First time using a milling machine

Hello all

thought I would share my first experience using my newly bought milling machine

although the quality of the part I've made isn't great I'm sure with some more practice it should improve

anybody have any tips on getting a smooth finish and recommended cutting speeds?

Im working with aluminium

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

The usual advice when milling is to use either a flood of coolant or none. The argument being that a little coolant just stops the chips from being flung out of the way. My experience is that with aluminium the occasional squirt of WD40 is beneficial - I think it helps to stop build up on the cutting edge. I'm sure paraffin would be as good, the WD40 just happens to be in a convenient spray can.

HTH

Rod

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

Thank you all

i will slow the speed Down a bit and take my time for the next pieces and try fluid as I did not use any previously and there was times when the alu clogged a bit again I'm learning as I go

I've read that techniques such as climb milling are useful so feeding the work against the cutter

on this piece I made I just went back and forth most of my time was taken up setting the work piece I guess this is where accuracy comes to play

I'm certainly enjoying it so far especially if the mechanism does actually work

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.

The term either flood or cut dry relates mainly to carbide tools. HSS tools are best with some lub like kero on aluminium, or WD 40 works OK.

When will the A - 340 be finished. Ian S C

Mike I'm not sure what you mean by rake head?

I created this structure from the above drawing at roughly the size it needs to be to fit into the rear of the wing trailing edge

as in the full size there isn't a lot of room under there especially with spoilers and servos underneath

this prototype was just to get a feel for the machine as I've never used one before

the problem with it apart from a few rough edges is the top part of the angled edge

a carriage has to slide up and down and this bit needs to be very accurate I really need a thinner end mill

what I should have done was mill out all the gaps parallel in one go instead of re setting the work piece

the angled slope was actually cut with a jigsaw and sanded smooth with a belt sander

that was my 2nd mistake because it's not straight enough really

the sliding carriage is going to be the most difficult piece to make

it will probably take another 12 months to finish the plane completely as I keep adding more scale detail I must also consider the weight as it's intending to be a flying model (I hope)

In order to make any sensible suggestions it would be useful to know what the material is, presumably an aluminium alloy rather than straight aluminium? Also, what sort of milling machine you have, and what is the overall size of the part, I assume not full size.

Regards,

Andrew

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

Here are some pictures of the machine I'm using

the alu is 1/4inch thick not sure if it's alloy ? It didn't say in the listing I bought from ebay it is extruded alu

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

=) same mill as the one I started with although mine was the long table in red from ArcEuro =) - just put a cutter in the chuck and hold a DTI or regular dial gauge perpendicular against the smooth shank as it rotates - the needle shouldn't move more than 0.002" or 0.05mm if your metric like me. For comparison I bought my ER25 collet chuck from **LINK** and it is almost bang on spec at 0.0008 - I did change the C spanner for a safety type to save my nut and my knuckles.

you enemies are the adjustment of the gib strips (they go from to loose to locked with little in between), and that tilting column might be the source of deflection later down the line

- the best, easiest and cheapest thing I did was, change the steel gibs to brass which meant I could tighten the table up more and it wouldn't lock solid - this really gave me great stability and only cost a few quid, just mill a 55° angle on a couple of bits of brass - I laid mine flat on the table and cut steps in the X direction and finished with a file, then flipped it over and aligned it with a DTI in the chuck and away I went again - cheap and easy but effective.

The only reason I sold it was the 150w motor, after I'd gone through and eliminated the weakness I could without spending a fortune (well the column was £35 + £60 postage from LMS.com in the states) I was then at a point where the only thing stopping me taking bigger cuts was the power of the motor - I was going to upgrade that too, but thought better of it and eventually settled on a Chester Champion 20V.

I found the 150w motor just couldn't pull the high speed range unless cutting wood or plastic, so I used the low range with better results and it gave me more cutting power - just keep at least one pinion gear for the motor spare - they sacrificial although I only ever broke one when fly cutting with a blunt cutter

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.

Derek,

Would you not get the caps with new brushes?

search "motor brush cap" on eBay, there are a host of various size generic Chinese ones - any good??

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.

Well tonight's progress has been halted

End mill has broken

it looks to be a 4 flute hss type so I'm going to try a 3 flute it was clogging up quite a bit

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

A couple of years ago I got some from here:

**LINK**

Do you know the thread/pitch 'cos I have some here if they just plastic discs or are they the ones with a threaded brass insert?

BC

Edited By Dave Daniels on 03/06/2014 20:43:48

Edited By Dave Daniels on 03/06/2014 20:46:21

Thanks for the advice everyone still much learning to do

Andrew would what thickness end ill should I use for the part it's around 4inch long and 1/4 inch thick extruded alu