Balancing a Lathe Faceplate

[HasBean]

Now this is embarrasing as I should know how to do this, but I don't .
Have to mount a casting on the lathe & I reckon the faceplate is the only way, having chucks has made me lazy & turning between centres & faceplate work are a long & distant memory. In fact I've never used a faceplate
Centring the casting & clamping for boring isn't a problem but as there is no way to 'spin' the faceplate to get an idea of how to balance it. Will adding some weight of somesort where I think it should go and running the spindle at a low speed suffice?
Also it's cast iron & I usually use sintered carbide tooling for that to get 'under the skin' initially but at a higher cutting speed as it's carbide tooling, but being unbalanced etc etc....
Any ideas peeps?:

Paul

 

[piman]

Hello Paul,

not something I have had to do, but I would say that you need to do it by trial and error. Judge how much off centre weight there is and bolt some counter weights to the best guess you have. Take the lathe out of gear and spin by hand a couple of times, if it stops with the casting down you need to add more weight. keep adjusting until it stops randomly. Try a run at slow speed first to see how it runs. As I say, trial and error?

Alec

 

[Richm]

Exactly as said above

 

[penfold]

As above plus running at the lowest speed commensurate with a satisfactory finish; at least that's what the book tells me.

 

[HasBean]

Thanks guys,
Even if I disconnect the belts and gearbox/changewheels etc the spindle doesn't spin freely so I've bolted some tee nuts and a small angleplate to hopefully counteract things.
It's a Myford Super 7 so in backgear I can get some quite low speeds if needs be.
I have some books at home that mention that chucks were a luxury and centre/faceplate work was always the way to go.
Must say that it can only be beneficial to learn how to use the faceplate etc.... we will see....

 

[wyn]

Maybe you could fix the work to the faceplate, then remove the faceplate from the lathe and balance it on a ballbearing or something similar. Then add weight in the right area until it is somewhere near/exactly balanced.

 

[chap]

Maybe you could fix the work to the faceplate, then remove the faceplate from the lathe and balance it on a ballbearing or something similar. Then add weight in the right area until it is somewhere near/exactly balanced.

I like this idea

As for the cutter, could you not grind a HSS tool up, knocking off the sharp corner ('cos of the intermitant cut). No idea the best geometry for Cast iron though

 

[jugs]

Thanks guys,
Even if I disconnect the belts and gearbox/changewheels etc the spindle doesn't spin freely so I've bolted some tee nuts and a small angleplate to hopefully counteract things.

It's a Myford Super 7 so in backgear I can get some quite low speeds if needs be.

Hi hasbean,
on a Myford Super 7 -
put the feed fwd/rev in the neutral (center)pos.
move the lever on the large gear wheel next to the big pulley 1/2 turn, the spinde should now revolve freely.

If it wont revolve freely -
1-the bearings are probably over tight, reajust.
or
2- the pulley bearing maybe dry
[test(with pulley dog out as above & the backgear lever disengaged), start motor, the spinde should not revolve]

 

[HasBean]

Thanks guys

Jugs, I'll give that a try tonight

 

[graffian]

I use a face plate pretty often. To balance off cet stuff I just make a guess with a some weight opposite where I guessed the center of mass is.
I have quiet a few face plates and they are variously drilled and slotted, so I can pic one that suits the job best, including bolting balance weight's. I try and always bolt the weights to one of the slots, my plates are all slotted, all the way to the edge, so I can slide the weight in or out to shift the center of mass. then I run the lathe and see what it's like, if the part is really well held in place I will run it pretty fast. Even with two tons of lathe you can easily feel any out of balance, you just balance till it seems OK.

 

[HasBean]

Well I had a go this afternoon. Disengaging the spindle dog and leaving it out of backgear is a vast improvement, although it rubs against the rest of the spindle a bit and is a tad tight but I've oiled the bits I can see (having checked the headstock oiler was working ok in the first place, on mine its a wick feed up to the front bearing).
I've since found an article in a copy of Model Engineers Workshop where a balancing 'tool' was made to do just that.
The casting I need to bore is only smallish but quite a nice chunk of cast iron so should have the mass to make the faceplate turn.
If I'm feeling brave I'll post some pics for your amusement

Paul