Balancing

dave enrico

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im fairly new at machining after 40 year lay off,can anyone tell me if theres an attachment for balancing rotating parts on the lathe, thanks dave
 
I'm not aware of anything available for a lathe. I would say is would be almost impossible to do any balancing in a lathe because you have to take into account the balance of the the rotating parts in the lathe also.

For a static balance you can use parallel knife edges and just set the part on those and it will rotate to the heavy side down. This works pretty well for some things.

If you have only one part to do, I think I remember a motor rewind shop in the Ontario industrial area, or maybe Pomona, it's been a few years, but many have balancing equipment. Also many automotive machine shops have balancing equipment.

If you are doing a lot of parts, then searching Craigslist for a used Stewart-Warner balancer would be the way I would go. I see them come up for sale occasionally.
 
You should be able to static balance on the lathe by putting the part between two centers. If you don't have a center drill on the end of the shaft, a tight slip fit cap with a center drilled end could be turned to permit using the centers. For maximum sensitivity, use only enough force to secure the part between the centers and add a drop of light machine oil to each.
 
If you are talking about offsetting the off balance condition caused by parts that are not symmetrical or are mounted off center, so that your lathe is not jumping up and down, yes, that can be done. It is easiest to do if the work is mounted to a face plate, because there are slots for mounting counterweights. You can test the balance by taking the lathe out of gear so the spindle turns freely. The heavy side will of course be pointing down and the counterweight needs to be mounted at the top. When the spindle does not turn by itself when you let go of it, regardless of clock position, you are probably close enough. Test the results at low RPM, gradually increasing the speed. With standard chucks, it is tough to mount a counterbalance. Sometimes a balancing feature can be added to the part, either bolted on or sacrificial after completing the turning.

WARNING: Be careful, and try not to lash up something stupid. A lot of centrifugal force is created by spinning stuff, and you REALLY do not want anything flying off.

I am not aware of any commercial attachment for easily achieving a balanced condition. There are an infinite number of possible things that might be mounted to the lathe, and no attachment would work for all of them. You will need to be creative...
 
thanks for the imput, remember years back and old machinist would mark the part on top the spin it the heavy side would always come up and he would drill if necessary on the heavy side ,after numerous times it would stop at a different location each time and he new he was close,that was when i was taking my apprenticeship in 1969 have only been in a machine shop (a real machine shop) once since then,my how things have changed no more manual machines i didnt even see a sunnen hone in the shop, no manual mill no manual lathe a whole different world now it seems like theres a program that does the work for you how 45 year abscent changes things, dave
 
Your experience as an apprentice would get things kind of close, sort of. I guess it depends on the acceptable out of balance condition.
 
Sounds like a viable project and one for thought. Dynamic balancing is more involved than meets the eye, but I don't see why an attachment couldn't be built. It wouldn't be simple, but probably feasible.
Static balancing is sometimes close enough, depending on application, but dynamic balancing is vastly superior.
 
well tony think about it and well see if its doable id help but im 1 step above an idiot in todays machining, if i live to be a hundred ill never be the machinist you guys are,i get on this website daily 1 because everyone is friendly even to my stupid questions, 2 because i learn alot from reading questions and answers,when i was an apprentice id ask so many questions the journeymen would get irritated,id come home at night and my dad would tell me keep asking and doing thats how we learn, dave
 
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