# Magnetic Chuck - Testing and Troubleshooting Questions



## joe_m

Life is about to get in the way of my hobbies again, so if anyone responds it will be a few days until I can get around to thanking you. Until then, I leave you with a couple of questions on magnetic chucks - specifically the ones where you throw a lever (manual?) to operate, not electronically charged.

Question 1: How strong should these things be?
A. They should hold a metal object but you can pull it off with just about as much force as it takes to remove a playschool letter magnet from the fridge. (M is for Machinist).
B. So strong that if you bend over to get a close look it will pull the metal plate in your head out through your nose.
C. Somewhere in between A and B.

Question 2 depends on the answer to Question 1. 
If you answered A above - no problem, nothing to see here, move along.
If you answered B above - what are the usual suspects to check when it stops working correctly? (Short of mailing it off to a professional for rebuild).
If you answered C above - could you provide a criteria that is measurable using items commonly found in a hobbyist workshop devoid of thousand dollar nuclear, ultrasonic, magnetic microwave measuring devices. 

Thanks in advance.
Joe


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## Ray C

The answer is C -kinda...  If you have say a 3x3" piece of metal, you shouldn't be able to budge it.

I've rebuild many of these things and there's only a few ways they go bad and most can be repaired.

1)  There's a cam, lever and pin in there to slide the internal plates together.  Sometimes something wears out.
2)  The lamination that holds the plates together has cracked.  Sometimes it can be pinned back together -sometimes not.
3)  Someone has demagnetized it with some other device.  -It's a doorstop now.
4)  The internal oil is contaminated with a huge amount of swarf and magnets won't align or the magnetic field is rerouted through it.  -Just needs cleaning.
5)  The top plate is very uneven and dinged and metal pieces can't be set flat on it.  -Needs to be milled and reground.

And that's that!

Ray




joe_m said:


> Life is about to get in the way of my hobbies again, so if anyone responds it will be a few days until I can get around to thanking you. Until then, I leave you with a couple of questions on magnetic chucks - specifically the ones where you throw a lever (manual?) to operate, not electronically charged.
> 
> Question 1: How strong should these things be?
> A. They should hold a metal object but you can pull it off with just about as much force as it takes to remove a playschool letter magnet from the fridge. (M is for Machinist).
> B. So strong that if you bend over to get a close look it will pull the metal plate in your head out through your nose.
> C. Somewhere in between A and B.
> 
> Question 2 depends on the answer to Question 1.
> If you answered A above - no problem, nothing to see here, move along.
> If you answered B above - what are the usual suspects to check when it stops working correctly? (Short of mailing it off to a professional for rebuild).
> If you answered C above - could you provide a criteria that is measurable using items commonly found in a hobbyist workshop devoid of thousand dollar nuclear, ultrasonic, magnetic microwave measuring devices.
> 
> Thanks in advance.
> Joe


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## RWL

Ray.  I may be hijacking the thread.  How do you open one of these up and how do you keep the magnets from losing their magnetism once you've got it open?


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## Ray C

All the ones I've encountered have about 8-10 socket screws on the bottom.  Flip it over, remove the screws and separate the halves.  Do the work inside of a big aluminum turkey basting pan or tray because they're filled with heavy weight oil.  -And I guarantee it will be nasty and contaminated with swarf and coolant.  Contaminants enter through the O-ring seal on the handle.  It may take some jigging of the handle and sideways manipulation to get the handle actuating pin out of the internal cam/lever.  There will be several leaf springs inside under low tension.  Those only ensure the internal plate stays in-contact with the bottom of the top plate.

The internal plate is just a smaller version of the external top-plate.  Each plate is a laminate of North/South permanent magnets.  The internal plate just slides against the bottom of the top plate.  In one position, the magnets align and cancel-out and the other position, they align the magnetism additively.  Don't separate the two halves (it would be next to impossible) as there is no reason to. 

