Mag Chuck Restoration Questions

Robo_Pi

Robo_Pi

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I've been watching a few YouTube video on restoring antique machines. This is something I would be interested in getting into. I thought I might get my feet wet on what I'm thinking could be a relatively easy beginning project. I found the following Taft Peirce mag chuck that I can purchase for about $100 including shipping. I can't go see it in person as it's too far away. I'd like to have a mag chuck and so this seems like a nice resto project to start with. Although I have absolutely no idea how this chuck works, or how to restore. So it will be a total learning process if I decide to get it.

Here's the photos:

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It's a permanent magnet chuck. No electronics involved.

Like I say, I have no idea how these work. Can these be taken apart and cleaned and reassembled? Where might I find an exploded view of this type of chuck?

There doesn't appear to be any model number on it. I also have no idea what year it was made but it looks quite old.

I'm guessing that the handle manually flips a bunch of magnets up and down inside the body of the chuck. I have no clue if this thing even works. I was going to buy it and take a chance on seeing if I can restore it.

How could I clean up the top surface? Could I clean it up on a mill? Or while I need to use a surface grinder to re-grind the surface?

I don't know if I'll get this or not, but it looks like a fairly simple first restoration project. And I wouldn't mind having a magnetic chuck anyway. I'm hoping to buy an old surface grinder to restore at some point eventually.

I was going to post this in Antique and Vintage Machinery forum since that's what I'm hoping to get into restoring. But I don't know how old this chuck is.

Anyone every restore an old mag chuck? Any information would be appreciated. Especially an exploded view that shows how it comes apart. Thanks.
 
There is a good chance the magnets are of an older material and may not have the strength they had when new. Buyer beware.
Mark
 
Might be a fun project. But not a very useful tool if you don't have a surface grinder. It can be used on the milling machine with some extreme care but you can't get too greedy with the cut.

I can't tell from the pictures if the surface is beat up or if it is just dirty. Normally these are resurfaced on a surface grinder because that is the tool they are normally used on. They work by sliding the magnets back and forth to align the magnets with the poles on the chuck or to move them off alignment to release. Normally they just work unless they are rusted up from coolant getting inside. There is no real maintenance required, they are greased on assembly and that lasts for years.

Here is a video (6 of 6) showing the reassembly of a chuck.

 
Thanks for posting that video series Jim, that helps a lot. I watched all 6 parts of that rebuild. Lots of interesting info in there. That was great.
 
I rebuilt mine wasn’t difficult at all. First I’d clean the outer surfaces. Then flip upside down there’s gonna be 8-10 Allen bolts on the bottom sandwiching the center piece to the top. Remove those. Take bottom off which should expose the magnet and linkage. Mine the linkage holes were oblong shortening the throw of the magnets and engagement. I slide my magnet off the bottom of top plate and cleaned everything. My inside was perfect so I put some grease on all sliding surfaces and reassembled. I used silicone to seal the chuck and ground the top surface after mounting on s&g.
One thing I read was you do not wanna take the magnets apart. They are poled and need to stay in the same orientation. Don’t use a lot of grease between mag and top surface heard it can lessen magnetism. This is what mine looked like.
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The chuck looks like it has sat around for decades. You will want to know what if feels like to move the handle. If there is play and stickiness, there can be real problems inside, and working with the magnets and other parts inside can be dangerous work. Cleaning one up is straightforward. Then the chuck is precision ground, first the surface it will be set on, then the bottom of the chuck, then grind the top when mounted in place, held down with very light bolt tension. That is how it is done on the surface grinder.

A mag chuck on a surface grinder is a high precision work holding device. Grinding it in so it is flat and parallel with the travel, to as high a degree of precision as possible, is the goal, and it is probably the most difficult job we do on a surface grinder, and also likely one of the very first tasks we attempt. It is difficult. I would not relish trying to clean up the surfaces on a milling machine, but I guess it could be done. The top surface is made from mild steel and babbitt metal, so it is relatively soft. I would use a flycutter with a really sharp tool and very light cuts on a mill. As stated above, do not expect a really good grip on the work, depending on shape, size, and thickness. Blocking in the part with other steel pieces for a more secure setup helps a lot, but grinders do not pull up on a part like an end mill does.
 
I would use caution in grinding the table of SG. I read from Richard king somewhere that grinding the table top can relieve stresses in the table and it will move. “Banana” So if you plan to scrape go ahead. If not I wouldn’t touch the table top or bottom of chuck. You can induce twisting if the bottom of chuck isn’t flat and bolted to table surface. First thing would be inspect on a know flat surface.
 
Cadillac said:
I would use caution in grinding the table of SG. I read from Richard king somewhere that grinding the table top can relieve stresses in the table and it will move. “Banana” So if you plan to scrape go ahead. If not I wouldn’t touch the table top or bottom of chuck. You can induce twisting if the bottom of chuck isn’t flat and bolted to table surface. First thing would be inspect on a know flat surface.
Click to expand...
Grinding the table would likely make the ends pull up, if anything, and tables tend to sag over time, like the 60 years mine has been around. Had to do something to get rid of the corrosion that had built up there over the decades. A chuck corroded on the bottom mated to a table corroded on the top does not make a great bed for a chuck mounting. No warping of the chuck bottom or table top was noticed while grinding them, and I tested both with a tenths indicator after every pass. I used heavy grease between the bottom of the chuck and the top of the table to hopefully stop rust from forming again, hope it works...

Scraping them and using a surface plate to test them would probably be a very good idea. Surface grinders, like mills, tend to make convex parts when they get some wear. I may use that idea in the future.
 
As you said older equipment tends to make a convex cut. So without knowing the condition of the ways and grinding the table to a convex most likely to some degree. Then flipping the mag and grinding that to a convex of some degree. When flipping back you have two convex shapes getting bolted together which will stress the table even more. Without knowing the condition of the machine prior too I would leave the table clean all matting surfaces. Get the machine operational mount the chuck and grind some parts. See what see does. Then see if there’s problems get comfortable with her. Then maybe grind in the chuck do some test and see what that does for you.
Putting a mag chuck on the mill and cutting it will probably decrease the holding power by the surface finish. The chuck needs a clean smooth flat surface to get proper transfer of mag. Really a job for a surface grinder. Just my 2 cents
 
Cadillac said:
As you said older equipment tends to make a convex cut. So without knowing the condition of the ways and grinding the table to a convex most likely to some degree. Then flipping the mag and grinding that to a convex of some degree. When flipping back you have two convex shapes getting bolted together which will stress the table even more. Without knowing the condition of the machine prior too I would leave the table clean all matting surfaces. Get the machine operational mount the chuck and grind some parts. See what see does. Then see if there’s problems get comfortable with her. Then maybe grind in the chuck do some test and see what that does for you.
Putting a mag chuck on the mill and cutting it will probably decrease the holding power by the surface finish. The chuck needs a clean smooth flat surface to get proper transfer of mag. Really a job for a surface grinder. Just my 2 cents
Click to expand...
Good ideas, Cadillac. Where were you when I needed you? ;) I have ended up with a chuck that is convex on the top and bottom surfaces, though slightly. A single .001" shim at each end of the chuck cancels it out. Of course, that is not good enough for a surface grinder, but I am where I can make decent parts now, and I am also still learning all the time. At some point when I think I understand things well enough, I will make things right. Thanks for helping me to see those issues, I saw part of the picture, but not all of it.
 
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