Do Magnetic Chucks Retain Chips?

[HAP]

Been considering looking for a magnetic chuck for work-holding on a mill table when clamping plates and such. But I was wondering, wont all of the chips be attracted to the magnetic surface and cause other problems? They seem to be useful in some applications, however, I have never used one. Just curious.
HAP

[tdmidget]

Magnetic chucks are for grind, not milling.

[macona]

You can do light cut on mills and they do make mag chucks for lathes as well.

Yes, chips will stick... Big time... Not necessarily on the plate you are milling though, the exposed areas.

[Liger Zero]

Magnetic chucks are for grind, not milling.

Only if you lack imagination.

And yes... they do retain chips. Brush or blow between cycles.

You have to be careful though, you can launch parts if the force of the milling overrides the magnetic force.

I had a production job that I used a small magnetic chuck from a DOA grinder. I set it up so you put the part between two restraint fingers, turn on the mag for "grippyness" and then start the CNC program.

Low tolerance, very forgiving job... but high volume. Brackets for a "custom installed closet racking manufacturer."

[George Bulliss]

We had one on a CNC mill at the last place I worked. It was made specifically for mill use. Even with the degaussing feature, chips retained plenty of magnetism and it looked like a pain to clean up afterwards.

Also, we had several blocks shift while using it. The answer to that was to block things in with clamps and rails, but by the time all that was done, it usually took longer than traditional methods to set something up. Since milled items are typically a little rougher than what you run through a grinder, it didn’t take long before the magnet was all dinged up.

I was less than impressed, but the guy that talked the boss into buying it seemed happy.

George

[Carld]

I would not want to use a mag table on a mill or lathe. The thought of the part flying off the mag chuck scares the heck out of me. I used to run a Blanchard grinder and sometimes it would throw the part off and it was a good thing there were heavy shields around the table. The Blanchard is a controlled feed just as a mill or lathe would be but parts still came off.

I have also had parts fly off a manual and automatic surface grinder. Mag tables and chucks can be dangerous.

Unless you put heavy shields around the mill table or the lathe chuck it could kill or injure you or someone else.

[Dan Dubeau]

I've use one on the CMM before for a quicky fixture for measuring large quantities of stampings. Set up a couple of secondary and tertiary datum points, and use the mag chuck as primary. first part of the program picks up the part datums, co-od shifts to the part, and measures the rest of the features. REALLY make things go quicker. Only turn on the mag half way though, as full would suck the part flat if it was warped.

[Mcgyver]

I would not want to use a mag table on a mill or lathe.

mostly I agree with that Carl, the cutting forces with most milling just are not compatible with the mag chuck's holding power...but there are always exceptions and we don't know excactly what you're planning on doing. I need to taper some thin pieces and use a sine mag chuck....the work HAS to go against a fence and you take the lightest of light cuts.

imo it's some you can press into service for very rare weird job but I wouldn't go acquire one for general purpouse milling; they just don't hold well enough with enough force. One use I can see is if you're mlling a lot of thin plate that has to be fully supported...still I'd use a couple of strap clamps as well to stop shifting....the mag chuck would allow the clamps to be easily repositioned as required

[Carld]

I'm with you, if done carefully it will work but we all know we sometimes get in a hurry or take chances. When I have a setup I am leery of I always take it slow. I have never used a mag chuck to machine parts and just don't feel it's a good idea.

[winchman]

It seems like the holding force would gradually decrease as the chips built up on the table.

You can turn the table "off", but the chips may retain some magnetic attraction, which would make removal a hassle.

[Walter]

I've never milled on a mag chuck, although I might be inclined to try it in a desperate situation. Most likely not. I'd definitely hope it would be a good electromag, not some worn out Perm mag =) On the other hand I've done a ton of pressure turning and never had one issue.

I HAVE had parts come off a mag chuck, I HAVE had wheels blow up. For those that haven't experienced it count yourselves lucky and hope you never do. It's rather scary, several minutes after you get past the initial shock of a catastrophic wheel failure. Last time took me several days to even go near that $&$^# grinder again.

[PeteF]

We had one on a CNC mill at the last place I worked. It was made specifically for mill use. Even with the degaussing feature, chips retained plenty of magnetism and it looked like a pain to clean up afterwards.

George

George, I take it then that work held in a magnetic chuck (permanent magnet type) will be magnetised to a greater or lesser extent after being placed on a grinder's chuck? I'm just waiting to pick up my surface grinder (cursing Christmas/New Year as all the business' closures ) and am finding there's a heck of a lot more to this grinding business than I initially imagined!

[Jaakko Fagerlund]

It seems like the holding force would gradually decrease as the chips built up on the table.

Umm, no, the force remains the same. Otherwise it would mean that bigger objects would be held with less force than smaller ones

I'd definitely hope it would be a good electromag, not some worn out Perm mag

If it is an old chuck that has rare earth magnets then yes, it wears out over time, but nowadays the chuck have neodymium magnets which retain their magnetism unless heated too much or shocked very good.

At least on a surface grinder cleaning up is easy, if you attach a hose to the coolant pump and put a ball valve on the end to use it when needed Just switch off magnet, take the hose, open valve and slosh away the chips.

[Dan Dubeau]

I HAVE had wheels blow up. For those that haven't experienced it count yourselves lucky and hope you never do. It's rather scary, several minutes after you get past the initial shock of a catastrophic wheel failure. Last time took me several days to even go near that $&$^# grinder again.

I've never had one blow up on me personally but have had the same guy blow a wheel up on back to back days with me on the next grinder behind him. This was in college. First time I chalked it up to an accident, **** happens, second time, I never worked within 20 feet of him. Same guy also launched a chuck key, and was responsible for the ubiquitous motor housing dent on the mill.

First time he was winding the wheel down to dress it, and talking to his buddy about the weekend. crashed it into the diamond dresser. 2nd was forgetting to turn the mag on, part shifted (sine vise up at a 45) and BOOM. I caught a piece of shrapnel from that one in the forehead. Still makes me think every time I use the grinders.

[Walter]

Dan, yup!

I'm extremely cautious anymore. there is no time between oops and boom. I've done a lot in my life but rarely anything that drives a point home like that, by the time you realize something bad happened it's been over and done for a while, but the dust probably hasn't settled yet.