Clean all the gunk out, wash everything in the parts cleaning tank, make or repair any worn cams or actuating levers etc. fill with NON-detergent heavy weight oil (Way oil, hydraulic oil etc) and reassemble.  You want non-detergent oil because the laminated plates are pinned together and also have an epoxy sealer.  Err on the side of caution and assume that detergent oil could break-down the epoxy.  There's anywhere from a pint to a quart of oil depending on the geometry of the unit.  I always re-bore the hole that the handle pivots through and I re-make the shaft that goes through.  This usually involves remaking the cam or cutting off the shaft and TIGing a new shaft onto it.  The passage way for the handle pivot is almost always beat-up marred and just putting a new seal in there is just cheating the customer since it wont last long.

BTW:  For anyone who owns a mag chuck, it's not a half bad idea to flip it over on it's topside for just a few moments once every blue moon or so.  This will ensure there's a film of heavy oil between the plates to ensure smooth operation.

If the bottom plate is cracked, they can be repaired (sometimes) by pinning an aluminum plate to hold the pieces together.    Perfectly legitimate way to fix them.  I had two this way and to be on the safe side, did not re-sell them.  They are my shop chucks and work fine.


Oh, surface grinding the top and bottom...  Just mill the bottom flat.  Flip it face down on the table and activate the magnet.  Take off as little as possible.  Flip it over and true-up the top side with a GOOD face cutter.   Use the inherent hold down clamps to hold it in place.  Don't try to remove any dings that are too deep (judgement call).  Throw it in the surface grinder and do the top only.  It's not easy (and you'll find-out just how imperfect a mill cut really is).  Do no more than a 0.010 step with no more than half thou downward.  Takes 2 hours usually to do the top.   Don't let anything get hot unless you're running coolant.  If you feel heat, it will not be flat and square.  The ones I've done came-out within a few tenths (measured on the granite and TDI) from corner to corner.

----More than you wanted to know but now you know it and can restore life to things...  They look almost brand new when done.

Ray


EDIT:  Hint.  When you SG the top and if you dont run coolant (I don't), preheat the entire chuck to about 150degrees in an oven.  This will keep your starting and terminal temps about the same; otherwise, you'll be chasing your tail to keep the tenths in line.




RWL said:


> Ray.  I may be hijacking the thread.  How do you open one of these up and how do you keep the magnets from losing their magnetism once you've got it open?


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## RWL

Thanks for the description.  There are a mixture of posts on the net about magnetic chuck repair, but nothing quite as specific as your description.  If you happen to have one open at the moment, can you shoot a picture of what they look like inside?  Mine is working, but getting harder and harder to turn the lever.  The magnetism doesn't seem even over the entire top, and doesn't quite go away as much as I think it should would when it's in the off position.  What I'm somewhat concerned about repairing is the actuating mechanism.  My lever is at the long end rather than along the side, and I suspect it works on a helix in the shaft.  Replacing that could be a problem.  The chuck is by Magnetool of Hazel Park, MI.  They're still in business, but whether parts are available is another question.


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## Ray C

Sorry to say, I don't have one open at this time and I'd prefer not to open one gratuitously since that would pretty-much blow the surface grinding job since the two halves wouldn't go back together exactly the same way.  If another comes along, I'll take pictures.  I got my hands on a bunch of abused ones for cheap and rebuilt them all.  I'd never opened one prior to that so, I just had to figure it out.  There is no rocket science at all.

They all suffer the same symptoms you describe but you won't know what's wrong until you see the guts.

I view your situation as win-win by taking it apart... At the moment, you have a dysfunctional device that's not safe to use for surface grinding -you can't make it much worse and only stand to possibly find something simple to fix.  If things look really screwed-up, take pictures and post them and we can assess the problem.  It's gotten to be common knowledge by now that folks often send me stuff to make and if it can be done with shop-drops, all I ask is that you pay postage both ways.  If it's something I can make, I'll let you know.


Ray




RWL said:


> Thanks for the description.  There are a mixture of posts on the net about magnetic chuck repair, but nothing quite as specific as your description.  If you happen to have one open at the moment, can you shoot a picture of what they look like inside?  Mine is working, but getting harder and harder to turn the lever.  The magnetism doesn't seem even over the entire top, and doesn't quite go away as much as I think it should would when it's in the off position.  What I'm somewhat concerned about repairing is the actuating mechanism.  My lever is at the long end rather than along the side, and I suspect it works on a helix in the shaft.  Replacing that could be a problem.  The chuck is by Magnetool of Hazel Park, MI.  They're still in business, but whether parts are available is another question.


