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Oscillation/Vibration in lathe

@calgaryguy - do everything that @RobinHood has suggested.

As the last step, take him up on his offer. But my wise old advice is to make sure you have religiously done as he suggests first. You can bet when he comes he will do them over. You want your vibration fixed but you don't want that "RobinHood Look" as he draws his bow either. ;)

It's an ideal outcome for you. Some great advice and an old guy as per my earlier advice.

Susquatch said:
Best indicator for stuff that shakes is an old guy who grew up around machines like that.
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If it doesn't get handled, then I would say you are gunna have to learn to live with it.

If he bites on your tailstock, we all want a picture......
 
Try remounting your pulleys, that can be a little out, same with some of your shafts. Remounting can negate the effect or make it worse, but at least you know where it is.

The second suggestion is change you belts, if the have a touch of variation in them well the faster they travel the more you notice the vibration induced.
 
Degen said:
Try remounting your pulleys, that can be a little out, same with some of your shafts. Remounting can negate the effect or make it worse, but at least you know where it is.

The second suggestion is change you belts, if the have a touch of variation in them well the faster they travel the more you notice the vibration induced.
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I'm using a 'link belt'. I had a brand new V belt on it before and the link belt, while a tad noisier, is smoother.
 
My answers to Robinhood's questions/suggestions inline below

Disconnect the belt. Run the motor with the drive pulley installed.
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Much less oscillation in this config. I'd call it negligible.

Connect the belt. Leave the lathe in neutral and feed disconnected. Run the motor. Repeat for all pulley combos.
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Oscillation is present in this config as previous reported/video'd. This tells me if its in the headstock its isolated to the input shaft.

Run the lathe in all spindle speeds (feed disconnected), no chuck installed.
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Havent done this one yet

Run lathe in all speeds with feed connected (run in all spindle speeds and all feed speeds).
Repeat for reverse feed.
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I have done this with and without the 3J installed. Same oscillation as previously reported/recorded - most noticable at the 900 RPM belt speed.

Run the lathe in all speeds (feed disconnected) with 3J and then 4J.
Run lathe with 3J and 4J and feed connected (both forward and reverse) in all spindle speeds and all feed speeds.
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I havent done this yet.

I really suspect the headstock 4 step pulley. Visually there seems to be no runout in it, but these kind of cast aluminum pulleys have given me vibration/harmonic issues in the past.

*If* I do narrow it down to the headstock 4 step pulley, what can I do about it? Can new pullies be sourced? Can I have this one balanced? And I'm back to asking 'does it really matter' on a lathe of this size?



I would make a spread sheet or a table. This is going to take a while.

You should be able to find which combo causes the issue.

If you need help, let me know and I can come over at a mutually convenient time.
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Thanks so much Mr R. I sincerely appreciate the offer.
 
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There have been some posts where people inherited an out of balance backplate adapter for their chuck or the chuck itself. The cavity pattern was not cast properly so has a counterweight effect. But I think it was described as mild at low rpm & really bad at increased rpm, which makes sense. Reading between the lines of your latest investigations, sounds like you've ruled that out.
 
Any time Chris.

Just thought of something now that you suspect the pulley on the input shaft: how about taking it off and mounting it on the motor directly. Run the motor. If the vibration is present, it is definitely the pulley. If there is no vibration, then it is the input shaft itself. Could be a bad bearing (or both of them) on that shaft. My 9” Utilathe had bad input shaft bearings. The new owner replaced them first thing and reported noise/vibes went away.

One could try and balance the pulley. Or find a replacement/make one. A shop made one should be more balanced from the get go compared to a cast one.

I would try and reduce the vibes as much as possible. The lathe will be much more pleasant to run after.
 
calgaryguy said:
Oscillation is present without chuck mounted. Thanks for the link tho!
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I thought that but didn't want to reply on your behalf cuz I wasn't positive.

I sorta like @Degen s suggestion to use an app, but couldn't find anything on Android that would do Fourier analysis to my satisfaction. Basically, you need something that does more than just comfirm that it's shaking. You need to know the component frequencies and their amplitudes to be able to use the info effectively. If you can find one with good ratings that is in your budget, it might be WAY better than biting down on the tailstock. Prolly not as effective as an old guy like @RobinHood though.
 
Susquatch said:
I thought that but didn't want to reply on your behalf cuz I wasn't positive.

I sorta like @Degen s suggestion to use an app, but couldn't find anything on Android that would do Fourier analysis to my satisfaction. Basically, you need something that does more than just comfirm that it's shaking. You need to know the component frequencies and their amplitudes to be able to use the info effectively. If you can find one with good ratings that is in your budget, it might be WAY better than biting down on the tailstock. Prolly not as effective as an old guy like @RobinHood though.
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Some of the apps have 2 or 3 axis vibration sensors output (using the phones internals). Lay your phone on the lathe and it tells you which axis is the worst. Even if you rotate slowly by hand you can determine the source.

There is a video on YouTube of a guy setting up a machine eliminating the vibrations with this type of application (about 3-4 years ago).
 
Degen said:
Some of the apps have 2 or 3 axis vibration sensors output (using the phones internals). Lay your phone on the lathe and it tells you which axis is the worst. Even if you rotate slowly by hand you can determine the source.

There is a video on YouTube of a guy setting up a machine eliminating the vibrations with this type of application (about 3-4 years ago).
Click to expand...

Degen has a very good point @calgaryguy. I was thinking more in terms of the frequency components, but directional components might be even more useful and there are lots of that kind of app out there.
 
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