Rectangular magnetic chucks for milling?

[choochoo_balooParticipant @choochoo_baloo]

Hello all. I was browsing the Eclipse Magnetics (current generation of Sheffield made stuff) catalogue, and am curious as to whether a rectangular magnetic chuck would make a a traditional vice redundant for milling ferrous work?

From my initial understanding:

1. Large clamping contact area (via the magnetic field lines) in contrast to the two jaws
2. Due to one, less vibration/resonance through the work as cuttetr works?
3. Easier to hold weird shapes by using those flux extender blocks vs say normal screw clamps that may obstruct the cutters route

On a downside:

Wont all work have residual magnetism?

If so, how is this overcome aside from an expensive demagnetiser?

[choochoo_balooParticipant @choochoo_baloo]

[not done it yetParticipant @notdoneityet]

Never thought of work pieces that are not flat?

[Paul KempParticipant @paulkemp46892]

I don't think I have ever seen a magnetic chuck used for milling, only grinding. I don't think I would be at all confident using one on a mill to do anything but very light work and managing the swarf would surely be a problem?

Paul.

[JasonBModerator @jasonb]

OK if you don't mind your work flying off the table. Not that strong a hold and even when grinding they have a stop on one edge to help stop the work being thrown off.

[martin perman 1Participant @martinperman1]

I managed to chuck a lump of metal off a grinding table whilst grinding as an apprentice, I certainly would not even consider them whilst trying to mill a piece of metal.

Martin P

[larry phelan 1Participant @larryphelan1]

I bought one of those chucks,thinking it would be good for milling. Big mistake ! No way will they hold a workpiece firm enough,might be OK for grinding,dont know about that. I think a good vice or good clamps might be a better idea. Failing that,stay well out of the line of fire !!.

[Mick B1Participant @mickb1]

I'd expect grinding with its continuous force and light cuts to exert a far lower peak force on the magnetic grip than the rapid succession of impacts from milling cutter flutes.

[Anonymous]

This has been discussed before, with pretty much the same advice, but there is a link to an interesting publication by Eclipse:

**LINK**

The document discusses using a special magnetic chuck for milling. They strongly recommend climb milling, which has it's own issues for MEs. Oh, and the chuck needs a 32A 3-phase supply to operate, which might be a bit spendy if you don't already have it.

I use a permanent magnet chuck on the surface grinder and nowhere else.

Andrew

[Andrew Moyes 1Participant @andrewmoyes1]

I recently tried an Eclipse magnetic chuck for light milling on a Dore Westbury. It wasn't a success and I won't do it again. The chuck and end mill became magnetised and it all became a swirling mess of swarf. That doesn't happen with a (non-ferrous) grinding wheel of course.

Andrew M

Edited By Andrew Moyes 1 on 31/03/2019 19:43:10

[Neil WyattModerator @neilwyatt]

Posted by Andrew Moyes 1 on 31/03/2019 19:42:29:

The chuck and end mill became magnetised and it all became a swirling mess of swarf.

An obvious problem — in hindsight!

[Andrew Moyes 1Participant @andrewmoyes1]

Quite.

A

[peak4Participant @peak4]

The issue with swarf is a problem, but an airline helps, provided you don't blow the swarf into daft places.

Obviously you need a good flat surface, on the workpiece to chuck interface,chuck for maximum adhesion, and even then, one can't just plonk the workpiece on the mag chuck an mill away.

It's something I do occasionally, such as when I wanted to take a few thou of a length of thin metal strip for use in the table groove on my bandsaw. I didn't have a protractor cutting guide, so needed to adapt one from a different machine. The metal strip was the right width for the slot, but a shade too thick.

Mag chuck set up on the mill, with a side and end fence to stop anything sliding off. Next to the fence was a length of steel bar a bit thinner than the workpiece, to provide something for the workpiece to butt up against. On the other side of the workpiece was a further bit of steel plate, all to maximise the area in contact with the mag chuck to stop my prospective bandsaw fence from sliding around.

It works fine with light cuts and a sharp milling cutter, though the surface finish can sometimmes be a bit poor due to the swarf scratching it.

I also have a 6" round mag chuck on a Myford backplate which is quite handy for thinning washers a little.
Same basic plan; workpiece bang in the middle, but surrounded by several concentric circles of more thinner washers, or something similar. Seems to work OK for me with very light cuts anbd a home made diamond toolholder.

As I've mentioned before, I've had little formal training, so no-one ever told be it couldn't/shouldn't be done.

I do however have a reasonable level of common sense, and a good sense of self preservation, so I don't stand in the way of an escaping workpiece; not that I've ever had one make a bit for freedom (so far anyway).

Bill

Edited By peak4 on 01/04/2019 00:05:41

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