magnetic chuck for milling machine

[aytactParticipant @aytact]

Hi,

Recently I have purchased Warco WM18B and relevant accessories.

I need to clean surfaces of 6 mm x 30 cm mild steels with fly cutter and vice can not support whole length.

My options are either buying another vice or buying a magnetic chuck. I can not think any other option.

Do you ever used magnetic chuck on milling machine? Which one do you suggest?

Or do you have other opinion?

Thank you

[JasonBModerator @jasonb]

Magnetic chucks are not really made to take great side loads so your flycutter may well just launch the bar across the workshop, though suitable placement of stops will help. I am assuming it is the 30mm face you want to work on.

A better approach may be to buy or make some low profile side clamps which will grip the edged of the bar and pull it down to the table leaving the top clear for machining.

If you have a lot to do consider getting a face/shell mill as you will be able to feed a lot faster than you can with a flycutter.

[noel shelleyParticipant @noelshelley55608]

I’m with Jason, The forces involved may be more than a magnetic chuck will hold. These units are not cheap – even second hand and to hold 300mm you will need a big vice. Noel

[Neil LickfoldParticipant @neillickfold44316]

There are mag chucks for milling machines. Really expensive and need care using them. When the material gets thin, ie under 4mm thickness, their ability to hold properly really starts to diminish. Even with packers around it.

Vacuum chucks work really well on supported thin stock, and so does double sided tape also works well. Just can’t expect to be taking big cuts or cuts with high loads. Sharp tools help to keep the loads down.

Need to be careful taking thin stock off that has been held down with double sided tape as it can bend etc.

A plate held in the vice or clamped to the mill bed can be used.

Got a pic of the part? There are many ways of holding parts these days and there are also non traditional vices that work well for parts that a normal vice does not hold well. Can be made from 2 long pieces of steel, with hold down bolts and studding or bolts to bring together etc.

Then there is the softjaw method, where it is cut to support the part and has slightly tapered sides to force the part to fall to the inner of the softjaws instead of flexing up for example.

Neil

[bernard towersParticipant @bernardtowers37738]

Im with Neil sharp tools are the secret I do some turning with a magnetic chuck on my S7, boxing parts in helps as well. One of the problems encountered is fitting parts to amag chuck that are too thin as they are under the focus point of the magnetism.

[peak4Participant @peak4]

My ow magnetic chucks are both 5×10″ so just too short, but 12×6″ are certainly listed in the Eclipse range.
The ones my size are often expensive on eBay, but as you get larger, they sometimes get cheaper, and are often collection only, which might work to your advantage.
Yes I have used mine on the Centec for similar jobs, but there’s a few things to consider.
One is surface finish on the chuck side of the workpiece, as a poor finish will adversely affect the magnetic circuit, and thus the holding power.
Consider the direction of cut and loading, then make sure the end and side stops/fences are in the right places.
For a long narrow workpiece, you’ve not listed the width, I’d add a pair of thinner strips either side of your workpieces, say 5mm thick, to add more resistance to sliding.
One problem is chip clearance, less an issue with a fly cutter, or maybe a shell cutter, but certainly a potential problem with smaller mills and slot cutters. The chips don’t clear well leading to a poor surface finish, or even cutter breakage. Vacuum and paintbrush helps clearing up after a run when changing workpiece.
I was looking for an on-line copy of the Eclipse manual, and found one on here;
https://www.model-engineer.co.uk/wp-content/uploads/sites/4/documents/eclipsemagneticchuckhandbook.pdf
There is a specific section on milling using a mag chuck.

The later brochure is available on their own site, and even lists a model called Supermill, though I guess you’d need deep pockets to buy new.
https://www.eclipsemagnetics.com/site/assets/files/2866/magnetic_workholding_literature.pdf

Bill

[Clive FosterParticipant @clivefoster55965]

The problem of holding thin work for operations on the whole upper surface is an old one and various methods have been developed to keep the job in place. Unfortunately naming conventions are, um, “inconsistent”.

Time to research toe clamps, edge clamps and hold-downs for something either affordable or DIY friendly. Unfortunately searches for hold-downs generate a lot more wood worker specific information than metal worker stuff.

There are various devices using a screw and wedge principle to generate both sideways and downwards forces. For example Mitee-Bite sell most versions. Variations on the eccentric tightened style appear to be the most favoured DIY version.

Its often necessary to put the job on a flat spacer to make room for the clamping device to work.

The primary old style devices were hold-downs used in conjunction with a vice or solid stops to generate the necessary forces. Basically a shallow triangle with the shallow end having either a sharp edge or small radius and the deep end either angled a bit over 90° relative to the base (92° – 95° are typically specified) or having a larger radius. Pushing the device down against the stop with the sharp end a bit above the middle of the job thickness generates both downwards and horizontal forces needed to keep things in place.

Couple of pictures found on the internet of the Starrett 54c hold downs. Commercial product and slightly more sophisticated than a simple wedge. The size pictured is about 4″ long

End profile

In use

One oft confusing point about hold downs is that they can be made to work either pointing downwards, which intuitively appears more correct, or pointing upwards as in the picture above. The angle on the short side defines which way up they work. Putting them in upside down will lift the work. All the textbook diagrams I’ve seen show the pointing down variety but Mr Starrett must have had a reason for going the other way.

Clive

[Chris GunnParticipant @chrisgunn36534]

If you have a lot to do, you could always make a jig to hold the bars, from thicker bar you could bolt to the machine bed. clamping by a series of 4 or 5mm screws holding the edge, or a 300mm long hold down.

Chris Gunn

[duncan webster 1Participant @duncanwebster1]

Clamp it down both ends and middle, skim what you can access. Fit 3 more clamps, remove first three and do what’s left. Might not be perfect, but easy

[Chris CrewParticipant @chriscrew66644]

I would consider sweating the part you can’t hold to a piece of material you can hold with soft solder. Then simply un-sweat it off and clean it with wire wool afterwards. I have done this with parts that are hard to hold in a conventional 3 or 4 jaw chuck.

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