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## RWL

I'll take you up on your offer to trouble shoot photos.   It may have to wait until this weekend.   By the way - turn the magnets on or off before taking it apart?  I've read that the two halves are joined tightly.  What did you use to wedge them open a little - knife blade?


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## Ray C

Magnets disengaged for disassembly -or it will never come apart.

Don't bother separating the two halves.  If the top plate is cracked, it's toast anyhow because you certainly cannot fix it from the exterior top side and it cannot be repaired on it's other side as the bottom plate needs to make flush contact.  If the bottom plate is cracked, depending on where it's cracked and the space you have to do the repair, it can be done as an assembly.  The residual magnetism holding the pieces together is considerable and you'll likely hurt yourself or break the epoxy getting them apart.  I suspect it's done with a large sliding fixture of some sort with hydraulic or other mechanical means of leverage.  When you see what's inside there, you'll see there's no reason for further disassembly -trust me on this...

You will need a parts cleaning tank with some light solvent cleaner or even some rubbing alcohol as well as compressed air to blow it all dry.

I had one where an area of the bottom plate where the pin that goes through a swivel-pinned lever was worn out.  I just built it up with TIG, reformed the area and re-drilled the hole.  I was in and out with the TIG in under 10 seconds and the heat never traveled.  On that unit, I also had to re-make the cam that was worn to nothing.  Good as new!  I often wonder how many hundreds-of-thousands of times that was operated to wear it out so bad.


BTW:  I'm reasonably well convinced that the reason these things break in the first place is because nobody every flips e'm over once in a great while to let the oil lubricate the upper half of the internals.  -And that's why you want to use really heavy oil; so it sticks up there for a long time.  -Just my theory from seeing the insides of about 7 of these things.  I just took a gamble, bought a bunch of broken ones on the bet I could fix e'm and flip e'm and I came out with Aces.

Ray




RWL said:


> I'll take you up on your offer to trouble shoot photos.   It may have to wait until this weekend.   By the way - turn the magnets on or off before taking it apart?  I've read that the two halves are joined tightly.  What did you use to wedge them open a little - knife blade?


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## RWL

I've got the chuck opened but how do I get the top disengaged from the linkage?  I think that's what's holding it in place.  The actuator is at one end of the chuck.  I can lift the top / magnets up about 3/8" at the end opposite from the actuator, and only slightly at the actuator end.  There is about 1/8" of space between the magnets and the sides of the case, except at the end with the actuator, where there is a little more space.  Note again that the actuator is at the end, and not along one of the sides.  Photos below.                                                                                                                                        .                                                                                                                                                                                                                      
	

		
			
		

		
	





	

		
			
		

		
	
 In the last photo, the screwdriver is in the end opposite to the actuator.


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## Ray C

Look'n good so far.  Yeah, they're reluctant to come apart.  All the ones I've done had the handle on the side, not the end -and they had a cam with a pin on the end of the handle shaft.  The pin fit into a lever.  You had to move the base sideways to get the pin out of the lever hole.  Sometimes the pin is worn and it forms a groove so it doesn't easily slide out of the lever hole.

Since yours is a little different, I'd have to see it.  Look in there with a flashlight.  Admittedly, the first time I did this, it had me scratching my head but once you've done it, the rest are a snap.

Was it filled with gunky oil?

Ray


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## RWL

Ray C said:


> Since yours is a little different, I'd have to see it.  Look in there with a flashlight.  Admittedly, the first time I did this, it had me scratching my head but once you've done it, the rest are a snap.
> 
> Was it filled with gunky oil?
> 
> Ray


                              I have not had much luck shining light into the area with the actuator.  I can't get that end lifted up much to let me see in.  It was filled with oil, but not too gunky.  I suspect the chuck was used for dry grinding all of its life.


