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Magnetic chucks on smallish mills

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Use of Magnetic Chucks for Milling and Turning

Use of Magnetic Chucks for Milling and Turning

Following questions on the use of magnetic chucks for milling and turning, we have been supplied the following manuals for the use of Eclipse magnetic chucks.

RJKflyer22/07/2014 10:46:24
49 forum posts
3 photos

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.

Robbo22/07/2014 11:31:47
1504 forum posts
142 photos

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

Neil Wyatt22/07/2014 12:17:47
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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

Ady122/07/2014 12:27:28
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3462 forum posts
513 photos

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

SteveW22/07/2014 12:30:33
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110 forum posts
10 photos

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

MadMike22/07/2014 13:05:02
181 forum posts

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.

jason udall22/07/2014 16:19:32
2004 forum posts
41 photos
Hold DOWN force is a function of number of poles covered ( area) , gap ( how flat base of part is)...and material. ...
Now I have seen a few jobbing milling shops...never seen mag chucks on mills..all over the place for other jobs...

One place I have seen them used...palletised jobs on cnc mills.....pallet held down on to dowels...to allow quick change "floor to floor"..

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

Michael Gilligan22/07/2014 18:09:33
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12779 forum posts
554 photos

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.

.

See here

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

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

RJKflyer22/07/2014 18:19:31
49 forum posts
3 photos

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."

Nigel McBurney 122/07/2014 20:04:43
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549 forum posts
3 photos

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.

Michael Gilligan22/07/2014 20:22:09
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12779 forum posts
554 photos

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

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

MichaelG.

Ian Welford22/07/2014 22:37:03
272 forum posts

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

Michael Gilligan22/07/2014 23:10:39
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12779 forum posts
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Posted by Ian Welford on 22/07/2014 22:37:03:

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

.

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.

RJKflyer23/07/2014 07:46:02
49 forum posts
3 photos
Posted by Michael Gilligan on 22/07/2014 23:10:39:
Posted by Ian Welford on 22/07/2014 22:37:03:

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

.

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.

John McNamara23/07/2014 09:04:52
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1285 forum posts
113 photos

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

Michael Gilligan23/07/2014 09:14:04
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12779 forum posts
554 photos
Posted by John McNamara on 23/07/2014 09:04:52:

A friend just gave me a 8" circular magnetic chuck. ...

.

You lucky man !!

MichaelG.

David Colwill23/07/2014 09:33:56
563 forum posts
32 photos

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

steamdave23/07/2014 12:24:05
403 forum posts
34 photos
Posted by David Colwill on 23/07/2014 09:33:56:

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.

Note quite the answer to the original question, but for occasional use on a lathe, a superglue chuck would be a lot more compact, lighter and cheaper for the small jobs that seem to be mentioned as being suitable for magnetic chucks. Also, a superglue chuck can be used for non-ferrous work.

Dave
The Emerald Isle


David Colwill23/07/2014 12:51:07
563 forum posts
32 photos

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.

Ian S C24/07/2014 11:03:32
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7262 forum posts
227 photos

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

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