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.
Truing up jaws in lathe chuck
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muddstopper
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Bill Shields
Grinding
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.
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.
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muddstopper
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.
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.
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Bill Shields
collets
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...
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...
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muddstopper
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.
That's the same make chuck I run on my Graziano. Not the best chuck in the world, but certainly not a bad chuck. I've had good results with mine, which measures 8" in diameter.It has the letters MP, over top of a T, inside a Triangle and made in Italy stamped on the face.
What you found is exactly what I described, and it's quite common with older chucks. It is generally caused by holding items by only the tips of the jaws, where there's considerable leverage trying to spring the jaws outwards, just as yours has. The slides get deformed in the process, otherwise they jaws wouldn't be tipped outwards as they are.
Worth fixing?
Sort of a judgment call. If you buy a different chuck, unless it's new (big$$), how will you insure you don't buy another like it? As I suggested, that's a common problem with chucks.
I'd suggest you dismantle the chuck and work on the slides a little, making sure that each jaw will slide reasonably well in the body. Don't be afraid to deburr where necessary, but I wouldn't remove anything that isn't necessary, for the jaws will be real sloppy if you do. The chuck is probably hard to turn because the slides are distorted and don't permit free movement of the jaws. As I said in an earlier post, you may even be able to straighten them to some degree. Hard to say without being able to see the chuck.
Pay attention to the area where the scroll anchors and turns, making sure there's no burrs hanging up the scroll. Clean everything with solvent (NO GASOLINE---use paint thinner (mineral spirits) or --Stoddard solvent).
Once you get the jaws where they will move without excessive force, put the chuck back together and grind the jaws until they clean up. Be sure to block the jaws as I suggested. Don't avoid that step for any reason. If you don't observe that suggestion (you can call it a demand, if you wish), in use, the chuck will still run out, and the backs of the jaws will still be the only place they make intimate contact, although you'll have made the gap at the front smaller. Observing this process, I promise you, will restore the chuck to a reasonable operating condition.
To avoid springing the jaws further, don't hold items by the tips of the jaws, and if you must, don't over tighten them. Change to a 4 jaw when you need greater holding power. They have not only a closer holding interval (90° instead of 120°), but often have jaws that are serrated for better holding power. That would be especially true in this instance, because you'll have ground your jaws to the point where they might be free of any kind of serrations and you're left with smooth jaws. No problem, they will still work quite well.
The option available to you beyond this is to forget using the hardened jaws and run only soft jaws. They're real easy to turn, you don't have to do any grinding, and they hold perfectly well. Fact is, I use my three jaw that way almost exclusively, rarely using the hardened jaws. I keep one set of jaws that are bored through, so I can hold bar stock accurately, and seldom re-machine them. They grip full length, and hold stock far closer than the hardened jaws did, even when they were new.
Bottom line is the chuck doesn't sound like it's beyond use to me, but you're the one that has it in his hands and must make the final decision. If the damage on the slides isn't excessive, it's still a very useful chuck, especially if all the jaws are sprung somewhat equally.
Harold
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J Tiers
The man with the plan on chuck jaw grinding in place is Rich Carlstedt...
Since he hasn't popped up on this, I'll take the liberty of posting what he told me (us, really, he posted it).
First, drill a hole of a convenient size in the END of each of the chuck jaws. Use carbide, masonry bit if you have to. Precision doesn't hurt, nor help much, either.
Put a pin that fits close in each hole.
Close the jaws on a slice of pipe that holds them open enough to get your grinding point in.
Proceed to grind them all with TP grinder and point, Dremel on compound, etc, etc, as the chuck is rotated slowly. Move in and out axially to get the whole jaw. Spark out thoroughly.
Since the loading is same as in use, your jaw position is right. You will end up with no bellmouth, and good centering at that spot on the scroll, at least.
This isn't going to bring it back in everywhere, but it will start it right. And it may not be that far out even on other parts of the scroll, etc.
The one thing is that the jaws have a small amount of cylincricity ground into the faces.
You could get rid of that by feeding in and out with the jaw at bottom, if the ring and grinder work out that bottom is the contact point. Otherwise, ignore it, your goal was salvage, not necessarily perfection. (of course, if grinder is on a milling slide, you could set up to hit the bottom).
Since he hasn't popped up on this, I'll take the liberty of posting what he told me (us, really, he posted it).
First, drill a hole of a convenient size in the END of each of the chuck jaws. Use carbide, masonry bit if you have to. Precision doesn't hurt, nor help much, either.
Put a pin that fits close in each hole.
Close the jaws on a slice of pipe that holds them open enough to get your grinding point in.
Proceed to grind them all with TP grinder and point, Dremel on compound, etc, etc, as the chuck is rotated slowly. Move in and out axially to get the whole jaw. Spark out thoroughly.
Since the loading is same as in use, your jaw position is right. You will end up with no bellmouth, and good centering at that spot on the scroll, at least.
This isn't going to bring it back in everywhere, but it will start it right. And it may not be that far out even on other parts of the scroll, etc.
The one thing is that the jaws have a small amount of cylincricity ground into the faces.
