Most ambitious milling project so far...

[John Hill]

Most ambitious milling project so far:-

flywheel by aardvark_akubra, on Flickr

A simply flywheel gnawed out of a scrap of 20mm plate.

[Stilldrillin]

Nicely done John! 

David D

[John Hill]

Thanks David.  To be truthful it is not really very neat when looked at closely.

I am still coming to grips with this whole matter of milling.   For example I used a 6mm slot drill (i.e. two flutes) and I found something was no 'right' when trying to slot the 5mm or so thickness of the wheel.  The slot drill went through it easy enough but when I applied feed to cut the full depth in one go it seemed very reluctant so I wound up taking cuts of about .75mm, that did the trick but to my mind most of the tool was not being used and all the wear was on the very end of the tool.  Surely the tool should have been able to cut that in one go?

[Stilldrillin]

John.
I also, am coming to grips with "our" type of milling. After a lifetime of grown up milling........

Your 6mm slot drill should be ok (happy), at 2mm depth of cuts. Dependent on rigidity of set up, and type of material to be cut.

With my mini mill and r/t. I would have slot drilled 5mm dia, in the corners. Then milled around with a 6mm endmill, at 3mm depth/ pass. If it seemed happy.......


No traditional milling cutter can (sensibly) cut full flute depth. Except in a gentle facing situation.

Hope this makes sense.

David D

[sbwhart]

Nice work John

As Dave said with our light machines you have to take things more steady, the trick is to be let your machine tell you what its comfortable with, if it seems to be strugling reduce the cut until it seems happy.

Drill the corners first with a roughing drill thats just a touch smaller than the cutter, also helps to get a neater job.

Stew

[John Hill]

David, Stew, thanks guys,  I tried to do the the 'right thing' and bought what I think is a decent size mill, a Luxcut turret mill*** and my fear was of snapping off the 6mm cutter (like I have done to my 3mm, and my 4mm cutters  )

I did think about drilling the corners first and it would have been better if I had, as it was I had a page full of numbers to follow and sort of got distracted..


Also, I am thinking that maybe I should invest in power feeds so that I can set to a comfortable feed and stand back as it is just too easy to push a bit too hard and bring blue chips to the surface.  The coolant is not set up as I am still waiting to get my shop organised and the machine into its final position.

***It is this mill http://www.scottmachinery.co.nz/conventional.php?s=110&ss=140&scode=MTUR-0-0001

[sbwhart]

Hi John

A power feed does give more control, I fitted one to my X3 late last year and wonder how I managed without it.

Stew

[DaveH]

John,
Looks good to me.

Most do drill the corners first, and it can be helpful.

Milling is a slow job, at the best of times. Especially in the home workshop.

A 6mm slot drill cutting 1 mm deep, now a 6mm slot drill cutting 5 mm deep - is removing 5 times more metal - thats a lot more chips to get rid of. The chips have to be removed as quick as they are being made. If the chips are not removed you will cut the same chip over and over again. There is just a limit on how much it can cut and if you force it - it will give up and break.

Have a quick look at this
 http://madmodder.net/index.php?topic=4678.msg51465#msg51465
may help a little.

Another way to cut (fly wheels) in the mill is to cut it out with a slot drill, then change to a 4 flute end mill, and finish it with small cuts to give a much better finish. This is the way I tend to do it.

With the end mill try to cut only  in conventional milling manner.

With milling I find it better to creep up on it -so it don't see you coming

It is slow and steady.

Your fly wheel still looks good.

Hope this has helped a little.

DaveH

[DaveH]

John,

Your mill is just begging for a power feed - you will not regret it. The control of the total cutting process is so useful, and the improvement in the finish - will really please you.

My 2p's worth

DaveH

[doubleboost]

Hi
John
Like people are saying the machine will tell you how far to push things
To take real deep cuts you need lots of coolant not only to keep things cool but to wash away the chips
This tends to be very messy on most home mills
John

[metalmad]

Hi John
that mill looks the part Mate 
but why are u only using a 6 mm bit?

[kvom]

using the G-Wizard calculator, the recommended DOC for slotting is .73mm at 1734RPM for a 6mm HSS endmill.  The criterion used by the calculator is to limit the deflection to less than .02mm (any more there is risk of breakage with more chatter).  The deflection depends on how far the tool extends from the collet.  I set it to 25mm.  Reducing the "stickout" to 20mm allows a 1.45mm DOC, as the endmill is thus stiffer.

While a power feed is great, you lose the feel.  It helps if your DRO will indicate feedrate.  Else, you'd want to calibrate to the feed knob.  Being able to calculate feedrate for a given tool is then very useful.  I'd recommend you try G-Wizard.