magnetic chucks

[frankie]

Can the magnet in a magnetic chuck be recharged if so how is it done? I have one that does not seem to hold well.

frankie

 

[Ray C]

I don't feel it's feasible/possible to re-magnetize them due to how they are constructed. Unless it got demagnetized somehow, it should last for a VERY long time -as in, outlive you. I've repaired many of them and it's likely the sliding cam is worn out and the poles from the two plates are not aligning properly.

Take it apart and have a look see. They are filled with heavy oil. Dump the old stuff and replace with 20 or 30W non-detergent oil or ISO 68 or 100 hydraulic oil.

You probably need to make a new cam. Easy to do but it must be hardened or it will wear quickly.

Ray

EDIT: Don't use detergent oil. The plates are usually bound with an epoxy and I have no idea what detergent oil could do to that epoxy.
Second Note: Don't even try to slide the two plates together by hand. A) you'll likely injure yourself B) if you somehow manage to get them aligned, good luck getting them un-aligned.

Another Edit: People probably aren't aware of this but, for all your mag chucks, you should flip them over once in a great while so the oil can reach the top plate. There's about 10-12 oz of oil in a 6x12 and it doesn't naturally reach the top plates.

Can the magnet in a magnetic chuck be recharged if so how is it done? I have one that does not seem to hold well.

frankie

 

[Richard King]

I learned something today, thanks Ray! atty I would say yes to that. Be sure to turn on the mag and grind with a open dressed wheel and lots of coolant. In some of the real old chucks before I grind them I use a sharpened pin bunch to lower the lead as I have found it will plug the wheel if it's off a few thousands. Be sure not to reef the T bolts down to tight as you can break the T-Slot and warp the table on the little machines.

 

[Ray C]

Oh, what I meant by flipping them over, is just to take it off the grinder and lay it face down on a piece of wood etc. to let the oil seep into the cracks between the two plates. After a few moments set it upright and reinstall on the table.

It's not possible to reassemble with an inverted top plate because there's a connecting cam lever in there.

Sorry for the confusion there...


Ray

......and I assume if we're talking a mag chuck on a surface grinder, it would be a good idea to re-cut the chuck to eliminate any error from the "flip over"?

 

[Ray C]

Man, you got that right. I've rebuild a couple dozen and resurfacing 6x18 inches of wide-open steel is no picnic. Fortuantely, it's usually good quality steel -soft though because of it's magnetic permeability characteristics.

You wouldn't believe some of the chucks I've seen... gouges, drill holes -good heavens! The big shame-marks cannot be removed but I can get e'm flat again. Believe it or not, it's a tricky procedure and you first have to fix the base because some of them are pretty well messed-up with drop dings and most are warped from gorilla death. -Hate like heck to know what that does to the SG table. -Can't be good. It takes a good 4-6 hours to rebuild one and that's if it doesn't need internal parts or pin strapping.

Also, light passes or coolant on the mag surface is wise because, like I said, the pole plates within the primary and secondary plates are epoxied together. I'm guessing it's not good to heat the epoxy too much.

Have you ever seen a mag chuck that appears to be bleeding oil from the top side? That's because the epoxy is leaking there. -No real harm -just a sign of age or abuse.

I got most of my chucks from scrappers for next to nothing and all were repaired to 90-95% cosmetic beauty and 100% flatness and functionality. This is where I really learned to use granite tables etc...

Ray

I learned something today, thanks Ray! atty I would say yes to that. Be sure to turn on the mag and grind with a open dressed wheel and lots of coolant. In some of the real old chucks before I grind them I use a sharpened pin bunch to lower the lead as I have found it will plug the wheel if it's off a few thousands. Be sure not to reef the T bolts down to tight as you can break the T-Slot and warp the table on the little machines.

 

[Ray C]

Atty,

You're probably in good shape if you never removed it provided it was not over-torqued when installed. I really suspect that overtightening things can damage a table/bed. Richard King is in a better position to comment on that. I've often wondered how much flex CI can tolerate before deforming.

Anyhow, I only use steel clamps for mill-cut setups and use aluminum for all other light and medium holding work. -Theory being the AL will do the job fine and will give-way before damage occurs to anything else. Of course, it's all controlled by the gorilla with the wrench in it's hand... I also use a lot of aluminum strips and various shims on all the steel mill-cutting clamp fixtures. Yes, it's tedious but beats dinging-up the mill table. I also have custom sized aluminum shim plates that match the base patterns of all the vises, rotary tables, indexers etc. The protective shims are 3/32" thick and don't seem to have any negative effects at all.

Here are AL table clamps I use on the mag chucks...

Thanks, Ray. I have an old Kent KGS-200 that's probably 20 years or so down the calendar, and I'm sure the chuck has never been removed from the day the factory bolted it on. Never knew that a flip was in order. 'Nuther project to the add to the list.

 

[Charley Davidson]

I need a 6X12

 

[Ray C]

6x12's are common -a standard size. Check eBay. Also, I've seen some new manufacture ones at Shars and other discount houses in the $2-300 range.

I need a 6X12

 

[Ray C]

That would depend on the construction of the chuck. I haven't seen anything that would work though because the base comes within about 1/2" from the ends. Check around the discount houses. 10x16 is also a standard size.

Probably a dumb question but I'll ask anyway.
Could a 6x18 PM magnetic chuck be shortened to say 6x16.

Or , I just thought of this, how about milling the chuck face one inch on each end
below the surface to make the effective length 16 inch. How much lower
should I mill it down.

Reason for this is I have an Abrasive 1-1/2 manual surface grinder that
travels are made for a maximum 10x16 chuck. I was given a 6x18.

 

[Charley Davidson]

6x12's are common -a standard size. Check eBay. Also, I've seen some new manufacture ones at Shars and other discount houses in the $2-300 range.

More than I paid for the surface grinder