3" 4-jaw independent Sanou mini lathe chuck K72-80

[WobblyHand]

Took your advise and sent LMS a nice email explaining the issues, along with photos, asking if there is something that can be done that's good for both of us. Not expecting a good outcome but, I tried.

Best you can do. If it works, you are ahead. If not, you are no worse off, than you were before. Hoping for a good result.

 

[jaek]

I vote pull the jaws and worms and deburr everything with a dremel and needle file. The end result will work much better than any replacement chuck you’d get.

It’s annoying to get a janky chuck but this is a much easier fix than cleaning up a collet chuck taper or whatever.

 

[redvan22]

UPDATE:
LMS replied and offered to send me replacement worm screws and they confirmed that the plugs in the back are just that, plugs. They suggested threading a 6mm screw into the plugs and using a pry bar (?!?) to pull them out. I think a slightly more sophisticated method should be employed to extract the plugs to prevent damage to the mounting flange and plugs but if they said use a pry bar, they cannot (should not?) be too hard to remove.

Michael

 

[WobblyHand]

UPDATE:
LMS replied and offered to send me replacement worm screws and they confirmed that the plugs in the back are just that, plugs. They suggested threading a 6mm screw into the plugs and using a pry bar (?!?) to pull them out. I think a slightly more sophisticated method should be employed to extract the plugs to prevent damage to the mounting flange and plugs but if they said use a pry bar, they cannot (should not?) be too hard to remove.

Michael

What I would do is to make a puller. Just use a piece of rod. ? 3/4" or so? Drill it through with clearance for M6. Then drill it partially with a drill that is wider than the plug. Put an M6 screw through the piece and tighten the screw. It will pull out the plug (if the counterbore is deep enough!). I presume you have another chuck. You can use your three jaw to make this. Kind of like this: 1" long. 3/4" diameter. M6 clearance hole. I used 14mm for the counterbore, in this quick model.


I think you did ok. Whatever you do, don't use a pry bar!

 

[Manual Mac]

Slide hammer?

 

[redvan22]

What I would do is to make a puller. Just use a piece of rod. ? 3/4" or so? Drill it through with clearance for M6. Then drill it partially with a drill that is wider than the plug. Put an M6 screw through the piece and tighten the screw. It will pull out the plug (if the counterbore is deep enough!). I presume you have another chuck. You can use your three jaw to make this. Kind of like this: 1" long. 3/4" diameter. M6 clearance hole. I used 14mm for the counterbore, in this quick model.
View attachment 425317

I think you did ok. Whatever you do, don't use a pry bar!

Great idea for a start but there needs to some sort of a lifting mechanism, like a jack, that will pull up the plug once the 6mm screw is inserted. There is not a through hole in the plug that would allow tightening of the screw to lift it out. In your model, once the screw has been inserted into the plug through the block, there's no way to lift it up and out.

I'm thinking about a very large bolt and nut, or several nuts, fully tightened, with a hole through it to allow the 6mm bolt and a bored out bottom to allow room for the plug as it's pulled. Then loosen the nut causing the bolt to lift or I need to make something and I don't have stock that large in diameter. Not to mention, I'm back to cutting internal and external threads again or buy a puller that will do this all.

Unfortunately, most pullers push down in the middle, on a shaft, and pull up on the gear. I need something that will push down on the outside and pull up in the middle.

 

[redvan22]

UPDATE:
LMS replied and offered to send me replacement worm screws and they confirmed that the plugs in the back are just that, plugs. They suggested threading a 6mm screw into the plugs and using a pry bar (?!?) to pull them out. I think a slightly more sophisticated method should be employed to extract the plugs to prevent damage to the mounting flange and plugs but if they said use a pry bar, they cannot (should not?) be too hard to remove.

Michael

Further update:
LMS sent me a full rebuilding kit for the chuck, all four worms and plugs. However, the worms appear to be the right diameter, pitch and length but the plugs are larger so I cannot damage the existing ones when removing. They cannot twist in the holes when being extracted.

 

[WobblyHand]

Great idea for a start but there needs to some sort of a lifting mechanism, like a jack, that will pull up the plug once the 6mm screw is inserted. There is not a through hole in the plug that would allow tightening of the screw to lift it out. In your model, once the screw has been inserted into the plug through the block, there's no way to lift it up and out.

I'm thinking about a very large bolt and nut, or several nuts, fully tightened, with a hole through it to allow the 6mm bolt and a bored out bottom to allow room for the plug as it's pulled. Then loosen the nut causing the bolt to lift or I need to make something and I don't have stock that large in diameter. Not to mention, I'm back to cutting internal and external threads again or buy a puller that will do this all.

Unfortunately, most pullers push down in the middle, on a shaft, and pull up on the gear. I need something that will push down on the outside and pull up in the middle.

The plugs have a thread. Use a screw through the holder that just threads into the plug. The screw head is retained by the holder. Keep turning the screw and the plug is pulled out of the hole into the tool. It's simple and works. I've used these before. No internal threading needed. Only thing you need is the right length screw.

This puller does exactly what you need. The big end straddles the plug. Then the screw goes through the small end. The screw pulls up the plug into the large end.

 

[mattthemuppet2]

Tap them out from the top with a small screw driver. That's what I've done on all the 4 jaw chucks I've serviced.

 

[redvan22]

The plugs have a thread. Use a screw through the holder that just threads into the plug. The screw head is retained by the holder. Keep turning the screw and the plug is pulled out of the hole into the tool. It's simple and works. I've used these before. No internal threading needed. Only thing you need is the right length screw.

This puller does exactly what you need. The big end straddles the plug. Then the screw goes through the small end. The screw pulls up the plug into the large end.

Oh, I see now what you mean. Yes, that would work. Sorry didn't understand at first.