lathe to the floor but heard of some issues with a solid mount. Thought of making some holdown brackets and just securing the headstock pads and leave the tailstock move? Or just make up a new base section with some real plate and tool boxes that had some real weight to it. I’d have to adapt the foot brake, linkage and chip pan. Idk. I do feel like the base is alittle narrow for the height of the machine. The lathebed is centered on bases and the 3hp motor is arranged hanging off the back of the headstock. With the weight of the motor kind of cantilevered out there then spinning something off balance I think is starts the issues of wobble???
How’s your comparable lathe size react to offset weight spinning?
 

Cobra

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I had the same experience and from that point forward used a faceplate that I could balance.
 

savarin

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I also think those cabinet stands are a major problem. They are not particularly rigid. My 9x20 will also rock like mad with an unbalanced work piece and you can see the case flex.
Its enough to make me consider a much stronger base.
 

Mitch Alsup

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I also think those cabinet stands are a major problem. They are not particularly rigid. My 9x20 will also rock like mad with an unbalanced work piece and you can see the case flex.
Its enough to make me consider a much stronger base.
I have considered taking my cabinets and filling them with concrete, as I am not using them for storage.
 

benmychree

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Out of balance is the cause, the flimsy base just
I have considered taking my cabinets and filling them with concrete, as I am not using them for storage.
If you do, use a concrete that expands in setting, unlike the ordinary variety.
makes it worse
 

mmcmdl

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Even our larger lathes had to be counter balanced when doing off center projects , I could imagine smaller lathes wouldn't like that at all . Kinda like bar whip .
 

JimDawson

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I have a 13x40 on a sheet metal base, about the same weight as your machine, and I have not noticed much problem with wobbling. Maybe some additional bracing or maybe make sure all of your feet are loaded evenly.
 

Bob Korves

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Make sure all the screws and bolts are tight.
 

Cadillac

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I have a 13x40 on a sheet metal base, about the same weight as your machine, and I have not noticed much problem with wobbling. Maybe some additional bracing or maybe make sure all of your feet are loaded evenly.
What would be the best way to make sure the feet are loaded evenly? After my last wobble event I did pull the levels out. It was good in my book. Now the feet on the headstock I initially used the ones directly under the chuck. Then after all settled in I ran the outer ones down while watching a indicator off the floor and stopped once I saw the needle move. I didn't like so much because I was still able to spin the rubber pad so I adjusted till I couldn't spin the rubber pads. So I really don't know how much pressure is on each of them?
Ive really been kickin around the idea of making a hold down bracket that straddles the studs/nuts and bends to a 90 to the floor. Then drill a anchor in the floor and tighten the bracket down so the foot pad is sandwiched to the floor. Do that front and back. I do not want to anchor all six points for sake of drilling so many holes in the floor and how rigid it would be in case of floor movement and twisting of lathe bed. I can see where the big cast bases of the old iron really helped.
 

Bob Korves

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It is quite possible to have two diagonal pads carrying a heavy load on both ends, and the opposite diagonals carrying a lesser load on both ends. The lathe can be level with that situation, but not solidly supported. The 4 pads on the headstock and 2 on the tailstock can also cause issues. They should all require similar torque on the bolts, with the level showing constant readings along the ways at the same time.
 

Cadillac

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Make sure all the screws and bolts are tight.
If you mean the base there are no bolts except for the center connector piece. The cabinets are like 1/8" material bent and welded together. Tops feels like 1/4" and bottom is more like 3/8 material welded in the recesses of the cabinet for the feet not continuous bottom piece. The shelves are just some 18g maybe welded on the ends. Definitely as cheap as can be done.
 

Cadillac

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It is quite possible to have two diagonal pads carrying a heavy load on both ends, and the opposite diagonals carrying a lesser load on both ends. The lathe can be level with that situation, but not solidly supported. The 4 pads on the headstock and 2 on the tailstock can also cause issues. They should all require similar torque on the bolts, with the level showing constant readings along the ways at the same time.
I've thought that might be my situation but have not come up with a way to guarantee which ones are contacting evenly?
 

