Magnetic Chuck questions x2

[7HC]

Chuck in question is the flat permanent magnet type as commonly used on a surface grinder.

Q1: In absence of said surface grinder, can the chuck face be safely trued with a face/shell mill cutter?

Q2: Segmented (aluminum/steel or brass/steel) 'V' blocks and spacers are usually used for work-piece location.
Is this (a): to prevent the work-piece from becoming permanently magnetized, or (b): to protect the magnetic chuck, or (c): some other reason?

Thanks,


M

 

[kd4gij]

Q1) If the mill is in perfect tram you might get away with it.

Q2) Segmented V- blocks and 123 blocks are used th transfer the magnatizem ( ? spelling ) to the work pice. In outher words thay becoum part of the chuck.

 

[Frank Ford]

I suspect you could mill a magnetic chuck, but I wonder why one would want to do that. Magnetic chucks have only limited holding power, so they don't have much use other than with a surface grinder which would be the most appropriate tool for truing as well.


If you're not into surface grinding, you need to know that in general, the amount of material being removed is very small, and forces very low - generally a lot lower than even very light milling.

 

[kd4gij]

What make of chuck do you have. And what do you plan on using it for. Post up some pic's. We love pic's you know.

 

[Ray C]

Magnetic chucks can be clamped to a mill bed and "worked-on" as I've done it many times to restore old units to excellent working condition. Don't take off much -only enough to get most of the dings out of it. Don't chase after the deep ones. Make sure the bolts holding the mag chuck together are all evenly tightened or your work will be for naught.

While you're at it, make sure the bottom (base) of the chuck is not dinged-up either. Fix as needed.

The mag surface of a chuck benefits from being surfaced ground once it's been milled. Mills are only a close approximation to producing a truly flat surface. Surface grinding a whole mag chuck surface is not easy. I've done about 5-6 and each one took several hours at least.


Ray

 

[7HC]

What make of chuck do you have. And what do you plan on using it for. Post up some pic's. We love pic's you know.

It's a 6x12, but not in front of me at the moment so I can't give a name.
It will sit on the mill table of a RF45 mill from time to time when a tool grinder is attached to the mill head, thereby converting the mill to a surface grinder of sorts.

Obviously my brain isn't fully operational at the moment as I'm having trouble understanding why a regular steel 'V' block wouldn't transmit the magnetism when on the table. :thinking:

Anticipated uses at the moment would be to reduce washers and spacers to accurately sized shims.

I'll be able to attach a pic or two a bit later.

Thanks,

M

EDIT: It's a 'Kanetsu' (Don't know if that's good or bad) )

 

[hman]

Obviously my brain isn't fully operational at the moment as I'm having trouble understanding why a regular steel 'V' block wouldn't transmit the magnetism when on the table. :thinking:

OK ... think back to when you were a kid and first saw a horseshoe magnet. Now remember that it always had a "keeper" - a steel bar that went across the ends (to keep the magnetization of the iron horseshoe from being dissipated). Did you note that, with the keeper in place, there was very little or no magnetic magic going on, and it wouldn't pick up nails any more?

Now consider the magnetic table to be a bunch of such magnets next to each other - each steel slice being the opposite polarity to the one next to it. Each gap between the slices has a strong magnetic field when the table is "on". If you place a segmented V-block on top, each slice of the V-block acts as a separate extension of the table slice it's on to of. Think of adding short pieces of iron or steel to the ends of the horseshoe magnet - it still has lots of mojo to pick up nails with.

Using a regular V-block is like placing a keeper across the poles of the horseshoe magnet. The solid steel V-blocks will shunt the field that occurs between the table segments, and durn near none will appear at the "v"s. Think of magnetism as being akin to electricity - it likes to follow the path of least resistance.

Hope this helps!

 

[7HC]

OK, here's the pic.


Obviously well used and there's plenty of surface scratches but no heavy dings, holes, or hollows.
I found the strength of the magnetic hold to be amazing, but I guess that's probably normal.

Can it be damaged by mounting a steel work-piece directly on it, or must the special 'v' blocks and spacers be used?

M

 

[Ray C]

Nice looking chuck!

Nothing wrong at all by putting things on the surface. Just be careful not to scratch, ding or put shame marks on it.

Wipe the chuck and workpiece very carefully as anything between them will throw off your dimensions and also get ground-in and damage either or both surfaces. Also, don't over-tighten the bed bolts lest you bend/distort the chuck.

Ray

OK, here's the pic.


Obviously well used and there's plenty of surface scratches but no heavy dings, holes, or hollows.
I found the strength of the magnetic hold to be amazing, but I guess that's probably normal.

Can it be damaged by mounting a steel work-piece directly on it, or must the special 'v' blocks and spacers be used?

M

 

[kd4gij]

You typically mount parts right on the chuck. For washers like you refired to I trap it betwine two parallels on eather side to help hold it.