The Home Machinist!

That's plenty, even if you have to make custom T nuts that are tapped maybe as small as 1/4"-20. It would probably be wise to use SHCS (socket head cap screws) for mounting----they're not only strong, but small in size, so they'll fit within that ½" of space you have at your disposal. Sounds like a damned good plan to me.



My knee jerk reaction is no. Reason? The jaws, unlike the body, are heat treated, so the vast majority of the wear will have come at the expense of the body of the chuck. The vast majority of the error due to wear, therefore, won't be corrected by new jaws. Given the fact that they'd need to be ground anyway (I agree with your logic), the only thing you'd really gain is a lighter wallet and shiny jaws. The end result won't be any better. I'd keep those hard earned dollars for something more useful. Besides, it's possible you'd get jaws that don't fit the scroll well. I have a replacement set in my 3 jaw, of necessity because I broke the teeth off one of the original jaws when the chuck fell on the floor (don't ask ). They've worked well enough, but they don't fit the same way the originals did.



Better save the thanks until you get done! You might want to cuss me a little.

(Just kidding. Use good sense and this shouldn't be a hard job to accomplish, just tedious. This kind of work is lots of fun when you don't get in a hurry, and leaves you with a wondeful feeling of accomplshment, having made something useful from what is, potentially, a piece of junk.)

Be sure to let us know how it turns out!

Harold

Harold...don't you ever sleep?
The socket head screws...my thoughts exactly. I've already made some extra long T-nuts for the slots and had planned on using 1/4" screws.
The 1/4" adapter plate'll be turned and trued from 3/8" plate.
Thanks for the heads up about the chuck jaws. Makes semse to me!
I had a 3" chuck that would have been easier the mount than the 5" one but it was just too small for my needs.
Thanks!
Russ

If you are seeing "light" under one jaw.
Did you open it up and make sure the jaws are installed correctly?
Just a thought.Jim

Jim...I'm not quite following you. If the jaws where not installed properley there would be a considerable amount of runnout.
Don't ask me how I know this
Russ

A lot of replies since I was here yesterday. I havent done anything YET. As for the question about daylight, yes I did check to make sure the jaws where, for lack of a better word, threaded right in the chuck and that they where in the correct slot. I think Harold may have unknowingly found what has caused the problem in the first place. he mentioned a crash where an object was thrown from the chuck. When I first got the lathe, I did chuck in a 2 in peice of pipe and I did have it thrown across the room. I had tighten the chuck so hard that it had actually crushed the pipe where the jaws made contact. When I turned the lathe on it sent the pipe flying. I think it would be safe to say this is probably what has caused my problem. Now how do i fix it? I am guessing that the number one jaw is badly sprung, hence the daylight, well not actually daylight but it doesnt seem to contact the material like the other jaws. The jaws are two piece. Another question, just in case I run across another chuck how do I determine if it will fit my lathe. This is an old Monarch 14in lathe with about a 1-1/2in spindle bore, maybe a tad bigger but I would need to measure to be sure. I aint close to the lathe at the moment so i cant just run outside and get the measurement. In case you cant tell from my post, I own a lathe, I aint a machinist.

Any chuck will fit as long as the backplate fits the spindle nose...

So, the nose knows....

There are 3 commonly used types of noses used in the USA, and you lathe could have either:

Threaded - the chuck just screws on
Camlock (A or D) - the chuck has 3 or 4 (or more) posts sticking out the back that are locked in place with a 'key'
L - tapered with a square keyway and locking collar.

When you get a chuck, you just get the appropriate back plate to fit the lathe....

Clear as mud?

http://shopswarf.orcon.net.nz/chuckmt.html

As I recall, A lacks the studs, and is not a cam lock type spindle. The chuck or other accessory is typically held in place by SHCS's through the face of the device, but each share a similar, if not identical, taper that the D device enjoys for registering the devices properly.

No, I've never used one like that, but I recall that the W&S turret lathes were equipped with such a spindle where I worked in my youth. I was never assigned to them.

Harold

Heh! Not exactly unknowingly. You see a lot when you've been around machines as long as I have. You can trust me on this one----you're not the first guy to have something come out of a chuck. (Don't ask!)



