Beginner machinist question

[Captain Ledd]

I've recently purchased a decent sized lathe and have some questions.

Got a good deal on it, $500, 14" swing, roughly 36" long piece. Definitely big enough for just about anything I'll need to do. Came with 2 chucks but neither are adjustable. Both are 10" one is a 3 jaw, the other is 4. Came with a big box of other stuff too.

I'm looking into a new adjustable chuck to try and keep the tolerances in order, the current 3 jaw one I can't get less than .008" true, even that took some playing with. I know it'll have some play, as it's really friggen old.

So, now the question:

Do I go with another 10" chuck? Or do I splurge the extra $$$ for a 12" chuck?

Would it limit how small of a piece I can hold with a larger chuck? Or is it pretty insignificant?

 

[doorgunner]

Welllllllllllllllllllll........first things first.........put the lathe in the lowest gear range so the chcu.....chuck will be hard to rotate.

Then set a dial indicator up so the pointer is resting on top of the chuck in order to check up/down play.

Then get a 2" x 4" that is about 5' long...place one end under the chuck & use the way for leverage.

Put your weight on the other end of the board & watch the dial indicator to see how much slack is in the mainshaft bearings. Do this several times to get a good idea of how much slack there is. If there's more than .001 up/down movement.....you need to remove the gearbox cover and tighten the main front & rear bearings.

Let us know how that turns out...it might save you from buying another chuck for the time being.

 

[Captain Ledd]

Welllllllllllllllllllll........first things first.........put the lathe in the lowest gear range so the chcu.....chuck will be hard to rotate.

Then set a dial indicator up so the pointer is resting on top of the chuck in order to check up/down play.

Then get a 2" x 4" that is about 5' long...place one end under the chuck & use the way for leverage.

Put your weight on the other end of the board & watch the dial indicator to see how much slack is in the mainshaft bearings. Do this several times to get a good idea of how much slack there is. If there's more than .001 up/down movement.....you need to remove the gearbox cover and tighten the main front & rear bearings.

Let us know how that turns out...it might save you from buying another chuck for the time being.

Allright, I'll give that a shot. buuut, I'm not so sure it's going to be as much tightening the bearings, as pouring new babbit.

When I said it's old, I meant it's OLD. I don't exactly know how old, bu it came out of a water powered factory and the plate for the thread cutting speeds says "Patented June 1912"

I'm also on the prowl for a new leather drive belt as the one on it has some stitching coming out of one end.

but I'll see just how much play I actually have.

 

[doorgunner]

AAAAAAAAAAAAAAAAHAAAAAA......now we're gettin somewhere....it's a museum piece......don't bother spending money on ANYTHING unless you can repair the babbit or upgrade to a bronze bushing...(you know already that you won't be able to make halfway accurate parts with slack in the spindle)

 

[Kage]

Looks like DG beat me too it. Find out where the play is (If its in the machine, chuck mounting face, or in the chuck itself) before spending money on another chuck.

What does the chuck mounting surface look like? I've been able to clean up some really nasty ones before with a tool post grinder to get them closer to being 'right'.

 

[Captain Ledd]

I can get it pretty regularly to within .008" But not any closer. Haven't got the 4 jaw chuck on there yet.

I'll check the tolerances later tonight.

The chuck simply bolts to a plate with 4 bolts (actually 3, it was missing one). That flat plate screws off of the shaft.

 

[robertc1024]

If you have to pour a new babbit bearing (not really all that hard) I think I can hook you up with the material to melt. We used to make o-ring backup rings out of that stuff and I think we've still got a couple of raw ingots here at work that are just trash to us now.

 

[Captain Ledd]

If you have to pour a new babbit bearing (not really all that hard) I think I can hook you up with the material to melt. We used to make o-ring backup rings out of that stuff and I think we've still got a couple of raw ingots here at work that are just trash to us now.

I'll take them anyways, sooner or later I knew I would have to mess with them. I can offer to help with shipping too, you have a PM. Sounds a lot better than the engine bearing pile I had going, which I may still use it, it is recyclable, just in other experimental projects.

Spindle play is .003"

And yes, I never expected this thing to hold super tolerances from the get-go, but I would like it to at least be fairly concentric. I imagine the bed is worn to the point of having a slight taper, but that's a whole 'nother can of worms. I'd still like the shorter stuff to be accurate.

People restore all kinds of things, a lathe is no different. And in a lot of cases more useful than a car

 

[doorgunner]

.003 !!!! Not bad for an antique....it's like you said...the ways might cause more problems than the bearings.....

why don't you get it operating good first (adjust all the slack out of everything)

then machine a simple part to see how accurate it is...


When you say the chuck is running out .008.....do you mean the O.D. of the chuck is running out .008?


OR.......


do you mean that the part that is chucked in the jaws is running out .008?


the reason I ask is.....if the O.D. of the chuch is running out.....no big deal.....


BUT...if the piece of metal that is chucked up runs out .008....you could carefully grind the gripping face of the damaged jaw until the part runs true when the chuck is rotated....(just giving you some options....you may already know all of these things)

 

[Captain Ledd]

The part that is chucked into the jaws.

While I don't necessarily have a round gage piece to stick in there, I did put in a few of my nicer sockets. I imagined they'd be truer than .008", they're usually out as much as .025" when I first stick them in there.

I had a semester class in college (years ago) on machining, and I remember getting frustrated that when I put my part back in the next day it was off just a bit, and my professors told me it would be, but never told me how to correct it (I ended up figuring it out afterwards). But they also said it would be just a little bit off a few thousandths regardless. Play in the clamping jaws or something.

I have heard of the grinding trick, I'm not sure I want to get into that. I've also heard about marking the jaws, taking it apart and re-assembling it in different positions to try to find a truer center. This will be my next step if I try anything.

If I do wanter across something suitable for cheap on E-bay or something I may order it. I've also seen damaged chucks for sale for ridiculous prices of machine tool websites.

 

[Metallheadd]

The 4 jaw chuck is the indicatable one, each jaw moves independently. I have used shims in a 3 jaw before though too.

 

[Captain Ledd]

The 4 jaw chuck is the indicatable one, each jaw moves independently. I have used shims in a 3 jaw before though too.

That was why I was trying to put the 4 jaw one on. I knew sooner or later I could get that one correct. It's just time. I can center the adjustable 3-jaw one in a Jiffy.

 

[doorgunner]

Exactly!!! If you've got the extra cash--get an adjustable 3-jaw....just make sure that it's not too big or the jaws will hit the ways when opened....

 

[det107]

The 4 jaw chuck is more reliable than the 3 jaw chuck. If you get .003 w/ 3 jaw, that is a feat ! To machine a part, it is better to leave it in until it's done machining. If the operator must remove the part, it will take practice to "finesse" in order to place it back in exact place.
DG is right about using a dial indicator, it is a revered machinist tool-

 

[Captain Ledd]

To machine a part, it is better to leave it in until it's done machining. If the operator must remove the part, it will take practice to "finesse" in order to place it back in exact place.

That's exactly what they told me in my class. But I can't quite seem to finesse it past .008".

So 4-Jaw chuck it is!

I'll cruise around E-bay or something and maybe the blemished chuck sections on online retailers and get a deal on a 10" adjustable chuck.

And I know some of you are getting curious...