Hi Andy,

congratulations with your new toy, the more you practice the more you learn. For milling aluminium you need sharp cutters, you could try using paraffin (kerosene) as a cutting fluid. You can find recommendations for cutting speeds for various metals here. Milling aluminium is discussed here.

Thor

Edited By Thor on 03/06/2014 10:53:37

Slower speeds and even backgear can be advantageous with aluminium because they don't generate as much heat when cutting

Andy, climb milling is often mentioned on here. It is a way of removing metal very quickly. However I have not seen anybody on here mention one very important requirement, presumably everybody already knows, and that is backlash on your milling table. Wear on your lead screw and/or lead nut will create clearance and this translates into backlash when climb milling.

In order to get the best metal removal rate and a good finish it is essential that the backlash is taken out. Unfortunately many, perhaps most, hobby size mills do not have this facility. The result is severe snatching when cutting, which in turn spoils both finish and accuracy and can even result in components becoming dislodged.

As a matter of interest did you machine out the raked head cut outs by marking the shape on the metal and then locating your cutter by eye? This is where you may want to practice re-setting your work piece to allow a straight cut parallel with the outer surface.

Well done incidentally on your first attempt.

Andy,

The first work I did was on a seig SX1 mill also on aluminium, it was a budget a machine – as cheap as they come but I had good results after learning a few essentials which I'll share, I'm certainly no expert so please keep that in mind. I was cutting some cheap mushy extruded aluminium profile and it was difficult, spongy and really not ideal – a 3/4" loc-line hose made for a great vacuum to keep pesky chips out the way – they really spoil the surface finish and generate heat.

First things first, tram the mill if you haven't already and adjust the gibs and backlash on all axis – don't aim for some extreme high precision setup if you don't need it, you'll just end up wasting time aligning the Z axis and with a leadscrew nuts that are tight and it will wear out in to time, backlash is normal and working with it in my opinion is normal.

Hold the cutters with a milling arbour don't use a drill chuck, they tend to spin visibly of axis – my absolute favourite arbour is a £70 Chinese ER25 collet & chuck set, these will hold anything between 1-16mm (metric imperial etc) – I also use mine in the lathe to hold anything that fit., if you need larger diameters consider ER32 but the price jumps up a bit. – its a one off purchase you'll keep through every machine you have and they hold their value 2nd hand should you wish to sell it on – but so few come up 2nd hand for a good reason.

regarding rpm, start low – really low – 300rpm for a 4-6mm cutter and feed the material into the cutter while feeling the pressure of the cut and watching the surface finish and work your way up to a speed and feed the looks and feels comfortable – its difficult to take a number out of book and apply it as your machine or cutter might not be strong/sharp enough to withstand the forces, and the sharpness varies which makes it even harder to quantify!

I only feed X and Y at the same time if I really have to (complex curves etc) otherwise, set up and then lock anything that doesn't move (y, z and the quill in my case) and crack on in a nice straight lines.

Don't use carbide cutters unless your machine and you are capable of driving them in deep – they seem to like cutting hard and fast – they're a bit like duracell batterys – they really come in to their own on high demand application.

– more flutes doesn't equal better =), the more flutes there are, the less space there is for the chips to get out of the way. the best cutter I have is specifically ground for a aluminium and its a 3 flute, carbide with a high helix – and it will tear through aluminium at double the speed of my regular HSS and carbide bits – any less and it doesn't clear the chips and instantly clogs and makes a mess – I don't have flood cooling to clear chips and as other have said, a wet of WD or kero frequently just prevents the chips sticking.

don't go to easy on it, once its set up and rigid take nice deep cuts if the situation allows – the cutter will cut more mass in its life taking one cut 1/2 its diameter deep rather than 10 cuts at 1/20th its diameter – just get stuck in =)

remember these are just uneducated experiences – I hope some of the points might help and I'm sure people could spend all day pointing out errors in my ways – I'm just trying to keep it simple for myself – I'm not aiming for perfection unless the scenario calls for it – its surprising what can be polished out…….. =)

All the best,

RussB

Hi Anthony,

Try to get some HE30 aluminium alloy, it machines really nicely when you get everything right.

Your machine is essentially the same as an X1, though small they are well thought of and capable of good accurate work, if you keep the cutting loads modest.

It's a good choice for making small, complex parts for scale models – a rotary table or even a relatively cheap rotary vice will make milling out complex parts a lot easier – you can rotate the work so each cut lies along an axis of the mill, so just one wheel to turn and your ribs all have parallel sides..

Neil

Hi Russ, you have obviously gone the same route as me, starting with an X1L and moving up to a Champion 20V. sadly the X1 has been out of action for about 12 months now as the small plastic grub screws that hold the motor brushes in place both shattered when removing them to check the brushes. They are not available as spares so if anyone out there has a burnt out motor I would love to buy the brush grub screws of you.

Cheers Derek.

P.S. Sorry for using your thread Andy, you have done a good bit of work for a first attempt. Better than my first efforts.

Russ

Lots of places to get the brushes but NOWHERE to get the caps. Sadly they do not come with the brushes, I suspect that any given size of brush will fit various motors, all of them having different holders. Just a guess, don't really know why.

Cheers Derek.

The metal is unlikely to be pure aluminium, usually designated 1050A. Pure aluminium machines like toffee only worse, and is normally only available as sheet, as it bends well without cracking. My guess would be 6082 (HE30 as was) which is the most common aluminium alloy, and machines beautifully.

As you have discovered 4 flutes for aluminium is a no-no, 2 or 3 flutes at most. I don't feel it sensible to give machining data, as I have bigger mills and I run with high spindle speeds and commensurately high feedrates, so not really appropriate. For pocketing a part like yours I use flood coolant, primarily to prevent sticking of the chips to the cutter and to wash the swarf away. For manual drilling WD40 seems to prevent swarf sticking to the drill.

For your part I would be tempted to chain drill the outlines to remove much of the metal, and then use the milling cutter to clean up the edges. In that way the chips can fall away rather than get trapped.

Regards,

Andrew

Andy: I'm not sure what you mean by end mill thickness. I would use a 2 or 3 flute slot drill, HSS will be fine. Since the part isn't particularly thick I would use a stub version, for enhanced stiffness. The diameter of the slot drill will be determined by the radius you want internally on the pockets. Looking at the picture of the part somewhere between 4 and 6mm? Use the largest diameter you can, as the tool will be less prone to deflection.

Regards,

Andrew

Biggest enemy for surface finish when milling is recutting the chips already cut.

Think about it, take John's drawing above and imagine the flutes full of previously cut chips, depending if the cutter is in a slot or open those chips will force the cutter either into the work [ gouging ] or away from the work [ steps ]

It doesn't take much to get the chips away, a small airbrush compressor at hobby level is plenty good enough but some form of shielding or guarding is ideal to contain the mess.

The less the number of flutes for alloy the better, this is to give space for the chips and to try to prevent the recutting. They do make just single flute cutters especially for alloy.

Aluminium is a nice material to machine being soft, most alloys that is. The pure sheet alloys are very gummy as mentioned but they are not easily available in bar form so most bar forms cut well.

Some form of coolant is a must, more for stopping the alloy welding to the cutter than actual cooling. Not much is required and as been mentioned Paraffin or WD 40 is ideal or make your own cutting fluid up with a 75% paraffin mix and 25% neat cutting oil, hydraulic oil or ATF, that red automatic transmission fluid.

On hobby machines you will have no maximum speed limit of Aluminium and the fast the cut the better. Run fast, light cuts and many of them.