This is where a careful inspection is the word of the day.

Take the jaws out and look at the slide area in the chuck body. Compare one to the other, paying particular attention to the one you suspect is damaged. It's highly unlikely the jaws will have any damage, they're generally well heat treated and have considerably greater tensile strength than does the body.

Look for irregularities in the slide area---a step, maybe a fractured area----what ever. If the body is steel, it's unlikely to be fractured, but it could be deformed. If that be the case, depending on how the chuck is built, you may just have to live with it. You may envision a way to press the slide back straight, using a heat treated well fitting object and pressing in a large press, several tons capacity. It's a long shot, all depends on what you find, if anything.



That may change, to a minor degree, how you go about grinding the jaws, assuming you do. If your chuck is built such that the top jaw makes contact with the material, but the portion that runs in the slide doesn't, all you have to do is place your spacer (the disc you'd use for grinding) in that area, then grind only the top portions until they all clean up. The same rules set forth earlier still apply, only the "kill the small area" would change, for it may not touch, and won't matter. Make sense?

That you have two piece jaws is really a good thing. If you get interested in using soft jaws, you're already there. If you're not familiar with soft jaws, and want to be, there's a long post I made a few years ago that addresses them well, and should provide all the guidance necessary for you to have a firm understanding on how to make them, and how to apply them. I could provide a link for the post if you're interested. The pictures that went with it won't be available any longer, but I could repost them if necessary. The new software wasn't compatible in that regard, so pictures, for the most part, have all been lost.



Bill has addressed that nicely. The only thing I'd add is that you should keep in mind the size of the hole in your spindle, and make sure any chuck you acquire has a hole in the chuck body no smaller than the spindle bore. Only is you mount an unusually small chuck would that be a consideration, however. If your lathe is an early Monarch, that's probably not much of an issue, but later machines can have larger spindle bores, and it would be a shame to lose the capacity, especially if you're inclined to run fairly large diameter pieces.

One more thing. Assuming the slide is damaged, and the damage is general in nature (not a sharp ridge, for example), the grinding operation we've talked about will improve the chuck drastically, even if you don't make any corrections on the slide.

If you do find it is sprung, only one slide, select the average of the sizes you intend (or expect) to machine, and set the jaws for the average. That way the amount of error you get from the jaw will be split evenly from top to bottom size, with a perfect (?? You know what I mean) fit in the middle. In the end, you'll be quite surprised how well the chuck runs as compared to how it is now.

If you're real lucky, and the damage is well spread between all three slides, which I really think it is (sprung chucks are not uncommon), the chuck will run beautifully when you're finished.

Don't get discouraged with this thing yet----



None of us were born with machining knowledge. It happens I've spent more time in the environment than you have-----that's the difference. Otherwise we each put our pants on one leg at a time. What really matters is your attitude----and yours is healthy. Not everyone welcomes input as you do, and that's an ongoing problem for people like me that run their mouths overtime----it's not always welcome.

Thanks for putting up with me.

Harold

Lets say it like this. I welcome your phone calls from noon on, even at 3:00 AM, but it is always a kindness if folks don't disturb me between 4:00 AM and noon.

We're both night people. By choice, we stay up most of the night.



Sounds like you have the thing firmly in hand. Should turn out great. The thinner plate (mine is 1" aluminum) makes for a little more space under the spindle. By the time you add a rotab and chuck, you often have very little left. A quarter inch can spell the difference between success or failure.

I used to have a 3" three jaw----bought it with my little Craftsman lathe when I was a boy. Nice little chucks, but quite worthless when you have some serious work to do. Might be nice to use under certain circumstances, though, like small work. You made a smart decision to go with a larger chuck for general purpose. Not only for holding larger items, but for holding power. The small one would likely let you down when you least expected. They're not very strong.

How about a picture when you're finished?

