Am I being too gentle milling?

A *raw* beginner milling question (so be gentle)....

I used my new milling machine (SIEG X2P) for the first time this evening, basically to cut a 6mm slot 6mm deep in a piece of 4mm thick mild steel.

Being cautious, I feel that I "nibbled" at it with the 6mm end mill, and took too many passes to reach the depth of the slot. How deep a pass would be "sensible"? (i.e. how many passes?)

Thanks
Rod

Depends on your milling machine, you don't want to take too heavy a cut with the smaller ones, motors and controllers can go pop! I would probably do this in 3 cuts but my machine is fairly heavy with no fragile electronics. If the cutter is cutting without making horrible noises then it should be OK. A squirt of oil helps. Harold Halls book on milling is worth getting if you don't already have it. Don't worry too much about weather you are doing it 'properly', time isn't too important for hobby work, it's the result that counts.

Dave

Not having knowledge of this machine I would of thought that 2 x 3 mm or 3 x2 mm cuts would have been feasible in that piece. To much ' nibbling' will end up with your cutting edges rubbing rather than cutting & becoming dull very quickly. As you get to know your machine you will be able to 'feel & hear' what your machine is capable of.

Cheers

George.

Edited By Frances IoM on 05/05/2016 23:05:49

Well, I managed to. See the photo above.

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Frances,

I think the picture that Rod posted answers that ^^^

MichaelG.

.

Edit: You beat me to it, Rod.

Edited By Michael Gilligan on 05/05/2016 23:12:42

Well..... I compromised, still being cautious, and took 1mm cuts on the second one I needed to make. The machine and the cutter didn't complain, and the revs stayed consistent on the display.

One thing which I noticed, is that on the "exit" side, there was a pretty large noticeable burr on the edge of the steel.

Thanks for your help folks. Much appreciated. Maybe I will be a little more brave next time I need to do a similar task, and take 2mm cuts.

Rod

Edited By Rod Neep on 06/05/2016 01:13:17

Hi Rod,

I'm relatively new to machining and have a Warco WM-16 milling machine which I think is the same size or maybe just a little larger than the X2P. It has a 2MT spindle and 750W motor.

For a long time I've been using end mills and the occasional 2-flute slot drill from kit inherited from my Dad and have always taken very cautious milling cuts.

I noticed Jason.B mention the other day about trying out a roughing endmill from ARC and I've always wondered what these were like so I bought a 10mm HSS-AL 4flute and I have to say I am amazed at how much more metal I felt comfortable removing in a single pass, this was tried on EN3B mild steel to make some T-nuts. It also feels different when winding the axes, seems to have more feedback through the winding handles.

I would highly recommend anyone new to hobby machining to invest in at least one roughing endmill as it turns what can be a tedious exercise into an enjoyable step in making something on smaller milling machines. Wish I'd done this sooner.

Ed.

Edited By Ed Duffner on 06/05/2016 06:20:22

A simple rule of thumb when using the full width of the cutter is 1/4 of the diameter so 4 passes of 1.5mm, use that as a starting point and go up or down depending on the machine. One other thing to watch if you were using a 4-flute end mill is that the more it has to remove in one pass the more the cutting action will pull it to one side so you could end up with a slot wider than 6mm.

Feed rate wise again don't tickle it, about one turn of teh handwheel per second would be a reasonable starting point

One other thing, that black coating on the hot rolled bar is not kind to cutting edges

J

Edited By JasonB on 06/05/2016 08:17:33

Great information for me. On all points. Thanks!!

I really appreciate that information.

Rod

On the vertical mill I'd cut the slot in two or three passes with a 6mm cutter. On the horizontal mill straight through in one pass.

With these small cuts you are unlikely to be power limited, even on a small mill. I'd concur with JasonB; the biggest mistake is pussyfooting around with feedrates. Slower isn't better, it just rubs the cutter and squeals or chatters.

Andrew

To be even kinder to your machine/cutter, you could have removed the bulk of waste by hand......in this instance..

Hacksaw springs to mind.....

Indeed you are perfectly right....

And I am quite capable of cutting and filing a 6 x 6mm slot in the edge of that metal, especially as there was no need for fine tolerances in this case, as it is a clearance slot. (A pair of clamping plates).

But I have a new toy! And I wanted to use it.
It is all part of the learning process.

Cheers
Rod

Looking at Ketan's recent post about mini mills, it seems the SX2 has a brushless motor rated at around 500W mechanical (shaft) power. That's pretty respectable and should be capable of shifting some metal.

You should get yourself a decent block of mild steel and do some experimentation to get a feel of what are the limitations. You shouldn't be able to blow up the drive and the worst you can do is break a few cutters. You might be surprised what can be achieved.

There are plenty of free machining calculators out there - and a few paid for ones if you insist. They will tell you what maximum feed rate, depth of cut etc the cutters can tolerate, so you can use them to put a ceiling on what you try but within those it's the machine that will limit performance. What have you got to lose?

Get half a dozen cutters in and be prepared to sacrifice some of them in the name of learning - and try a roughing cutter, as suggested above. Go on!!

Murray

Rod,

I just tried the cut you made with a 6mm 4 flute ripper cutter on my old style x2 (the one with the tilting column).

Went through in one pass, 6mm deep without any significant complaining.

Regards,

Dan

Seeing Ed seems pleased with Arc's roughing end mill I have just ordered one and looking forward to trying it on my wm14

Mick

Thanks folks. This machine is obviously capable of more than I thought.

Rod

This may sound counter intuitive, but depending upon how much value you attach to your cutters, another approach would be to lay the plate flat,(as for drilling), and then use the very top of your cutter to cut the slot leaving a full rad on the bottom to be removed on a second setup. The reasons for this approach are that you get to use the part of the cutter seldom used(the top bit), thus minimising cutter flexing and preserving the bottom portion for creating square accurate corners. The life of cutters or lathe tools is measured by the time the tool is actually in cutting, so if you take three cuts, then, in theory, it will wear out three times quicker. Once the edge has gone, cutter flexing and poor size and finish will result. Roy K.

Although the rougher/ripper may go through in one pass if the work needs a good finish you will have to go through with a normal cutter to clean up the edge so choose your cutter diameters accordingly to allow for a finishing cut.

Have a look about 2/3rds down this page where I'm milling the cylinder as you can see the rougher in action and the finish it leaves compared to a 3 flute "normal" cutter