Magnetic chucks on smallish mills

I've seen a few threads asking about magnetic chucks, but they've not (so far as I could search) been very illuminating (to mix metaphors...!)

I have a Wabeco mill and am curious as to whether I could use a quality magnetic chuck on occasions when it would be very convenient (and possibly more accurate) to be able to access '5 sides' etc. without removing the workpiece.

There clearly ARE many quite industrial MCs on the market for pretty substantial work in a mill, but has anyone used an e.g. 6" x 4" Vertex or similar to do milling work?

(And, yes, I know that I could probably spend some time setting up the workpiece with all manner of other bits and pieces I have, but that's not my question!)

I appreciate that it would need extra care - flatness, cleanliness, adequate pole coverage etc.

Many thanks.

There is probably a clue to the answer in that mag chucks of the table variety have side and end fences, so spacers can be inserted between the fences and the workpiece to prevent any lateral movement. However have only seen these on one end and one side, so any side pressure on the other two sides might move the workpiece.

Have only used my Eclipse mag chucks on the surface grinder (and on the bench) so haven't experienced any milling problems to give an answer.

If you are in Preston area of Lancs you can borrow one of my Eclipses and try it - but no digs into the table!

Phil

My understand is that magnetic chucks are designed to take light constant loads, as in grinding, not the big intermittent loads associated with milling.

There are low-profile clamps designed to hold work in the way you suggest, or use a milling vice with stepped jaws. In either case cuts will still need to be kept light.

Neil

When I messed with magnetism I found that it was great in the vertical but far too variable in the horizontal "sliding" directions

I thought magnetic chucks were only for surface grinding, but perhaps that reflects where I have worked and their 'custom and practice' Ii guess light cuts & fairly fast cutter speeds but fly-cutting - possibly not !!?

SteveW

I well remember suggesting to my toolroom foreman, as a young and much too clever apprentice, that "I didn't understand why we messed about with bolting components/material to the mills and jig borers when there loads of spare magnetic chucks lying aroung on the grinders".

His reply was both loud and full of expletives that are not suited to a family site like this.

But roughly translated he suggested that if I ever contemplated putting a magnetic chuck onto a mill then I should be aware that I would very soon find it inserted into the main downward pointing orifice in my body. He then went on to explaiin in a very kind way that the loads generated on a grinder were nowhere as large or interupted as those created by a milling cutter. The milling cutter may have been removing substantial amounts of metal at any one time, whereas the grinder "cut" would be measured, in the pre-Napoleoic measurement days, in a few thou or tenths at most.

Simply put I guess my advice is clamps/vices for milling and magnetic chucks for grinding alone. HTH.

Edited By jason udall on 22/07/2014 16:21:00

I do have sympathy with the general opinion that Magnetic Chucks are best used for grinding, but I would just mention that we had [and used] several round ones on Lathes, when I worked at BAe.

MichaelG.

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See here

Edited By Michael Gilligan on 22/07/2014 18:12:13

Edited By Michael Gilligan on 22/07/2014 18:13:15

Yes, interesting re lathe use as this is possibly the worst type of 'disengaging' action - a complete twisting of the workpiece???

Also, looking at the page MichaelG links to, I see flat mag chucks annotated "Standard shape of magnetic chuck for most grinding, cutting, milling and lapping purposes."

I spent many years round trade shops as a procurement engineer and have never seen a magnetic chuck on a mill, I have an 18inch chuck on my J&S 540 and I dont think I would try it on my mill,When grinding thin or small area work I usually stop the work from moving under load by using gauge plate parallels ,which are thinner than the work,hard up against the workpiece . Now when you think about it work skidding on a mag chuck on a grinder is potentially more dangerous than work moving on mag chuck on a mill,on a mill the work may be spoiled but it will not go flying around the shop milling very light work with very small cutters may be possible on the top surface but not around the sides ,but I let someone else try it first . Once a mag chuck is installed on a grinder its best left in place to maintain the accuracy,grinder operators in industry are very fussy about their chucks. Overall its better to find another method to hold work on the mill.

I just noticed hat Eclipse have some items available at Half Price.

... the file name is a bit of a giveaway

MichaelG.

tried it with a medium eclipse chuck a few years back. Work piece moved and scared the living day lights out of me.

Not worth it- secure it with clamps, as has already been said the intermittent nature of the cutting action moves things.

Never tried it on the lathe with a circular chuck- any any experience?

Ian

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We had no problem with light cuts on on a particular item, but I'm still unsure about their general applicabilty. I do note that the chucks are rated in terms of Newtons per square centimetre ... presumably therefore, workpiece design [contact patch] is a significant factor.

MichaelG.

Yes I spotted the N/cm2 bit for one MC - it was 27, which is about 40lbf/sqin. This seems pretty low when you start to calculate the cutting forces and add on the safety factor and coeff of friction for an oily bed.

A friend just gave me a 8" circular magnetic chuck. He used to run an engineering manufacturing and jobbing works. The chuck has a small tapered hole in the middle for pinning a locating boss made specially to match the centre diameter of the work piece.

He told me it was used on the lathe a rather nice DS&G hmmm I wish! to face thin disks and that with a fine feed and small depth of cut it worked well, The pin in the centre stops parts being slung off.

It needs a new back plate to match my lathe, When I have made one I will give it a try and post the results.

Regards
John

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You lucky man !!

MichaelG.

I have a round magnetic chuck which I use on my lathe in exactly the way John McNamara describes, it works very well even on small items. You can only take fine cuts but I find it extremely useful.

Regards.

David.

Edited By David Colwill on 23/07/2014 09:34:19

I have tried the superglue chuck but found it a waste of time. I usually have more than 1 item to make and the mag chuck wins every time.

Regards.

David.

For thin stuff I have used the method I used to use when I was wood turning; a block of wood, sheet of paper glued on, then the item glued on that ( for wood just use white PVA glue), after the job is done, a chisel between the two bits, and the paper splits, for wood, quite a large bowl can be done this way, and you can get stuck in, I'v never had a failure. Ian S C