Harold

If I get the jest of this information, since my chuck just screws on the spindle, any threaded chuck should work. provided that I choose one that has a similar hole thru the spindle. If I choose a chuck with a smaller spindle hole, it should still work, I just loose the ability to stick a larger dia shaft thru the spindle. Actually, i wouldnt mind a little smaller chuck. the big chuck gets in the way of the cross slide if trying to cut close to the chuck

I ran into a person today that does a little hobby machining, he has a jig made to hold a dremel grinder like a boreing bar onto the cross slide via the tool post. He said it should work on my machine. He suggested that I use a grinding stone, said it would probably take several, LOL and just run it inside each jaw until I got everything cleared up. he also said the same thing about using a small disk at the very back of the jaws to provide tension. He is going to come over and help me set it up properly. Ready made jig and help to boot, cant beat that!!!

I am going to take the chuck off the machine and take it apart for a better inspection before doing anything. Right now its a little to cold in my unheated shop so probably be a week or two before i actually do anything.

Whoops, Bill i didnt see the link at the bottom of your post until after i had posted above, Makes a little more sense now. Thanks for the link

mudstopper:

When I grind my chuck jaws, I don't grind one jaw at a time, I set the lathe running and run the grinder in slowly, hitting all the jaws as the spindle turns.

As an aside...please keep in mind that for really true work, use an independent jaw chuck, where you can adjust as necessary for each job. ...or a collet

This way you are SURE that the part is centered every time.

Thanks for the tip. I plan on doing one jaw at a time until I get them all pretty close and then turning on the lathe for the final pass. I think it might save me a little on grinding stones, that click, click, click as the chuck turns is probably hard on rocks.

I do have a 4 jaw chuck but I have never had it on the machine, if I was to try to get down to the nitty gritty, I will probably give it a try. I have been wondering about a collet, aint sure what I need to attach one to my lathe. I assume it would just bolt to that big backplate I have laying in the corner. I havent had it on the lather either. Or could I find one that would just screw on the spindle nose?? I have very little tooling for this lathe, basically just a tool post, and a few cutting bits, I did buy a drill chuck for the tail stop last week and an adapter from m4 to m2 taper so I can use some of the easier to find tools, in case I run across something I think I might need, but will probably never use. I am also looking for a vise to put on my cross slide so i can do some limited milling. Wait a min, I aint catching that machinist flue am I? I hear its pretty hard to cure. They quarantine you in your work shop and just feed you scraps of metal until you die.

ms:

The collet typically goes IN the spindle...using typicaly a morse taper adapter to something like 5C collets. ..this you buy to fit the spindle.

There ARE nose-bolt-on collet adapters...I haven't had terribly good luck with them..they don't always run true, esp on a lathe with threaded nose....so if I had my 'druthers.....

A drawbar is used to pull the collet shut. This typically is purchased, but can be made...the length has to match the lathe...if you get one that is 'too long' you can cut it off...

An extraction / nose cover is used to protect threads and pull the adapter out when you are done. Typically these are made, but can be purchased..cheaper to make....

Then, the collets....get good collets, as many as you can afford.

Couldn't live without them, but then I know people that never use them. I do a lot of work with keystock, and hex stock and small round bar...

Well the weather warmed up so I decided to play with the chuck to see If I could fix it or really screw it up. I took one of those cutoff weel like used in a die ginder and chucked it up in the tail chuck. I then just tightend the 3 jaw just enough for it to touch the cutoff wheel. I turned on the lathe and fed the cutoff wheel into the 3jaw. It quickly didnt look like I thought it would. You know cutting a little of as it was feeding into the jaws. I stopped and took a harder look at what was going on. It was visible that the outer edge of the jaws was a lot wider than the in inner edge. The jaws are actually leaning outward. I chucked up a 3/4 in peice of round stock and tightened the jaws. No matter how hard I tighten the chuck. it wouldnt clamp the roundstock all the way, just catching at the very back and not even by the jaws but by the part the jaws bolt to. I could wiggle the roundstock by hand with just a little bit of effort. I took the chuck off the lathe and laid it on a table. the outside edge of the jaws are definatley sprung outward. to get the jaws to be parallel all the way from front to back is going to take a lot of grinding. the chuck has always been hard to tighten the jaws. Is this chuck worth any more effort, or should I just start looking for another chuck. I did find marking on the chuck. It has the letters MP, over top of a T, inside a Triangle and made in Italy stamped on the face. No other markings that I have seen. Outside dia of chuck body is about 9-1/2.