You could get rid of that by feeding in and out with the jaw at bottom, if the ring and grinder work out that bottom is the contact point. Otherwise, ignore it, your goal was salvage, not necessarily perfection. (of course, if grinder is on a milling slide, you could set up to hit the bottom).
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J Tiers
Grrrr... can't edit.....
The slice of pipe is held by the PINS, of course...... (and what the heck is "cylincricity?)
This has worked VERY well for me. I used a humble Dremel tool, since I have no mounted point adapter for my small Dumore TP grinder.
If you first check eccentricity of work held at several diameters, you can survey how bad the scroll is vs other factors. That may affect whether you bother or not....
The slice of pipe is held by the PINS, of course...... (and what the heck is "cylincricity?)
This has worked VERY well for me. I used a humble Dremel tool, since I have no mounted point adapter for my small Dumore TP grinder.
If you first check eccentricity of work held at several diameters, you can survey how bad the scroll is vs other factors. That may affect whether you bother or not....
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Bill Shields
UP Chuck
Cannot tell you if a chuck is worth the effort.
I WOULD suggest that you try spinning the grinding wheel a LOT faster than the chuck can spin..this will do a better job of metal removal...simply holding the wheel in the tailstock will normally not provide enough speed.
Surface cutting speeds for grinders need to be MUCH faster than standard lathe cutting tools.
Even if you end up scrapping the chuck, consider it a learning experience.
If you scrap it, then you can say that you absolutely gave up chucking..
I know, don't give up my day job.....
I WOULD suggest that you try spinning the grinding wheel a LOT faster than the chuck can spin..this will do a better job of metal removal...simply holding the wheel in the tailstock will normally not provide enough speed.
Surface cutting speeds for grinders need to be MUCH faster than standard lathe cutting tools.
Even if you end up scrapping the chuck, consider it a learning experience.
If you scrap it, then you can say that you absolutely gave up chucking..
I know, don't give up my day job.....
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muddstopper
Three jaw chuck problems
Gentlemen:
My 6" 3 jaw chuck is less than satisfactory when I chuck up round stock, (what else is new?). I have read and re-read this thread and searched for others on the subject of truing up a 3 jaw chuck until my eyes started to blur. I attempted to grind the jaws using the method described by Harold which made perfect sense to me. However, my results were less than satisfactory. I used a 1.5" slug set in the back of the jaw, tightened the chuck, and ground the rotating jaws with a stone point mounted to the tool post. The operation went well. The jaws were sprung open on the outside as has been mentioned. I ground until the stone sparked on all jaws front to back. It still was way off.
Since no keys were marked I experimented and found the one key of the three that seemed to be the best. Better. Next I found that using .002" shim stock between jaw #2 and the work improved things. I assumed this meant somehow jaw 2 was short? I disassembled the chuck and measured the jaw heights on the back sides, turns out #3 is taller than 1 & 2 by about .012"! Adding to the problems is the fact that someone at one time ground the back edges of the jaws, (why?) and this is where I had the slug clamped, (and where I measured). I hope the photo shows in the post as you can clearly see the ground area.
I'm seeking any ideas on what to do next. Would grinding that tall jaw to match the others and then repeat the process do the trick?
I understand 3 jaw chucks are not perfect and I do have a 4 jaw chuck but I would like to make the 3 jaw at least acceptable. Old as the chuck is it seems of good quality and otherwise in not that bad of shape.
Thanks
Ernie F.
Photo shows the bottom of the jaw from the back side.
My 6" 3 jaw chuck is less than satisfactory when I chuck up round stock, (what else is new?). I have read and re-read this thread and searched for others on the subject of truing up a 3 jaw chuck until my eyes started to blur. I attempted to grind the jaws using the method described by Harold which made perfect sense to me. However, my results were less than satisfactory. I used a 1.5" slug set in the back of the jaw, tightened the chuck, and ground the rotating jaws with a stone point mounted to the tool post. The operation went well. The jaws were sprung open on the outside as has been mentioned. I ground until the stone sparked on all jaws front to back. It still was way off.
Since no keys were marked I experimented and found the one key of the three that seemed to be the best. Better. Next I found that using .002" shim stock between jaw #2 and the work improved things. I assumed this meant somehow jaw 2 was short? I disassembled the chuck and measured the jaw heights on the back sides, turns out #3 is taller than 1 & 2 by about .012"! Adding to the problems is the fact that someone at one time ground the back edges of the jaws, (why?) and this is where I had the slug clamped, (and where I measured). I hope the photo shows in the post as you can clearly see the ground area.
I'm seeking any ideas on what to do next. Would grinding that tall jaw to match the others and then repeat the process do the trick?
I understand 3 jaw chucks are not perfect and I do have a 4 jaw chuck but I would like to make the 3 jaw at least acceptable. Old as the chuck is it seems of good quality and otherwise in not that bad of shape.
Thanks
Ernie F.
Photo shows the bottom of the jaw from the back side.
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Last edited by Metalman on Mon Mar 13, 2006 12:39 am, edited 1 time in total.