Bob Korves

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The wrench should feel like it is applying a similar torque on all the feet, Not the same torque, because the loads are different on each row from left to right and from front to back, but the diagonals should feel fairly equal to the opposite diagonal. Yes, the head stock end is heavier, and the motor is a heavy component, etc, so they will not all be equal. The cabinet also might we warped or not built to equal heights. Understand the various loads and get an idea of what to expect, then consider any discrepancies.
 

Superburban

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I have a set of lathe dogs, that the PO brazed some small nuts on each side of the bolt, Then ground some weight off, to balance them.

There is also other styles that could stay in balance easier.

LD01.jpg

LD03.jpg
 

Cobra

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I was not happy with the base on the Grizzly G750G. Not sheet metal but kind of narrow in my view.
I added to the bases to provide for a means to adjust the alignment of the bed.
The sheet metal between the bases was just a waste. Filled the space with drawers on significant slides to take weight.

290443

I used 4X4X1/4 angle with adjustable feet. The threaded rod (5/8-18), with a 60 degree cone, sits on a 3/8 thick washer with a centre hole that then sits on a hockey puck. Three per side.


290444

The angles were attached with 3/16 pop rivets to the cast iron of the bases. Bolts on each end. Note that the angles extend almost the same depth of the base to the rear. Resulted in a much more stable operation. Still means you have to balance things!

290445

The adjustment screws were then locked in place against Fine thread nuts that were welded to the angles.

290446

The adjustment screws mated to the heavy washer that sat on the hockey pucks.

290447

Made the adjustment of the bed alignment very easy. Used the two outboard screws and then just snugged up the centre screw.
 

savarin

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My flexi 9x20 has one bolt under the headstock and one bolt under the tailstock end of the bed.
It has to wobble
 

Tozguy

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With my 12x36 lathe on sheet metal cabinets, the cabinets were bolted tight to the lathe without shims. The objective was to use adjustable feet on the cabinets to get them all bearing evenly on the uneven cement floor. Each cabinet has four feet so tuning 8 feet to act together was the crux (like tuning the spokes on a bicycle).
A thin soft aluminum pad was cut for each foot to use as a resident feeler gauge between floor and feet. The aluminum pad is slightly larger than the foot. The soft aluminum gives good traction on the floor and foot. There is less 'flex' in aluminum than in rubber so I avoided rubber completely. From time to time I give the aluminum pads a tap with a small hammer to check for any change in tension on the foot.
When a lathe is not bolted to the floor or wall, it is seriously limited as to how much harmonic vibration it can take. When the lathe starts shaking from imbalance sometimes a change of speed is enough to calm things down. But there is really no substitute for using a counterweight system to get things somewhat in balance even if the lathe is bolted to a solid floor.

I do not want to anchor all six points for sake of drilling so many holes in the floor and how rigid it would be in case of floor movement and twisting of lathe bed.
What is the floor made of for you to expect movement?
 
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Cadillac

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I’m not worried of the floor moving. 10yr old garage I poured the foundation and 6” thick. I do worry about seasonal changes though. Between the lathe and the floor I’m sure they move a touch. I’m gonna look at the construction of the cabinet alittle closer to see if there worth strengthening or just make new ones.
 

Latinrascalrg1

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I have considered taking my cabinets and filling them with concrete, as I am not using them for storage.
Seems sorta permanent! Why not fill them with sand or maybe a combination of some cinder blocks filled in with sand so that you get to keep your cake and if you need to eat it too its not a problem returning back to stock. Just make sure the doors are locked closed so they dont get opened accidentally.
 

richl

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I did something along the lines of what cobra did to my 13x40 enco circa 2000 lathe. In my case I made a full 2x3 frame for the lathe to sit in. I also extended the outriggers at the ends about 4"-6". It gives the lathe more footprint to the base. I drilled and bolted down the lathe cabinet to the new base. It's definitely more stable. You need to be mindful of the outriggers though.

Ymmv
Rich
 
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