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## Ray C

Well, how's it going?  Did wiggling sideways help.  On the ones I did, you have to lift slightly and move it sideways.  I see that the magnets on your are aligned the same way as all the ones I've done.  Yours has a slightly different actuating mechanism no-doubt.  Anyhow whatever you do, forceful prying is probably not the answer.


Ray

EDIT:  The base looks like aluminum -fortunately for you!  One of my 6x18's has a CI base and it weighs 75lbs.  -Real fun getting it apart as I recall...


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## RWL

No dice.  I never forced it hard enough to bend anything inside (hopefully).  The wiggling sounded like it had potential, but that didn't seem to loosen anything up.  I tried putting a long wood clamp on it and putting a little longitudinal pressure on it, but that didn't do anything.  I didn't see any set screws in the actuator hub that might release the top to slide a little farther.  I didn't go over it carefully to see if there was a taper pin holding it on that was well hidden though.


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## kd4gij

try here. http://www.magnetoolinc.com/contact.php


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## RWL

kd4gij said:


> try here. http://www.magnetoolinc.com/contact.php



I may wind up having to do that.


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## RWL

Ray C said:


> Look in there with a flashlight.  Admittedly, the first time I did this, it had me scratching my head but once you've done it, the rest are a snap.
> Ray



I was able to wiggle it apart enough at the actuator end to get a look.  The actuator is a coarse screw - probably a multiple thread screw - that just pushes and pulls the magnet pack back and forth.  What I thought was just an oil fill plug at the opposite end is a pair of back to back set screws that apparently keep the magnet pack from going too far toward the opposite end when the magnet is turned on.  It must be for aligning the magnets with the top for maximum strength. The strategy seems to be to turn the actuator in the on position, which unscrews the pack from the screw.  The problem is that it hits the opposite wall before it's fully disengaged.  Even lifting it up a little hoping to guide it out of the bottom doesn't seem to be doing it.


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## kd4gij

there must be a lock ring on the screw then.


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## RWL

kd4gij said:


> there must be a lock ring on the screw then.


Where would I find it?  I don't think it would be inside the case because I don't think there's a way to reach it in there.  There is what appears to be a narrow spring steel shim beneath the head of the actuator, but I can't see any break in it to allow it to open and let the actuator slide out or into the case.


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## Ray C

Definitely sounds like a slightly different configuration than the ones I've worked that had the lever on the side.   I wish we lived nearby.  I'm intrigued.


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## Dave Smith

Ray--I enjoyed this forum and I have a question for you.  are all walker 6x18 manual chucks filled with oil?  I rebuilt mine and it had no oil in it at all.  I had to design and make the shaft and cam pieces by myself because I didn't know any specs for them--well I finally got them made and used grease on all moving parts and put it back together.  It works good finally but will not having oil in it bother it later?   it was quite an ordeal of assembly/disassemblys untill I got the cam made to lift inner end of magnet and slide it just enough to line up without hitting end.   I don't want to take it apart again unless it quits working.     Dave


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## Ray C

Dave,

I truly don't know if all mag chucks have oil in them.  I've taken apart 7 units from about 4-5 different brands and all had oil.  That's all I can say for sure...

Just yesterday, I noticed my 618 CERAMAX was stiff to operate.  I flipped it over for about an hour or so (purely due to other things going on) and it worked fine afterward...  It seems to help for the ones I have.   I could indeed imagine newer ones having some sort of long-lasting synthetic coating or plastic that obviates oil.  -Maybe, but that's just a guess on my part.

Ray



Dave Smith said:


> Ray--I enjoyed this forum and I have a question for you.  are all walker 6x18 manual chucks filled with oil?  I rebuilt mine and it had no oil in it at all.  I had to design and make the shaft and cam pieces by myself because I didn't know any specs for them--well I finally got them made and used grease on all moving parts and put it back together.  It works good finally but will not having oil in it bother it later?   it was quite an ordeal of assembly/disassemblys untill I got the cam made to lift inner end of magnet and slide it just enough to line up without hitting end.   I don't want to take it apart again unless it quits working.     Dave


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## Dave Smith

Ray--mine is not a new one---pretty old that I couldn't find any specs on it--my problem the the previous owner took it apart and tried but couldn't get the cam to work. he then just put it back together with bad parts and ----so I had no correct cam shape to go from.   You know how difficult it is to just take them apart and reassemble them--I think I made the cam and pin out of stronger material than when it was new--but I think it is asking a lot out of those small parts. I rebuilt mine about 8 years ago.  well thanks for all your info     Dave


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## Ray C

Dave,

Here's another guess on my part...  Don't take this as advice but just a guess.

