Strange Vibrations...

[Luke Maddux]

I bought a new lathe yesterday. It's a Jet 1642EVS. The one with 2hp. I got a killer deal on it so, in light of the purchase, I've decided to take a break from furniture and get back to turning.

As one might expect, I was like a kid on Christmas morning rushing down the stairs, only I was rushing at it with a 12" Tiger Myrtle bowl blank that I had been saving for this very moment.

Roughed the blank on the bandsaw and then mounted it and roughed it to round at around 450rpm. I had hoped to rough at around 550, but was getting some vibration so I turned her down a bit. Roughed it and was having no problem at around 600, but at around 750, which is considered the upper end for safety on a blank this size, I'm still getting a bit of shake.

To clarify, I'm not talking about anything violent and the lathe is not moving or at risk of moving, but I just kind of expected that this would not be the case, as this lathe is pushing 500lbs. It's just a bit of wiggle that reduces my tool control to a slight degree.

Could I be looking at a foot that's not doing its share of the lifting? It doesn't have the feeling of uneven legs. There's no rocking, but that's not to say that the legs aren't flexing slightly under its weight so that it's not noticeable to me but there is a discrepancy in its weight distribution.

I feel pretty confident that the lathe is functioning as it should, so it's probably some sort of setup issue.

I should probably also mention that this piece of wood was kiln dried in Tasmania about 8 months ago and sent to me in QLD shortly thereafter. I kind of doubt it's a moisture distribution issue but I'm not ruling that out.

Any thoughts appreciated.

Cheers,
Luke

[Colin62]

I assume the lathe is rock steady with no blank? Have you got another blank you can try? It doesn't need to be rounded, you could mount it still square and get an idea of whether it's balanced or not.

[Luke Maddux]

Rock steady with nothing. Purrs like a kitten. Also had no problem "playing" with a 3" spindle right after setting it up.

[Paul39]

Luke,

Timber is not homogenous. Your blank may be denser & heavier on one side. As you hollow it sthe vibrations should go away. I would use the RPM that has the least vibration and keep cutting. As long as you have a firm grip with your chuck you should be OK.

I have a Hegner 175 with a square tube bed. New, this was an expensive lathe. With an out of balance blank the bed flexes and everything shakes like a dog pooping peach seeds. Slowest speed is 700 RPM. As I remove out of balance timber it calms down, and by finishing time everything is smooth.

[Tangoman]

Luke,The above answers suggest,IMHO, that there isn't a problem here,it's quite normal for timbers density to vary throughout a piece hence the vibes.I do suggest you bolt the lathe to the floor if you haven't done so already !Regards,Cam

[Luke Maddux]

Luke,The above answers suggest,IMHO, that there isn't a problem here,it's quite normal for timbers density to vary throughout a piece hence the vibes.I do suggest you bolt the lathe to the floor if you haven't done so already !Regards,Cam

Cheers Fellas. I honestly was kind of thinking the same thing. Paul, you're right, as it loses mass the vibrations are reduced.

Chances are I'm just not used to the ins and outs of turning pieces this size.

Still interested to to hear anyone else's idea.

Cheers,
Luke

[artful bodger]

Hi Luke
Is your lathe dynabolted firmly to the (hopefully concrete slab) floor?.

[RoyG]

I assume you've got the cast iron legs shown in the photo below. The lathe does work best if it's bolted down via the holes in the bottom of each leg. If the lathe is on a timber floor, and each leg is carrying it's fair share of the weight, you could be experiencing a bit of flex in the wooden floor. If you're on a concrete floor that is a bit uneven, you'll see some vibration. BUT, if you decide to bolt the lathe down, please shim under the legs to get all legs carrying their share of the load, before you bolt it down - otherwise you may twist the lathe bed by bolting it down to an uneven floor.

http://ecx.images-amazon.com/images/I/41Y12EV06AL.jpg


In lieu of bolting the lathe to the floor, if that's not practical in your workshop, you could try the old trick of adding a bit more (read "Lots more") mass to the lathe.

Try placing a strong plank lengthwise between the horizontal cross members that run across each leg about a 200mm off the floor. Bung a lot of heavy weight on the plank and see how you go with vibration reduction. A couple of bags of cement, a stack of old bricks, etc - anything heavy. If the extra mass works, then maybe make it permanent by building a box like enclosure that sits between those two cross members and is filled with sand.

Regards,

Roy