Noisy Lathe

[compact8]

I have an Emco Compact 8 lathe which is belt driven and therefore supposed to be quiet but in reality it is far from being true. At 500 RPM, the noise level is acceptable but the noise will increase very substantially to it's peak at 850 RPM and then subsides a bit at 1700 RPM. When the noise is at it’s peak, I can see the spring for maintaining tension in the belt vibrating along it’s axis. I therefore suspect that the spring is resonating when the machine is running at 850 RPM , may I know if there are anything that can be done to reduce the noise ? E.g. Can I attach some weight to the spring to change it’s resonating frequency ? may be put the spring in a tightly fit tube and coat the spring with spring tar ? Here are the videos of the driving pulley system running at different RPM :

500 RPM :

850 RPM, you can see that the spring is vibrating :

1700 RPM, the noise level is lower but my camera failed to capture the difference very well :

 

[chevydyl]

Stupid double post.

 

[chevydyl]

Did it start making noise all the sudden or has it sounded like that since you got it, it sounds to me like it's just the gears, and that's very quiet compared to my atlas lathe when the gear box is engaged, try putting a new belt on, and if you can adjust the mesh of the gears. When I adjust mine I roll a piece of printer paper between the teeth and then lock em down.

 

[francist]

Compact -- what about a little pillow of soft foam stuck to the inside of your gear cover? Carefully placed and not too big, but just enough to provide a gentle push to the side of the spring when the cover is closed? It's kinda hard to visualize the actual clearances from the photos, but if there's enough safety room so there's no risk of catching on any of the gears it might be a quick and dirty to see if the noise goes away.

-frank

 

[chips&more]

Your best bet is to find the problem and not band-aid the fix. What I mean is, do not put foam, change the spring tension or whatever, but find the problem. And it sounds like a balance problem somewhere. Take off the motors belt. Run the motor alone and see what happens. Continue adding more to the drive train, testing as you go. Maybe search the net, could be a common problem with the lathe and is documented…Good Luck, Dave.

 

[compact8]

Thanks for all the replies.

The machine has been making such noise since the day I got it. I brought it brand new many years ago. I think finding the source of the problem is a good suggestion so I took away all the belts and let the motor runs alone. Quite to my surprise, it is still noisy. I can’t understand it because it looks like an ordinary brushless motor which is supposed to be very quiet. I don’t believe the rotor is off balance because as soon as I switch off the motor, the noise stops immediately although the rotor still runs for a brief moment at the same speed before slowing down gradually. This is. Here is the video :

you can hear the sound of the switch being operated.

I have got the mini mill head that came with the lathe . That mill head is driven by a smaller motor which seems to be of the same kind and it is very very quiet.

So there is something wrong with the motor ? I tried to take it apart by removing the four bolts holding the front and back cover. The bolt has got a very strange head which I have never seen before :

I managed to remove only one bolt with a pair of plier. Is there some special driver for this kind of screw ? Is it worthwhile to make one by myself so that I can continue with the investigation ?

 

[kd4gij]

What is the spec's on the motor? Sounds like a cheap inport. Is the motor ac or dc?
As for the bolt I would say a cresent wrench.

 

[compact8]

OK, I just made a simple tool to remove the bolts with weird heads. Turns out to be just a piece of cake.



As expected the motor is just a simple AC squirrel cage motor which are supposed to be very quiet :









Visual examination shows nothing wrong. I really don’t understand how the noise is generated.

 

[John Hasler]

Loose lamination (or other part in the magnetic circuit) in the stator? Would make sort of a buzzing or growling noise which would stop instantly when you turned off power. Sound isn't working on my computer right now so I can't listen to it.

 

[chevydyl]

it definitely sounds like its in the circuit/windings