If the unit is more than 15 or 20 years old, I'd say it was meant to hold oil.  If the PO took it apart, he may have drained the oil and not refilled it -not knowing any better otherwise.


Ray



Dave Smith said:


> Ray--mine is not a new one---pretty old that I couldn't find any specs on it--my problem the the previous owner took it apart and tried but couldn't get the cam to work. he then just put it back together with bad parts and ----so I had no correct cam shape to go from.   You know how difficult it is to just take them apart and reassemble them--I think I made the cam and pin out of stronger material than when it was new--but I think it is asking a lot out of those small parts. I rebuilt mine about 8 years ago.  well thanks for all your info     Dave


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## Dave Smith

yes Ray that was probably what happened--I know if I have to work on it again that I will drill and tap a small hole in on one end to fill and top off with oil--I can think back how inconvient it would be to fill it with oil each time I dissembled it----it was difficult and wearing on me just to figure a new cam and linkage---at least I didn't give up on a hard challenge.  I admire you for fixing as many as you have.  thanks for all your info.   Dave


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## Ray C

I think one of the reasons they're typically not topped-off with oil, is because it will eventually leak out of the operating lever thru-hole.  I've not seen a unit with a bearing to support the shaft so, a good deal of pressure invariably ends-up on the seal.

Oh, no need for admiration -not in the least.  I live to take things apart and have a pretty good track record of successful reassembly...

I'm really sorry yours is putting up so much struggle and in a way, I feel badly since it was my suggestion to take it apart.  On the flip side though, it was previously not usable so at the least, it's a learning experience...

Ray



Dave Smith said:


> yes Ray that was probably what happened--I know if I have to work on it again that I will drill and tap a small hole in on one end to fill and top off with oil--I can think back how inconvient it would be to fill it with oil each time I dissembled it----it was difficult and wearing on me just to figure a new cam and linkage---at least I didn't give up on a hard challenge.  I admire you for fixing as many as you have.  thanks for all your info.   Dave


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## RWL

The technical staff at Magnetool sent me instructions on how to disassemble the chuck.  Different than I would have thought.  I'll have to put two of the screws back in.  Their instructions say to pry the chuck top off of the magnet box and grind the top and magnet box if either need it.  That's a lot different than what you see on the net where the instructions are to never separate the magnets from the top.  On reassembly they say to grease the top of the magnet box with Molykote Grease BR2-5 or equivalent and say not to use regular machine grease.  The case was filled with oil, so here's another one with oil in it despite the advice to grease the top.  I don't have time to work on it tonight, but hopefully tomorrow I can get it apart and show some pictures.


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## RWL

I got the top off.  For those with a Magnetool Magnetic Chuck, here is the procedure:                                                                       .        .                                                                                         1.  Remove  all  screws  with  the  exception  of  the  2  screws  on  the  opposite  end  of  the  ON-OFF  knob  and  on  each  side .     2.  Loosen  the  two  remaining  screws  but  leave  enough  thread  in   the  top  p l a t e  so  these  two  screws  will  act  as  a  fulcrum.    3.  With  a  screw  driver,  using  the  ON-OFF  knob  as  fulcrum,  pry  the  top  p l a t e  up.  This  leverage  will  "break"  the  top  p l a t e  from  the  magnet  box.  Pry  only  enough  to  insert  small  screw  drivers ,  flat  pieces,  or  wedges  between  the  top  p l a t e  and  magnet  box.  (On  an  8  x  24  and  10  x  15),  use  two  pieces  per  side  or  two  pieces  long  enough  to  go  more  than  half  way  across  the  chuck. 
 4.  Remove  the  two  remaining  screws.  Lift  off  the  top  p l a t e . 
 CAUTION:  Keep  the  wedges  in  place  u n t i l  the  top  p l a t e  is  completely  removed.  Regrind  magnet  box  and  underside  of  top  p l a t e  if  necessary.  Photos below of magnets in off position, the top off, closeup of actuator screw, magnets in on position.  That's epoxy between the magnets and a box holding them all together.  My questions now are:  What's an equivalent to Molykote BR-2?, and what gear oil is compatible with that grease?  Man, the text editor for the forums is not particularly user friendly.  I tried to format this into paragraphs and spaces in the appropriate places, but it won't let me.


