small lathe gears wobbling

[Robert1998]

Hello.

I have a warco wm 180 lathe. I have observe a little bit of wobbling in the upper gear, and sometimes ut has a litlle bit of touch with the pulley ot the left.



The screws and the nuts are tight. So, is it that normal?

Thank you

 

[brightspark]

fit a thin shim washer on the gear spindle to the left of it. probably just a bit of wear or like that from new .not a bad lathe but not the best of machining

 

[Brad93]

The bore has not been machined concentric to the outside diameter or the gear/pulley is too loose on the shaft, throwing it off.

 

[Agroshield]

The bore has not been machined concentric to the outside diameter or the gear/pulley is too loose on the shaft, throwing it off.

A non-concentric bore would lead to vertical movement of the gear, loosening and tightening the mesh. His arrows show a horizontal movement.

Looseness on the shaft, as you say, will have undesirable effects.

As it is a compound gear, it is possible that the keyed bush onto which the two gears fit is a little too long. That could allow left-right movement of the gears on the bush even though its securing nut is tight.

There is not really sufficient information in the original post to identify the problem. If we take his left-right arrows literally, he is only showing lateral movement. If the top can go left while the bottom goes right, there is rotational movement.

 

[Brad93]

A non-concentric bore would lead to vertical movement of the gear, loosening and tightening the mesh. His arrows show a horizontal movement.

Looseness on the shaft, as you say, will have undesirable effects.

As it is a compound gear, it is possible that the keyed bush onto which the two gears fit is a little too long. That could allow left-right movement of the gears on the bush even though its securing nut is tight.

There is not really sufficient information in the original post to identify the problem. If we take his left-right arrows literally, he is only showing lateral movement. If the top can go left while the bottom goes right, there is rotational movement.

I should have said bore not machines perpendicular to the gear then.

 

[roofman]

Its Chinese tolerances...Just don't look at it and the world will be fine again.

 

[not done it yet]

It may be quite normal for cheap chinese machinery. Often, fettling is necessary to get them running even reasonably.

Shims or washers required to control the end-float is hopefully all that is required. Possibly been lost when someone has changed around the gearing for different thread pitches, or the gear is wearing away…

 

[Kram]

I have the wm240 and it had the same issue. The concentricity is not great but its adequate, what you'd expect from a sintered gear, its not the problem.
The nut and washer combination is not a good way of securing the gears as if its in contact if will try to turn the nut, if it gets loose it will wobble, as I found out when the middle pair popped out.

Threading

60 degree tool will remove more material than needed, thread will be weaker, but I am using high tensile Im sure it will be fine, I was just very unsure about the numbers above! Thread depth I was expecting 2.34 on my diamter dials (1.17). I calculated 21.03mm for a one wire using .98mm drill...

www.mig-welding.co.uk

Solution is simple, Id already done it on the top gear, add a spring between the washer and nut to preload the gear.

 

[Robert1998]

Thanks for your answers.

Reading you an idea come to my mind. I have measured the screws that support the gears and one of them is slightly shorter than the other one, so I have interchanged the screws and now it seems to be fixed.

But in the other hand, and not related whith this, I realized that the tailstock is not totally centered with the spindle. if I put near the spindle, is 0,2 or 0,3 mm over the center and I think I can´t fix that. Are 0,2 mm somethin to worry about?

Thank you

 

[Agroshield]

... I realized that the tailstock is not totally centered with the spindle. if I put near the spindle, is 0,2 or 0,3 mm over the center...

You need to tell us in which plane it is over centre. It can be incorrect in two ways, up and down (high and low) or front and back (left and right). The solution to the two issues differs.

Before you fiddle with this problem, you also need to check it is parallel with the lathe axis and parallel with the bed - i.e. not twisted/rotated when looked at from above or from the side.

The tailstock has four degrees of freedom which affect its accuracy. You need to know its error relative to all four before you try to correct it.

 

[not done it yet]

As Agroshield. Does the tailstock centre height change as the tailstock is extended? You might find there is a ‘sweet point’ where they do align reasonably well.

Vertical misalignment, although not good, has little effect on turning parallel (compared to horizontal alignment). Ability to turn parallel is, after all, the usual requirement from a lathe.

 

[Robert1998]

Thanks for your answers.

My english isn´t very good. This picture explain it better



The tip is 0,2mm over the center of rotation and this desviation seems to be the same all along. I don´t really mind, but I don´t know if this is important

 

[Brad93]

Shorten that bar and turn a taper to a point on the end.

Then compare your tailstock.

 

[daedalusminos]

Turn a bar to exactly the same diameter as the tailstock 'quill', bring the tailstock up to the bar and measure offset using dial gauge.
Tailstock insert should be retracted and lock engaged.

 

[Robert1998]

EDITED: Ok, I have tried with the dead center and I think everithing is OK. Because everytime I extract and put again the dead center in the headstock spindle, the position change, so the problme must be smaall irregularities.

But there is no problem if the work is 0,1 or 0,2 mm out the center, right?

And thank you again for all your help, this forum is great

 

[MattF]

Put a dead centre in both the tailstock & the headstock spindle. Then see if there's any deviation between the points, when you bring them together.

 

[roofman]

EDITED: Ok, I have tried with the dead center and I think everithing is OK. Because everytime I extract and put again the dead center in the headstock spindle, the position change, so the problme must be smaall irregularities.

But there is no problem if the work is 0,1 or 0,2 mm out the center, right?

And thank you again for all your help, this forum is great

The problem will be a chuck problem holding the bar and given that it is a 3 jaw then to be honest what you have there in relation to center differences after moving is pretty good

 

[MattF]

EDITED: Ok, I have tried with the dead center and I think everithing is OK. Because everytime I extract and put again the dead center in the headstock spindle, the position change, so the problme must be smaall irregularities.

But there is no problem if the work is 0,1 or 0,2 mm out the center, right?

And thank you again for all your help, this forum is great

If position is changing on extraction & reinsertion, that suggests one of the centres is likely slightly imperfect. If it was the tailstock or headstock taper or alignment, it should be consistently off. Even that amount you have in those photo's isn't a problem as such, unless you're working to tight tolerances.

 

[Robert1998]

Ok ok thank you!