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## Ray C

Congrats!  -And that is very different from the insides of the ones I've seen.


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## RWL

I finished cleaning it up and reassembled it.  The directions do not call for any oil, only Molykote grease or its equivalent.  I used Mobilux EP since I had it around.  I need to look it up to see if it's an equivalent, although since it's an extreme pressure grease I suspect it is.  Here are the rest of the instructions from Magnetool.  It has the instructions to adjust the off position.  That was one of the things that had been giving me problems.  I had difficulty lifting things off the chuck.  I thought the screw had worn to the point where the magnets weren't being pulled back far enough.  It turns out they were being allowed to move too far.  Turning the adjustment screw in fixed that.                                                            ,                                    .                   .    5.  To  keep  the  end  play  in  the  operating  screw  to  a  minimum,  use 
the  following  procedure: 
(a.)  Replace  magnet  box  with  operating  nut  in  casting. 
(b.)  Turn  in  operating  screw. 
(c.)  Drop  yoke  in  place. 
(d.)  Move  operating  screw  back  &  forth.  Take  up  excessive  play 
with  shims. 
Note:  If  casting  does  not  have  Bushing  (1256-3)  it  must  be  d r i l l e d 
and  reamed  to  7/8"  d i a .  so  the  bushing  can  be  pressed  i n . 
6.  Grease  the  top  of  the  magnet  box  with  Molykote  grease  #BR2-5  or 
equivalent.  Do  not  use  regular  machine  grease.  Put  four  screws  in  the 
casting  -  two  on  each  end.  Hold  the  top  p l a t e  at  an  angle  and  place 
the  threaded  holes  of  the  top  p l a t e  on  the  two  screws  at  one  end  of  the 
casting.  Let  the  other  end  down  on  the  other  screws.  The  top  p l a t e 
will  be  drawn  to  the  magnet  box  with  a  great  deal  of  power  and  snap. 
(Keep  fingers  out  of  way).  Turn  the  four  screws  in  loosely  before 
turning  the  chuck  over. 
7.  Adjust  the  "OFF"  position  with  the  set  screws  located  in  the 
end  of  the  c a s t i n g . 
(a.)  Loosen  set  screw. 
(b.)  Turn  handle  to  "ON". 
(c.)  With  the  s t e e l  piece  on  the  chuck,  move  the  handle  slowly 
to  "OFF"  at  the  same  time  trying  to  move  the  s t e e l  piece. 
When  the  s t e e l  piece  comes  off  with  ease,  hold  the  handle 
in  that  p o s i t i o n .  Move  the  set  screw  in  u n t i l  it  r e s t s 
against  a  solid  stop  -  which  is  the  end  of  the  magnet  box. 
This  prevents  the  magnet  box  from  moving  too  f a r .  Replace 
the  locking  set  screw.


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## RWL

Further follow up on the chuck.  I spoke with an engineer at Magnetool today.  They do not use oil in their chucks, just grease.  He said that Walker and the foreign manufacturers use oil in their chucks.  They haven't used Molykote grease in decades and said that NAPA bearing grease is what they use.  Their chucks contain ceramic magnets and don't suffer from removing them from the top plate.  He said the magnets were actually in the epoxy between the steel bars of the magnet.  The old Alnico magnets lost charge if removed from the top plate, ceramic ones don't.  They rebuild all makes of magnetic chuck and have the capability to recharge old Alnico magnets.


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